Overheated, now stumbling/stalling above 3K RPM

[GT_M3]

Car had been sitting for a while. Battery was dead, so I jumped it and let it idle. Came back outside about 15–20 minutes later to find it steaming and clearly overheated, coolant everywhere.

I did a full cooling system refresh last year, minus the expansion tank — which I found split in two. That's been replaced now. Could the thermostat have stuck closed? I haven't pulled it to inspect yet.

The engine starts ok, but won't pull cleanly past 2,500–3,000 RPM. No codes on scan. No white smoke from the exhaust. Oil looks clean — no milky residue on the cap or dipstick.

What should I be looking at for overheat damage? Spark plugs? Coils? VANOS? Compression test?

[sapote]

What should I be looking at for overheat damage? Spark plugs? Coils? VANOS? Compression test?

Fill up coolant to proper level, drive it normally until reaching operating temp ~ 85C, shut off let cool overnight. Next early cool morning, remove each plug look carefully for condensation at the tip which indicates cracked head.

[JakeM346]

Odd. The shake between 2500-3000 rpm is something I have to in standstill. I believe probably most have it but don’t notice because why would you normally rev the engine in standstill. I’d figure it’s probably due to some clutch/ flywheel harmonics

[01SG]

That's what my e36 did when the head gasket went.

[ChapterM3]

Oh man, reading your post made me immediately think head gasket. Leak down test would tell you immediately if cylinders are sharing compression from a broken head gasket - that’s how I ultimately found out mine was gone between Cyl 5 and 6

[GT_M3]

Following up here - Well I finally had time to get around to a leakdown test.

Cylinder 1: 5%
Cylinder 5: 5%
Cylinder 3: 3%
Cylinder 6: 80% womp womp

I can hear a small amount of air noise from the exhaust, and feel air coming out of the cylinder 5 spark plug hole. Any else I should check prior to ripping out the top end?

[bigjae46]

Following up here - Well I finally had time to get around to a leakdown test.

Cylinder 1: 5%
Cylinder 5: 5%
Cylinder 3: 3%
Cylinder 6: 80% womp womp

I can hear a small amount of air noise from the exhaust, and feel air coming out of the cylinder 5 spark plug hole. Any else I should check prior to ripping out the top end?

I think it is time to pull the head. If the engine overheated and boiled over...then the head will need to be checked.

[GT_M3]

I think it is time to pull the head. If the engine overheated and boiled over...then the head will need to be checked.

Yup, rebuilt a few M20's but this will be my first time taking off the head on the S54. Slightly tempted to look at schrick cams "while I'm in there", but that's probably not a good idea lol

[nuc1]

Yup, rebuilt a few M20's but this will be my first time taking off the head on the S54. Slightly tempted to look at schrick cams "while I'm in there", but that's probably not a good idea lol

Now would be the time to do it. They aren’t cheap though…

Mike

[EthanolTurbo]

I knew it was the head gasket as soon as I read the thread title. The S54 headgasket will always go bad at some point, usually between cylinder 5/6.

[GT_M3]

Now would be the time to do it. They aren’t cheap though…

Mike

Yea for sure it's tempting, but I also have no supporting mods (airbox, headers/high flow cats). I feel like I'd have to pour a lot of money in to get the full benefit. My m3 is nearly bone stock.

[nuc1]

So you're saying its a start....

Mike

[GT_M3]

So you're saying its a start....

Mike

Yeaaaaa. We'll see. Not high on the priority list, but its possible

[tr3flip]

I recently went through the exact same scenario. My water pump completely failed and the engine overheated 5 minutes from home. I limped it back home (big mistake) and blew the head gasket. I ended up pulling the head and had it checked for cracks and resurfaced it. I did all the Beisans Vanos upgrades while I had everything apart. Engine feels solid and sounds much smoother.