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hi josh, i have a 96 model 316 its the M43 engine its overheated quite a few times and had the head gasket done once already, i just had to do it again but it still not right im getting sluge building up under the oil cap and the hoses are getting extremly pressurized, it has had a new radiator and cap, water pump and thermostat and when its warmed up it misfires slightly could it be a cracked head or warped?
Answer -
Andrew,
It is very likely that the head is cracked/warped. Overheating an engine is BAD!!! Most people report that the engine NEVER runs the same again. If the head is warped it will not make contact with the head gasket in spots, and allow for the gasket to "blow". You can have the head resurfaced and made flat again. If it were my engine I would have the head decked (resurfaced) and possibly my block to make sure that the headgasket will be squeezed with even pressure across its entire surface.
Hope this helps,
Josh
Thanks for the advice josh very helpful i wish i knew of you earlier, i just got hold of a compression tester and i looked in the manual and the compression should be betweeen 10 - 11 bar and three cylinders are running at 12 bar and No.2 cylinder at 11, if it was to be a cracked head how could i tell would i be able to see a crack or can it be tested somewhere or would it be cheaper to get a replacement engine, many thanxs andrew.
AnswerAndrew,
The compression test seems ok, I am a little concerned about the #2 cylinder though... why is it 14.7psi lower than the rest of them? The numbers are good on all the cylinders, but they all should be within 0.25 - 0.5 bar of each other (optimally).
The good news is that you are going to remove the head to have it checked (more on that shortly) so you can check the piston then. You should take note of how each piston looks compaired to the rest of them. Most of them will be black with carbon deposits on top of them, but I have a feeling #2 will look slightly different. Somehow it's not building the same compression that the other pistons are, so air is leaking somewhere. This can happen in several ways. The piston rings are not sealing well, and air is passing beside the piston. Or you have a leak in the headgasket, and it's allowing a small ammount of that compression to escape.
But like I said, OVERALL... it's not too bad.
Back to the problem at hand, if you are going to check the head for cracks, drop it off at a machine shop and have then "Magnaflux" the head. This will find any hair-line cracks and make them easily seen. If a crack is found, you should probably find another head. Repair is expensive (if possible) and you would still need to deck the head.
I dont know if I would attempt to get another USED head, because you could run into the same problems. You should be able to find a rebuilt head that has new parts in it, and it's is "like-new".
Hope this helps,
Josh
