Ok, here's the deal. I just did a head gasket swap on my 91' 318 with the M42. It is running a little rough right now and it is still blowing out some white smoke. Could this smoke just be left overs from the prior bad gasket??? After assembly I did an oil change and also used some lubo-molly engine flush. I ran it for 15 min then drained it and did another oil and filter change. I also topped off all of the other fliuds. Unfortunitly I know I should've sent the head to a machine shop prior to finishing the job but this is my only car at the moment and I couldn't wait to get it back a week or so later since I'm broke and I work over 60 miles away. So I took the chance that the head itself was ok, and that the problem WAS just the gasket. Now after seeing the smoke I'm begining to wonder if my gamble was wrong and the head itself is actually the issue? Mabey cracked or something?? I checked compression and all cylinders are between 170 and 180 lbs per square inch running, so I think thats ok? I got @ 95lbs per cyl give or take if I just did a quick 2 or 3 turns of the engine. As for it running rough I believe thats a timing issue but I think I can figure that one out (I hope anyway) If any of you have had the same experience please help me out here! Any info would be EXTREMELY appreciated!!
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If the head was warped or something and you reinstalled it its gonna leak. It should have been decked at a machine shop. try a cylinder leakage test and see whats up. you should be able to determine where the leak is.
How come you opted to do a head gasket in the first place? was it blown?
Timing is adjustable on the m42 +or - 6 degrees on the cam gears. If you removed the cam gears from the cam might wanna check and see if there positioned right -
Ok what exactly do you mean by cylinder leakage test? Are you talking about compresion or something else? As for why I did the gasket.. Well I just bought the car for $300 from someone off of craigslist and was told he thought it was blown. It was over heating, blowing thick white smoke and the oil looked like mayonase. However I saw no issues with the old gasket once removed?? So at that point it was like a 50/50 chance, do I throw it back on and hope it WAS the gasket and still get to work on mon? Or do I send it out to be checked wait a week or so and get screwed by not getting to work till I got it back and re-installed it?? Well I opted for option 1. As for the cams and timing, I did remove the gears after marking them. Uppon re-assembly I put both cams and the crank at TDC or as close as I could. I checked the square blocks on the back of the cams with a straight edge to make sure they were even. BUT I did notice the bolt position on one gear was just a lil off from the other but not by much when I locked them down. If their off just a lil bit will that cause my rough idle? would it really matter since they were at TDC when locked down?Comment
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A cylinder leakage test consists of pressurizing the combustion chamber while the valves are closed. It requires some doing in getting the valves closed and what not but its just like a compression test except you used pump compressed air into the cylinder and check for leaks with a gauge.
As far as your idle it could be a number of things. you may be a tooth off on the cams or crank. not sure. The new gasket you put in could be leaking so bad that its causing a cylinder to miss??
What sucks is you dont know how hot the engine got. If the previous owner overheated the motor badly it most likely warped the head and thats why you still have an issue.
Also your head bolts are not reusable. they may be stretched beyond working specs and are not fastening the head correctly to the block also causing leaks.
Theres a ton of issues why it could be leaking still. what about torque sequence?? did you torque in the right order. I believe head torque is 60 pound feet + 90 degrees??Comment
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Pull your spark plugs out and tell us what you see.
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well as fot the head bolts I DID use new bolts and they were tourqed down in the right sequence. I followed the bentley bible for that and did 22ftlbs then two stages of 90deg each time. Reguarding the plugs, I did pull them after it ran for @ half an hour. Number3&2 were dry but 1 and 4 cylinders plugs were wet. I smelled them to see what it might have been and the smelled like old crappy gas but not really oily or like anti freeze.Comment
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So no white chalk, huh? You probably should have had the head magnafluxed and decked.
Sounds like you're on a budget. <Given your current level of investment>, if I was you I'd roll it, watch the coolant level and temp. guage, and see what happens.Comment
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these babaies are known for cracking
if you still have issues, get to a machine shop
on craigs list overheating, p.o prob knew what what was going on
if he and you ran it overheating, its cracked
also note, cylinder leak down tests are not always 100% right on. my particular case, the head was cracked in the exsaust valve seat passage, leak down was good, as when the valve closed . compression good, but when heated up and running, the crack got bigger, water and oil mixed, but not much as most of the water was going out of the exsaust
rebuilt head new valves, etc, $700
it too was a craigs list car, that " only overheated one time and then towed it home"
yes towed it home after many miles, removing the thremostat, and ........................Comment
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just an update
Well as it turns out you guys were right. We did a leakdown on the enginge and found #2 cyl as the culprit. After further inspection there was a crack between the water jacket and the exhaust valve seat. So now I`m off to find another head... Does anyone here have a good one they can do without and could let go fairly cheap? If so PLEASE let me know ASAP!
Thanks again guys!Comment
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