Audi A4 Heater problems

[Pete K]

Hi,

I've been having various problems with my heaters. I'll give some background, as it may be linked to other issues.

Car had service, then a monthish later ...

About 2 months ago a pipe burst/split around the back of the engine, which caused the coolant to leak out and the engine management light (eml) to come on.
The garage fixed the pipe and changed the timing chain (as it was due) and also changed the water pump at the same time (as they said that they usually wear out (impellers brake) around the same time and it would save 4 hours labour). However, 50 miles later the eml was on again, the water temp gauge said 55 and I noticed the heaters were blowing luke warm.

They ran some diagnostic tests which showed a temp sensor failure. They said there is one near the back/top of the engine, which is simple to change and one in a pipe unit which is more work. They thought it was the latter, but checked the first as it was an easy job. This was leaking wax and when replaced (for free as it was new at service), stopped the eml and the temp gauge showed 90 - great.

The next day, you guessed it, eml on again and temp gauge at 55.
They ran the diagnostic tests again which showed a temp sensor failure so I booked it in for the other sensor. Once replaced, stopped the eml and the temp gauge showed 90 - great.

The next day I realised that the heaters were still luke warm (as they had been, on and off throughout all this). Arrgghh !
I tried to determine once more, what the exact symptoms were. I tried the heaters on LO to HI and low to full fan etc. At each setting, it would be hot sometimes and other times not. I then noticed that when I really revved the engine, it would belt out heat correctly. Sometimes this was just temporary, but it often cured the problem for some time (eg, for the rest of the journey (say 6 miles)).

While I have been deciding what to do, last Sunday, I drove off the drive in the morning and the Coolant light can on. The coolant was right down near the bottom of the reservoir. I filled it up with water and it's been ok since. Monday night I noticed a large wet mark under the car, but the reservoir seamed ok. I've just check now and it's just below minimum and there is a saucer size wet make on the floor (it's been parked 7 hours).

It seems to me that there is a blockage somewhere, that is getting cleared by revving it.
Could it have been a faulty water pump they installed? I suggested this to the garage and they now say it must be, but wouldn't that make the engine overheat? I'm loathed to change it and get billed for it if it still doesn't fix it.
Could it be an air lock?
An obstruction in the pipe?
Could this have caused the burst pipe and the temp sensors to break?

Sorry if this was abit rambley, but I wanted to give the full picture!

Anyone got any ideas???

Pete K

[Desdesigner]

That’s bloody interesting mate, I’ve got a 2002 Audi 1.8T and my temp gauge is rather iritic. Sometimes it reads 90 deg.c. Other times it doesn’t venture past 55 deg.c. I’ve also noticed a saucer sized wet patch on the ground under the block where the car had been parked.

I have suspected the temp sender or possibly the thermostat but I’m not sure. I haven’t owned the Audi long and the coolant is dropping slowly. It’s been suggested that I’ve got a leak somewhere in the heater matrix but I don’t know what to do as I am unsure of the total cost if taken to an Audi dealer.

The car runs fine, just I’m loosing coolant and I could change the temp sender myself if I knew it was that for definite.

I think we share the same predicament!

-Desdesigner

[Pete K]

Well, the heaters have been fine since the coolant dropped and I filled it up. It must have been an air lock all along.
Still seeing wet patches under the car but coolant level is staying put.

Pete