New 968 Custom Engine w/ Pressure in Coolant

[JivenJim]

Hey Guru's,

So I test drove my new 968 Build and noticed I have overflow coolant bleeding off about 25 Oz after a 20 min easy drive. Coolant Temp never went above 190F. New Cometic Head Gasket and Racer's edge Non-stretch Head Studs. This is exactly what happen last time to this Engine on New Rebuild that ended with leaking in to #3 with Coolant and Bent Connecting Rod. (that time I had a Standard Widefire) This Engine is Pristine and everything is Fresh. Any Non-Head Gasket ideas??

It's not making Milk Shake or oil in Coolant.. Yet.. Some Spiting on start up..
It's not leaving Vapor Trails, but I still think some coolant is getting in there..

Should I try a "Stop Leak coolant additive", thinking pin hole leak somewhere.

The Machine shop has the Car and is doing a Leakdown Monday.

Any Ideas welcome.

Thanks guys,

[ae1969]

When you say fresh.....they machined the head and the deck ? Otherwise I am leaning towards that cometic gasket.

You may be able to torque down the head again........

[JivenJim]

Yep, The Head was milled about .003" Engine was completed machined and matched, Blueprinted, and I can't think of what could be causing this. The Cometic gasket is multi-layer metal so it is suppose to be really top notche. I even had the Shop put it on and toque and check..Can't be gasket. That's been done Twice before now.

Other ideas?

[FRporsche]

Maybe it overflowed simply because it was overfilled.

Are you sure the coolant system was properly bled?

[JivenJim]

Coolant was Bled, burped & spanked. And tank was properly filled.. Twice with same results.

[Razorback1980]

Did you have the head checked for cracks? Head gasket and small crack in the cylinder/head areas is the only places I can think of that would allow compression to get to coolant system.

[JivenJim]

The Machine shop is very good on these cars. I think they look for things like that but don't know about cracks. I'm thinking that has to be the case. (Maybe in the Head) Is there a coolant additive that might work to fill the void in my life? Like Stop Leak??

Hope to hear back from the shop on Weds.
I really don't want to pull a brand new engine again!! As I said, same problem gave me only 300 miles on this engine earlly this year.

I apprisiate the help guys... If you think of anything else..

[hpservertech]

Well it kind of sounds like your answering your own question. It did it before the rebuild and it did it after. So something has to be bad right?

I wouldn't put someting like stop leak in on something that you just did all that work to. Would only be a temp fix anyway.

[Lizard944]

I may be way off base here, but possibly a bad or binding thermostat? Is there pressure in the coolant tank immediately after starting? That would indicate HG. Try a coolant pressure tester and see if coolant system is not holding pressure, and has no obvious leaks, (coolant seeping into cylinders via failed HG. You can also use this same pressure tester to see if pressure is present in the expansion tank after start up.

--Lizard

[2Tight]

I've been watching this thread closely. It wasn't on my Porsche but I had a very similar issue with my BMW that drove me crazy for months. After a bad HG failure I had the head tanked, machined, and valves done. Even before this work the car would lose coolant somewhere in normal driving but never overheat unless it got very low. It did the same thing after repair. Turns out there was a very small crack in the head that the shop had missed during the rebuild. When the head was torqued the crack grew and when heated it was even worse.

I agree with Lizard, get the pressure test first and look for a wet cylinder or plug. You could even have a slight crack at the top of your cylinder that opens under high compression or the block is slightly bowed and not machined well enough to the head. Having this problem before makes me think it's a crack or poor block/head fitment.

[nynor]

is it possible it is coming out of the overflow tube? if i fill mine to the max line, it will just leak out of the tube when it gets hot. then it stays just above the minimum line. my friend's 944 does the exact same thing, and so did my '83. all of the cars got new tank caps and had the same results.

[JivenJim]

Update:
Testing today by machine shop said no spitting (overflow tank leaking) during 30 minutes of Idle. Ran to 180F and stayed there. They pressurized tank to 15psi and had no leakage (so said). Plugs looked the right color of brown.

It was overflowing through the overflow tube. Seemed to stop if the level was about or a little bellow the min line. At least cold. When it was hot the level was a little above max on tank.

And the overflow only occurs after driving, not idle. (and not race driving, just normal) Told you this would be a good one for the brain trust or P-gods.

I told the shop to keep looking. I love the shop and we treat each other well, but I let them know that if there is something wrong/leaking from after the last build, it's on them..

So they calling the other Porsche shops for advice. Might be that micro crack that heats up in the head and leaked on to the #3 Cylinder. That one had slight cleaning lines on top of piston last time.

Nynor, did your cars keep running well even after clearing their throat down the overflow?

I don't know what or how a binding thermostat is or how to check. Wouldn't that Make the Head temp go to the moon. My temps are perfect. But, heck I'll try anything at this point. If you have suggestion on that.
.
Update you as I find out and thanks for your continued interest.

[JivenJim]

Last year picture but still about the same.

[Razorback1980]

The thermostat on a 944 engine is in the water pump housing...probably the same for a 968 motor as well. I would tend to agree with you that if the thermostat was stuck, it would run hot all the time...especially while idleing. I'm still thinking it's a crack in the head or cylinders. Just not sure of the best way to test that. Have to think about that. I'm thinking that getting it warm and then running the compression leak down test would be something to try.

[968turboS]

Any decent machine shop should 1st test the head for cracks before they rebuild or mill it. The cost is minimal.
Your best bet is to remove the head again and hopefully they find something. The reason I say that is that if they find something in the head, then you don't have to worry about your deck or your block.
Regards.

[flash968]

agreed - however, now that you are past that point, and the horse is out of the barn, a leakdown test should show where things are going

if the shop can't do it, depending on timing, i could do it here if you could get the car here without blowing it up - lol - i have a brand new kit i have been dying to test out - drop me a note

[nynor]

yep, they ran/run fine. when cold, the water level lowers (yes, it still does this, i've bled it three times) to about the min line, when hot it raises to about midway or almost to the max line, i am thinking it is due to the expansion of the coolant. my temp gauge never even hits the halfway mark and i don't lose more coolant after the initial drop. and, like i said, i've replaced the 'radiator' cap on all these vehicles.

[Aufenbahn]

I'd have to agree - mine runs at a low level in the tank too - never seems to get any lower though

[JivenJim]

Update: I put on a new Radiator Cap for a 968 on the 944 tank. I believe this had a 16 PSI overflow Vs 14. It seem to reduce the overflow. Then I put in almost a full bottle of Bars Stop leak. (I know other guys said not to) Well, I was Desperate. The average Temperature went up 6-8 degrees F on my autometer gauge, but the leak stopped perfectly. I was up and racing!

Now after 12 track days and 5 months: I got this really subtle white smoke on start up the other day on the way to the track. Bad omen! Ran good on the 5 hour drive up there in 110 F outside temps. Then at the end of a 25 minute track session she started dumping coolant out overflow really fast. The Bars Holiday was over and the pressure in coolant tank was back! Left a day early and drove straight home and dumped about 3/4 the reserve tank out the overflow (I presume) On my last track session this M3 (on my butt) said he smelled coolant and was speckled on his windshield. Does that mean it cam through exhaust? Yes that also means I was holding off an M3 race car.
Colant Temp never went above 210F on track and about 180-190F normal.

Anyway, got the backup 968 Head prepped and looking at swapping. I’m believing it may be that expanding pin hole in the Head. New Head Gasket along the way and will check for lines on Piston heads and gasket tears or stains. If that does not work then maybe Block Pin Hole?

Got some PM on this issue (others have had same issue) and just wanted to update on what I'm doing.

Maybe I should use Bars Leak Radiator "heavy Duty” Stop Leak

Heck I’d buy a new Radiator, to compensate, if that got me another 6 months without pulling an engine..

Love to hear your commits and insights.

Thanks in advance

[nynor]

i think you are better off pouring the beer in there. YMMV.