No coolant flow - interior heating not working

[Naseem]

Hi all, I haven't posted on here in a very long time, but thought I'd come back for some help....

Basically a I bought an A4 Avant SE 2L petrol 2005 in Summer 2011. The following winter I noticed that the interior heater stopped working. It just blew ice-cold air like if the climate control was set right down and the only way to get it slightly warm was if you rev it really hard. I took it to my local mechanic who diagnosed it as an airlock in the coolant system and managed to sort it out. Everything had been fine until for about a year.

I had noticed over the space of around 6 or so months that the coolant level dropped slightly below the maximum mark, but just passed this off as normal as it was very little.

About a month ago I noticed that the interior heating stopped working again, so took it back in for a check. First tried the airlock which worked for a couple of days. Then no interior heating again. Tried all the usual checks and then he did flushed the heater core (no gunk). Next came the thermostat and he realised that the thermostat wasn't working so replaced it, then again when he thought that one wasn't working, and then with a manual thermostat and still not working. The car then overheated. The cambelt and water-pump were due for a change anyway and that was the next job, but it still didn't help.

We'd both been reading up and calling around and apparently it's a common fault but majority of people seem to sort it after the heater-core flush and the rest with the water-pump replacement.

However, a few people still had problems and found that changing the head gasket fixed the issue. So head was taken off and sure-enough there were signs of a minor leak in to piston 1, hence the fractional loss of coolant over time. Head has been skimmed and gasket replaced.

We're both baffled now and can't figure out what might be wrong. He's asked a friend of his to take a look at it, so it's gone there this week. Hopefully he might be-able to sort something out, or at least make a suggestion.


Summary problems and solutions to date:

1. No interior heating- even revving the engine would only get it warm and as soon as foot is off gas so the heat stops too.
2. Noticed coolant level reducing very slowly over the space of around 6months.
3. At this point the engine was getting 90C and staying there without any other noticeable engine problems.
4. Local independent suggested airlock, and sorted it out - heating working
5. Few days after it's blowing cold again.
6. Bottom pipe to heater-core was cold
7. Flushed core and pipes - still no joy
8. Changed thermostat - started overheating
9. Changed thermostat again in case a dodgy one was sent - noticed water flow stopped at thermostat pipe
10. Tried a manual thermostat
11. Water pump and cambelt kit changed (was due anyway) - still overheating and no heating in interior
12. Head gasket changed - was a minor leak into piston 1
13. coolant checked and bled
14. No coolant to bottom of engine (?)

I even called up Audi to see if they might be able to advise - they can if I pay the £120/hr labour charge and get it looked at...

Anyone who's probably come across a similar issue I'd really appreciate any input.

Thanks in advance.

[runsub5]

Originally Posted by Naseem

Hi all, I haven't posted on here in a very long time, but thought I'd come back for some help....

Basically a I bought an A4 Avant SE 2L petrol 2005 in Summer 2011. The following winter I noticed that the interior heater stopped working. It just blew ice-cold air like if the climate control was set right down and the only way to get it slightly warm was if you rev it really hard. I took it to my local mechanic who diagnosed it as an airlock in the coolant system and managed to sort it out. Everything had been fine until for about a year.

I had noticed over the space of around 6 or so months that the coolant level dropped slightly below the maximum mark, but just passed this off as normal as it was very little.

About a month ago I noticed that the interior heating stopped working again, so took it back in for a check. First tried the airlock which worked for a couple of days. Then no interior heating again. Tried all the usual checks and then he did flushed the heater core (no gunk). Next came the thermostat and he realised that the thermostat wasn't working so replaced it, then again when he thought that one wasn't working, and then with a manual thermostat and still not working. The car then overheated. The cambelt and water-pump were due for a change anyway and that was the next job, but it still didn't help.

We'd both been reading up and calling around and apparently it's a common fault but majority of people seem to sort it after the heater-core flush and the rest with the water-pump replacement.

However, a few people still had problems and found that changing the head gasket fixed the issue. So head was taken off and sure-enough there were signs of a minor leak in to piston 1, hence the fractional loss of coolant over time. Head has been skimmed and gasket replaced.

We're both baffled now and can't figure out what might be wrong. He's asked a friend of his to take a look at it, so it's gone there this week. Hopefully he might be-able to sort something out, or at least make a suggestion.


Summary problems and solutions to date:

1. No interior heating- even revving the engine would only get it warm and as soon as foot is off gas so the heat stops too.
2. Noticed coolant level reducing very slowly over the space of around 6months.
3. At this point the engine was getting 90C and staying there without any other noticeable engine problems.
4. Local independent suggested airlock, and sorted it out - heating working
5. Few days after it's blowing cold again.
6. Bottom pipe to heater-core was cold
7. Flushed core and pipes - still no joy
8. Changed thermostat - started overheating
9. Changed thermostat again in case a dodgy one was sent - noticed water flow stopped at thermostat pipe
10. Tried a manual thermostat
11. Water pump and cambelt kit changed (was due anyway) - still overheating and no heating in interior
12. Head gasket changed - was a minor leak into piston 1
13. coolant checked and bled
14. No coolant to bottom of engine (?)

I even called up Audi to see if they might be able to advise - they can if I pay the £120/hr labour charge and get it looked at...

Anyone who's probably come across a similar issue I'd really appreciate any input.

Thanks in advance.

Have you checked to see if the temperature control valve is opening? This is the valve that allows coolant to circulate through the heater core. On C4 cars it was in the cowl beneath the windshield wiper mechanism. Don't know location on A4.

[maxim_s45]

Hey, I am sure you did that, but just to check, did you read A/C errors? No flaps errors?

Did you replace the heater core? Someone used this magic leak stopped on mine and it let approx 5% of flow to go through...