924Board.org

sheffield924 · Joined: 16 Jun 2005 Posts: 2 Location: sheffield england

Can anyone tell me what the recessed hole is on the expansion tank. Its located just behind the pressure cap. Everytime my engine gets hot this hole slowly fills up with coolant and drips out. My car is a 924n/a Uk spec 1981 [/b]

teo · Joined: 07 Sep 2001 Posts: 637 Location: Hungary, Europe

That's what it's for, to release pressure when the system is overpressurized. There should be a plastic hose that goes from the hole for aout 50-60 cm down to let the water out under the bumber or so.

Edit: OK, didn't read it carefully, that's one is not for that, but there should be another like above. The one you ask is there to perform magic when needed...

sheffield924 · Joined: 16 Jun 2005 Posts: 2 Location: sheffield england

.[The hole im talking about is not the one under the pressure cap with rubber pipe leading to the bumper its on top of the expansion tank at the side of the cap its about 10mm diameter and 20mm deep and seems to be sealed on the bottom inside the tank]

emoore924 · Joined: 13 Apr 2004 Posts: 2822

I've hear various stories on this one but my understanding is that it is an engineered bit that is put there so the tank can take pressure without bulging or cracking. That's a weak spot and they chose to relieve it by putting that little depression there.

Or much more plausible is that it could be your car's belly button. You have an "innie" car.

If yours is getting coolant in it, you have a crack somewhere that shouldn't be. Better be getting a new tank.