Preparing my 560SEL for a 4,800km road trip

I will be taking my 560SEL on a 4,800km road trip to outback Queensland soon.  Over the past couple of months I have been slowly sorting out a few things that could impact its reliability.  This was beyond routine things like oil and filter changes.

I created a list of items I wanted to address, with the first being the critical one.

• Occasional coolant leak after long drives
• Fix a transmission leak
• Windscreen washer not working
• Oil pressure gauge odd readings
• Slight noise from alternator
• Poor A/C performance
• Fit battery monitor

My 560SEL has 342,000km on the clock, but I use it quite a lot so it is in good mechanical shape.   Any older car can have an issue, but sorting that list out would give me confidence for the trip.  I also packed some spares with me, such as radiator hoses, fuses, the old alternator and the like.

Poor A/C Performance, Alternator & Transmission leak

I started with the A/C performance, largely because I hadn’t noticed the coolant leak at that time.   Late last year, the freon leaked out of the system, so it felt like a good opportunity to not only address that issue, but fit the same uprated condenser I have on my 560SEC.   I started this upgrade at roughly the same time as I upgraded the condenser on my 450SLC.

As with before, I got the kit from Klima Design works, and my mechanic fitted it for me.   There wasn’t any real issue fitting the kit, but the leak was found to me my compressor.   The compressor had been replaced by the previous owner about 10-12 years prior.   Based on the leaky compressor, we didn’t re-gas the system and I sourced a new compressor to be fitted on my next visit.

The transmission leak turned out to be the secondary transmission pump.   The seals were replaced, as well as the transmission cooler hoses.   At the time my mechanic noted it looked like the radiator had been leaking coolant.

I had heard some noise from the alternator, so had him replace it with a Bosch rebuilt unit.   After my experience last time, I figured the swap meant I would also have the old one as a spare before it failed.

A few months later I had the compressor changed and now had working A/C again.   It didn’t seem as cold as the 560SEC is, but it is a good improvement on what I had before.

Coolant Leak

I was only able to see the coolant leak after a long drive, and after that I would have a small puddle of coolant under the car.    The puddle was always under the middle of the car, but I could not see any evidence of leaks from the coolant hoses.

To try and narrow it down to see if it was the radiator or something else, I ran the car while up on the hoist.  I couldn’t get it to leak coolant and I checked carefully around the radiator and heater hoses.   I changed the oil pressure sender unit while the car was up in the air.

After leaving the car overnight, I had a small pool of coolant on the floor underneath where the starter was.  At least the oil pressure gauge was working correctly.

Since the leak was not conclusive, I took the car back to my mechanic so he could pressure test it.   Turns out the radiator would leak from the seams when under pressure.  I guess the coolant was running down the undershield, or being blown back onto the engine before leaking onto the ground.   A new Radiator fixed the problem.

Windscreen washer and battery monitor

Having a working windscreen washer is quite useful for country driving.  The first and most obvious test was that I had fluid in the tank, which I did.  I was also able to test the headlight washers, which did spray when the headlights were switched on.    The pumps from my parts car were really crusty.  I simply swapped the headlight and windcreen pumps over.  I now have a working windscreen washer at the expense of the headlight washer.   The headlight washer is really for snowy environments.

I also fitted a BM2 battery monitor, which I use for most of my cars.  Since Mercedes-Benz didn’t provide a voltage gauge, the battery monitor allows my phone to act as a voltage gauge.