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SprintStar · Joined: 26 Aug 2003 Posts: 150

New thermostat, no thermostat, new headgasket, top end rebuild. The water system is tight. I pressurized it to 20psi and it held.

But after driving around a while, the water boils. Why?

If it helps any, I converted to a 944 water tank while doing the rebuild.

Thanks for any help.

Sprint.

924RACR · Posted: Sat Nov 13, 2004 12:21 am Post subject:

Did you bleed the cooling system? Is the waterpump leaking, could be bad? Do the fans work? How quickly does it get to the 1st mark if just idling? Can you see it drop after it does, when the t-stat opens?
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
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924RACR · Posted: Sat Nov 13, 2004 12:26 am Post subject:

Another possible problem, how clean is the radiator inside? Feel for hot or cold spots, you might need to flush it out, may even need to remove it and have it cleaned (rodded out).
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Smoothie · Posted: Sat Nov 13, 2004 6:25 am Post subject:

And - Don't even bother trying it without a thermostat installed. Due to the path the coolant takes, you need a good thermostat of the correct type with the extra disc at the bottom. -And running with a thermostat without the disc is equivalent to going with no thermostat at all because to direct the flow correctly, when the thermostat opens that disc has to move down and seal the lower passage of the thermostat housing to direct the flow through the radiator. If that lower passage isn't blocked, the path of least resistance is directly down to the water pump and back through the engine without going through the radiator.

the thermostat should look like this -

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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

An often overlooked source of overheating is due to the y shaped pipe being plugged. This pipe runs from the front of the head, back to the heater valve and y's off as a bypass to the head. If plugged, it can cause poor or no circulation of coolant to the head.

Dennis
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