CO951

I was looking at HGs on Lindsey and for $10 they offer a mod to the gasket that improves cooling to the exhaust valves. Is anyone familiar with this? Is it something I should do?

Adker

If the reading were that low the car would be hard to start and WAY down on power. You need to do the test with a warm engine, DME relay pulled, and the throttle held open so the engine can breath during the test. If you did this, get another gauge and try it again.

I do believe you have a HG going out, I just don't think those numbers look right.

CO951

Ok, there's the problem. I did it with a cold engine and didn't have touch the throttle. I will try again tomorrow. Thanks!

black944 turbo

Cold and no throttle won't make that much of a difference( meaning double numbers). I would be willing to bet the gauge is bad. I take the numbers themselves with a grain of salt anyways as it is not as important as the difference between cylinders. Should be no greater than 10% is the old timer rule.

MooreBoost

Dave is a nice guy. I go up and hang out with him almost every weekend.

CO951

I checked the gauge against a high quality tire pressure gauge and at 60psi it read 3psi higher. There is definitely more that a 10% difference between cylinders.
I may have not done the test perfectly, but, from what I'm hearing, it sounds like I got enough info to reasonably assume it is the HG.

Adker

Good luck replacing the HG. Remember to derate your compression number next time you test for your altitude. I am guessing you are above a mile in altitude.

odurandina

just go drive it.

if it's the head gasket the car will start running hot soon enough, and you'll know.

btw, I'm past 30 k miles since dumping in the 60 dollar bottle of jungle juice.

just drove from Miami to Chicago yesterday and the goop is still holding.

onspeed

I agree with the rest about the numbers being low. As mentioned, it doesn't matter if it's warm/cold or throttle open/closed since you're looking for a relative difference. If you checked all cylinders with the same method, the error is systemic and doesn't matter.

That said, did you let it crank for a few seconds? Either that or a broken gauge. Maybe it reads fine, but doesn't hold pressure properly so the measurement you read after you stop cranking isn't what it actually is. With the loaner tools from autozone you never know.

ehall

Onspeed is correct. However, if you get an accurate read, those numbers may end up being FAR different, by comparison to one another! What you have is basically HALF of the average cylinder pressure of a factory fresh 944 turbo. That suggests that your test failed, as a test. HOWEVER, if you double those numbers, just for the sake of argument, they are not good numbers, by percentage.

Here's what you do. Take it to a non-dealer Porsche shop, in it's currently driveable condition. Ask for a compression test and insist on standing there while they do it. See their numbers, FIRST HAND. THEN, make some decisions. For what it's worth, if you have tools, time and space, the HG job sounds MUCH harder than it is! If you are missing one of those AND common sense, pay the guy to fix the car.

ehall

I don't mean to be flippant......wait, I know nothing ELSE!...but anyway, what I gave you was solid. Feel free to pm me with questions or advice. BTDT too many times. I'm no expert, but I do love these cars and I want to see you come out in good shape!

chrenan

This is true. Here's my thread from a local track rat forum that follows my head gasket job over the winter - I take pictures at each step of the car and the tools used.

http://www.straightpipe.ca/forums/showthread.php?t=1539

crooster

Great writeup!

CO951

I hadn't had time to mess with this for a while, but I got out and drove it a little last night and figured a couple more things out. The smoke doesn't start right away, like it has to heat up a little first. If it were coolant in the combustion chamber it would be turning to steam right away wouldn't it. In fact it started about the same time as the smoke I get from the small oil leak that drips on the cross over pipe. I also had a good tail wind that blew the smoke forward when I came to a stop. There wasn’t a strong smell, but it seemed more like smoke than steam. I had previously said white smoke, but maybe it's a light grey. I also noticed that when I turn it off it will get some smoke coming back out the intake filter. I'm beginning to think it might be oil in the exhaust, but I don’t think that would explain the smoke coming out the oil cap. Anymore ideas?

So to summarize: I suddenly got large amounts of white/light grey smoke out the back, but still runs pretty well. It will boost, but not get to full boost. I don't seem to be loosing any coolant under boost and nothing significant otherwise. There is no sign of cross contamination between the oil and the coolant. My compression test was questionable, since all values were low. When I turn it off, I get steam/smoke coming out when I remove the oil cap and also out of the intake filter. When starting it cold, it takes 1-2min to get significant smoke (about the same time as it takes to get smoke from the little bit of oil that drips on the cross-over pipe.)

ehall

If you are getting smoke in all of those places then, by definition, it doesn't "still run pretty well". If you have just barely blown the HG, you won't necessarily get any smoke until the engine gets warmed up. You also may not see much milkshake. Either way that car is not still running pretty well. It's screaming HEY! I'm broken! Fix me! That's what the smoke is.