As a recap, my 1986 300SE started showing low oil pressure. I tried changing the oil and filter, replaced the sender and checked with a mechanical gauge. Still low oil pressure. I decided to do some final oil pressure troubleshooting before I took it into a mechanic to lift the engine and remove the sump.
I was advised on the ozBenz forum that another possible cause was the oiler tube for the camshaft coming loose. The oiler tube is held down by a couple of bolts that if overtightened can strip the threads. Since I don’t have a lot of history on the car, but the head was off 10,000km ago, it was a good test.
This last oil pressure troubleshooting was also something I could do at home. Its a fairly simple matter to remove the cam cover on the M103. Unlike on the M117, there are no fuel lines etc in the way. Unfortunately my results were the same. This oiler tube was in fine condition and so not my problem.
The photo below shows the engine with the cam cover removed. The engine is actually running in this picture, and you can see the oil pooling at the bottom of the picture before it drains back into the sump. I’ve never run one of these engines without the cam cover before, so I have no comparison, but I could see a steady stream of oil dripping over the cam lobes.
The engine ran like absolute crap without the cover. I assume due to vacuum leaks due to the disassembled state. In any case I have gone as far as I can at home. The car will go in to a mechanic in a couple of weeks. I am hoping there is not major damage and an oil pump change will fix the problem.
The Mercedes Club have been running regular ‘pop up’ drives mid week. These are informal drives at a couple of days notice. I’ve been able to get to a few over the last couple of months. Today was a really big one. We started early at our meeting point in Pheasants Nest, just south of Sydney. The plan was to drive down to Goulburn and take the back roads up to Oberon. I’ve done this drive a few times recently and am never tired of it.
While it was a Mercedes Club event, I took my Jaguar E-Type. I would have driven my 560SEC, but I am still waiting on new brake hoses for it. When I last drove the car, the pedal was quite soft and the hoses look quite old. The E-Type is a great car for these fast B-Roads. I don’t normally drive the E-Type during the day during summer as it gets quite hot, but I could not pass up this drive.
In a nod to the route, most of the other cars were high performance cars. In fact, the E-Type may have been the slowest vehicle there. There was an AMG GT, a C63 AMG, CLA45 AMG, CLA45S AMG, E400 Cabriolet and a C250. Bit of a theme to those cars.
The starting point was the service station at Pheasants Nest, south of Sydney. From there, we proceeded in convoy down to Goulburn. At Goulburn, we turned off the M31 and proceeded up towards Oberon. The first part of the drive was a bit dull, as we were stuck behind a slow Mitsubishi crossover. These top heavy vehicles struggle on these sorts of roads and it had to slow down quite a lot for each corner. The second part of the drive was much better and we were able to open up the taps of the cars a little.
When we got to Oberon, it was only 11:30AM. It was suggested that instead of returning, we continue on to Bathurst and do a lap of Mt Panorama. One of the people on the drive knew the roads around this area quite well and found us an excellent set of roads to take us through to Bathurst. This part of the drive was probably the highlight of the day. Instead of going directly to Bathurst, we first drove back towards Oberon until Black Springs. We then turned onto the road for Bathurst. I’ve been on Google maps trying to work out the road we used so I an visit again, and I think it might be Dog Rocks Road. Looking at the map, I am assuming we must have gone through Rockly and towards Bathurst.
Once in Bathurst, we then did a (slow) lap around Mt Panorama. The circuit is just a regular road when there are not races. It has a low speed limit and and is heavily policed. I’ve previously taken my 560SEC around the circuit. Once we finished our lap, we drove back via Lithgow for a fuel stop and then up via Bells Line of Road to Bilpin.
The only part of the drive that wasn’t particularly enjoyable was the drive through Sydney from Richmond. By afternoon it was a really hot day. Normally I enjoy the wood steering steering wheel in my E-Type, but it was so hot I found it hard to grip with my sweaty hands. Despite the reputation of English cars, and E-Types in particular for overheating, the car never went over 90 degrees. The only thing that did overheat was my iPhone, which shut itself off due to the heat. I guess British cars are more reliable than Apple products.
All in all, it was a really good day and great to take the E-Type out for a long drive on such good roads. I’ll be back in Bathurst with the E-Type in April for the 60 years of the E-Type celebration. I would recommend Bathurst via Goulburn and Oberon as a drive to anyone. In the end, we covered more than 700km. Some classics are not driven this much in an entire year!
In my last update, I had ruled out the sender unit when it came to the low oil pressure readings on my 300SE. My intention had been to take the car to a mechanic to test it on a mechanical oil pressure gauge. Two things changed that. Firstly, my area of Sydney went into lock down. Secondly, most mechanics are on holidays until after the new year. I therefore purchased my own mechanical oil pressure gauge off eBay.
I hooked up the gauge and sadly the results were much the same as the dashboard gauge. The mechanical oil pressure gauge I purchased has a number of fittings and one of them was correct for the M103. It also had a quite useful elbow connector.
It is much easier to attach it with the oil filter removed. Don’t make the same mistake I did, and not attach the filter properly! You’ll end up with a lot of oil on the floor very quickly.
As can be seen by the readings below, they are not what they should be. The first one is immediately after start up, and the second is after a couple of minutes of running.
As can be seen from the next photo, there is oil at the top of the engine, so something is working properly.
I also made a short video about taking these readings. Still not very good at this video thing, as the gauge itself is not readable, and when looking at the senders, they are out of picture, but plenty of room for improvement.
As I mentioned on the video, I will take the car down to my workshop and remove the cam cover. From there, I should be able to inspect if the oiler tube has come loose. This was suggested to me on a thread in the ozBenz forum.
The December night drive was the last official night drive of the year took us through the eastern suburbs. Yet again, the late night drive proved popular, as we had 25 registrations and a lot of cars show up on the day. The meeting point, at Bradfield Park (near Luna Park), under the Sydney Harbour bridge probably helped.
The meeting point also provided the opportunity for some nice photos with the bridge in the background. I took my 250SE which is nice to drive on warm summer nights with the top down.
There was a good range of cars from old to new at the event. My car was the oldest, but we had two W108 3.5 saloons, a 450SLC, 560SL, a couple of 420SELs, a 380SEC, 190E, 280CE and some modern Mercedes, most of which were convertibles.
The day had been very humid and rainy, and the storm was continuing southwest of Sydney. Luckily we were spared any rain and those of us with Convertibles were able to open the top.
From there, we proceeded over the Harbour Bridge to Dudley Page Reserve in Dover Heights. I had not been there before, but it offered nice views back to the City from its elevated position.
We were also able to get a few more photos of the cars outside the reserve. One of the 280SE 3.5s was decked out as a Christmas car.
The plan was then to out to watsons bay and the chapel at HMAS Watson. This is in the secured part of the Naval base, so we were not able to get in. A few cars stopped off and got some photos near the lighthouse at Watsons’ bay. This one is particularly impressive.
From there, the December Night Drive convoy drove down to Bondi beach and stopped off at McDonalds. It was pretty much the only thing open that wasn’t a swanky bar with a bouncer. This night drive was a bit different from the previous ones we have done as it was less about the drive and more about the sights. It was a nice change. The next official one is planned for late January and the route takes us on the Old Pacific Highway. A reprise of one of the drives we did before they were official.
A few weeks ago my 300SE started to show low oil pressure on the gauge. It happened all of a sudden while on a drive. At the time, I surmised that I had a dead M103 Oil pressure sender. They are apparently a common fault. I ordered a new one and fitted it today.
The M103 oil pressure sender can be found on the side of the oil filter housing at the back of the engine. Most of the threads you’ll find on the various forums are referred to the W124. Apparently on the W124 space is tight and it is a paint to remove the sender. I can only imagine how hard it must be on the W201 then. On the W126 there is loads of space, as can be seen in the photo.
With the right spanner, you could probably remove it with the oil filter in place. I elected to remove the oil filter first. It made it dead simple to disconnect the wire, and then unscrew the sender unit with a 17mm spanner. As can be seen in the photo below, there is loads of room without the oil filter in the way.
I went with a new VDO sender. VDO are the OEM brand. There are also Meyle sensors availabe, which are much cheaper. Meyle is a brand I try to avoid. There was somebody on one of the facebook groups complaining they have replaced two sensors in as many years. I bet they used Meyle. Comparing the new M103 oil pressure sender, the original one was still on the car. It was dated 7/86. I put a new 9/19 unit on. Still made in Germany.
Re-installation is even easier than removal. There is a little washer that goes back on. In my case it had remained stuck to the housing. The new one is certainly a lot cleaner!
I then fired the car up. I expected to see the oil pressure reading jump to three. But it didn’t. Instead, the pressure was the same as before. Around the middle of the gauge after a cold start.
Clearly there was nothing wrong with my older sender. I think my next step will be to take the car to a mechanic to hook up a mechanical oil pressure gauge. This will eliminate the wiring, gauge etc and check the actual oil pressure of the car.
I can think of a few possibilities in order of likelihood.
Oil pressure relief valve stuck
Faulty Gauge
Bad wiring to gauge or sender
Worn Oil pump
I think the oil pressure relief valve is built into the motor on the M103, so not a quick change to see what happens. The mechanical gauge will at least determine if there is a problem.
My 560SEL was sold new by West Orange Motors, in Orange NSW. The original owner lived in Western Sydney, but had business in Orange and Dubbo. While it was sold new in Orange, it was serviced at Marshalls in Parramatta until 230,000km. Presumably, the car made a fair few trips up to Orange, Dubbo and the surrounding area over its life. The original stamp from West Orange motors is still in the service book. I can’t imagine that many 560SELs were sold outside the main dealers in Sydney, Sydney Eastern Suburbs, Melbourne City and suburbs like Toorak. The original owner dealt in tractor spares, so he may have had a business relationship with this dealer.
The previous (and original) owner told me that at least one of the camshafts was replaced under some kind of recall in the first couple of years of the cars life. Other than that, it had normal servicing at the dealer as you would expect of such a car.
I was out for a long drive yesterday. When I got to Bathurst, I thought it would be interesting to see if the original selling dealer was still in the same location. Mercedes helpfully provided a booklet of dealerships and service centres in the owners manual pouch. I plugged in the 1987 address of West Orange Motors and set off. A lot has changed in 33 years. I thought that the chances were quite low that the Mercedes dealer was still in that exact spot. Most likely there would be a different dealership, or that the site would have been redeveloped.
I was wrong, West Orange Motors are still there, in their 1987 location, still selling Mercedes-Benz. They also sell Mitsubishi, Toyota, and a few more brands. Plus have a dedicated truck entry. I parked the car outside and took a few pictures. The salesman even came out while I was doing so and had a chat. He thought I might be trying to sell the car!
Its a little over 33 years and 330,000KM since the car was delivered new by that dealership. I wonder how many of the other cars they sold in 1987 are still on the road and still in good condition? Country cars are more likely to be, as highway driving is better than stop/start and there is less likelihood of rust.
Obviously, as my car has traveled 330,000KM over 33 years, it has averaged about 10,000km per year. However, it reached 200,000KM in only 13 years and was generally averaging about 18,000km per year over this time. For the next 10 years or so, it averaged about 7,000KM per year and since it has reached 300,000KM, 3500 per year. I’ve already put 4,000KM since the purchase, so I am a bit ahead of recent trends.
The 560SEL still remains an excellent highway car. It is comfortable, smooth, powerful and even somewhat efficient at highway speeds for a 5.5 litre v8 under the bonnet. Even though my car has working cruise control, I never find the need to use it in a W126. The long travel accelerator is comfortable to rest your foot on it and keep the speed where you want to, without getting tired. The seats are supportive, without being so hard.
Contrast this to a modern car, Mercedes included and the accelerator pedal is so sensitive that you are pretty much obligated to use the cruise. I always do when driving the 2007 E350 we own.
Most of the articles on Sydney Scenic drives list the same old drives everyone knows. I’ve had a free day once a week for the last couple of months. Its given me the opportunity to explore different roads a day trip away from Sydney. I don’t normally get the chance to go long drives, to it was also a good opportunity to give all the cars a good run. The idea was to leave about 7:30AM, and return by 6PM, leaving time for a few breaks.
The idea was to find some good roads for the classic car driver who wants to get out and explore the area a couple of hours around Sydney.
Mudgee via Bells Line of Road
The first drive I did was to Mudgee. I took Cattai ridge road from Glenorie through Maraylya. This is a drive I do quite a bit as it can be done in a couple of hours. Instead of returning, I then took Bells line of road up through Lithgow and then up the road to Mudgee.
Bells line of road is always an enjoyable drive, especially during the week without much traffic. The road up to Mudgee is a nice undulating road with some fast sections and some tighter sections.
I made the mistake of coming back via the Great Western Highway. It really is a horrible road. Congested, insanely low speed limits, speed cameras on every corner. Next time I would go back via Bells Line of road again.
I took my DS. On the way up the DS drove really well, but it was a bit unhappy on the way home and I had to nurse it back. It felt like something was dragging on the motor, perhaps one of the accessories? I did this drive first, before the hot summer weather came in. The DS isn’t the best as a hot weather car. It is really comfortable and soaks up the bumps on a rough road like few other cars.
I really enjoyed this drive and would do it again.
Putty road, returning via Wollombi
I did this drive as part of a mid week drive with the Mercedes Club. This drive is already covered here. I took my SLC. The Putty road is so much better mid-week than on the weekend. The return via Wollombi is much nicer than going on the M1. This drive is on most Sydney Scenic drives list.
Bylong Valley
This one was a surprise because I just started looking at google maps to find roads that might be interesting. The self-leveling rear suspension had just been re-installed in my 560SEL and I wanted a good drive to give it a work out and make sure my used struts were not leaking. Not only was this a good drive, but it fulfiled that requirement as the road was quite rough. The car was transformed. The horrible old ute feel was gone and it was back to driving like an S-Class again.
I started by driving up to Singleton where I had lunch. I then took the Golden Highway to Bylong Vally Way. The Bylong Valley Way is a really enjoyable road. A bit rough in times, but scenic and twisty as you cross the mountains.
Return was via Lithgow and Bells Line of Road. You pop out very close to Mudgee so the return is very similar to the drive above. The SEL is better than most people would expect on twisty roads. It also has plenty of power to accelerate up hilly roads. This drive really cemented my decision to put the SLS back in.
You could probably make this drive even better by taking the Putty road up to the Hunter and then continuing the drive from there. Large sections of this route have no phone reception.
Oberon to Goulburn
I’ve been wanting to do the Oberon to Goulburn drive for years. I’ve always heard it was good but never got a chance to try it. After I got the cooling system working again, I took my 560SEC. I figured of the cars I own, the SEC with its 220KW engine or the E-Type are the most ideal cars for this drive, and given the weather was iffy at the start of the day, the SEC was the best choice.
I took Bells Line of Road to get to Oberon and then proceeded to Goulburn. This road really lived up to expectations. There are some long fast sections were I got to push the SEC along as well as some curvy bits decending down the mountains. The road to Oberon from the Great Western Highway is really picturesque as you can see from the photo below.
The only real downside to this drive, is that the return journey on the freeway is a bit boring.
Goulburn to Oberon
I enjoyed the Goulburn drive so much I decided to do it again, but in reverse. I just had the E-Type ready after its new fuel pump. The E-Type drove really well and was really in its element on this drive. I did this one as a pop up drive with the Mercedes Club. It is kind of funny the one I did on my own, I did in a Mercedes, but the one I did with the Mercedes Club I did in a Jaguar.
I think its slightly better to do it in this direction. Not because the drive is better, but it’s easier to manage traffic that way, especially if you live north of the Harbour like I do.
Grand Pacific Drive
I’ve done the Grand Pacific Drive through the Royal National park many times. Both on club events and on my own. Most recently I did two variants, one that took me inland to Berry and another over Macquarie pass through to Mittagong. We didn’t have time, but the Berry drive would have probably been even better to return via Kangaroo Valley. The drive through the Royal National Park is nicer during the week and very scenic, if a bit slow. The speed limits are artificially slow and heavily policed. There are also a lot of cyclists.
I took my 250SE on the drive through Berry and the 300SE on the other drive. Like Putty road, this one is also on most of the Sydney scenic drives list.
Wollombi, returning via Wisemans Ferry
I had a bit less time this day so did a shorter drive. I took the old Pacific highway to Peats Ridge, and followed the roads north to Wollombi. On the way back, I turned off and went via Wisemans Ferry. This is quite a nice drive if you don’t want to spend the full day. The roads up to Wollombi are in decent shape although the one to Wisemans Ferry not as much.
I took my 560SEC. The Old Northern Road after you cross Wisemans Ferry is a nice drive too.
Hunter Valley – Scone – Merriwa
On this drive, I took the freeway up to the Hunter Valley and then went up towards Scone, where I had lunch. From Scone, I took the road to Merriwa, which was scenic and deserted. I was able to push the 450SLC along a bit. This was quite a nice drive once I got up to the Hunter but the freeway section was boring. It could be combined with Putty road or Old Pacific Highway. I think Bylong Valley was better though.
Barrington Tops
This one was a bit speculative. There looked like there could be a nice road through the Barrington Tops national park from Barrington across to Scone. And there is. Problem is that its unsealed for about 80km. I took my 560SEL, and while it could easily do an 80km unsealed road, I didn’t want to. I drove on the unsealed bit for about 5KM until an information kiosk. When the extent of the unsealed section was apparent, I turned back.
I had tried to get up there without using freeways. Getting up to Peats Ridge via the Old Pacific Highway was good, and then I went towards the coast towards Alison. From there I should have taken the motorway as I ended up driving through the Newcastle suburbs. The other Alternative would have been Putty road and skip the whole area.
During my navigation, I discovered some key differences between Google maps and Waze. When you avoid Motorways on Google Maps, it just avoids Motorways with an M prefix. A roads that are built to almost motorway standards are OK. Waze is stricter. Major A roads that are dual carrigeways are also avoided. Thus, Waze will tell you the only way to get up there without using Motorways is to drive up to Queensland and take the silly route around the top. Google will take you on the A roads.
Waze has an option to avoid Dirt roads, but it doesn’t show them on the map. Google doesn’t show them at all. I wish it would. Maybe I need to invest in a proper printed road atlas to explore more Sydney scenic drives.
It may be worth at some point exploring up Thunderbolts Way. This takes up towards Tamworth which is too far, but there could be some good intermediate stops.
Future
If I get more time to explore more Sydney Scenic Drives, I may look at more roads on the other side of the great dividing range. From Oberon, as an alternative to Goulburn, it looks like you can turn off earlier and go via Wollondilly. There may also be some roads in the area between Bathurst, Mudgee and Lithgow. I can probably explore further West too.
When I wrote my W126 buyers guide earlier in the year, I did not include price information. Pricing is very specific to each location and changes frequently. This W126 price guide covers my observations about the prices of W126s in Australia. Its likely to be valid for the next year or so.
There are a few factors that impact the price of a W126. Some models, years and options are worth more than others. This is particularly the case for the W126 which had different body styles, engines and even two distinct series. As an example, the V8 models are worth more than the sixes, the coupes are worth more than the saloons and so on. Some options can even impact value.
The next is the KMs on the odometer, which must be verified with service history. Despite the W126 wearing high mileages with ease, this is a huge factor when it comes to price. Its also a great way of getting a nice car for reasonable money if you don’t mind a high mileage car. My 560SEL with 330,000km is an example of this.
Obviously condition is also very important too. This is sometimes correlated with mileage, but can vary widely. I’ve seen beautiful cars with 450,000kms on them and parts cars with less than 100,000.
I’ve started with a baseline car of a 280SE from the first series. The car has 250-350,000km on the clock, partial service history and is at a 6/10 when it comes to condition. I define 6/10 as good driver quality. I estimate this car is worth $5,000.
The W126 price guide works by adding up the factors to get a total multiplier over that original price. I assume a minimum value of $1,000
Model Attributes:
Series 2: +75%
V8 (except 560): +50%
V8 (560): +100%
High compression engine: +25%
Soft Leather: +25%
SEC (series 1): +200%
SEC (series 2): +300%
Private import: -25%
The first set of attributes concerns the model of the car. As indicated above, V8s are worth quite a bit more than sixes, and the 560 in particular. The series 2 cars have a decent price premium over series 1, and that only increases when the soft leather and other interior improvements was done for the 89 model year. The biggest impact is coupe vs saloon. SECs are just a lot more valued than saloons. Interestingly, I can find no real difference between short or long wheelbase cars when comparing the engines where both were easily available.
Assuming the same condition and mileage, the baseline prices by my model are as follows below. I didn’t include the private imports, but they can be calculated readily. They are more complex as the high compression series 2 imports are worth more. For the local cars I have assumed they do not have soft leather.
Series 1:
280SE: $5,000
380SE: $7,500
380SEL: $7,500
380SEC: $17,500
500SEC: $16,250
Series 2:
300SE: $8,750
300SEL: $8,750
420SE: $11,250
420SEL: $11,250
560SEL: $13,750
560SEC: $28,750
Mileage
Mileage seems to have a major impact on the W126 price guide. In my mind, too big an impact. The market is pretty clear on this. Low mileage cars demand a massive price premium, and high mileage cars are hard to sell. They can be a good buy if you are planning long term ownership though. The factors assume at least some service history to validate it, and for the very low mileages complete service history. Obviously cars with an MPH speedometer are converted into KMs for the purpose of this. e.g. my 167,000 mile 560SEC would be counted in the 250-349 range.
<100,000KM: +300%
100-149,999KM: +200%
150-199,999KM: +75%
200-249,999KM: +25%
250-349,999KM: (baseline)
350-449,999KM: -25%
450-549,999KM+: -50%
550,000KM+: -85%
Adding in mileage, lets consider some examples. This does not yet include condition, so all cars are assumed to be 6/10 driver quality cars.
280SE with 400,000KM: $3,750
380SEL with 160,000KM: $11,250
300SE with 600,000KM: $4,500
420SEL with 51,000KM: $26,250
560SEC with 300,000KM: $28,750
Condition
Obviously condition is a huge factor here. Cars in excellent condition sell at a massive price premium. This is what many classic car buyers/sellers fail to understand that 10/10 cars are incredibly rare and sell at a massive premium over everything else. At the same time there are probably only a handful of 10/10 cars in the world.
10/10: This is a car that could be invited to the world’s pre-eminent events like Pebble beach: (case by case)
9/10: This is a show winning car at regional and national events: 350%
8/10: This is a car that would be proudly entered for judging, not look out of place at regional events: 150%
7/10: This is a really nice car that could be seen at show and shine events and people who see it comment on how nice it is: 75%
6/10: This is a nice driver car. No rust, good paint with some minor scratches, minor wear on the interior: (baseline)
5/10: This is a normal driver car. May have very minor rust, a few scratches, some interior wear. A/C may not work: -50%
4/10: This is an average driver car. Has some rust here and there. Interior a little worn, scratches on the exterior, a few mechanical issues. -65%
3/10: This is a very scruffy driver car. -80%
2/10: This car is bordering on being a parts car but runs and drives. -90%
1/10: This is a non running parts car. Scrap value only.
Comparing the cars we looked at above, but now adding condition.
280SE with 400,000KM and 5/10: $1,250
380SEL with 160,000KM and 7/10: $15,000
300SE with 600,000KM and 2/10: $1,000
420SEL with 51,000KM and 9/10: $28,750
560SEC with 300,000KM and 5/10: $21,250
Options and customization
There are a few options that can change the value of a car. For some, there are not enough that sell to really know. For example a HPF2 car is very rare and worth more, but there are so few in Australia and they quickly change hands via word of mouth. Anything that is genuine AMG is worth a lot of money, but so few of these cars exist it is more of a case by case basis.
I’m less confident in some of these because the sample sizes
Towbar: -25%
No sunroof: -20%
Original Becker: 20%
ASR: -25%
Aftermarket wheels (no AMG, Lorinser etc): -25%
Medium modifications that can mostly be reversed (e.g. bagged, LPG): -25%
Major modifications (e.g. different engine, bodywork etc): -50%
The final factor is colour. Colour is highly subjective but there are colours that are popular, colours that are neutral and colours that are negatives. For example white and gold are not popular W126 colours and harder to sell. Colours like smoke silver are neutral and colours like Blue/Black, Pearl Grey etc are popular. I would estimate a +50% for a really popular colour and a -50% for a really unpopular colour but I am not going to go through subjectively giving them ratings.
This W126 price guide is my opinion based on looking at a lot of cars. It is likely to change over time. I would also suggest to anyone buying a W126 is to buy the best condition car you can afford, even if it is not the model you wanted. A poor condition car will never be worth much and will more likely become a money pit.
Under normal operation, the auxiliary fan on the M117 engine cuts in at 105C. It can also be triggered by A/C system pressure. These settings work fine to keep the engine at the correct temperature. The challenge is that most of these cars have been converted to R134A refrigerant. R134A is far less efficient than R12. The A/C system in the W126 was designed for R12 so is now under specified. Add in the hot Australian climate and stop/go Sydney traffic and you end up with a hot engine and poor A/C performance.
I’ve noticed that once the coolant temperature gets up towards 100C, it has a big impact on the A/C. I’m assuming the condenser, already marginal, is just not able to pull enough heat out of the system in hot weather with a 100C radiator next to it. My thinking is by modifying the auxiliary fan cut-in point, I can keep the temperatures a bit lower, and provide more air over the condenser.
My 300SE has gone beyond auxiliary fan cut-in modifications to hard wire the fan to run any time the compressor is engaged. This does help with A/C performance, as you get constant air cover the condenser. But it has some drawbacks I am hoping to avoid on the 560SEC. Firstly, the auxiliary fan only runs when the A/C is on. This isn’t the end of the world, as the A/C will generally be running on hot days. Its not ideal though. Secondly, as the fan is always running, it even runs at freeway speeds which is not a good idea.
Instead of hacking the system like that, with a lower cut in point, I should have the best of both worlds. More air flow during stop and go traffic, protection even without the A/C and no unnecessary running of the fan. My 450SLC already has this modification and it works quite well. The 107 A/C system is even more marginal than the 126 with R134A so it needs all the help it can get.
To perform the auxiliary fan cut-in modification, a resistor is placed between the two wires that come from the temperature sensor unit on the thermostat housing. From reading various forum posts, a 1100 ohm resistor should result in a cut in point of around 94C. This seemed ideal, as with an 80C thermostat, it should be fully open around 92-93C. Having the fan running before the thermostat is open is just going to have them running cross purposes.
The picture below shows the temperature sensor (the green sender unit). The harness with the two wires is the one where the resistor must be placed. Jaycar had the resistors I needed in stock.
Most people simply solder the resistor between the two posts and call it a day. I tried this, but the modification didn’t work. I’m terrible at soldering and avoid it where I can. After that, I came up with a better solution anyway. I could build something small and removable on the bench, so the car can go back to stock at any time.
Lukcily, I had a set of bullet connectors that fitted the factory connector. I crimped them together and tested my work using a multi-meter. My handiwork can be seen below. A little messy, but no permanent modification to the car. I may try and make a neater version and replace this one.
This was actually V2. On V1, I used shrink wrap to make it look neater. Even though I only used the heat gun for a couple of seconds, it warped my connectors to the point I could no longer push them onto the sender unit poles. Back to the drawing board and using electrical tape this time.
After I installed my auxiliary fan cut-in modification, I took the car for a brisk test drive and then let it idle for a bit. It worked, but not quite as I expected. The cut in point seemed more like the high 90s rather than mid 90s. I don’t know if this is just because my gauge is not particularly accurate. I may swap the modification over to the SEC for a side-by-side test. That will have to wait as the SEC needs new brake hoses.
The picture below shows the temperature not long after the fan kicked in. Before that I will see how the car performs in the real world.
Obviously, the auxiliary fan needs to work properly before this modification is performed. I have just replaced the fan on the car, and have tested it working fine.
Now we have hit summer here in Sydney, it was apparent that the auxiliary fan was not working. The fan is triggered either by high coolant temperature, or refrigerant pressure. High coolant temperature causes the fan to run at full speed. Refrigerant temperature can trigger a slower fan speed based on a resistor. Before I just jumped into W126 auxiliary fan replacement, I tested the existing fan.
The first test is to jump the wires at the coolant temperature probe. This should trigger high speed running. The next is the sensor on the A/C receiver/drier which should trigger low speed running. In my case, neither of these tests triggered the fan.
The last test is to apply 12v directly to the fan. This will eliminate the relays and temperature sensors. In my case, the fan didn’t work here either. Time to replace the fan.
I’ve done this job before on my 1987 560SEC and had the same symptoms. The W126 auxiliary fan replacement procedure is identical on the saloon as compared with the coupe. The only difference is that there is more room to work on a saloon.
Like when I did this job a year or so ago, I went with a Meyle fan. I’m really not a fan of the Meyle brand and avoid it where I can. The trouble is, that the Meyle fan is about USD$120, and the genuine fan is about USD$500. By the time you add in shipping and GST, the cost of the genuine fan is over $1,000. I wish there was a manufacturer that made a higher quality product somewhere in the middle. As the fan is so easy to replace, the Meyle one made sense.
The picture above shows the fan removed. The little bit of extra room makes a big difference and you can have the fan out in 10 minutes. I found it easier to leave the brackets on the fan and remove the whole assembly, then transfer the brackets to the new fan.
With the fan removed, it is worth cleaning the condenser. The W126 A/C is marginal on very hot days running R134A. It needs all the help it can get. I used compressed air to blow a lot of junk out of the fins.
The new Meyle fan came in a different box than the last one. While it looked the same, there was an improvement. The mounting holes for the finger guard were now in the right spot so I was able to mount it.
Jumping the temperature sensor had the new fan whirring into life. The resistor that controls the slow speed running looked quite crusty and I tested it with a multimeter. Looks like the wire is broken inside so I have one of those on order. This resistor looks the same as the ballast resistors Mercedes use in the ignition system, just with a different resistance. I have one on order and will fit it as soon as it arrives. I got a genuine one and now they are showing as no longer available so maybe I got the last one?
I’ve had to do quite a bit of work on the cooling system of my 560SEL. When I purchased the car, the thermostat was stuck open, the fan clutch was not operating correctly and neither was the Auxiliary fan. I feel much better about driving it on hot summer days with these systems all fixed. I also plan to adjust the cut in point for the Auxiliary fan, which will be covered in a later article.
The engine ran like absolute crap without the cover. I assume due to vacuum leaks due to the disassembled state. In any case I have gone as far as I can at home. The car will go in to a mechanic in a couple of weeks. I am hoping there is not major damage and an oil pump change will fix the problem.
