Evaluating my 420SEL parts car

Today I spent a bit more time evaluating the 420SEL parts car and the more I look at it the happier I am with my purchase.   It has too much wrong with it to make it a viable restoration project, but there are loads of good parts.    It didn’t come with a battery, so I hooked up a spare and most of the electrics seem to work.   I’ve started to keep a log of what is/isn’t working before I start properly dismantling the car.

I did not want to start the car, firstly because the fuel cap is missing so I have no idea what is in the tank.   In addition, the fuel injection system has been partially dismantled. I did want to see if the engine would turn over however. I removed the fuel pump relay and the engine turned over happily. At least I know it isn’t seized. I suspect it had a timing chain problem early in its life. The left valve cover is the older 450 style. The timing chain probably came through that cover and the car was repaired, but the earlier style cover used as a replacement.

Before I brought it inside, I had to give it a quick wash.   It has been sitting outside in the mud for the last 6-12 months and it was filthy.   I didn’t want to use my Bowdens car wash, so I just used dish washing soap. The car looks much better after a wash, especially after some of the flaky clear coat came off.

420SEL partsGetting the car inside was a major mission.   I did it mostly by myself and I shouldn’t have.   A neighbor helped me a little, but I found myself stuck with the car half in the garage door and half out, not able to move.   The front calipers are locked up, so the car is incredibly hard to push.   I have a set of dollies, but I find they take a lot of effort to push.   The little wheels also struggled to get over the small lip into the garage and then the hoist cable run.

In the end I had to lift the front of the car with a floor jack and gently pull it over the hoist cable run with the 450SLC.   I didn’t have a tow rope, but I did have a long picture hanging wire, so doubling that up allowed me to gently pull the car over the lip.   I was a bit worried about the wire breaking, flicking up and damaging the paint, but I could not leave the door open with a car stuck half in and half out.    Pushing it back out also wasn’t a solution as I couldn’t make it move that way either!

420SEL partsIn the end, I was able to get it in enough to make room for the other cars by about 10;30PM.   I’ll go back and position it properly another day.  A dead 420SEL with locked up brakes is very heavy.   The dollies are an ok solution, but there must be something better. I struggle to push the cars with them and I would be stronger than average.

420SEL parts

At least its in and I can start to properly dismantle it.    I’ve already had some interest in a few parts from some MBCNSW members which is great.    If I ever get another parts car, one that rolls easily would be nice!  Even better would be one that can move on its own.

My 420SEL parts car

I’ve been thinking about buying a W126 parts car for some time.   The number of affordable parts cars is getting thin on the ground as the W126 transitions from everyday transport to classic.   I would have had better options five years ago, but there are still some decent ones out there.   I was particularly looking for an SLS equipped car as I wanted the struts and ideally a S2 V8. Given the numbers sold, this was likely to be a 420SEL parts car.

I found a car on Facebook marketplace last week and went out to see it on Saturday.   As it was a parts car, I wasn’t going to be too picky but I needed to make sure it wasn’t full of water and mostly stripped.    What I found was a very high mileage 420SEL that had developed a problem with the fuel distributor and sat for a while.   It has been slightly vandalized, but is otherwise complete.

2021-10-19 11.37.51

The car was an Australian delivered, 1987 model (1986 production) and had originally been champagne. At some point, it was painted white. I suspect it had been used as a hire car given the colour and mileage (497,000). The previous owner to me had purchased it from the country and towed it back to Sydney.  He spent a fair amount of money trying to get it going ($2500 he said). It had new fuel pumps etc, but the problem was suspected to be a bad fuel distributor.

420SEL parts car

I’m not sure the full story, but the repairs were never completed and the car was brought back half dismantled, and it sat on the nature strip out the front of this owners house for a while. I am assuming it was at that point it was slightly vandalized.  It looks like somebody tried to rip off the front grille, and things like the catalytic converter, jack, first aid kit and spare tyre were presumably stolen.

For a 420SEL parts car, the interior is not in such bad shape.   Its a testament to the build quality of the W126 that it could cover almost half a million kilometers and still be somewhat ok inside.

420SEL parts car

I want to keep things like the SLS struts, headlights, tail lights, key relays, plugs, clips etc. The rest will be sold to recoup the purchase price of the car. I already took my first part off the car, one of the indicator lenses.

420SEL parts car

I have also hooked up a battery and checked some of the electrical systems. A lot of things seem to work fine, I won’t check the windows until I can get the car inside. I wouldn’t want the windows to get stuck down and it rain.  Dismantling this car will also build my knowledge of how the W126 fits together.

In finding my 420SEL parts car, I didn’t want to wreck a car that had any reasonable chance of getting back on the road.   I’ve seen otherwise nice cars get parted out due to a bad head gasket or transmission.   This car needs pretty much everything and is not a prospect to get back on the road.

Troubleshooting stuttering and stalling in my 250SE

My 250SE has not been running well lately.      Back in April, I hit a Kangaroo and the car was repaired during May and June.    In July, the state of NSW plunged into a strict lockdown for COVID-19, preventing more than minor trips up to the shops for necessities.    It was during one of those trips that I noticed that car was stuttering and stalling.  It felt like it was not getting enough fuel.

In some ways it reminded me of a fuel delivery problem I had on my 1967 250SE Coupe.   That car had been laid up for some years and the swirl pot had become clogged up.   The swirl pot is the solution Mercedes-Benz used to ensure that the car still gets fuel during brisk cornering, and on long uphill and downhill sections.   Inside the fuel tank there is a plastic structure that looks like a flower pot.   It is open at the top, but (mostly) closed on the sides.   When the tank is quite full, the swirl pot is unnecessary and fuel is above the top rim.   Once it gets down to about 1/3 level, the swirl pot acts almost like a tank in a tank.   Without it, fuel would slosh around and the fuel pickup would not be submerged at all times.   The pickup for the fuel pump is at the bottom of the swirl pot, and the return line comes in the side, swirling fuel around inside the pot.   This draws further fuel from the rest of the tank through a small hole in the bottom of the pot.   When it is working properly, there is always plenty of fuel inside the swirl pot, ensuring that the car has a reliable fuel supply.

On my 1967 250SE, the small hole in the bottom of the pot had become partially blocked with debris.   Once driving for a while, the car would use fuel faster than the pot would refill, causing the car to stall.  On that car, it would refuse to start for a few minutes until fuel slowly entered the swirl pot.   I fixed the problem by dropping the tank and cleaning it out as best I could.

There was a difference in this situation however.   When the car would stall, I could start it right away.   I also didn’t get many stalls, mostly stuttering and hiccupping.    It did feel like fuel starvation and so worth further exploration.

The first thing I did was change the fuel filter.   The filter is quite easy to get to on this era of mechanical fuel injection engines.   It is rather like the oil filter with a removable element inside a housing next to the engine.    It only takes a few minutes to drop the housing and replace the element.   I had a spare filter on hand from my old 250SE Coupe, so I figured this would be a good place to start.   The filter was very dirty on my coupe as the debris that blocked the swirl pot was also making it up to the fuel filter.

stuttering and stalling

Unlikely on my previous 250SE, this filter was pristine.   The fuel in the housing was also very clean and the old filter was so good, I could have almost put it back in.    It had been a while since the filter was changed, so I didn’t.   I also wanted to cut the filter open and make sure that there was no debris.

While changing the filter, there are a couple of gotchas, the first is the felt attachments on the filter detach once they get old.   Its pretty normal to find the top one still on the engine and the bottom one stuck in the bottom of the housing.   These should be removed.   Secondly, there is an O-ring between the housing and the flange.   Mine was not in great shape, so I replaced it.

stuttering and stalling

Cutting open the filter confirmed my suspicions.  It was very clean inside, so highly unlikely to be debris in the tank causing my problem.   Changing the filter is good routine maintenance anyway, so nothing lost.  While I was under the car I checked the condition of the steering shock too, which was still good.

I did one more test to eliminate the swirl pot from the equation.   The pot can be partially seen through the opening in the tank for the sender unit.   The sender unit is very easy to remove on the W111 and derivatives (e.g. W112, W108, W109, W113 etc).    It is simply behind a plastic cover on the boot floor.   I removed mine and then let the pump run.     Everything looked really clean.  I could see fuel swirling around the pot as normal.    This is not a definitive test as I did not measure the flow rate, but given how clean the tank was that didn’t seem necessary.

While I was there I replaced the cork gasket for the sender.   Mine was disintegrating and I had a spare on hand, again from my 1967 car.   An old gasket can cause fuel smells.

My next theory was bad or off fuel.   Modern fuel seems to have a short shelf life.    My Jaguar is particularly sensitive to this.  It doesn’t stall, but it can run poorly if old fuel is still in the tank.  I took the car for a drive to get the level down below 1/4 of a tank and then filled it up with a fresh tank of 98.   I probably should have driven longer as I added 60 liters.   As the tank capacity is 80 litres there was still almost 20 liters of old fuel in there.

There was a huge difference.   The stuttering was almost gone.  I had one minor stutter during a 20 minute drive and a stall when parking the car.   the performance was transformed, and I am attributing these smaller issues to the 20 litres of old fuel still in the tank.    I will have to drive the car more to really be certain, but it is looking more and more like the reason the car was stuttering and stalling and running so badly was old fuel.

Mercedes lug bolt restoration

I have recently purchased a set of 15×7 AMG ‘Penta’ wheels for my 1977 450SLC.   These wheels did not come with lug bolts, but I had a set from when I had the replica Fuchs alloys on the car.   The other day I got those bolts out to check them for when I install the wheels on the car.

The bolts were in pretty good condition overall, but suffering from surface rust, particularly on the heads.  That wouldn’t look very good with the new nice wheels.  Instead of buying new bolts, I decided to see if I could perform some lug bolt restoration.

My first try was using the Autosol Metal life saver.    The first picture shows the bolts pre-restoration.

lug bolt restoration
The Metal life saver did a good job on the bolts that only had light corrosion, but not such a great job on the worst of the bolts.   It also took quite a long time doing each bolt.   The photo below shows the results of about 90 minutes of work on the bolts.   An improvement, but enough to use with the nice new wheels.

lug bolt restoration

I figured as the Autosol product had been working reasonably well, it might make sense to soak the bolts in that solution.

lug bolt restoration

After about 48 hours, I could see a noticable improvement, so I added more autosol to submerge the bolts and left them for a few more days. After about a week of total time in the solution, I was able to clean the bolts with a rag and an old toothbrush. They came out great.

lug bolt restorationthe final product looked really good.   These bolts would look great and not spoil the look of the nice new wheels.   I figured job done – I was wrong.

A week later I went back to take the bolts down to where wheels for when I mount them.   I was in for a nasty surprise.   All the bolts were really rusty again – worse than when I started.   I surmised that the bolts must have come with some kind of rust resistant coating.   This degrades over time, allowing the rust to start, and explains why some bolts were worse than others.   Soaking the bolts on the autosol solution not only ate away the rust, but the remainder of that coating.   I should note that nowhere on the Autosol bottle does it suggest to soak metal in their product for days.

My thinking was that I needed some way of adding a coating that would stop the rust from starting.    I didn’t want to paint the bolt heads silver, as I thought they would clash with the colour of the actual wheels – even if very close.

I finally settled on trying to paint the bolt heads with some clear coat.   This should stop them from rusting, but also mean I have to be quite careful when tightening them.    The clear coat probably would not survive a mechanics rattle gun, so its going to be a short to medium length solution – if it works.   I started by soaking and cleaning the bolts in Autosol – again!

The next stage of my lug bolt restoration was applying the clear coat.   I used cardboard to ensure that the clear coat did not get on the threads.

lug bolt restoration

Per the directions on the rattle can, I did a few lighter coats on the bolts.  The glossy clear coat made the bolts look like they are wet.   I don’t think this will be too much of a problem.    The picture below shows the results after applying the final coat.   Note that there is not white residue on the bolts, that is reflection.

lug bolt restorationOverall I think they came out pretty well.   I won’t really know until I have the wheels mounted for a couple of weeks to see if rust will form.   In order to protect the threads, I have applied a small amount of copper grease.   Normally I would do this when installing the bolts, but I have done it now to help protect them.

I won’t be using these bolts for a couple of weeks.   The car is going in to have the front subframe mounts done, so I won’t mount the new wheels until after that.

If I was doing another lug bolt restoration I am not sure if I would do it this way again.   I may try soaking them in a less potent cleaner to preserve the original coating.    Having said that, the coating was already compromised where the rust had formed, so I am not sure what difference it would made.

W107 Foglight lens replacement

Earlier this year I managed to smash a foglight lens on a MBCNSW drive to Berry.   I drove over a large stick on the road that flicked up and smashed the lens.   I saw the stick, but there wasn’t really a way of avoiding it without risking an accident.   The low slung floglights on the 107 model look cool, but they are always at risk of road debris.   I’m pretty lucky that after 18 years of ownership, this is the first time I’ve smashed a W107 foglight lens.

W107 foglight lensIn the short term, I removed the broken lens so I didn’t have anything sharp sticking out of the front of the car.     Not only was the lens broken, but the bulb was dead too.    I then set about trying to find a replacement lens.   There are a lot of lenses out there, but I wanted a proper Bosch lens to match the other side.

I could have purchased a URO Parts lens for a song, but given my experience with the quality of that brand, I imagined it would break just by looking at it.   I eventually found some Bosch lenses for a decent price in the USA and ordered a pair so I would have a spare.

Unfortunately, that package was lost by FedEx.   It was a real shame as I had some rare workshop manuals and some used SLS struts I found for a really good price.   Not only that, but by the time I re-ordered the lenses they had significantly increased in cost.

W107 foglight lensToday I went about fitting the lens and replacing the bulb.    It is pretty easy to get the frame off, it is held on by two screws.   Once the frame is removed, the reflector and bulb assembly are removed from the light assembly.   This isn’t required to change the lens, but it is required to change the bulb.

The H3 bulb used by the foglights has a wire built into the bulb that can be seen in the picture below.   It was pretty easy to remove, being held in by a metal clip.

W107 foglight lensOnce I had the new bulb in place, I gave it a quick test before I refitted the lens.   The lens is mostly held on the frame.  There are also four metal tabs that hold it into place against the reflector and bulb assembly.     It was pretty easy to get it in and tighten down the frame so that the lens was snug against the light.

This was a very simple job – replacing the W107 foglight lens is something any owner could do.

W107 foglight lensAnother quick test showed the foglight lens still working.   Living in Australia, fog lights very rarely get used.   Consequently not many drivers know how to use them.   Additionally, Australian delivery cars are wired up so they can’t be run at the same time as the headlights.   They are only available with the parking lights.

C107 rear windscreen installation

Back in May, I had the rear windscreen removed on my 450SLC.   The idea was to replace the old windscreen that was delaminated with a good used unit I had purchased from the MB Spares clearance sale.   I had the rust under the screen fixed in 2006, so I assumed it would be a straight swap.   Sadly, during the C107 rear windscreen installation, no sealant was used.   over the years since, water had seeped between the seal and the body creating rust.

Obviously I wasn’t going to put the new window in with the rust around the aperture, so I had the car fixed.   This wasn’t a cheap exercise, but much better to do it now before the rust was too bad.     The car being finished coincided with the COVID19 lockdown in Sydney, so it has been sitting for the last couple of months.

C107 rear windscreen installation

This week, I was finally able to have the C107 rear windscreen installation completed.    The first step was putting the chrome surround into the window seal.

C107 rear windscreen installation

The windscreen installer used a lubricant to work the chrome into the seal. He then used tape to prevent the chrome popping out when the screen went into the car. At the same time he put some thin rope into a cavity in the seal. Then it was on to the harder part – the actual C107 rear windscreen installation.

I was surprised how much force was needed to get the screen in.   It was lined up against the aperture and then a combination of pressure while the thin rope was removed with fairly hard whacks the ball of the hand got the screen to slowly work its way into place.   I was a bit nervous during this part of the install as I heard the reputation that these screens have for being fragile.   I was very glad I wasn’t doing it!

This time, the installer used sealant so there is far less chance of the rust coming back.     On historic rego, the 450SLC does not get wet as often as it did on full rego either.

C107 rear windscreen installationThe new screen was finally in and looked great.   From there, it was a simple matter of reconnecting the electrical connection for the heated rear glass.    For some reason, a previous owner had cut a rough hole in the aperture for the electrical cable.  This is rather odd when there is a factory hole only a few CM away.   During the rust repair I had the rough hole removed.

I have not yet tested the electrical function, so I am not sure it still works.  It certainly didn’t on my old screen, so any function here would be a bonus.   Since the SLC had not been driven properly since may, but the time the screen was installed it was running on 6 cylinders.   A new tank of petrol, and a 20km drive sorted that out.

Choosing tyres for my 15×7 AMG Penta wheels

My new 15″ AMG Penta wheels did not come with tyres.   Choosing a set turned out to be a lot more complicated than I thought.

The big downside of the 15s over the 16s is the tyre availability.     The table below outlines possible sizes I could have considered.    They are all compared to the overall circumference of the original wheel/tyre combination.

Tyre SizeRevs per KMDifference
205/70 R14496Standard
205/65 R15492+0.8%
205/60 R15508- 2.4%
215/65 R15482+ 2.8%
215/60 R15498- 0.4%
225/60 R15489+ 1.2%
225/55 R15506- 2.4%
235/55 R15498- 0.4%

The easiest and most obvious choice would have been one of the 205 sizes.   Both are a fairly standard tyre size still used by many mainstream cars.   As an example, 205/65R15 is the standard size of the later R107 models with 15″ wheels.   I have the Michelin Energy XM2 tyre on my 560SEL in this size and it seems like a good tyre.

However, for the AMG wheels I wanted something wider with a bit more grip.   Certainly, looking at old AMG catalogs, they mostly offered the wheels with wider tyres.    I was immediately able to rule out two sizes – 225/55 and 235/55.  There were no tyres at all available in those sizes.

The next most obvious size would have been 215/60R15.   This is only 0.4% different to standard, so had the least speedometer impact.  However, when looking for tyres in this size, the availability of anything I would want to use was terrible.   There were some light truck/van tyres available, but they would have given the 450SLC a terrible ride.   There was one model that looked promising at first – the Radar Dimax classic tyre.   This tyre is advertised as specifically designed for classic use.  While I didn’t find any reviews of their classic tyre, I found pretty poor reviews of Radar tyres in general.   I couldn’t find anyone who had tried these tyres at all, let alone liked them.

Finally, I settled on 225/60R15.   These seemed closest to the size AMG would have used then new for 15″ AMG Penta wheels.   I was able to verify with somebody who used this size with Penta wheels on a 450SLC, which gave me confidence.

The tyre selection was not great in this size either, but there were a few options.    In the end I went with the Hankook Kinergy Eco2 K435.  The Eco2 name put me off a bit, as I assumed they were probably optimized for long tread life and fuel consumption vs performance.   However, they got by far the best reviews I could find in that size.   It also helped that there was a buy three, get four deal on at the time.

15The tyres are now mounted and ready to go on the car.   I also have the correct centre caps ready.   The 450SLC is about to go in and have the front subframe mounts changed, so I’ll fit the new tyres after that.

Guest Post: W126 parking brake shoes

I purchased my 1989 420SEL about two years ago and have been busy doing a lot of work to the car to bring it up to my standard.   My most recent job was to inspect and replace the W126 parking brake shoes.   The parking brake was not holding the car, even after I adjusted it.   The Mercedes W126 uses a separate set of drum brake shoes that act on the inside of the brake disc for the parking brake.

Last weekend I started the job, and at first it was pretty easy.   The wheel and caliper was off in no time.   However, despite removing the small bolt holding the rotor to the hub, it would not come off.   Normally a couple of quick whacks with a rubber mallet will break it free and it will easily come off.

I first went back and checked that the parking brake was off, and it was not adjusted too tightly.   No issue there.   Next I tried WD40, a heat gun and even more enthusiastic whacking with the mallet.   Still no joy.   I persevered for two days with these methods, with time for the WD40 to soak in, but it still wouldn’t budge.

I called a friend in the MBCNSW who had done a similar job on his 450SLC (the owner of this website).  His rotor came off with a few hits with the mallet, but he suggested if that wasn’t working to buy a puller from the auto parts store.   He suggested one that looked like it would work from Super Cheap Auto, which is only 10 minutes away.

After a quick trip to purchase the tool, I had the rotor off in two minutes.   The long thread centres on the hex head of the hub, and the three hands grip the rotor.   Once you start winding the thread, the rotor will pop off like a spring with no warning at all.   I’m glad I wasn’t too close to it!   Once the rotor was off, I could clearly see the surface rust on the hub and rotor that had been preventing me from removing it.
W126 parking brake shoes

Once the rotor was removed, I was finally able to get to work removing the W126 parking brake shoes.   I used a special tool to remove them, which can be bought from MercedesSource or eBay.   I had purchased new parking brake shoes but once I had the old ones off, it was clear that my new shoes did not match.   Luckily they had the right shoes in stock and I was able to go and exchange them.
2W126 parking brake shoes

The special tool popped the springs back and allowed me to fit the new shoes fairly easily.   I checked the rear rotors and they were still well within specification.  Instead of replacing them I cleaned them up with a wire bush on the end of my drill.   I was then able to re-fit the rotors and calipers (using Loctite on the caliper bolts).    Once the rotor is back in place, the handbrake must be adjusted.   There is a small star like adjuster that you can see through one of the bolt holes and adjust using a flat head screwdriver.   I first adjusted it so the rotor would not turn, then released three notches.
2W126 parking brake shoes

After that I put the wheels back on and took the car for a test drive.

Author: James Faydherbe De Maudave.   James is a member of the Mercedes-Benz Club of NSW and the proud owner of this 1989 420SEL.   He is the owner of All Aspects Auto Detail, who specialize in classic Mercedes-Benz vehicles in the Sydney area.   

16″ AMG Aero I wheels for my 560SEC

When I purchased my 1987 560SEC it came with Simmons B45 Wheels.   These are a high quality Australian made three piece wheel.   I pretty quickly replaced these for a couple of reasons.   The 245 profile tyres rubbed quite badly; There was a terrible wheel wobble; and I didn’t think the suited the car.   I sold those wheels and replaced them with the replica 8 hole wheels I had on my 450SLC at the time.   I only saw those wheels as a temporary solution.   They look good, but I still didn’t think they were quite right for the car.     I started keeping an eye out for pre-merger 16″ AMG Aero I wheels, as I think they are the best looking wheel for the C126.

AMG offered a few different wheels for these cars.   There is the earlier ‘Penta’ style, which bolt up to the W126 although I think they are best fitted to the 107 and 116 series.  Then, there were a few styles of the ‘monoblock’, of which I like the Aero I the most.   The AMG Aero I was available in various widths and offsets for the W126, W124 and so on.   I have type 2801B which is 7.5J x 16 ET17.   AMG didn’t make their own wheels – they contracted the manufacture to OZ Racing.     There were also the three piece 17″ wheels, which are even more coveted by collectors.   I prefer the 16’s as I think this is the best size for the W126 and I don’t like the exposed bolts where the pieces join together.

I finally found a set of AMG Aero I wheels for sale back in June.   They were from a wrecker and were in pretty bad shape.   They had been on a terribly rusty 380SL.   The price was reasonable, given their condition and the rarity of the wheels.

AMG Aero IAs can be seen from the picture above, the wheels needed a complete refurbish.   The wheels had received so many coats of paint in their life that you could hardly see the AMG logo, let alone the smaller text along the rim.   Some of this paint was now flaking off and they had curb rash and other marks.

I started looking at various options to get them refinished.   I had originally thought I could get away with a strip and repaint.   In looking at the options it quickly became apparent this wasn’t going to be the case.   To do this properly, it was going to cost 3/4 of a complete refurbish.   There were also quite a few places that did not want to take on a refurbish of aluminium wheels with complex curves.

Based on a few recommendations I went with Barrel Bros.   Their quote was one of the highest I got, but actually the best value.   It included a complete refurbish, straightening and as close to like new as possible finish.  I’m really glad I went this route.   The wheels look amazing.   I can’t wait to get them on the car.

AMG Aero IThe next step was obviously tyres.   The advantage of the 16″ wheels is tyre selection is excellent.   I went with Michelin Primacy 4, 225/55 R16.    I purchased them before June 30 to take advantage of the $50 cashback from Michelin.   At the time I was able to agree that I would keep the tyres until the wheels were finished and then have them fitted.     They are now fitted and ready to be mounted on the car.

AMG Aero I

I now don’t really have a need for the 8 hole replicas, so they will probably be for sale once the lockdown is over.    I also have a set of replica Bundt wheels that will be fore sale too.

M272 Camshaft position sensors

When you own a modern Mercedes-Benz, you seem to be playing constant whack-a-mole with the check engine light.   I’ve written before how silly I think the check engine light is, but we’re stuck with it.   Personally, I would just drive older cars, but this is not for everyone and my wife has a 2007 E350 Wagon.    There were two codes this time.

The first set of codes were complaining about the correlation of the camshaft and the crankshaft on one bank.   I had previously changed the magnetic actuators, which temporarily fixed the problem.    If the car didn’t sit outside the engine numbers with the soft balancer shaft, I would have probably assumed that this was my issue.

The second set of codes were about the tumble flaps in the intake manifold.   They are made from plastic and the hot engine makes them brittle and fail.   Mercedes will try and sell you a whole new intake manifold, but there are aftermarket solutions to replace the plastic with metal.   You would have thought Mercedes-Benz would have learned by now about brittle pastic on their engines.   I didn’t want to tackle this one myself, so had it done by a professional.   While the car was there having this and the front suspension rebuilt, we checked the codes.    The various camshaft codes were there, but the actual values of the camshafts seemed correct.

That got me thinking that perhaps it was the sensors sometimes giving bad readings.   I probably should have changed them at the same time as the magnetic actuators.   In any case, the M272 camshaft position sensors are not particularly expensive and very easy to change.

M272 camshaft position sensors
As the M272 is a DOHC engine, there are four sensors.   The right hand sensors are slightly harder to change, but each one can be done in less than five minutes.   The new sensors came with o-rings, which was good as the old ones were very hard.     I don’t know what it was, but there was some kind of residue on a couple of the sensors.   I doubt it was impacting how they worked, but at least the new ones do not have it.

M272 Camshaft position sensorsAfter replacing all four sensors and re-setting the codes, I was able to drive for 15 minutes without the check engine light.   It’s been a long time since that was possible.   The proof of the fix will be if the light is still not illuminated after a couple of weeks.   It was worth trying as four M272 camshaft position sensors are not expensive and the time to change them is negligible.

Update 22/9/21:  The Check engine light is back on.   Only lasted two days.    Back to the drawing board.