Heating does not work properly (slow start)

[smarthomes4u]

Hi all, my first post here. thank you.

I have an A4 saloon (B8, 14 plate).

Its heating does not work properly (start very slowly). Normally it takes 10mins to get mild warm air if it's a warm day or 20mins if it's a cold day (4degC ish). Defrost does not work properly either.

From a cold start in the morning (cold outside), at about 4mins when I get to my boy's school, engine temperature on dash gets to normal, but the coolant tank is still cold. At about 10mins when I get to my girl's nursery, the coolant tank get warm (not hot). Then it takes nearly another 10mins before warm air blows out.


Engine temperature does not drop during my trip. it stays at the normal 90degC, no overheating

I had the coolant tank replaced a few weeks ago as the old one leaked, but not sure it's related.

Really frustrated, not sure it's airlock or stuck open thermostat.

[fourringsrus]

I think you may have answered your own question, you had a new coolant tank fitted recently, so it could well be in need of a system bleed.
As for the thermostat, that is also feasible, when was it last changed (maybe when the cambelt was done last, or not )
Is the car petrol or diesel, some diesels can take forever to warm up at this time of year, has the heating issue only recently occurred or has it been an ongoing problem.

[smarthomes4u]

Thanks mate.

It's petrol. As far as i know the thermostat is the original one and never replaced. (This car has a chain).
The heating problem was noticed when weather became cold about one month ago when i tried to warm up. The colant tank was replaced about 7 weeks ago, when the weather was not cold.

Thanks again.

[smarthomes4u]

popped into a garage nearby while the engine was warm and heating was working (I had a long trip before this)

VAG plug in check did not show anything. After hearing 10mins to get heating or 20 mins on a cold day, the technician who claimed to work for VW dealer before, hesitated for a moment and then tried to persuade me that my car does not have any problem. (charged 24 quids for this inspection)

However, I am not convinced, at least, last winter, there wasn't such a long process to get heating and defrost


it seems that I will have to take it to someone and let is cool down overnight before it's inspected and tested

[MatC]

Hi, that sounds exactly the same problem I am having with my 2015 B8 2.0TDI. I have found myself turning the temperature guage up to 26 to get some warmish air out. I haven't had anything changed - all original coolant tank, thermometers, etc. I was beginning to think its my imagination, but I just jumped in my wife's car in the frost this morning, and it was blowing out hot air by the time i had started it and scrapped the windscreen, with it set to 22.

[MatC]

I've just seen another post about disabling an aux heater - its got me wondering.

[smarthomes4u]

All, an update.

The garage near my home had a check and said the water pump leaks and is weak.

They claimed that a replacement pump has to be Audi's because it has this and that. And 5 hrs work. So they want to charge £650 for pump replacement.

However , clickamechanic or whocanfixmycar both quote around £250.

Really wondering what's thr next step. Can i trust clickamechanic or whocanfixmycar?

[Passata]

I have just had the thermostat and waterpump changed on my A5 2.0 tfsi engine as it was doing exactly the same as your car,but mine was throwing a CEL light.
The thermostats on these are basically an electrically controlled rotary valve and are very prone to failure according to my TPS guy.They have been revised several times apparently and with the waterpump it costs £280.00.
I had a independent garage replace mine and it is a bugger to do as it is under the inlet manifold driven by a small belt off the back of the engine,they told me that Audi book it as a 3-4 hour job.
I was lucky as the garage I used did it for mates rates and the total was £480.00 including a complete coolant flush.
I asked for the old thermostat/waterpump housing back so I could dissect it to find out why it had failed and to my amazement all that was wrong with it was the little brass gear on the motor spindle that had come off.
I also found a small crack to the housing as it was leaking ever so slightly.
The revised waterpump has now got a metal body as opposed to the plastic original so the cost that you have been quoted is about right.
I wouldn't take the clickamechanic or whocanfixmycar quotes to seriously if I was you because of the cost of the parts alone is more than they have said for the whole job.
Hope this is of help to you.

[smarthomes4u]

Further update if it helps others.

Had the auxiliary pump (electric) replaced - the auxiliary pump drives coolant circulation through the heater core . It was quite cold this morning (2degC outside, engine temp steady at 4 mins and heating came on at around 8mins). To me, it's much much better than before.

Nothing else has been replaced

[Renars]

Further update if it helps others.

Had the auxiliary pump (electric) replaced - the auxiliary pump drives coolant circulation through the heater core . It was quite cold this morning (2degC outside, engine temp steady at 4 mins and heating came on at around 8mins). To me, it's much much better than before.

Nothing else has been replaced

Yes, the aux electric pump circulates coolant through heater matrix while car is warming up.
Is this same pump garage identified as weak and leaking ?
If main pump was leaking dont ignore it for too long...

[smarthomes4u]

No, not the same garage. The first one said pump leaks and is weak, but i have never had a chance to check with them which pump due to xmas closure. Their diagnosis is free but the charge for pump replacement is too much.

So i went to the 2nd garage. They said the main pump is all good. Their charge for the auxiliary pump replacement is only £202, compared to £646 quote from the first garage.

[Renars]

No, not the same garage. The first one said pump leaks and is weak, but i have never had a chance to check with them which pump due to xmas closure. Their diagnosis is free but the charge for pump replacement is too much.

So i went to the 2nd garage. They said the main pump is all good. Their charge for the auxiliary pump replacement is only £202, compared to £646 quote from the first garage.

Yes aux pump for heater is cheaper and easy to change.
VCDS fault scan would pick up failure of this part and saved you some time and guessing.

[smarthomes4u]

Yes aux pump for heater is cheaper and easy to change.
VCDS fault scan would pick up failure of this part and saved you some time and guessing.

I was hoping so. I went to 3 garages totally. two of them did VAG plugin and did not see any related error codes.

[smarthomes4u]

sadly, the no heating problem has not been solved despite my feeling a bit better just after the axillary pump replacement.

it still takes ages to get heating (warm air) if parked and idle in the morning. Slightly better if driven on road.

When parked and idle, heating turned on, blown cold air and I touched the two hoses connecting to the heater core, one is quite hot and the other is much less warm. Apparently not enough coolant flow/heat into the core?

When heating comes on, if I put fan on a higher power, air become less warm or not warm.

Still parked, if I rev the engine to 3000 or 4000 rpm, warm air comes out very quickly, even if fan is at full power.

Now I believe more and more that it's trapped air or clogged heater core. Have booked with another garage for a flush and bleeding of the heater core.

[fourringsrus]

I feel it would be prudent to properly clean through the microbore of the matrix or potentially be prepared to renew the matrix

[smarthomes4u]

Got car back from technician. He said that flush was done, however when they tried to purge compressed air through, air came back. Technician said the matrix is blocked. A big bill to take.




I feel it would be prudent to properly clean through the microbore of the matrix or potentially be prepared to renew the matrix