Head Gasket/Low compression test numbers.

[F1Dryvr]

I think i got my head gasket at the last track day. Had a red flag and stopped in the pits but they let us go again and just on pit exit i saw the temp at the hot line. Fresh 80+mph airflow solved the temp issue and it ran just fine and after discovered a disconnected wire to my aux fan. Fixed that and Ran the rest of the day without issue, no power loss, or other symptoms. Over the break my project has been extensive. CMP reinforcement, full solid bushings etc, etc, among many other things. I decided to flush the coolant and it was pretty dusky, greyish. Its only been in 2 years 5% coolant to water and strictly track days 8/10 per year. Refilled thinking it just must have gotten dirty and on refiring the car yesterday letting the new coolant circulate i saw a few puffs of white come out the exhaust. I couldn't believe that short time in the red got the gasket. But its a 150k mile engine so i did compression test. Not knowing what im doing my numbers were 1-6: 145, 130, 145, 145, 95 and 145. Terrible numbers. Added the oil to cylinder 1 and i got 280?? I guess i dont know what im doing. But cylinder 5 spark plug hole had rusty material in it and the plug had what looked like water deposits and also a good bit of corrosion.

Does this sound like a head/valve job and new gaskets or full on pull the engine and rebuild with new rings and other rebuild items? Ive recently (in miles) done the rod bearings, so its not like those are needed.

What do we think about sending the head to Lange for the stage 3? Is that treatment worth the coin or is a local rebuild nearly as good?

Thanks for the input.

Pic shows cylinder 5plug down on compression.

[Robert's_BMW]

Does this sound like a head/valve job and new gaskets or full on pull the engine and rebuild with new rings and other rebuild items? Ive recently (in miles) done the rod bearings, so its not like those are needed

It sounds like Cylinder 5 has a break in the head gasket going to a water jacket which is why compression is so low and you have the rusty spark plug. You could verify by doing a leak down test on that cylinder and seeing if you get air in the radiator expansion tank (or pressurize the coolant system and crank the engine by hand and see if you get coolant in the spark plug hole). You need, at a minimum, to pull the head and replace the head gasket but since it’s off you might as well get a valve job too (and Beisan VANOS upgrades, if not already, since the VANOS will be removed). Whether you want to go down the rabbit hole of refreshing everything else “since your in there” is up to you and how much you want to spend.

[F1Dryvr]

The numbers, if they are to be trusted suggest blow by on all cylinders. I think it probably doesnt make sense to go through all the work of pulling the head and then have a bottom end problem soon after. Its only money right? lol.

[Robert's_BMW]

The numbers, if they are to be trusted suggest blow by on all cylinders. I think it probably doesnt make sense to go through all the work of pulling the head and then have a bottom end problem soon after. Its only money right? lol.

The rest of the compression numbers are all similar, albeit low, but it is a 150K motor, so it's probably piston ring wear. So most likely a break in the head gasket on Cylinder 5 and piston ring wear on all cylinders.

[Slideways]

Cylinder 5 does seem to have an issue, but the other cylinders reading low compared to what the TIS says can be down to the compression tester gauge you are using. Usually, the numbers need to be within 5-10psi of each other.

[mrgizmo04]

Gotta pull the head...but not a typical head gasket failure where 2 adjacent cylinders would show low numbers.

[ethan]

The numbers, if they are to be trusted suggest blow by on all cylinders. I think it probably doesnt make sense to go through all the work of pulling the head and then have a bottom end problem soon after. Its only money right? lol.

But do we trust the numbers? You don't sound confident in the results (that 280 is weird!)

Was the engine hot? I get very different results hot vs. cold on my 196k S54, but there's less difference on my recently rebuilt one.

Do you have stock cams? My recent rebuild has 288/280s and has 10psi lower compression than the 196k stock motor (but better clustering and MUCH better leakdown.)

Regardless, I'm with mrgizmo04 - the head's coming off anyway and you can make the call on the bottom end depending on what you see and what you want to spend.

[Robert's_BMW]

Gotta pull the head...but not a typical head gasket failure where 2 adjacent cylinders would show low numbers.

I agree. I blew my HG in Cylinders 5 & 6, so I was showing low compression on both those cylinders, but I never had an issue with overheating since it didn't affect any coolant channels.

[F1Dryvr]

The engine was cold. and I assume i put too much oil in to test for blow by. i only checked the one cylinder for blow by.

Yeah the head is def coming off, probably the engine rebuild will happen too. My cams are stock and i didnt plan on adding bigger(opening) ones on the rebuild. Im not really trying to get by cheaply here, but dont want to overspend on anything either(its already up there with me doing all the work and cams is 2k more!). Is the lang racing valve job and head treatment thing any better than say a local shop could do? Most important thing is bullet proof reliability, its a track car...

thanks all for the replies