[ausgeflippt951]

Just thought I'd post up some steps I followed recently to check for a perceived head gasket on my 'fo-fo.

Symptoms:
1) Often/usually, a head gasket failure happens fairly suddenly: the car loses power or may shut off altogether.

2) Additionally, the coolant will overpressurize and likely overflow somewhere. This is due to combustion gases leaking into the coolant system and adding pressure. The car will usually overheat.

3) On most cars the coolant and oil will mix, causing a milkshake-like fluid in the coolant. Note: on a 944 you will not be able to see the milkshake from the expansion tank, due to its remoteness: coolant does not flow through the tank, as it may on other types of cars. Consequently, the milkshake will not be visible unless you drain the coolant from other areas of the system.



At the DE a couple weeks ago, my car was suffering from a coolant issue: I would get back into the pits and it would start spewing coolant. In my case, overall temps were fine and there was definitely no lack of power.

What gives?

Well, I let the car sit for a couple of weeks and decided to take off the radiator cap: it was still holding a LOT of pressure. How weird.

I started to wonder if it was a head gasket failure. The kicker here is that if there was a leak in the head gasket, the coolant system should not be capable of holding pressure long term -- in my case, it did.



In the end, it wound up being an issue with bleeding the system: I seriously lucked out here. Improper bleeding of the system is arguably the #1 reason for head gasket failure, and on a 944 it's a particularly annoying process.



My recommendation: every 944 owner should buy a coolant pressure tester. I own a Stant unit I bought off Amazon for ~$75.


The pressure tester does three vital things:

1) Test for system pressure. With the engine off, bring the system up to the pressure that the cap is rated at. In the case of the 944, it's 1bar, or around 14.5psi. In my car's case, it held pressure perfectly, with no loss whatsoever after an hour.

2) Once you confirm the system is 100%, bleed the system using the tester: pressurize and open the needle valve in the coolant neck near the cam gear. This is where I realized I had not bled my system thoroughly -- a good amount of air came out!


3) Test for the propagation of combustion gases into the coolant system. To do this, connect the pressure tester to the expansion tank but do not pump it. Turn on the car and allow the car to self-pressurize. The car should level off, usually ~1/2 of what the radiator cap is rated to.

If your pressure continues to climb and never levels off, then you've got a combustion leak. Sorry.



I made up a short video for testing Step #3.

Head Gasket Testing, 944 Turbo

Head Gasket Testing, 944 Turbo

There are many on this board who are much more experienced than I, so please feel free to add colorful commentary.

[BlackTalon]

Good info. How about a linkee that workee for the tester?

[ausgeflippt951]

Originally Posted by BlackTalon

Good info. How about a linkee that workee for the tester?

How weird, when I insert a URL it gives me that silly Amazon Thumbnail. First example is with URL brackets; the second is simply copy/pasting without me inserting any HTML.

http://www.amazon.com/Stant-12270-Cooling-System-Pressure/dp/B0002SRGWU/ref=sr_1_1?s=automotive&ie=UTF8&qid=1384446918&sr=1-1&keywords=stant+pressure+tester

http://www.amazon.com/Stant-12270-Cooling-System-Pressure/dp/B0002SRGWU/ref=sr_1_1?s=automotive&ie=UTF8&qid=1384446918&sr=1-1&keywords=stant+pressure+tester

[BobNovas]

why is there liquid in your cooling system?

[RENN 951]

^^+2. It also makes the system self-bleeding.

Originally Posted by BobNovas

why is there liquid in your cooling system?

Bob - check your Boxster for this condition as well!

[Vicegrip]

Originally Posted by BobNovas

why is there liquid in your cooling system?

Trying to come up with a Porsche car that is not liquid cooled.....processing......404.

[TurboPooch]

Every 944 motor I have put together gets a Lindsey steam vent kit.
http://www.lindseyracing.com/LR/Parts/COOLSTEAM.html

I am convinced this is one modification that helps to keep the head cool and prevents warping of the head and gasket failure. The first motor I took apart to rebuild had a bulge in the fire ring of the #4 cylinder and was just about ready to pop. Cheap insurance IMHO.

[APKhaos]

^ +1. The Linsdey stem vent works

[TurboPooch]

Holy cow, I just looked at the price of this kit. Over $40 now. Last one I bought was about $25. The PTC fittings are available from McMaster for about $5 each and the tubing is about $.50 a foot. Build it yourself for under $20. As Renn says, it does self bleed. I always see a small amount of bubbles flowing thru the tube that may have otherwise got caught in the pocket at the back of the head.

[jerome951]

^^^ +3 on the steam vent kit. IMO a 'must-install' whenever the head is off on a 951.