A mate of mine recently discovered gundge in the expansion tank showing the tell tale signs of head gasket failure.
He took it to a mechanic to diagnose if it was head gasket or oil cooler and was told that the head gasket was a common fault on this engine.
The car doesn?t burn any oil and idles perfectly.
There are a few points that the mechanic has come up with that don?t totally make sense to me, and would be really grateful for any help to make sense of it all.
1. Mechanic said that he carried out a compression test and both banks of the engine are showing leaks. ? my understanding is that the failure of the gasket is between the oil ways and water jacket NOT the compression chamber, so compression test should be invalid.
2. Mechanic is insisting on fitting engineered shims between head gasket and cylinder head, reckoning that this is a must fix and Mercedes recommend this even though they do not sell the shims and they have to be made up- is this a money making ploy?
3. When questioned on how he intended to remove all the gundge from the engine block he said that he will take off the sump plug and pressure wash the engine out.- does this sound right and healthy for the rest of the engine (crankshaft, bearings etc)?
Any help would be much appreciated!
regs
Josh
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SFAIK head gaskets can fail in the area between 2 cylinders, allowing the pressure from one to leak into the other. Quite common where engines have been enlarged by boring out, thus reducing the distance between cylinder bores. I am sure much more informed comment will be along soon!
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>>Mechanic is insisting on fitting engineered shims between head gasket and cylinder head.
Higher up in your post, you mention both banks - is this a vee engine?
If so, and if you are going to skim the cylinder head surface to obtain a good seal, or to machine out damage, you may need to put some shim in there to keep the heads the right distance apart - if you don't, you may not be able to re-fit the inlet manifolds, because the heads will be in the wrong location relative to each other, and to the block.
I learnt this lesson the hard way many years ago on a Rover V8!
It may be the case that MB make head gaskets of differing thicknesses to allow the heads to be skimmed, which would be a much better solution than making a shim.
Number_Cruncher
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Sorry yes, thats right it is a V engine its a V6.
The thing is the mechanic isn't sending the heads off for skimming, as he said they dont need
to be skimmed because the car never overheated and the failure was totally on the gasket itself.
Josh
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In that case, I don't know what the shims are for.
I think that the mechanic is right to take both heads off - once the engine is stripped down enough to get one head off, the extra work to get the other off isn't so great. Added to this is the problem that as there is only one cooling system, which is common between both heads, it can be very difficult to be absolutley sure which head is causing the problem - and, if one head gasket has failed, how far behind it is the other?
Any residual water in the crankcase will soon enough evaporate off, and so, wouldn't concern me too much - I'm not sure about pressure washing though! I would be more concerned about how the cooling system is going to be cleaned out - sludge will tend to block up the main radiator, any switchover valves, and the heater matrix inside the car. I would also consider replacing all the rubber cooling hoses if they have been contaminated with oil.
Number_Cruncher
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Cheers mate for the replies, I think it is also a good idea to do both heads at the same time.
Autodata quote 9.5 hours for 1 head and 11.25 for both so not much difference.
What do you recon would be the best solution for cleaning out the cylinder block?
Josh
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I read all the MB stuff -- online and the mags -- and this is the first time I've a report of a head-gasket failure in this engine, and I have never seen it described as a common fault. One quote from an online source: "The headgasket problems are not common with the M111 engine". So I wonder how much experience your source has.
Shims recommended by MB but not available from them? I doubt it.
The heads should be tested for the need for skimming. My mechanic has never found a leaking head that didn't need skimming.
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Thanks for all your help! invaluable advice.
Im going to see the mechanic with my mate and discuss some of these issues. Will let you know what he says.
josh
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Just to complete the picture: head-gasket failure is very common (almost certain to happen) in the predecessor straight-six M103 and M104 engines (up to 1996), as I know only too well -- both my M103 engines have had to be fixed. No doubt MB resolved to minimize its risk in the V6 successor.
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Before leaping in at the deep end suggest you take a look at the oil cooler fitted to the side of the oil filter. This is an oil to water unit and should it develop a leak will mix the two. A chemical leak test on the cooling system will show up if it is a head gasket failure between cylinder and water jacket by reacting to carbon monoxide in the coolant but not a seep between oil and waterways in the heads/gaskets.The heads will need skimming and pressure testing,if removed, end of story. As long as only a few thousandths of an inch is removed to clean up the mating faces, the need for shimming is unlikely but go with the advice of the SPECIALIST machining the head (not the local engineering works!)
As for pressure washing the block with the sump off..............just use a chemical wash for the cooling system and an engine flush and short oil change (500 miles) after getting it back on the road.
Good luck
Andrew
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Simplicate and add lightness!!
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I've been wondering/worrying about that engine number, and rightly so: the V6 is in fact the M112. The M111 is a four-cylinder job.
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