Testing M103 Oil pressure with a mechanical oil pressure gauge

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 […]

M103 Oil pressure sender

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 […]

300SE low oil pressure gauge

Today I took my 300SE on a Mercedes Club Pop up drive. The Pop up drives are short notice mid-week drives. I normally take the other cars to club events, but the 300SE had not been on a decent run for a while and the weather was terrible. The drive was down through the Royal National park to Mt Kembla, Mt Kiera and then back.

The other cars on the drive were rather varied. There was a Ferrari 458 Spider, an Audi SUV, a race prepped Toyota Yaris and a couple of other Mercedes including a C63, C250 and E400 […]

W126 Klima Relay

A week or so ago, I diagnosed that the likely cause of my non functional A/C in the 300SE was the W126 Klima relay. The second generation W126 went to a Klima relay to control the A/C compressor.

The W126 Klima relay is more of a control unit than a simple relay. It has multiple inputs that determine if the A/C compressor should not engage. These include:

During full throttle When the engine is very hot Invalid compressor speed (e.g slipping belt) Not enough coolant in the system

This additional functionality makes these relays more sensitive than the little silver […]

W126 A/C no longer cooling

There is an old saying that deaths come in threes. I’ve not had any deaths in the family, but I had the A/C dead in three cars at the same time. The easiest was the A/C in my 450SLC that just needed a re-gas. The W126 A/C has been more problematic. Just as I got the system in my 560SEC mostly finished, the A/C stopped working on my 300SE.

I took the car in for the gas pressures to be checked and the gas was not below minimum spec. A tiny bit was added but my mechanic told me he […]

M103 Distributor cap and rotor

Today I changed the Distributor cap and rotor in my 1986 300SE. I bought the new cap and rotor about two years ago but only just got around to changing it. Unlike on the earlier engines, the M103 distributor cap is a fiddly job. Instead of sticking upwards, it comes out sideways as it attaches to the camshaft.

I find that whenever I buy one of these older cars, chances are the distributor cap needs changing. It is not generally an expensive part on the mainstream engines, and can make a big difference to the smooth and reliable running of […]

Youtube tips – shifter bushing and rounded bolts

Today I did an engine and transmission oil change on the 300SE. I don’t normally post basic maintenance to this website as it really isn’t that interesting. In this case, I used to tips I learned form MercedesSource videos that really sped up the job. MercedesSource are an online parts vendor, who also make some useful special tools. The owner, Kent, runs a youtube channel to promote the business. I’ve bought a couple of his special tools over the years and found them quite useful.

The first tip was for removing the bolt from the transmission oil pan. This […]

Mercedes self-leveling rear suspension flush

A common feature of Mercedes cars from the mid 70s through the mid 2000s is the self-leveling rear suspension. This system is standard on the wagons, but was commonly specified on the higher end sedans too. Mercedes-Benz Australia was particularly keen on the system fitting it to coupes and even mid size saloons.

The system ensures that even with a heavy load in the rear of the car, the suspension remains level. Keeping the car level improves handling and safety. It is actually quite a simple system, derived from the more complex system on the 6.9. This system, in turn […]

W126 Sedan Bonnet Insulation

A few months ago I replaced the under bonnet insulation pad on my 560SEC. This job also needed doing on the 300SE. I purchased both pads at the same time, and finally got a chance to do the second one today. Note, if you’re looking for more information on forums, American sites will refer to this as a hood pad. There are youtube videos by Kent Bergsma and Pierre Hedary on Hood Pad replacement.

For the 560SEC, I had a genuine Mercedes part. The coupe is different to the sedan. For the 300SE, I have one made by Febi. Unlike […]

End of financial year tyre sales

At least in Australia, by far the best month of the year to buy tyres is June. Both the tyre retailers and manufacturers offer attractive end of financial year sales. Most people don’t realize, but tread wear is not the only reason to replace tyres. As the rubber ages, it hardens. Once the tyres harden the handling, particularly in the wet is compromised.

When I first purchased by 250SE I nearly spun it in the rain on an innocuous corner. The tread in the tyres looked fine, and I had thought no more of it. But on closer inspection they […]