Hey guys i recently have been having some issues with my m42. it began over heating a few days ago i never let it get to the red though just 3/4 of the way up. i open the rad cap and its low on coolant. feel the hose and the upper hose is warm and the lower is cold and the radiator is cold to. as soon as i open the expansion cap the water starts to bubble/boil. so im assuming my tstat is stuck closed. another reason i believe so is because once it warms up the coolant starts leaking from the tstat housing or the water pump. so my plan was the replace both and go on my way but decided to do a compression test wile i was at it. and cyl 1 was 225 cyl2 was 210 cyl 3 was 195 and cyl 4 was 160. so im not sure if i have a hg leak or a cracked head. there is no coolant in the oil or white smoke. wile i was in there i decided to do the oil filter housing seal and front cover seals. so its all apart now but i could use your advice on what to do next. maybe replace the headgasket or leave it be put everything together and go from there? any help will be appreciated. thanks guys.
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Should I do a leakdown test and see where it could be leaking from?
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Did you put a squirt of oil in the cylinder and repeat the compression test to see if you got different numbers?Comment
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Yes I put to much tho and messed up my compression tester. Going to buy a new one and try again
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Did you repeat the test or get any new leads? With a blown head you should have significantly lower than 160, possible it's the piston seals that are just bad. When you pulled out the spark plugs was any one of them significantly cleaner than the others? With a blown HG you should have a lot of symptoms to confirm your suspicions. Sounds like a cooling component failed and you have a leak.The fun never ends :-?
89 318iS
R.I.P 89 325i coupe
89 335iCComment
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Ok did a leakdown test. The cylinder that got a 160 compression has a 18% leakdown. Cyl 3 has a 10% leakdown but cyl 2 that got a 210 compression has a 60% leak and its leaking out into cyl 3 out the exhaust. It seems like the exhaust valve in cyl 3 is closed so its a possible crack I'm assuming. My dilemma now is I have a spare motor with low leakdown numbers. Should I swap the motor? Or just swap heads? I just want to get this car running for another year or so
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Swapping the whole motor would cost less since you don't need to replace all the various gaskets and get the head decked. Having pulled M42 engines as well as swapping heads, I think that swapping the engine & tranny as a whole unit is easier than the head job, assuming that you have a hoist.Comment
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I have a hoist. What about leaving the tranny in the car and unbolting it?
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The engine I have is a m42 from a e36 so everything needs to be transfered over
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It is a lot more work to detach/reattach the tranny under the car than to hoist it all out as one unit. It will also be much easier to swap all of the accessories and other bolt-ons with the engine out of the car.Comment
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Yeah the new engine is on a stand Now. Gonna just pull everything out at once. Should I leave a jack under the trans after I remove the brace?
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Yeah, keep the tranny supported so it doesn't make the engine lean into the firewall.Comment
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Removing the engine and leaving the tranny in doesn't seem like to much work. Lining up the engine to the tranny seems kinda difficult though but doable
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