Heat problem.

[minny]

Following a timing belt exchange, where I swaped the the water pump and the termostat, the car has taken a long time to warm up, it was fine before.

I do get heat, including very hot heat, but it starts to get mildly warm around 20 mins and fully hot after an hour, stoping the car then going back it takes a while the warm up again. The temp gauage does not move, but after about an hour will go to 90.

I thought it was an air pocket, so today I tried the 'burp' the car, left it running for an hour, whilst doing so, I saw no movement of water in the expension tank, no bubbles, but more importanly the tank did not get warm at all, nor did the pipe going in to the cylinderhead which has the termostat on.

Hose to the radiator and heater matric both became very hot, I also could put my hand on top of the engine quite comfortably, it was also very warm, but not hot hot.

When I sqweezed any of the hoses, coolant would squirt into the expension tank.

Is this likely to be the termostat or water pump?

Other than taking a long time to heat up, that car drives beautifully and there are no other problems.

audi a4 1.9tdi Avant PD engine. 2000

[SpeedJunky]

I would still say thermostat.

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[Col]

I would also say that the new stat maybe faulty.

Another thing to check is the operation of the airflaps in the heaterbox, the temp one may be stuck in the cold position.

Also may be worth flushing the matrix.

[minny]

Yes, I've been reading up since and a bad pump seems to result in a car that over heats, mines cool, no heat out of the blowers, I get heat, and it doesn't demist, mine does when it gets hot.

[minny]

I would also say that the new stat maybe faulty.

Another thing to check is the operation of the airflaps in the heaterbox, the temp one may be stuck in the cold position.

Also may be worth flushing the matrix.

I don't seem to have any problems with the heaters.

[Col]

If you haven't done it, the coolant temp sensors are a known and common failure, it may not be running cool at all, just that the sensor is telling lies.

[Rob69]

If you have access to a half decent OBD diagnostic tool it should be able to tell you the temp sender output temperature rather than relying on the inaccurate dash gauge. I used VCDS measuring blocks and an infra red thermometer with a 'K' type thermocouple to confirm a dodgy thermostat last month. I taped the thermocouple to the radiator top hose and monitored that and the VCDS readings. I was getting low (mid 70's) coolant temp readings from VCDS and the thermometer, even though my dash gauge was reading 90.

[minny]

If you haven't done it, the coolant temp sensors are a known and common failure, it may not be running cool at all, just that the sensor is telling lies.

Yes, I've heard that too, I'm going on the fact it was perfectly fine before the timing belt swap.

But it's deffinately somehting to keep in mind.

[minny]

If you have access to a half decent OBD diagnostic tool it should be able to tell you the temp sender output temperature rather than relying on the inaccurate dash gauge. I used VCDS measuring blocks and an infra red thermometer with a 'K' type thermocouple to confirm a dodgy thermostat last month. I taped the thermocouple to the radiator top hose and monitored that and the VCDS readings. I was getting low (mid 70's) coolant temp readings from VCDS and the thermometer, even though my dash gauge was reading 90.

I actually do have VDS, the hose going into the thermostat was completely cold.

[Noony]

Have you bleed the system at the heater matrix pipe that exits the bulkhead? Sounds to me like air still in the system.
I have just had my heater matrix replaced and need to bleed mine as the heater just isn't as hot as it was before it went into the garage.