924Board.org

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

This thing is going to go down into Applebit infamy soon.

I just buttoned up the new engine. Startup from cold = steam billowing out of the exhaust. When warm, no steam and runs fine. Same trouble as before. After starting it up I drove it around for ~15 miles. I started it up this morning, from cold, and got the billowing steam exhaust all over again. A quick rev increases the billowing steam to fill up the neighborhood!

I can at least rule out a few more things this time around. Here's the list of what was just done-

New 88mm pistons, new rings
Block bored & honed
Deck milled true/flat
Head surface was skimmed a while ago, still looks perfect
Head was pressured tested - no bubbles
New valve guides
New headgasket
Raceware studs torqued to spec
Filled with 30wt non-detergent oil
Filled with phosphate free (orange) coolant & water

I just talk to my (new) machine shop guy and it has him befuddled. He said that a crack in the head would open up when warm and push out more steam when hot than when cold. This guy also said that a leak down probably won't show much unless it's a really big crack.

I'm going to pull the line off my brake booster and check it to see if it could be sucking in brake fluid. Just to rule out another possibility...

The only places that I can think of anything getting into the cylinders would be from a crack in the head, a crack in the block, a blown headgasket, or from the intake. On the intake, it could come from the brake booster line, a crack in an intake runner, or in from the turbo/air filter. That's it right??

When the steam was billowing this morning, I pulled the plugs and found #3 to be steaming out of the plug hole. I'll repeat this from cold a couple times and see if it's always #3, or if it moves around. If it moves to all the cylinders then it must be coming in from the intake, otherwise it has to be between the runner and the cylinder. Just trying to narrow down the possibilities.

Unless someone can think of something obvious. I think the next step is just to find a good hotrod shop with some clever guys and drop it off along with my wallet!
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

462avi · Posted: Tue Dec 19, 2006 12:06 pm Post subject:

Nick

I will admit this is a new one for me to. I have a couple of ideas. #1 the winter is upon us and maybe its air condensing in the exhaust system. I will admit it would have to be a lot of water but ????. #2 water/condensation in the intake system i.e. oil water separator. #3 water in your fuel. I know these are all long shots but if you are not missing any fluids (coolant, oil, or brake fluid) than the only thing left is condensation. Is there any performance loss due to this phenomenon

Hope this is a start
Geoff
_________________
2005 C230K
2002 grand cherokee with 4.7L

Paul · Posted: Tue Dec 19, 2006 12:18 pm Post subject:

Compression and blow down tests are the next steps....
_________________
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.

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Have you experienced any hydrostatic lock? That's when you crank the engine and it suddenly stops turning, labors, then eventually starts to turn over again.

This would indicate water in the cylinder (water is uncompressable). If you remove the plug when this is occurring, water will shoot out over your neighbor's house (fun, but sad).

Also, has your water level decreased?

This sounds like head/head gasket/cracked block to me. BTDT.

Get someone who can do real diagnostics on the car. Besides the pressure test/leakdown and compression check, you need to test for combustion gas in the coolant and water in the oil.

Good luck. If you get stuck for parts, LMK and I can look around and see what I have in the attic...

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

I haven't popped a compression gauge on it yet. I almost forgot to add that to my list.

The breather dumps to a catch can and doesn't recirculate back into the intake, so nothing is getting in from blow-by.

A crack in the block would have to be inside a cylinder - I think my machine shop would have noticed while boring!

I've only put ~20 miles on it, so I can't tell much via changing fluid levels.

It's nothing close to hydo-lock. And it definitely isn't just normal cold-weather water vapor.

So far my to-do list looks like:
- compression test - cold & hot
- check the brake booster line
- see if the smoke stays in #3 while pulling plugs during smoking
- swap back to stock headbolts (you never know...)
- pressurize the coolant reservoir and check for leaks into the combustion chamber

I want to do what I can to narrow it down before taking it to a shop. Unfortunately, I won't get much time to play with it over the holidays.[/i]
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

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

Nick,

Sorry to hear this isn't sorted yet, that sucks. Is there any chance you have a spare 931 head you could swap on? Is there anyone in the area near you that has one you could borrow? At least then you could narrow it down to the head, and even just swap out the springs and such from yours (if new) onto the spare head and dump the old one. All I can think is that there is some tiny passageway flaw in the head that is hidden from view, allowing coolant to somehow make it into the combustion chamber. Has the head been ported? Maybe something was damaged at that point?

Just ideas. If I was closer I'd come over to at least provide an extra set of hands for wrenching.

Chrenan
_________________
1987 951 - M193 Version for Japan

Smoothie · Posted: Wed Dec 20, 2006 10:08 am Post subject:

Actually, I wouldn't rule out a crack in a cylinder wall yet - unless the machine shop was specifically looking for and tested for cracks.

A crack in the head that lead to the water jacket would draw in some water to the combustion chamber on the intake stroke and force gasses the other way from the chamber to the water jacket on compression and combustion, right? A crack in the head or very high up in the cylinder wall could be diagnosed by pressurizing the cylinder while at tdc and looking/listening for air bubbles in the cooling system.
-While a crack further down in a cylinder wall would take water into the cylinder on the intake stroke, then drip into the oil sump whenever the piston's above the crack - so expect to find some coolant in the oil if that's the case. A compression test, leakdown test or pressurized cylinder and listening would be of no use in this case. -How about pressurizing the cooling system, then with each piston at bottom dead center, listen (and look if you can) through the spark plug hole for coolant spraying in or accumulating on the piston top? [Actually, you already mentioned this, didn't you.. I'd put it high on the list.]
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

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

I couldn't resist going out and playing tonight. Compression looks great!

#1 155
#2 155/156
#3 155/156
#4 156/157

My meter isn't accurate enough to give me readings better than about +/-1psi. Still, can't complain with those numbers!

My father actually had a very interesting idea - happens to him on occassion

Water in the fuel. This car was in a flood where the water made it up to about the top of the brake discs. I don't know if it could have leaked into a gas tank vent.

Anyone have any experience with water in the gas tank? If folks use straight water-injection, then I imagine it wouldn't necessarily make it run badly. I've been on the same tank since the car was flooded. Would also explain why the steam doesn't seem to smell like coolant or anything else. Although, it doesn't exactly explain why the steam would go away when it's hot.

I'm going to pop in a can of dry-gas and try to run the tank out and refill and another can of dry-gas. That should suck out any water I would think.

Thoughts? My hair is getting thinner over this crazy machine!
_________________
1980 931S
15psi boost, MS-II, EDIS, 951 IC, custom intake, Ford 5.0L throttle body, Forge BOV, WB o2, G31 w/LSD, 964 wheels, 968 rear sway, Bilsteins, 200# Welt. springs. A laptop, and a partridge in a pear tree.
1991 964 C4 Cabriolet

Paul · Posted: Wed Dec 20, 2006 10:36 am Post subject:

You're sure it's steam and not oil smoke?
_________________
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.

Paul · Posted: Wed Dec 20, 2006 10:40 am Post subject:

BTW water always seeks the lowest part of the fuel tank.

The car would not start on straight water.

If you want to make sure, let the car sit a few hours (outside) then loosen the hose from the tank to the pump and collect some "fuel" in a glass container.
_________________
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.

Smoothie · Posted: Wed Dec 20, 2006 11:40 am Post subject:

Could it be your charcoal canister is drenched from the flood?
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Paul · Posted: Wed Dec 20, 2006 11:46 am Post subject:

I thought of that too, but couldn't resolve in my mind why it would only smoke when the motor is cold....
_________________
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.

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

Good points guys. If you even suspect the fuel, I say pull the fuel return hose at the bottom of the tank and empty the tank and start with new fuel. That's an easy fix. Same with the charcoal cannister, empty it out and refill.
_________________
1987 951 - M193 Version for Japan

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

I think the turbo bearings/seals are suspect at this point. Nick said way back that his intake tubes were coated with oil.

Isn't this the same turbo that came with the flaky motor?
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Lizard · Posted: Thu Dec 21, 2006 2:07 am Post subject:

ask for a digital camera with a movie function for christmas then stand it by your rear exhaust when you start the car, and then put the vid on youtube let us see the smoke
_________________
3 928s,