Last Sunday morning at 8am I headed off in my 190E-2.3 Sportline 5-speed. Just over 3 hours and 300km later I arrived at my brother's house. He had already drained the coolant (most of what was still draining was oil!). We then proceeded with removing everything necessary to get the cylinder head off.

I had not done an M102 before but figured it should be similar to doing the M103 only easier. Most of it was except for some awkward inlet manifold nuts and bolts. I prefer to leave the inlet mainifold with all the injection and wiring in place in the engine bay rather than lifting it all out with the head as various workshop manuals suggest (this has been the topic of discussion here previously regarding the M103). The pins retaining the timing chain guide rail proved very stubborn. Even with the correct slide hammer we persisted for probably an hour before we had them out. I have a black thumbnail and skinned finger to show for that part of the job.

After about 4 hours we finally had the head off. Everything looked clean and in good condition (as it should after only 90,000km and 11 years) except for the head gasket which was badly corroded around the coolant passages. This had been the case with the head gasket on our M103 when it suffered the same oil-in-coolant symptoms. This appears to be a common fault with these gaskets. The problem looks to be that no provision is made to prevent coolant from soaking into the gasket thus causing the steel layers to rust. I now change coolant annually (rather than every 3 years as our owner's manuals recommend) in an attempt to prevent this happening again.

With everything packed away and the head wrapped-up in the boot (sorry, trunk) of my car I was on my way home late that afternoon. Incidently, my 190E drove faultlessly, cruising at around 115km/h (2700rpm in 5th) and using just over 7.5 litres per 100km or about 37 miles per imperial gallon.

Checking the head reveals that it is flat to within less than 0.002" or 0.05mm which is well within spec. A leak test on all the valves shows that they are sealing perfectly. For this reason I am not sending the head to an machine shop. I have cleaned it and will fit new valve stem seals when I get the gaskets etc. I have also decided to replace the head bolts after reading an article about "torque to yield" head bolts. It is also unclear as to the stretch limit of the bolts. Every shop manual I have for the M102 quotes the bolts at 119mm new with a max stretch length of 122mm. The bolts we removed all measure less than 115mm. Does anyone know the length they should be for a 1.8 litre M102?

Assuming I have all the parts I need, next weekend I will again make the journey to put it all back together. I have asked my brother to have everything clean and ready to reassemble. I have also asked him to flush the radiator, expansion reservoir and heater to remove as much oil contamination as possible. We will replace all the hoses that are easy to access. For the first week after reassembly I would recommend that he gives several flushes of the cooling system with water before refilling with the correct coolant mix.

I will report back when I have more news.

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107.023: 350SLC, 3-speed auto, icon gold, parchment MBtex (sold 2012 after 29 years ownership).
107.026: 500SLC, 4-speed auto, thistle green, green velour.
124.090: 300TE, 4-speed auto, arctic white, cream-beige MBtex.
201.028: 190E 2.3 Sportline, 5-speed manual, arctic white, blue leather.
201.028: 190E 2.3, 4-speed auto, blue-black, grey MBtex.
201.034: 190E 2.3-16, 5-speed manual, blue-black, black leather.