ENGINE WILL NOT HEAT UP IN WINTER, OVERHEATS IN SUMMER.

  • Tiny
  • FORUM720
  • 1994 Audi 100
  • 185,000 miles

Engine will not heat up in winter, overheats in summer.

Hey all, I drive a '94 Audi 100. In the dead of winter, I can start my car, and as long as it is sitting idling the engine will SLOWLY warm up--but rarely to full running temp. Once I start driving, engine temp quickly falls to near cold. Heat blows when engine gauge is warm (leading me to believe it's not a heater-core clog). Side note: Cardboard in front of my radiator seems to help it stay warm for a bit longer.

In summer, car will struggle to stay at running temp and want to overheat. When it starts overheating, heat blows VERY hot.

If it was just one or the other, I would pin it at bad T-Stat in a minute, but since it is both I am stumped. Don't think heater-core is clogged as stated since heat does blow eventually. Come to think of it I don't remember the last time I heard my fans kick on though. Clogged radiator? But this wouldn't explain my cold engine in winter. Possible weird T-Stat? I hope not as a T-Stat in an Audi 100 is a pain to get at. Side note: My oil pressure gauge likes to max out while motor is under power--no known cause. Thanks in advance!

Tuesday, April 10th, 2012 AT 11:36 PM

7 Answers

  • Tiny
  • ASEMaster6371
  • Expert
  • 25,502 posts

Change the thermostat. Get the radiator power flushed. You have a circulation issue and if you dont adress it, you may damage the head gasket.

Also, have the water pump checked. Impeller failure happens althought it is not common.

Roy

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Tuesday, April 10th, 2012 AT 11:41 PM
  • Tiny
  • FORUM720
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Thanks for the fast response Roy. I know Audis are notorious for bad coolant systems, and I am definitely mechanically inclined, this dual problem just has me stumped. Thanks for the advice, I'm thinking I'm dealing with 2 problems here at the same time. Someone said bad water: antifreeze ratio could be an issue, but it's hard for me to imagine it being this dramatic? And wouldn't an impeller failure allow me a warm engine in the winter?

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Tuesday, April 10th, 2012 AT 11:45 PM
  • Tiny
  • ASEMaster6371
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No, not a water issue at all. Yes, somewhat with the impeller. You are heating only portions of the motor.

Get this stuff checked. You dont want to damage the motor.

Roy

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Tuesday, April 10th, 2012 AT 11:47 PM
  • Tiny
  • FORUM720
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Do you recommend a back flush? I hear of these do-it-yourself home kits from Autozone you use a garden hose with--any opinions? And if back flushing, obviously putting in a new t-stat makes sense since it would need to be removed. I love Audis, but honestly who mounts a thermostat behind a timing belt?

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Tuesday, April 10th, 2012 AT 11:55 PM
  • Tiny
  • ASEMaster6371
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The flush I am referring to is done by a shop with acid and high pressure. Home kits never work.

Find a good radiator shop and get a bid.

Roy

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Wednesday, April 11th, 2012 AT 12:00 AM
  • Tiny
  • FORUM720
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Cheers!

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Wednesday, April 11th, 2012 AT 12:03 AM
  • Tiny
  • ASEMaster6371
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Roy

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Wednesday, April 11th, 2012 AT 12:03 AM

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