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Coolant overheating; Heater blows cold

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Coolant overheating; Heater blows cold

Old 04-01-2017, 12:53 PM
1st Gear
Thread Starter
Join Date: Mar 2017
Posts: 1
Smile Coolant overheating; Heater blows cold

I just bought a salvage title 06 Audi A3. I love the hatchback look. Added Raceland Coilovers and an intake for it.... Anyways, the day after I get my springs mounted I go outside to warm the car up. (That morning was icy cold) I let the car sit for about five minutes while I removed the snow. About 5 minutes down the road I get a "COOLANT" on my dash. I look at the temperature and it's 3/4 on the gauge. I turned back towards town to get some coolant from the nearest gas station. Somewhere along the line I noticed that my heater was blowing cold air. FYI coolant is a special type G12 for my car... Didn't know this at the time, but when I went to put coolant in the tank the tank was already above the min line. I thought that I would fill it up completely since that's what it was asking for. I slowly took off the cap. (should be pressurized, but mine wasn't too bad at the time) Topped the coolant off and proceeded towards out of town. Another 5 minutes later I have the same "COOLANT" popping up on the dash. I spoke with a friend to see if first, Does it have pressure? The cap may have been at fault. It wasn't the cap. Next he said that it looks like it might be the thermostat. That's a bigger do it yourself job, but I changed my thermostat by referencing
Flushed the coolant and changed the oil, just to make sure I didn't have a blown head gasket or anything. Drove the car for about five minutes and it was still doing the same thing. Heater blowing cold air and car would overheat after about 5-10 minutes. I took it to a professional who was convinced that I had an air block in the system. After a week of him toying with it he didn't get any further than I had. I looked at this other video
that gave me an idea that it might be the water pump. Big job for someone who is not experienced with cars let alone Audis. I ended up towing it to an Audi and VW mechanic who replaced the water pump and it now works like a charm. The problem with my water pump wasn't that it was leaking, but that the gear stripped so that it didn't rotate at the same speed of the belt. It would slowly turn, but once the belt speed was hire than idle the water pump wouldn't spin. Anyways, I'm glad I figured this out, and I hope that this helps someone out there.

Last edited by westibo; 04-01-2017 at 11:58 PM.
Old 04-02-2017, 10:39 PM
2nd Gear
Join Date: Jul 2009
Location: Colorado
Posts: 664

Awesome write up! Thanks for sharing.

I always recommend replacing the waterpump, thermostat and coolant sensor(s) at the same time so you don't have to work on an issue multiple times
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