Leaking head gasket (solved - oil pressure switch)

[ccchrisss]

Hey guys, I have an oil leak from the headgasket in the rear passenger side (m30b34). With the engine running I can see oil slowly seeping down from between the head and the block onto the bellhousing. I have been having slight overheating problems this summer, not too hot but definitely past 12 on the temp gauge while sitting at idle. I managed to swap out almost every part of the coolant system and finally got temps down but now I have this leak. How would I know if this is from a warped head? There is no oil in the coolant, no milky oil or smoke from the exhaust. I am considering changing out the HG but if it's a warped head I might have to hold off due to extra costs. Is there any way to tell what I'm dealing with, without having to tear everything apart first?

[Aldo525]

I suggest removing the valve cover and checking the inside for possible cracks. I had a similar problem (M10 engine) in the same place, rear passenger side, but it was a crack from the upper edge down to the #4 spark plug hole...imperceptible from the outside but evident from the inside and the oil was leaking out of the there and it seemed to come out from between the cylinder head and the block.....sad, but I had to change the cylinder head.

[Mike W.]

The first thing I'd do is to retorque the HG. I'd even do a slight overtorque. IIRC spec is 59 foot pounds. Probably won't do any good, but it's cheap enough, so why not?

I have never seen an M30 with an externally visible crack. Earlier ones liked to crack between the water jacket and the exhaust valve seat, but until run low on coolant and overheated that just resulted in a small loss of coolant, not an oil leak. B35s have been known to crack under the cam, but not earlier engines that I've heard of.

I would say it's unlikely to be a crack causing the leak, possibly a warped head, probably just a 40 year old engine. M30s are known to leak there, but not really visibly while it's running, just an ever so slow leak that gets things dirty and burns off on the exhaust manifold.

But there is no way to determine if the head has a minor warp without pulling it. You could throw a straightedge like a 24" level on it with the VC off, but it's going to be awfully hard to really measure a small warp. And a new HG will often even seal, at least for a while, a small amount of warpage and spec up to .004" is acceptable according to the literature I have. But generally a warped head gasket is a concern about coolant loss or overheating, not an oil leak.

Sorry, but you're not really going to know unless you pull the head.

[Aldo525]

Just for the records my (bad luck) case:

From outside can't see the crack....




Anyway I'm agree with Mike, first job should be check the Head bolts torque.....

[jdb]

I have had this cause miss diagnosis in the past.
I would recommend you look carefully at the oil pressure switch, it can leak then run down between the head and block then appear to be from the head gasket on the passenger side.
Clean the area, then watch as the engine idles..

Jeff

[Blue Shadow]

The first thing I'd do is to retorque the HG. I'd even do a slight overtorque. IIRC spec is 59 foot pounds. Probably won't do any good, but it's cheap enough, so why not?

Like Mike says, I would retorque the head gasket first. Easy enough and maybe a win.

I had an antifreeze leak at the front of the motor. Didn't retorque, just replaced the HG. Didn't use BMW spec of torque, put the motor back together, warm up and retorque to 27.349° a couple times or whatever. I just did old three-step torque and stopped at 85#Ft or so. The jury is still out but I did this work in 1990 or so and haven't had any issues with the work, yet.

[gwb72tii]

Just for the records my (bad luck) case:

From outside can't see the crack....




Anyway I'm agree with Mike, first job should be check the Head bolts torque.....

My tii had the same crack in the same location. My machine shop where i took all my work welded it up and no more leak.

[ccchrisss]

I have had this cause miss diagnosis in the past.
I would recommend you look carefully at the oil pressure switch, it can leak then run down between the head and block then appear to be from the head gasket on the passenger side.
Clean the area, then watch as the engine idles..

Jeff

Jeff you are a lifesaver! I just checked again, let the engine idle and it is doing exactly as you said. I can see oil start to slowly drip down from the switch and it goes around the back and ends up where I thought the HG was leaking. 90% sure that's it and not a bigger job. Thank you so much

[ccchrisss]

Also thanks to Aldo and Mike. Great advice and input I was going to dig deeper on those as well but thought I'd check the switch first.

[Blue Shadow]

Gonna be an easier fix, just need to know the proper torque for the new pressure switch. Glad you found the problem.