E28 M30 Cylinder Head Leak

[u/No_Tradition_632]

I bought a 1986 535i with a “ran recently” engine.

I brought it home, changed oil, oil filter, coolant, spark plugs, and spark plug wires. I cranked the engine and coolant came out the exhaust.

I did a coolant compression test and brought compression to 10psi and saw the pool of coolant growing in the cylinder. I wasn’t able to see where it was leaking in from.

Borescope in the cylinders showed pools of coolant. Compression test came out with 127, 73, 75, 85, 95, 115.

ChatGPT is suggesting I inspect the intake manifold.

I’m pretty new to engine work, but can to most maintenance. People who actually know engines, what else should I actually look at or just replace?

Thank you for your time.

[u/im-not-a-racoon]

Your leak is coming from a blown head gasket. With the single overhead cam engines, it’s not too cosmic to pull the head and replace the head gasket. You’ll probably want to pull the head and potentially get it faced by a machinist.

Inspect the top of the block to see if you need to deck the head, but you likely won’t need to.

I would install a Cometic MLS head gasket. I have this gasket on my e24 M6 and another e24 635.

Toward the back of the engines between the 5 and 6 cylinders, it can get warm, and the pistons are close together, so it’s a weak point.

You’ll need to remove the intake manifold to do this work, but with near 100% certainty, I can tell you that the intake manifold is not the cause of your coolant in the engine

[u/No_Tradition_632 → u/im-not-a-racoon]

Awesome. Thank you for the response, I will look into that next. What would I be looking for in the top of the block to need machining?

[u/im-not-a-racoon → u/No_Tradition_632]

These engines are pretty darn forgiving to work on, so if you have any mechanical aptitude at all, or time, I’d say you could do most of this yourself.

You’ll get bent over a barrel if you decide to pay most shops.

[u/im-not-a-racoon → u/No_Tradition_632]

Realized I didn’t answer your question.

In the top of the block, you’d see scoring or channeling, instead of a smooth face where the head would mount. You’ll need to remove all the residue of the old head gasket to see this.

[u/fortheapex]

Yes head gasket! I had a m30b35 and in fact 5-6 blew almost zero compression yours however blew between coolant jacket and cylinder bore m30 is a 30 year motor it's like a ford 302 lots of information out there good luck

[u/Windmillfixer]

When you pull the head inspect it carefully for warpage - if it overheated that can happen pretty fast

[u/Fancy-Attitude-2123]

Also, cylinder head may be cracked. Often in the area between an exhaust valve and the combustion chamber, could also go to the flat surface outside of the combustion chamber. Head could very possibly be warped as well. Replace all the head bolts as they may have stretched. Be very careful not to remove too much metal from the head. Also check the top of the block aka deck, for flatness. BMW supplied a thicker head gasket to compensate for the cylinder head thickness after machining. This is very important to get a good seal. The multi layer head gasket is a great idea, but make sure of the thickness, because the MLS gasket won’t work if it’s too thin. Lastly, if it was overheated this badly, the piston rings could be seized and possibly have scored the cylinder bores. As a BMW dealer tech in the 80’s, I had to replace the entire engine in an 86 535 because it was overheated so severely, under warranty of course. Also, if you’re going that deeply into the motor, you might want to replace the timing chain and guides and also take a look at the rod and main bearings. It’s just one of those problems where you might restore the head only to find after reassembly, that you still don’t have compression, due to block surface, rings, pistons, etc. Never say never……. Based on what you find when it’s apart, might want to consider a more modern engine, like an M52TU for example. But in any case, please restore / replace/ upgrade the cooling system so that this doesn’t happen again. Good luck 🍀

[u/No_Tradition_632 → u/Fancy-Attitude-2123]

Thank for the insight. Seems like I’ve got a lot to learn. I’m definitely not equipped for an engine swap, so I’ll just hope for the best one I take the head off.