Hello all,

We have an 2005 Audi A4 that has started to overheat. Here is what happens. We can run the motor on the driveway and the temp gauge remains at 'N'. We can run the heat and everything appears to run fine. However, if we take to the road, within 1 mile the gauge rapidly rises and we hit 'H' within seconds. Im assuming that's because the thermostat has opened.

I have noticed the following. When the car is at 'H' the radiator is barely warm to the touch. Therefore, I suspected the coolant pump. So I loosened the cap on the coolant pump while at 'H' and heard a distinct pop as the pressurized tank released its vacuum- a sign that the pump is working to some degree. The tanks fluid is also hot so fluid is circulating.

The top radiator hose is hot and the bottom appears cool.

Any ideas?

Thanks much.

 

You most likely either have a clogged coolant system or a bad water pump. The "pop" you heard isn't an indication that the pump is indeed working. It was caused by a pressure difference. As the coolant heats up it begins to expand, causing pressure to build up within the system. When you open the overflow expansion cap, the pressure is suddenly released.

You see the sudden "jump" to H when driving because the engine is under light load while idling in your driveway. Once you begin putting moderate stress on the engine (heat) it will rely on the coolant system to cool itself off.

Based on the information provided, I'm speculating your water pump is going. Either it's free-wheeling or the impeller has failed completely. You will be able to tell this if you have no flow coming from the top radiator hose. Significant damage can and will occur if you drive your car with this condition.

 

Thanks Nebuch. I too am now leaning towards a bad or partially working pump. I did some research on a DIY replacement pump but it seems beyond my skill-level.

Any ideas on what Ican expect to pay? We had the car 'de-sludged' last year at the Audi dealership and that cost us $2,000 (we did not have good service records so had to pay full price). Not too thrilled with Audi's right now.

 

If you take it to a dealer for water pump service (You might as well have the timing belt done as well since you said the service records are non-existent) you're looking at around $1500.

To be honest, I think an Audi timing belt / water pump job is more intimidating than it is hard. It isn't a first time job for a first time DIY-er, but with some general car knowledge and patience it can be done.

 

Hmmmm - I am tempted because Ive got a fair bit of experience on other car issues; replaced a clutch in an MGB, replaced a water pump, replaced carb and headers etc. Its just the whole timing belt issue that intimidates me. Im used to fan belts and engine simplicity. That and the fact that there is zero wiggle room in the engine bay. Im tempted.

Perhaps after I call the dealer tomorrow and they tell me $1500 to replace a $50 part I will suddenly get 'brave' . Thanks

 

Zero wiggle room? You have to take the front of your car off to get to the water pump!

I think you have the skill set to get the job done. Give them a call for the insane price, and then start reading around the DIYs and you'll be ready to go in no time!

 

Ouch - take the front off? It gets better.

I will give the dealership a call in the AM and report back.

I just watched a YouTube video of the process and my eyes began to glaze over. Im form the old school brand of mechanics.

Thanks for the vote of confidence I will let you know which way I go.

 

I was in the same boat as you. I have enough knowledge that I could probably handle changing out the blet and pump myself. In the end I figured parts were going to run me $300 to $400 and would take me two days to complete. I called around and found an independent shop tha quoted me just over $1k to do the job. In the end I decided that was $600 well spent to avoid potentially getting in over my head. The final bill ended up being about $950 which made me even happier. I agree that it sure sounds like you could handle this yourself if you want to avoid the labod cost.

 

Hi all,

UPDATE: We called Barrier Audi (our local Audi dealership) and they quoted $825 including parts. I think that's pretty reasonable after reading whats involved. I guesstimate it will cost me $350-400 for parts and tools to do it myself. So $400 extra to save me time and effort - I think that's a pretty good deal.

Audi also mentioned we wont need a new belt because that was replaced last year as part of the de-sludge process they performed on the car.

Thanks all.

 

$825... nice deal! Especially from a dealer, I'm shocked.