Hi, I'm new to the 996tt world, and searching for a vehicle. I just looked at one this morning, and had a question about he white residue you see in this picture.

Can you guys help me decipher the white residue around the black cylinder (please see pic)? It looks like it might be coming from within...

Is this something to be concerned about?

btw, what is that black cylinder? Is there a quick primer somewhere on how to get ones bearings regarding these engines?

 

Dry coolant, I would be concerned ... First, I would clean it up REALLY well. Then I would monitor this area for leaks over the next 2-3 weeks ... If it's leaking, I would get it addressed. If it doesn't return, just keep an eye on this area periodically.

 

Thanks for the quick response. Do you have any sense on what the functional impact of this apparent leak would be (immediate and/or long-term)?

What would be the cost to address?

btw, what is that black component? looks like it is part of the coolant reservoir, but I dont' understand its function.

 

The pic is small and not much detail visible but the residue is almost certainly dried anti-freeze. That "cylinder" on top of the coolant tank is a bleed valve. Either the valve proper or the valve assembly is leaking.

There is probably a new coolant tank in this car's future.

A new cap too if the old one has a part # (the last two digits) below "04".

For a good basic reference on these cars/engines:

http://www.amazon.com/Porsche-996-Essential-Companion-Supreme/dp/1845840968

Total 991 (a UK published indy Porsche mag) has done some nice write ups over the years on the 996 Turbo. You can buy the 1st 50 issues on DVD at the Total 911 web site. The mag has also published a couple of Turbo only specials that you should try to find available as back issues.

 

Anti-freeze residue is a sign of a coolant leak. This allows vapor to escape which over time lowers the coolant level. If you top up with just distilled water over time the anti-freeze/water ratio is out of whack. Not good.

But a more pressing concern is this represents a pressure leak and pressure is what keeps the very hot (~226F under extreme conditions) coolant from flashing to steam at the hotter spots in the engine.

If the coolant flashes to steam this can lead to localized overheating which can severely damage the engine. You think a used Turbo is expensive... price a replacement engine for one!

Now since the car is used it may (may...) have already suffered from some overheating. You have to be very thorough in your check out of the car. I would not consider the car until this is addressed properly and then give the car a thorough used car check out but first a test ride (15 miles) followed by a test drive (15 miles) to get the engine fully up to temp.

The cost to replace the tank I do not know. You'll have to get a quote from a qualified shop.

 

The black piece is the air bleed for the oil cooler. 1) someone could have over filled the coolant while they where prepping the car for sale. that would over pressurize the system and cause that. I also see coolant around the seam of the tank. Or the head gasket could be leaking. Get a PPI done.

 

It is possible someone overfilled the coolant tank and left the valve open and drove the car that way.

So a possible path would be to wash/rinse this area thoroughly to remove the residue and then drive the car and get the cooling system nice and hot. Leave the A/C off which means the radiator fans only come on when the coolant temp climbs to 212F.

Then park the car and watch this area and sniff around this area checking for any leaks. If any anti-freeze is smelled, any water vapor spotted -- ten tent the bleed valve with alum foil -- then there's a leak if not at the bleed valve somewhere that needs to be addressed.

 

These cars run a lot of psi in the coolant system.. I have not checked a stock car but on mine it makes so good psi..

 

At 226F pressure would have to be around 20psi or 1.3 bar to prevent the hot coolant from flashing to steam. (I have seen my Boxster's coolant temp reach 226F but I do not recall seeing the Turbo's coolant temp climbing much above 212F.)

IIRC the test pressure used to check the coolant system for a leak is at 1.4 bar. The newer cap is IIRC supposed to vent pressure at 1.4 bar then close at 1.2 bar.

 

It sounds like a detailed PPI, with someone who really knows these cars would be in order. I'll create a separate thread specifically asking for PPI recommendations.

Unless, does someone following this thread have suggestions for a PPI place around Cherry Hill, NJ or vicinity?

 

How would one identify potential localized overheating? E.g., does this picture from below the car help give any clues one way or another?

 

I see more then 1.4 bar and no coolant overflow. I am sampling at the cylinders so I may just be seeing some psi from the pump but I dont think that should matter that much.

 

All look normal. aftermarket exhaust...