engine and drivetrain Coolant in oil, misfires, but compression OK. Any ideas?

[MattL]

I'm posting this as a follow-up question to my original q posted under" New owner in Philly area." I bought a 74 2002 about a month ago with apparent head or head gasket issues, as evidenced by the milkshake oil in the engine. The car had been sitting for a long time, so I had hoped it was just condensation due to that.

I've now done a radiator pressure test, as somebody (Moosehead?) suggested, as well as a compression test on all cylinders. Both were done before I drained the oil.

The radiator pressure test (up to about 12 psi) revealed a slow leak at one of the hoses at the thermostat (the one closest to the engine). I couldn't get that hose tight enough to stop leaking, but I also didn't see the pressure go down at all, nor find any clear evidence of new coolant in the oil.

I then did a compression test on all cylinders (cold/dry only). 1 to 4 read 140-140-140-145. Those look low to me (maybe just because it was a cold/dry test?), but the good thing is that the numbers are so consistent across the board. I was encouraged by this, and hoped that it was evidence that maybe the milkiness was just condensation from a lengthy period of idleness.

I then started the engine and noticed how rough it was running (shaking all over the place, really - don't know why I didn't notice it before). I pulled the ignition wires one-by-one and learned that cylinders 1 and 3 are not firing. I also noticed a rhythmic "pfft" sound that I assume was air escaping from the misfiring cylinders. All the plugs look the same (very black, but no visible damage, and I regapped them all), and the misfiring cylinders' wires don't show any clear signs of damage.

I then drained the oil (very milky) and left the plug out for a week to let it drain completely until I could come back and continue my fact-finding mission. I opened the garage this morning and could clearly see a pool of green under the collection pan I had placed under the engine: too much and not in the right place to have come from the thermostat leak.

I then did another radiator pressure test, with the same results as before. I left the drain plug out, in case there was any chance of coolant leaking out there. Nope. Only at the thermostat.

So, the facts are as follows:

1. There IS coolant in the oil, not just water.

2. Cylinders 1 and 3 are not firing.

3. Compression is consistent across all cylinders.

4. There is the sound of bursts of escaping air when the engine is running, but I can't find the source.

5. Radiator pressure tests didn't reveal any clear leaks into the engine (although I guess the leak at the thermostat could have prevented that).

6. There is no smoke when running, and no sweet smell to the exhaust.

These things don't seem to add up to me. Any thoughts or ideas would be much appreciated.

Matt in NJ

[Scott Sislane]

have you pulled the head yet to inspect the gasket?

Scott

[ahlem]

You may have an exhaust gasket leak to hear the air escaping. Other 4 cylinder BMW engines tend to loosen their exhaust studs. Make sure the studs are all there. Do you have spark at 1 and 3 and still not firing? Any known work done on the car before you got it? I'd pull the head and see what's going on. Sounds a bit warped to me and the coolant and oil are intermixing. Any oil in the coolant? Hopefully you don't have a cracked something. Use a good quality headgasket and if all else checks out, have the head and timing chain cover faced on the mating surface. Check the valve guides and seats while you are in there. I'm doing the same thing on an M20 motor and feel your pain.

[DanOKC]

Probably have a warped head, cracked head, and/or blown headgasket. You can still have compression with any of these 3 results, depending on how bad it is. I'd put fresh oil & filter & fresh coolant in & start it again. But you need to make sure you have good spark on 1 & 3 first, and make sure the plugs are clean & not fouled. New plugs are cheap. If you have good spark on 1 & 3, and it still runs rough, then you can do some more troubleshooting, just watch the temp guage & don't let it overheat. Could have leaking ex manifold gasket for the air sound you hear, but that wouldn't make it run rough. I'd run it for 5 minutes, pull the plugs & look at them, also check the oil & coolant. also once the motor is warmed up ( temp guage in the middle, above the blue), the T-stat opens & if the head gasket is leaking, it could put pressure into the cooling system. You can remove the radiator cap & see if you have exhaust gas pressure coming from it, you will know if you do when you rev the motor. You can have a warped head that seals better once it cools down too, but leaks bad once the motor is warm.

[MattL]

Thanks for the ideas, info and suggestions, guys: very much appreciated. I haven't pulled the head yet, but after I check for spark on 1 and 3, I guess that'll be my next step. Smart point about the possibility of it only leaking when warm: I hadn't even thought of that.

I am brand new at this - this is my first project car and the first car that's "simple" enough to really work on myself. So, if anyone can point me towards resources/sites/writeups that may help me tackle the head removal/inspection/etc process, I'd be much obliged. I know I'll need to find a machine shop for the milling, but I want to do as much of everything else myself as I can.

Thanks again,

Matt

[codigoRojo]

You may or may not have a blown head gasket or cracked head or block. So far nothing is conclusive. I wouldn't pull the head quite yet until you rule everything else out. That's major surgery with an incomplete diagnosis.

With fuel, spark and compression, you should have fire in all the holes. Fix cylinders 1 and 3. Probably bad plugs, wires or distributor cap. Check your points too.

Fix your known external coolant leak. Coolant migrates all over when running down the outside of your engine. You know it's leaking externally, so no surprise that it's showing up in your drain pan.

Then you can change the oil and do some additional diagnosis. I hope it's just condensation or something else minor, but at least you will have fixed the things which are easy to do on the outside of the engine that need fixing anyway. Good luck.

-Rojo

[TobyB]

That's not bad advice, except that coolant has a real

propensity to eat the bearing material out of the shells.

So you really don't want coolant in the crankcase-

might be worth switching to water if you plan

on NOT popping the head. Use an additive to prevent electrolysis...

I don't find head removal to be a big job, but

I've been at this for rather longer that I care to admit.

t

[MattL]

Thanks for the continued suggestions, all. I'll let you know how subsequent diagnoses turn out. If the head does need to come off, etc., I guess at least that's an opportunity to check other internal things and maybe think about putting in a hotter cam...maybe.

Matt

[Cameron]

I think you can safely rule out a warped head... if you have misfires on 1 and 3, wouldn't a warped head be missing on 2 as well?

Make sure you have spark, and also make sure you have a sealed intake track. Hook up your coolant pressure tester to the car and don't pump it up. Run the engine and you will see the gauge build very quickly if you are getting combustion pressure into the cooling system. Do a leak down test if you are still having issues.

Pulling the head may be an easy job for some people and possibly even for you, but a teardown should be the last step. If you jump the gun and pull the head, if you can't find the problem then you will likely end up putting it back together with the same problem that could have been fixed without pulling the head off.

[Cameron]

Sort of a stretch, but I just thought of this - firing order is 1-3-4-2, is it possible that the cap wasn't put back on correctly?

Just remember, don't decide on a diagnosis and then look for things that make it true - add all the facts together and then decide on the problem.

[codigoRojo]

Cameron-

When you say put back on correctly, do you mean 1&3 are switched on the cap? I was thinking the same thing. Easy to do.

-Rojo

[Cameron]

Not nescesarily put on the wrong spot, but maybe the cap is tipped in a way that the 1 and 3 contacts aren't contacting the rotor.

[MattL]

I checked the cap orientation and order, so that's not the issue. I'll be out of town for a couple weeks, but when I return I'll check spark and go from there. I'll also try that reverse pressure test on the radiator. Thanks very much, everyone.

Matt

[TobyB]

Just to be safe, before you go, pull the plugs out and squirt a bunch of oil

in there. Roll the motor over by hand a few times to spread it around.

IF (and it's a big if) the gasket's letting water into the bores, this will

reduce the chance of rusting a lot. It can't hurt anything, so it's just a

'good practice butt cover' if you suspect water's getting places maybe it shouldn't.

I'd change the oil, too, just to try to dry things out a bit.

But then, I'd have had the head off by now, too...

Not critical, just covering all bases

t

[GoFaSSter]

Just to be safe, before you go, pull the plugs out and squirt a bunch of oil

in there. Roll the motor over by hand a few times to spread it around.

IF (and it's a big if) the gasket's letting water into the bores, this will

reduce the chance of rusting a lot. It can't hurt anything, so it's just a

'good practice butt cover' if you suspect water's getting places maybe it shouldn't.

I'd change the oil, too, just to try to dry things out a bit.

But then, I'd have had the head off by now, too...

Not critical, just covering all bases

t

This is good advice. If their is coolany in the oil it will eat your bearings and cause issues while it sits.