318i starting mystery

[shankster77]

A compression test showed just under 90 psi for 3 out of 4 cylinders, with the other cylinder at 78 psi. I did not actually buy new plugs to go with the new coils (for some reason) but I think I should be cause they are looking a little blackened. The one on the number 4 cylinder I believe, is a little charred and coated. the threads smell gassy. I'm throwing new plugs in tomorrow.

When I had tried spraying vaporized gas into the throttle body it had exploded back out at me, could that mean my timing is off? I'm starting to think I need to open this bad boy up and take a look.

[Big Evil]

You MAY have to pull the head (little more testing needed yet). I'd get the book double check the timing on the engine (cam/crank). 3 at 90 and one at 78 difference of 12 psi doesn't sound that bad but since 3 were consistent and one wasn't and they were all a bit low (120 is closer to normal usually) I'm thinking a cylinder leak down test is your next step. Have you done one before? It should give you a definite direction as to what needs attention base engine or head wise.

[shankster77]

I have not done such a test before. Yeah I was hoping I would not have to crack the engine open.

[Big Evil]

CLT, or Cylinder Leak Down, Test is preformed with the same basic stuff you use for the compression test. You need to pull the valve cover and crank the engine by hand (with a wrench) until you see both valves are fully closed on the cylinder you will be testing (piston needs to be top dead center, intake valve will open then close, and then go about 1/4 rotation on crank). You then have someone hold the crank in position (it will move so use a big breaker bar on the snout bolt, with a big friend) and you push compressed air into the engine at around 100 psi using compression kit adapter with an air fitting. Then you get listen for where its leaking from. Pull out the oil dipstick, if air is coming out you have bad rings or scored cylinders. Open the throttle plate, if air is leaking out the intake you have a bad intake valve, exhaust - bad exhaust valve. All the plugs should be out while you do this, if air is leaking out of the degas bottle for the cooling system or the adjacent cylinder then you have a bad head gasket. You should then be able to tell if you need head work (valves), base engine (pistons, rings, cylinders), or a head gasket. If you need a head gasket you'll need a straight edge (machined) and some feeler gauges to make sure the block and/or head isn't warped. The test will tell you with a good deal of certainty what, if you want to try a rebuild, or if you want to look for a secondhand running engine and swap 'em out. (Just keep the new ignition stuff and transfer it over as a second hander would most likely need it also). But yes, don't crack it open until you know what and why you would be doing it.

[shankster77]

Cool man, thanks for the detailed post. Looks like I will need to carve out a day or two to get this one done. I think I've got the right friend in mind to help out. Be back later with an update.

[shankster77]

alright I need to find a fitting so i can blow air in the cylinder. But with the valve cover off I can see part of the head gasket and it is hardened, bloated and looking like it is on the way out. On the opposite side of the engine the valve cover gasket looks the same way.. like i could push against the rubber and snap it off like plastic. uh oh.

[Big Evil]

Ok, sounds like time to pull the head, check the cylinder deck and head for flatness and put on a new head gasket. Still do the clt just to make sure there's no other damage that needs attention but it sounds like someone has run the dog piss out of that engine, beat it up, heated it up and put it away wet. Sucks royally.

[shankster77]

Yeah those cylinders are not holding much air in at all. It is leaking right out with the valves closed, back out through the oil it seems. It seems like it is going right past the rings. I had poured a little sea foam down the cylinders just in case they were stuck with a little gunk and then when the pressurized air came through it vaporized the sea foam back up through the engine. pretty sure thats what was happening.

[Big Evil]

Scored cylinder walls, bad piston rings. Damm, sucks. I guess that leaves in the unique position of being able to drop an m50 into the car now. Leave the 318 badge on, and when backwards hat billy and his plastic go fast honda thinks he can take you at a light.....................

[shankster77]

haha yeah those ricers... So with an m50 engine would I need a tranny to match? or what else makes that conversion complete?

[Big Evil]

Basically the best way to do it I've seen is to drop the front suspension, motor carriage, transmission all out the bottom as one unit. Do the same to a donor junker, fix all that can be fixed while it's out, heads, clutch, linkages, drive line, manifolds, do anything and everything you can before putting it all back in 'cause it stupid easy out of the car. Then replace the engine, cradle, front suspension, transmission as one unit. New ECU, tighten everything down and have fun. There were some posts in here I remember from some people that did just that, only in an E30 (the earlier 3 series). Do some browsing we're not breaking any new ground here I'd swear I saw the step by step somewhere.....

[shankster77]

sweet. sounds like a good winter project. Thanks again for all your help Big Evil.

[Big Evil]

No problem. I congratulate you on your tenacity. Keep it up you'll build a hell of a nice car.

[vixtanz]

I suspect the ECU - electronic Control Unit - or brain for your car is fried . Went through all this myself . Got a new one fitted and car rauns sweet now . Expensive suckers though - $NZ 700 !