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    Thread: !Why does my overflow tank bubble?!

    1. 10-10-2001 06:41 PM #1
      I have an 86 GTi 1.8 8V and my water temp. keeps going from hot to normal and if I open the cap to the over-flow tank it bubbles out. It seems like its coming out from the bottom of the tank. Do I have a crack somewhere? I think I'm losing coolant too. Whats the problem here? Where do I start? Any help would be greatly appreciated. - Andy

    2. 10-10-2001 06:48 PM #2
      You might have a bad thermometer switch that controls the fan. I'd would check that first before looking at the radiator. If radiator, you could have a small crack that is hard to check, happen to me before and didn't realize how bad it was, almost seized my engine.

    3. 10-11-2001 12:18 PM #3
      anyone else?

    4. 10-11-2001 12:22 PM #4
      check the seal on the cap to the coolant over flow tank. there should be a seal in there, and if it is cracked that could be the cause of the problem. from what i understand the seal builds up preasure, and thus does not allow the coolant/water mix to boil. if it is cracked, the preasure is going to be lower, and it will boil (which would explain the bubbles) hopefully this is the sourse of the problem, simple as replacing the rubber gasket on the overflow tank cap.
      PS. never open it while it is hot read post below

      [Modified by ChipGTi, 12:46 PM 10-11-2001]

    5. Member
      Join Date
      Nov 6th, 2000
      2012 A3, 2015 Q5
      10-11-2001 12:41 PM #5
      Yeah and NEVER open your tank when it's pressurized, if you squeeze the hose and it's firm, wait until it softens up again, then open it.
      Take it from someone who learned the hard way...
      - Jack
      Gentlemen, you had my curiosity. But now you have my attention.

    6. 10-11-2001 12:45 PM #6
      you have to wait until your engine cools down to open it. because it will bubble over if you unscrew your lid while your engine is hot, nothing is broken, thats the way it is on all cars.

    7. 10-11-2001 02:55 PM #7
      I think I need a water pump caues thats where its leaking from. How hard is this to do?

    8. Banned
      Join Date
      May 16th, 2001
      10-11-2001 02:57 PM #8
      Releaseing the pressure in a hot cooling system causes the water in the head (the hottest part) to boil and blow steam as bubbles, the head can distort causing the gasket to fail, you also risk an air lock in the system which will also blow the head gasket.
      Pressure test the system to look for a leak.

    9. 10-11-2001 03:13 PM #9
      It's leaking from my water pump...I just found out. How hard is this gonna be to fix

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