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-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

This engine is cursed!

After the first short run on the new build I noticed that a coolant hose was leaking. On the next startup after a cool-down, I was getting some smoke out of the exhaust that lingered until it warmed up. The intake tract was clean, so it must have come from either the valves, rings, or a headgasket leak. I thought it might just be the straight 30-weight oil leaking past someplace.

But it wasn't. The coolant leak showed up again - only after hitting positive boost pressure. When the smoke started up after another startup from cold, I pulled the plugs and #1 cylinder had smoke wafting out, while the other three didn't.

I mentioned that I was hearing some detonation at low-load and low-rpm. No salt&pepper on the plugs, and the headgasket looks just fine. My AFR's were rich, and the ignition was very conservative. I have no idea where the detonation could have come from? Unless the headgasket blew right away this was somehow contributing? The piston tops all look perfect. You can see a faint outline of the burn pattern - which looks like it's swirling - cool.

One of the oddities - I can't see anything that looks like a break in the gasket?

I retorqued the raceware studs to spec after letting the engine warm-up then cool down for the first time.

The big questions are -

1) where is the coolant coming from?
2) what was causing the detonation?

One thought is that I didn't have the block deck checked after the last nasty piston-melting detonation mess. Possibly it's warped from that debacle and the headgasket blew almost right away.

Two coolant passages in the head between the #1 and #2 cylinders are corroded and the opening is larger original. A possibility for the gasket breech?

In addition, the cylinder walls have some scoring - caused from the first run-in on this engine with the old JE pistons. Which ground themselves into the cylinder walls. The machine shop gave the walls a skim. I should have had my head examined for not boring it out to remove the gouges. These VW pistons are made in an 88mm set. Kind of pushing the bore, but 88mm should be useable. That's the next step.

Here are a couple pics-

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

To add insult to injury, the radiator drain plug came out with a chunk of the radiator! ARGH!!!

Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

Just posting to lend support, no answers from me unfortunately. I'll keep reading the thread as it goes in case there is any usefull input I can provide. Good luck, I'm sure you'll figure it out.
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Lizard · Posted: Mon Jul 10, 2006 10:51 am Post subject:

I think you are going to have the deck checked as well as the head.
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Chrenan · Joined: 15 Jan 2003 Posts: 3903 Location: Canada

You and Lizard are likely on the money with that thought...

"One thought is that I didn't have the block deck checked after the last nasty piston-melting detonation mess. Possibly it's warped from that debacle and the headgasket blew almost right away."

If the head gasket isn't blown, is there any other way for the coolant to make it to the combustion chamber other than a warped block or head?

Do you have room on both the head and block to have them re-skimmed?
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1987 951 - M193 Version for Japan

-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Well, there's one other way - cracks in the head... Probably unlikely. I just thought the headgasket would show more obvious signs.

There's always room to deck.

I'll just take some more cc's out of the head and add an adjustable cam sprocket to take up the distance on the timing belt.

Min · Posted: Mon Jul 10, 2006 12:04 pm Post subject:

oh my.... that really sucks :/ ....

Min
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Paul · Posted: Mon Jul 10, 2006 12:39 pm Post subject:

I've read this thread 3 times and I cannot figure out why you pulled the head.

Cylinder 1 was probably on the exhaust stroke when you shut it down, hence the smoke?

Did you do a compression or blow down check before removing the head?

Did the smoke at the tailpipe smell like coolant or oil?

I see no sign of coolant in #1 from your pictures.

You mentioned the first leak was a hose, where was the second leak?

Cylinder 2's exhaust valve looks wierd.....
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-nick · Joined: 16 Nov 2002 Posts: 2699 Location: Cambridge, MA

Ah, when I said smoke, I meant SMOKE

Enough to choke up the neighborhood for about 3-5 minutes while it warmed up from cold. My color-blind eyes aren't the best, but the smoke coming out of the tailpipe was very steamy and on the whitish side.

I let it cool all the way down, then ran it until it smoked and pulled the plugs twice. Both times, #1 was like a chimney. I've seen an exhaust stroke exit - about 10 seconds of fumes. This was a good 60 secs of thick smoke. The cylinder itself had wet water droplets in it while I spun the crank around with the head off to take a look at things. Of course, that could have seeped in while I pulled the head, but none of the other cylinders were wet like #1. The #1 plug ceramic was also very white and clean compared to the other three tan hued plugs.

Compression test showed #1 about 15-20psi under the other three cylinders. ps- I'm getting almost 175psi max, more than what I was shooting for anyway...

There was only one hose leak - from the lower radiator to water-pump. I pulled it off, tried to reseal it. It would hold if I went for a short test with no boost pressure. If I hit any boost, then it would squirt coolant out.

That's cylinder #1's valve. Just looks weird from being partially wiped off with a rag...

Paul · Posted: Mon Jul 10, 2006 1:12 pm Post subject:

Yep that head had to come off....

Congrats on getting the exhaust manifold unbolted, I've never had enough patience and the right tools to do that...
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

endwrench · Joined: 07 Dec 2002 Posts: 1631 Location: Victor, Montana

Wow Nick! Tough luck

You seem to be in better spirits than I could put forth!

By the looks of the piston and combustion chamber I would say there is no doubt these have been "steam" cleaned. Couple questions: Do you think the cooling system was being over pressurized when you got on the boost only? Did you stick with a stock type head gasket or did you go copper?

I have never actually seen a block deck warp. They will however "sink hole" in places over time. It is pretty rare for deck to cause gasket sealing problems though.

I had a Subaru drive me insane once with a water eating problem. It ended up being a crack in the exaust port (not the combustion chamber!). It passed all the usual test for CO in the coolant and water in the oil but it smoked like a steam engine once it was warmed up. If your did the same it would probably give the results you have. I would take the head to a competent engine machinest and have them pressure\vacuum check it. Make sure they have the tools to do it proper. Good Luck!

Todd

leadfoot · Posted: Mon Jul 10, 2006 2:43 pm Post subject:

sounds like you have either a cracked head or cracked cylinder, my money would be on he head...sorry... I think pressurising the coolant system should allow you to diagnose this problem though...
by the way are these the 10:1 forged type 4 VW pistons from mahle the same as what you are using??http://www.actionimport.com/cgi-bin/commerce.exe?preadd=action&key=EMPI-98-1989-B
leadfoot
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Raceboy · Joined: 01 Mar 2004 Posts: 2327 Location: Estonia, Europe

1st cylinder is definitely had some coolant in it, just compare it with the others.
Coolant in the cylinder causes detonation, we xperienced it with my friends 951 when his 3.0 conversion: too long (S2) head-studs with spacers didn't clamp the head well enough and raised the head under boost causing coolant enetring the cylinder and detonation already 3 degrees BTDC @ 1 bar of boost. Usually it can handle like 20-22 degrees under similar circumstances.
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Lizard · Posted: Tue Jul 11, 2006 12:40 am Post subject:

it can also bea cracked cylinder in the block, but that is unlikely as you would probably see some water in the oil too.
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Lizard · Posted: Tue Jul 11, 2006 12:41 am Post subject:

another thought, if it was the head or block that was cracked your cooling system would have over pressured and popped the cap, which you havent mentioned, so I would be assuming that it is that something is warped
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