I drove the 928 to work today and with the COLD Michigan air this morning it was flying! The car never skipped a beat...

That is until this afternoon when I got in the car and left work. When I first started it, it had dropped a cylinder. I tried re starting a few times and then it finally ran on all 8. Lots of white smoke, and very very sweet smelling.

I let it idle for a while and the smoke dissipated, but I already knew the prognosis. It drove home fine and after about 5 min into the drive the smoke was gone. But I won't drive it until the head is off and I can inspect it. Don't want to hydro-lock it.

Oil is clean, and the coolant appears to be okay on first glance, but I haven't drained it yet.

SO do I pull the motor, or just pull the head in situ? I was thinking I should pull the motor, but maybe I should just pull the one head (still don't know which side).

So what caused it? Boost? Maybe, but many people are running more boost than me without issue, so I've got to think it's probably the one-year of running it with MASSIVE amounts of knock that exacerbated it. But who knows. It could also be the green coolant that was in ti from the PO. I really don't know. The car does have 136k miles on it. The key is, the motor sounds fine, but I won't know for sure until I pull the head and replace the gasket.

I guess winter maintenance has started a bit early for me this year! LOL!

 

You know that if you find which side it is on and only replace that side that you will be doing it all over again soon for the other side...

2+ years at 12.5psi on Cometics, they do leak oil a little bit but the will not blow. 545rwhp on the 8th run in a row in 90+ degree temps with no cooling air. On a cool day and a cool engine I'm sure there is more there.

 

so, maybe a pin hole in the gasket cylinder ring. coolant under presssure, leaks in the cylinder and then upon starting, you see the water vapor and smell the coolant. if this is so, then during running conditions you should see some pressurization of the cooling system. get the "blue water" head gasket check kit at your local auto supply and follow the directions.

other possiblities would be cracked block, cracked head or warped heads . if its a water going somewhere leak, then Barr's stop leak is almost a perminant fix. if its a combustion chamber leaking to coolant jacket, nothing can topically fix that. that can be determined by the head gasket test kit.

the other test would be to wait until it does the "blowing white smoke thing" again. quickly turn it off and pull plugs until you see one that looks water wet or odd.

mk

 

Andrew.............try to do as much diagnosis before removing the heads/engine.

A leak down should show which cylinder/s are affected and where the issue is.

Althougth not easy, the gasket is leese painful compared to the alternatives $$$$$$$$$$.

 

Can you explain what exactly makes you think the head gasket is bad? I thought there could be lots of other reasons for white smoke...

Either way, I'm sorry to hear you are having shark trouble.

 

I'd look down the spark plug holes to see which piston is "Clean" - if one or two are, its been leaking for a while. If none are clean than its new.

 

Andrew:

Sorry to hear about your problem....do you mind indicating how much boost you were running?

I only ask after nervously bumping mine to about 8.3 indicated in the last evolution.....wish I was a little closer so that I could give you a hand.

Ken

 

I'd also talk to Tim Andrew - ask him about which cylinder leans out first (this really won't be seen on the main AFR)

 

Andrew,

Man, that does stink!! Sorry to hear about this, but as has been said, the worst case scenario isn't in play yet; check things out first.

I hope you know you can call on me anytime to lend a hand. The sooner you're back on the road, the better!

 

Stop breaking your car!

I hope it's a gasket and not a head.

 

Sorry to hear that Andrew, at least you know what to do during the winter months

/Peter

 

Don't blame the green coolant for this. I was expecting Mark to recommend Bars Leak and then after that, chastise you for not running Amsoil, but he showed amazing restraint.

 

Lots to talk about here...

First, let's take Nicole's Q: The reason I suspect the head gasket is that upon startup, the car dropped a cylinder and was blowing all kinds of white smoke - which smelled very sweet. This is a classic symptom of a bad head gasket, but I won't know for sure until I get in there.

I think Mark's suggestion of it being a pinhole leak is probably spot on, because after a few minutes of driving it's fine. I could probably put a bottle of Barr's Leaks and have it stop, but that's very much a band aid approach and not acceptable in a boosted application.

Ken, I was getting 7.6 psi in 80*F+ temps, and as much as 9.2 psi in 45*F. But I'm not sure of the boost is what cause the failure. I bought the car with 123k on the odo. It could be that someone overheated it at some point in it's life and warped the head slightly... I don't know. I'm sure the boost didn't help matters.

Brendan- Already spoke to Tim. He thinks I should just pull the one head, but the reality is that I've got some other things to do and as Ketchmi suggests, if I only do the one side, chances are I'll be doing the other side before I know it. So I think it's probably best that I earn my engine pulling stripes and yank the engine and do the whole thing while it's out.

Chaad- Thanks for the offer. I'm tentatively slating the pulling party for Oct 27th. Would like to get it out before the real cold weather sets in.

Stay tuned...

 

Andrew,

Sorry to hear about that. There's some point in analyzing the failure but with your description it's likely "all of the above" and comes with age and use and especially hard use.

Try this one: pull the plugs and crank the engine. The situation will become plenty clear.

I'll suggest pulling the engine and doing a full re-seal on it. Be aware that this effort can produce other problems (E.g., bad seal install) but at 16 years and 136K miles it needs it. It's actually nice to be back at a point where an oil spot is new.

Maybe Winter maintenance has started early but you've got, what, 6 months to finish it?

Regards!

 

Hi Andrew,

Sorry to hear that your car broke. Glad to hear you are tearing it down soon. You don't want coolant hanging around in the cylinder for long if it's going to sit. If you can find a set of MLS head gaskets, I'd run those. I have one on my 200 and it is holding 28 psi of boost just fine. As for machine work, I'd really recommend Thompson Automotive in Redford. They did all my block and head work. Very smart guys. They do V8 stuff for GM. I also have spare engine stands if you need one.

John