A3 1.8T 2003 Overheats when driving over 2000rpm, then loss of power

[rustopha]

Hi all, i have searched the web and these forums, but cant seem to find a match for the fault my car is suffering.
I only have a small drive of about 7miles per day to and from work, and if im in traffic for the duration, i dont actually notice any problems.
but when i get a chance to open up the power, i notice that the car seems to get very warm, and instead of it sitting happily on 90 degrees, it creeps up quite rapidly up to 120 degrees, setting off the overheating warning.
ive had a recovery driver go over the engine, and he confirmed he thought all was ok, oil good, water good, and water pump seemed to be working as do the fans.
i then had an auto electrician connect it up to his computer, and he came up with no faults. but he was curious enough to help investigate further, and we took it for a drive.. and he concluded that, what i was describing as loss of power, may be something to do with the clutch, as the engine seemed to be revving alot higher than the speed we were travelling (kind of like, riding the clutch).
now the only thing to note is, that when the engine is cold, in the morning or when i leave work at the end of the day, there is no evidence of loss of power, as the acceleration seems fine, but as soon as the car reaches its 90 degrees, at that point the loss of power begins to be evident, and the longer i drive it, the more it is evident, and with a hill to go up at the end of my drive home, if the car is too warm, i dont seem to have very much power to get up it without changing gears all the way down.. but then with the excess revs, the car just hits the 120 degrees and the warning light and bleeps start.
i was wondering if anyone on here, might have an inkling of an idea what might be the cause, as im not in a postion to be fleeced with exploratory hourly rates... so any advice would be massively helpful please,

oh, and also, another observation is, that when the car is either sat just ticking over, or in slow traffic, poodling along with just first and second gears the car seems happy at its 90 degrees, you'd never know there was a problem, and even when stationary and revving to 2-3000 revs for 10-15 mins, it still is sitting happy at 90 degrees.

[davemk]

sounds like ur thermostat or water pump.

Thermostat works on 2 cycles. one smaller cycle which allows a smallish amount of water cooling then the second cycle kicks in when the temps get too high and pumps more water through and cool down to regulate.

When the thermostat sticks, it doesnt open the second cycle, which is why normally you are ok idling or on a short drive as the first smaller cycle is fine for that and the second is only needed on a longer drive with increased engine temps.

[rustopha]

thanks for the reply davemk...and would a thermostat or water pump problem, also be the cuplrit for the loss of speed...

when the car is stationary and in neutral, i can rev the thing like crazy, and the temp doesnt go over the 90 degrees mark at all. but when its driving, and the engine is warm, the revs dont seem to the match the speed (if that makes sense), and then the temp goes rapidly up.

If i clutch down and rev while moving it seems all ok, but gears engaged and it seems that theres alot more revs than the speed im achieving.

[davemk]

it can make it feel sluggish, definately. When ur thermostat is screwed it and force ur car to run a rich mixture to help cool the engine which will make it drink fuel and run sluggishly.

i would try the thermostat first as they are cheap. £7-12. Make sure once its changed u go for a long drive to let the car sort itself out again.

[AwesomeSarah]

Sounds like the water pump to me
What happens is part of the water pump breaks off
When the car is ticking over , or going slow , the water pump that is left can keep pace
But open it up , the water pump can`t keep pace
So that is when the temp creaps up
Sorry
Sarah

[stevewicks]

I have exactly the same problem, fine poodling around town or sat in traffic, but when I open her up she hits 120 degrees and I get major loss of power.

Having the waterpump and timing belt changed on Monday, at the cost of £400 I might add.

Hope after that expense she runs sweet again.

Steve

Oh, i should add that the expansion tank stays luke warm no matter how hight the temperature guage shows, and code 51 on the climate control shows 75 degrees even when the shows from 90 degrees to 120 degrees. Water isn't pumping into the expansion tank either.

Any ideas?

I don't really want to change the water pump and timing belt if it's not the pump.

[gaz333]

fore sure it will be the water pump

[mcgyvah]

Did you find out what the problem was?
My car is a 2003 1.8t A3 FWD. I am having a similar issue.
Issue:
The car heats normally to about 90 on the gauge.
If I let it idle it doesn't overheat.
When I drive , after about 20klms, the temp increases rapidly (30sec) to 110. Stays for a few minutes then drops back to 90 ( in under 2 seconds).
then about 2 mins later it will repeat this cycle.
During the cycle the A/C will stop cooling and then start again ( although this does not seem totally in sync with the rise & fall of the temp gauge).
The center console temps are (coolant temp49c)=121C (engine temp51c)=75C.
Sometimes the temp will drop if I return to idle, sometimes it will not.

INFO:
Both fans working, appear to turn on and cycle as required.
water pump replaced approx. 10,000k ago with timing belt.
Radiator, reservoir bottle & cap replaced about 8000klms ago.
new larger radiator fan replaced 2 months ago due to it wasn't coming on and overheat warning in traffic. This fixed the overheating heating problem at the time.
The new problem started last week, mainly noticed because its hot weather and the A/C compressor is turning off
Thermostat replaced today. If anything it made it may have made it worse. Doesn't drop back to 90 as often and now sits at about 115 degrees.

Seems like the same issue this guy has. my gauge does the same thing.
Audi A3 2002 1.8T overheating - YouTube

Any input much appreciated.
Cheers

edit ** I forgot to mention that it sometimes misses a little if I accelerate when its at 110C

[mcgyvah]

Further to the above I just sat in the car for a long time and watched it.
I noted that-
The climate control temp 49c showed each degree of rise up to 121C
The gauge just jumps as if it only has 90 & 110.
The thermo fans only came on at high speed and were unable to cool the coolant according to gauge and 49c reading.
The Bottom cooling hose is hardly getting warm. (I got a tiny bit more air out by force feed coolant down the return pipe until it came out the reservoir backwards)
Symptoms lead me to believe I may have more air in system or.... faulty pump.. which is just out of warranty....
Any other suggests ?

[mcgyvah]

I hate reading these forums and so many people do not return & list their SOLUTION, so here it is
The Hose Thingy Solution

so I decided it was either an airlock or the water pump.
I have been going all day and didn't think there was any air left... trying everything I could find on how to remove any air.
Let it sit overnight and tried it this morning, still same issues.
While sleeping I came up with the idea- so I connected a garden hose to the bottom drain valve on the radiator and forced in water until it came out the top reservoir... what do you know ...bubbles.

Tried car but bottom radiator hose still wouldn't heat up.
Noted temp drop when stat opens several times as car heated.
Tried hose thing several times, being sure to limit the pressure so as to not run cold water into engine (please note here that the bottom of the radiator was cold, ie cold water. I don't think anyone should try this if it was hot).

After doing the above, the bottom radiator hose and radiator started getting warmer, the 49c moved between about 89 & 99 with the fans coming on at lower speed at 99 as required.
Car did not get over 99. Test drive all good, WOOHOOO!!. SO glad I don't need another water pump.
Clearly just a persistent airlock. For everybody out there keep trying, I was almost ready to start pulling off the timing cover and pull out the pump.

Thanks to everyone for all the.. mmm....input?