Cold start stumble for couple seconds and then everything is fine

[supes6]

I have some milky residue under the oil cap, but oil on the dipstick looks ok. It wasn't very long ago that I filled and bled the coolant - maybe 500 miles. I've actually drained and refilled it a few times in the past few months, but this was the first I noticed any major coolant loss so I think it must have gotten worse just recently. It's also possible that it's being forced out the overflow tube at high rpms due to the bad head gasket.. but either way it's done. I needed to fix a broken exhaust stud that is leaking anyway..

[FRporscheman]

So did this thread end up turning into a poll for which 944 owners have leaking head gaskets?

I'm not going to even touch my HG until something more happens. Stumbling for 10 seconds in the morning hardly justifies a HG job IMHO!

[supes6]

Originally Posted by FRporscheman

So did this thread end up turning into a poll for which 944 owners have leaking head gaskets?

I'm not going to even touch my HG until something more happens. Stumbling for 10 seconds in the morning hardly justifies a HG job IMHO!

the question is, how much damage is being done to the cylinder when it's running with coolant in there?

[Scott at Team Harco]

Originally Posted by supes6

I have some milky residue under the oil cap, but oil on the dipstick looks ok. It wasn't very long ago that I filled and bled the coolant - maybe 500 miles. I've actually drained and refilled it a few times in the past few months, but this was the first I noticed any major coolant loss so I think it must have gotten worse just recently. It's also possible that it's being forced out the overflow tube at high rpms due to the bad head gasket.. but either way it's done. I needed to fix a broken exhaust stud that is leaking anyway..

There's a lot of good information on this thread. Glad I stopped by.
One thing I would like to add...
If you have coolant in the oil - it's unlikely it will be evident on the dipstick. The coolant will sit at the bottom of the oil pan as water is more dense than oil. Unless you have several quarts of coolant in the pan - it won't show on the dipstick. And if you have several quarts of coolant in the oil - you've got bigger problems.

It might be a good idea to replace your oil cooler seals while the head gasket is being replaced. Also take a good look at the oil when it first starts to flow out of the oil pan. If there is coolant in there - it will be the first thing out (ask me how I know).

I take it that you have a mechanic on-call for your work. If you do you own work - there is a "how-to" on the cooler seals over at the Reutterwerk site (entitiled "Got Milk(shake)?")

Best of luck.

[DarylJ]

Originally Posted by Scott at Team Harco

There's a lot of good information on this thread. Glad I stopped by.
One thing I would like to add...
If you have coolant in the oil - it's unlikely it will be evident on the dipstick. The coolant will sit at the bottom of the oil pan as water is more dense than oil. Unless you have several quarts of coolant in the pan - it won't show on the dipstick. And if you have several quarts of coolant in the oil - you've got bigger problems.

It needs to be checked right after running it (before the oil and coolant have time to separate) to see the milkshake. Even a quart of coolant, after being run up to temperature and checked immediately, will show some sort of mocachino on the dip stick. It might not be totally obvious unless you know what you're looking for, but it will be there.

And to the OP - milky crap inside the oil cap is no big thing. If you don't drive the car up to temperature every day for a while when its humid out, condensation will do that. The cap on the AOS is so far from where the oil and coolant eventually mix that its almost diagnostically useless.

[944Ross]

Originally Posted by FRporscheman

So did this thread end up turning into a poll for which 944 owners have leaking head gaskets?

I'm not going to even touch my HG until something more happens. Stumbling for 10 seconds in the morning hardly justifies a HG job IMHO!

I think there are multiple problems with common symptoms in here. An all-aluminum engine starting from ambient temp is going to quench any initial heat almost immediately. It may not be feasible to dump enough gas in there to get a consistent fire without burning up the cat. conv.; who knows? I have a hard time believing everyone has a HG leak and that it only shows up for 10 seconds on start up.

[black944 turbo]

I had milkshake on my cap about two years ago and mine ended up being cooler seals, that could be your problem as well. That is definetly something to check.

[Scott at Team Harco]

Originally Posted by DarylJ

It needs to be checked right after running it (before the oil and coolant have time to separate) to see the milkshake. Even a quart of coolant, after being run up to temperature and checked immediately, will show some sort of mocachino on the dip stick. It might not be totally obvious unless you know what you're looking for, but it will be there.

And to the OP - milky crap inside the oil cap is no big thing. If you don't drive the car up to temperature every day for a while when its humid out, condensation will do that. The cap on the AOS is so far from where the oil and coolant eventually mix that its almost diagnostically useless.

Good point Daryl. I almost always wait at least 10 minutes before checking the oil level in my engines. It always takes a bit of time for the oil to drain back to the pan after shut-down. Taking a look right away should show a mix - if such exists.

[FRporscheman]

Originally Posted by 944Ross

I think there are multiple problems with common symptoms in here. An all-aluminum engine starting from ambient temp is going to quench any initial heat almost immediately. It may not be feasible to dump enough gas in there to get a consistent fire without burning up the cat. conv.; who knows? I have a hard time believing everyone has a HG leak and that it only shows up for 10 seconds on start up.

I'm sure not everyone on this thread has a blown HG - I was being dramatic. My car has a lot of miles and still has a 25 year old HG so it could be leaking... but I'm going to keep checking other things.

I don't think quenching is causing this. My 968 has basically the same engine, and it runs perfectly from the first second I turn it on.

Even if my oil cooler was leaking, it wouldn't put coolant in the cylinder, so that can't be causing the stumble problem.

[DarylJ]

Originally Posted by FRporscheman

I'm sure not everyone on this thread has a blown HG - I was being dramatic. My car has a lot of miles and still has a 25 year old HG so it could be leaking... but I'm going to keep checking other things.

I don't think quenching is causing this. My 968 has basically the same engine, and it runs perfectly from the first second I turn it on.

Even if my oil cooler was leaking, it wouldn't put coolant in the cylinder, so that can't be causing the stumble problem.

Well, there's always the stupid easy direct test for this: get the car to temperature, park it overnight, pull the plugs and a.) jam a bore scope down there if you have one or b.) jam a wooden dowel down there with some paper towel/rag/whatever carefully covering it (so you don't lose any).

If it comes up orange/green/wet at all, you know where to start. Could be coolant, could be fuel (leaky injector bleeding down your rail pressure as it sits). But you'll find out and know which direction to go in.

[supes6]

good idea with the dowel.. if the end comes out wet it should be pretty easy to tell if it's coolant or fuel.

[FRporscheman]

The spark plug hole doesn't face the bottom part of the cylinder though - where all the water would be sitting. My approach was to take out a spark plug and hold a towel over the hole, then crank the engine. The towel will catch whatever shoots out, and then I could smell it. I have not tried it yet...

[supes6]

Originally Posted by FRporscheman

The spark plug hole doesn't face the bottom part of the cylinder though - where all the water would be sitting. My approach was to take out a spark plug and hold a towel over the hole, then crank the engine. The towel will catch whatever shoots out, and then I could smell it. I have not tried it yet...

I guess that would explain why I just tried the dowel method and didn't find any water...

Also, my plugs are dirty and show no signs of being "steam cleaned". Drained the oil and no milkshake to be found, so hopefully I won't have any trouble with rod bearings in the future.

[FRporscheman]

Oh yeah, good point, my spark plugs were also dirty. Not excessively dirty, just dirty - not steam cleaned.

But then again, would a puddle of coolant turn to steam if the engine is cold? I know there is hot combustion in the chamber, but with the quenching effect, would there be enough heat to vaporize the coolant (and cause steam-cleaning action)? Or does the coolant just get shot out the exhaust in liquid form? Hmm.

I need to try my towel trick, or just use a coat hanger and towel.

[944Ross]

Pressurize the cooling system for a couple of hours (even overnight) with a tester and then search the cylinders.