Car overheating when accelerating but cooling when I slow

Sebastian Dangerfield

I was driving on the m50 and noticed the thermometer gauge start to slide up so I started to slow as I pulled into the hard shoulder. As soon as I got below 50 miles an hour the needle went back to the middle position again. I thought it was maybe an anomaly and went back onto the road and the same thing happens - the needle starts to go right when I go over 50, but comes back once I slow down again.

As I tried to get it somewhere I could park it, the point at which it was moving seemed to come down to 40, at which point I parked it up.

Anyone know what this could be? 03 Audi A4, 2.0 auto. I had my car overheat before due to a coolant leak, but there was a hole in the coolant pipe which was pretty self explanatory. Ill get it to a garage, but wanted to get an idea of what it might set me back.

Cee-Jay-Cee

Sticking thermostat. new thermostat needed and it's a simple fix soshoukdnt incur big labour charges. Any competent mechanic can do it, no need to go to Audi.

Sebastian Dangerfield

Do you think it would be safe to drive to the garage, or would a tow be a better idea?

H3llR4iser

Sebastian Dangerfield wrote: »

Do you think it would be safe to drive to the garage, or would a tow be a better idea?

Depends...If you start from cold, it takes quite a few minutes for the engine to even reach running temperature (especially if the thermostat sticks in the open flow position). It really depends on how the thermostat is misbehaving - it looks like it is opening if the temperature goes down at all (meaning, coolant is circulating through the radiator). Just keep an eye on it and you should be fine if it's not a long drive.

biko

I assume you checked coolant level this time and it was ok?

You can still drive (slowly) to a local garage, just don't let it overheat.

Sebastian Dangerfield

biko wrote: »

I assume you checked coolant level this time and it was ok?

You can still drive (slowly) to a local garage, just don't let it overheat.

I actually didn't (I was in a hurry) but theres a warning light that comes on when the coolant is low, and that didn't come on. I did top it up a couple of weeks back.

If it was the coolant though, would it still go back to normal when I slowed down?

Found a garage within 5 mins drive so Im just gonna take it up there myself. Thanks for all the replies.

H3llR4iser

Sebastian Dangerfield wrote: »

I actually didn't (I was in a hurry) but theres a warning light that comes on when the coolant is low, and that didn't come on. I did top it up a couple of weeks back.

If it was the coolant though, would it still go back to normal when I slowed down?

Found a garage within 5 mins drive so Im just gonna take it up there myself. Thanks for all the replies.

Always check the coolant (and oil) level periodically, don't rely on indicators to tell you something is wrong - normally, when they finally do it means it's been VERY wrong for quite a bit

The fact the temperature decreases when you slow down is a bit curious; It would suggest the thermostat is stuck halfway, so the radiator generates some cooling, but not enough at higher effort levels. Or, as it was suggested, that there isn't enough coolant...

hi5

I had that problem before, turned out to be blocked/old radiator.
High revs at high speed meant extra heat from the engine but no extra cooling from the forced outside air.

kyote00

Turn on the heater full heat to help keep things cool...

Might also be the water pump

Sebastian Dangerfield wrote: »

I was driving on the m50 and noticed the thermometer gauge start to slide up so I started to slow as I pulled into the hard shoulder. As soon as I got below 50 miles an hour the needle went back to the middle position again. I thought it was maybe an anomaly and went back onto the road and the same thing happens - the needle starts to go right when I go over 50, but comes back once I slow down again.

As I tried to get it somewhere I could park it, the point at which it was moving seemed to come down to 40, at which point I parked it up.

Anyone know what this could be? 03 Audi A4, 2.0 auto. I had my car overheat before due to a coolant leak, but there was a hole in the coolant pipe which was pretty self explanatory. Ill get it to a garage, but wanted to get an idea of what it might set me back.

Fundthementals

kyote00 wrote: »

Turn on the heater full heat to help keep things cool...

Might also be the water pump

Agreed - that generation of VAG water pump weren't known for their longevity. Impeller is probably slipping on its shaft.

Sebastian Dangerfield

Had the water pump and radiator replaced last year so hopefully not that!

seagull

3 most likely candidates
- thermostat
- water pump
- radiator

Sometimes a sticking thermostat can be sorted by taking it out and putting it in boiling water.