MERCEDES BENZ W203 C180K OVERHEATING

Mercedes Benz W203 C180 Kompressor

My wife is a merchandising agent and needed a larger car or at least one with larger boot space in which to cart her display boards; so I bought her a 2004 Mercedes Benz  W203 C180 Kompressor Estate with 180 000 km on the clock.   It was exactly what she needed, inconspicuous gun metal grey with light grey seats that folded down giving her the space she desired. Cosmetically, the car was in pretty decent condition and according to the seller, he had just forked out a ton of cash for parts and labour. He had replaced the timing chain and the A and E sprockets and even gave me the invoices for that job, but was selling the car, As Is. It was fitted with new tyres, the rims had been re-epoxyed and the interior was recently valeted. 

Overheating 

My wife took the car for a test drive and was impressed by its performance, however the very next day we started having problems. So much for buying a car in condition "As Is". The car overheated, steam blowing from beneath the bonnet and leaving large pools of water behind. After I diagnosed the problem, it was just a sticking thermostat that needed replacement. The thermostat housing is positioned below the timing chain sprockets and I surmised that the mechanic who fitted it, tightened it at an angle and in the process bent its plunger. Obviously thinking the worse, its owner probably wasn't prepared to pour money into this beast, so he sold it off at a bargain price. 

A week later my wife complained that she had to add water daily since the  the "add fluid" signal triggered repeatedly an alarmed her.  I knew there had to be a water leak but couldn't find it, until she phoned me to tell me that the garage attendant said that there was oil in the water. On later inspection, I found a layer of oil in the water expansion tank, but when I opened the oil cap, there was no white sludge in the oil. I was certain it wasn't the head gasket that blew and I suspected that the Oil Cooler had rotted internally. My thinking was that the oil pressure is much higher than the water pressure, and oil could therefore seep into the water but not the other way round. Besides, A and E sprockets, timing chain and Oil Coolers are common problems associated with the M271 engine.

The oil cooler, part no A2711880001 rots inside allowing the
higher oil pressure to seep into the water.

Oil Cooler

The Oil Cooler has four holes in it. An inlet and outlet for water and an inlet and outlet for the oil. Each running through seperate and intermingled veins inside the Oil Cooler. As such the water manages to cools down the oil. However it the veins corrode and the separation is breached, the oil finds it way into the water expansion tank. The Oil Cooler sits in such an obscure place on the W203,  that it would probably be easier to replace a cylinder head gasket than replace the Oil Cooler. To save myself the frustration, I took it to my mechanic who confirmed my suspicions and subsequently replaced it, but two weeks later. Apparently the Mercedes Benz agents didn't have any in stock because it sells out very quickly, hence we just had to wait. We hardly got the car back and the boiling continued. My thinking was that the Oil Cooler was the cause of the problem but it wasn't. It was probably also the reason the previous owner sold the car, knowing that the oil was mixing with the water, drained it and replaced it with clean water before flogging it to me. 

W203 expansion tank 

After a thorough diagnosis, I found that the expansion tank outlet under the hose clamp was leaking and that it had been Pratley Puttied by someone. So I bought a new tank and replaced it, thinking it would solve the problem but it didn't. After replacing the expansion bottle cap which is sold as a separate item, the problem was  finally solved. Ever since the car has been going really well for about four months. Occasionally the started slipped  when attempting to start the engine and I knew it was just a matter of time  before the bendix would have to be replaced.  

Continued here!
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