No Heat In Cabin

[miikeeyuk]

Hi all, I have a problem with my 2002 TDi Galaxy which started today. Drove to work this morning and realised half way that although the engine temperature gauge was sat normal at 90 degrees there was no heat blowing into the cabin. I noticed over the last week a humming noise coming from under the bonnet when i turned the ignition off, which lasted for a few seconds and that seemed to be getting louder as the days went by. But today i noticed there was no humming and no heat inside the cabin. Ive browsed the FAQ's on this site and I notice that others have experienced similar problems which has been caused in a few instances by the run on pump electric motor under the windscreen wipers failing. Does this sound probable given the lack humming after the ignition is turned off? also noticed that the engine temperature reached its normal position (90 degree) much quicker this morning.

 

Would certainly appreciate some feedback if anybody's experienced a similiar problem

Cheers

[Mirez]

The run on pump contributes to the heating system but its primary role is to prevent hotspots forming after the engine is turned off and to circulate heat to the rear heater. If it was failed (highly likely given you can't hear it anymore) then it certainly won't help but it should still get warm using the engines main water pump.

 

My number one concern would be that the primary water pump has failed and its been working using the electric pump only for the last x number of months/years, whats the mileage and do you have a history of when the pump was last inspected or changed? Because the TDI is so efficient then even without any pumps working it will generally sit at 90 providing its not being pushed or worked hard but of course the actual block temperature will be higher then that. As said thats a concern though, so don't worry that much at the moment but get the run on pump fixed ASAP as a precaution.

 

Its also worth checking the heater flap is moving in the cabin which allows the hot water into the matrix, if thats stopped then you'd also have the same symptoms - do you have heat from the rear heater?

[miikeeyuk]

Hi Mirez, thanks for the quick reply I certainly appreciate it. Ive owned the car for just over 7 months now and it didnt come with any service history other then old MOTs etc, so i dont know when or if the pumps been changed. The cars got 138k miles on the clock and this is the first problem Ive had with it. I did notice that the rear compartment heater only blows cold air which from memory its done since I had it, but I never thought that as a major problem. I was reading the FAQ's on how to remove the run on pump and replace the brushes which sounds fairly painless, but would the water pump be as easy or is there an easy way to test the pump is circulating water without removing it?

[miikeeyuk]

I forgot to ask, where is the heater flap located to test if it works?

[chrispb123456]

Hi there

All the flaps and doors are inside the heater unit, the flap/door motors can be checked with Vagcom for faults.

Any faults within the heater unit will almost certainly require removal which would involve removing dash.

As Mirez said there's a good posibility that the engine water pump impellor has broken off, also likely the booster heater is also not working and it's operation is also affected when the run on pump packs up, the rear compartment heater also relies on the run on pump to circulate the water.

You can check water pump impellor by removing thermostat

[miikeeyuk]

well the good news is that I managed to remove the aux water pump and replace the bushes by modifying a new set of alternator bushes from my local auto electrical garage for a quid. Put it all back to together and now the pump spins up nicely and sounds healthy again. Ive got heat back into the cabin, much hotter then before and also the rear compartment heater is throwing our hot air which it never did, so this seems to have done the trick. I'm still concerned the impella from the main water pump must be broken so ive got the car booked in for a new cam belt and water pump on Tuesday. I am right in saying the aux water pump main function is to circulate the water after ignition turned off to avoid hot spot damage to the block and not to be the main coolant pump?

[chrispb123456]

I am right in saying the aux water pump main function is to circulate the water after ignition turned off to avoid hot spot damage to the block and not to be the main coolant pump?

More or less correct. I would say to avoid hot spot damage to cylinder head.

You didn't mention whether your booster heater was working or not, (will only kick in if air temp is below 10deg approx) if it's not working you may notice a longer warm up time once engine water pump is changed. (Assuming it was knackered)