535ia HG replacement after overheat

[Dash01]

Got the head off. The HG does not have any signs of obvious damage or leakage. Smells burnt.

Some of the head bolts have thick, black heavy oil, such that they were hard to pull out of their holes. Others seem OK, but all of the bolt holes had oil in them.

Pistons look OK and no signs of cylinder wall scoring.

Is this normal?

This whole problem came on when the car suddenly overheated, accompanied by a low oil pressure light, and I assumed it was a shot HG.

[Mr Project]

Oil in the bolt holes is to be expected on a M30 head removal project. I'd carefully clean it up and not worry about it.

Your mentioning the low oil pressure is a bit odd, though. I guess if the HG blew on one of the oil passages it might have all gone into the coolant, and that would have dropped it to the pressure of the cooling system.

[Dash01]

Oil in the bolt holes is to be expected on a M30 head removal project. I'd carefully clean it up and not worry about it.

Your mentioning the low oil pressure is a bit odd, though. I guess if the HG blew on one of the oil passages it might have all gone into the coolant, and that would have dropped it to the pressure of the cooling system.

I expected there to be oil in the coolant, so drained it into a translucent plastic bucket: No oil whatever, though there was a bit of sheen in the runoff when I opened the still-hot reservoir.

Given the very thick oil on some of the head bolts, which were sticky and hard to pull our of the head (one bolt is still stuck in there, too tight for not-too-stout hand pulling), I am wondering if maybe the oil pump went south, causing the overheat.

Can you change rings and main bearings in this engine if engine block is still in the car? (I doubt it, but want to hear from those more experienced.)

[Jeff N.]

Get some extra length cotton swaps to clean it out. As I'm sure you know, it's critical you get those holes clean or you risk cracking the block. A thread chaser is good tool to clean up the threads - makes assembly very nice. I'd recommend it.

What were the symptoms of the failure that lead to the H/G replacement? That should tell you where to look on the gasket for signs. Failure between 5 and 6 is most typical IIR.

Oil in the coolant is not a requirement for an HG failure. You can blow water in to the cylinder and maintain oil integrity.

I think you can re-ring the block in the car. Joe S may have done this. You'd need to pull the pan and that would likely mean dropping the cross member. Might as well pull the block at that point.

Jeff



I expected there to be oil in the coolant, so drained it into a translucent plastic bucket: No oil whatever, though there was a bit of sheen in the runoff when I opened the still-hot reservoir.

Given the very thick oil on some of the head bolts, which were sticky and hard to pull our of the head (one bolt is still stuck in there, too tight for not-too-stout hand pulling), I am wondering if maybe the oil pump went south, causing the overheat.

Can you change rings and main bearings in this engine if engine block is still in the car? (I doubt it, but want to hear from those more experienced.)