Heater not very hot

[Alkurtz]

Before I start getting stuck in, thought I'd ask if anyone has any tips on why the heater doesn't heat up very well. Maybe the / a valve isn't opening on the matrix properly... Any experience of this shared will be appreciated..

[M2ki]

Air in the cooling system. Foam from flaps have blocked the matrix. Or beacause missing foam from temp regulating flap, air is not going through the matrix and goes directly to vents.
There are no valves on this system, matrix is always at maximum coolant temperature.

[montyrs2]

Hi All, i'm having a similar problem. The car gets up to temperature fine, although does run a bit hot as I fitted a hotter thermostat (not sure why but it's coming out soon). So it gets hot and when the engine revs build the heater blows lovely and hot. Pull up to idle and it's stone cold straight away. I've bled the living *&^% out of it,

To add some history;
Matrix was replaced when I bought the car approx 4 years ago. I've never used rad weld etc and passenger carpet is dry.
Foam replaced/re done whilst it was apart.
New expansion tank and cap
I've not changed the water pump in my ownership
Thermostat is clearly working just slightly too hot (will change)
Doesn't appear to be leaking anywhere.
If I drain and refil and re bleed it appears to work well for a short time then reverts back to cold when engine is <3k rpm.

I was thinking of doing a new thermostat, water pump (any suggestions? Euro do them cheap.) flush matrix, maybe do the metal pipe take off on back of engine then refill and bleed and see what it does?

Any other ideas?

[Antsa]

I've been having the exact same problems for quite some time now. Every time it stops blowing hot and I bleed the system by raising the reservoir and slightly take off the matrix hose, air comes out. So it's pretty obvious that air keeps entering the system. But without visible coolant leaks that seems very odd. My next step will be pressure testing the whole system and testing every connection with soap and water for leaks.

[Greg_S]

I was going to suggest changing the expansion cap but you have done that. Are you needing top up the fluid levels often? It does sound like air is getting in somewhere.

[newsh]

A couple of things to think about.
I’ve had 2 water leaks that were difficult to diagnose.
The first was from the bottom of the expansion tank, there was a crack where the hose joins on. This one cost me the head gasket when I got stuck in heavy traffic and it boiled up.
The second was a pin hole in the small core plug at the back of the head.
Then there was also the bottom of the rad where the bracket for the rubber mount is soldered on and the good old plastic spigot at the back which feeds the heater..

If there’s hot water getting round when revs are up perhaps the water pump impeller is loose.

[montyrs2]

A couple of things to think about.
I’ve had 2 water leaks that were difficult to diagnose.
The first was from the bottom of the expansion tank, there was a crack where the hose joins on. This one cost me the head gasket when I got stuck in heavy traffic and it boiled up.
The second was a pin hole in the small core plug at the back of the head.
Then there was also the bottom of the rad where the bracket for the rubber mount is soldered on and the good old plastic spigot at the back which feeds the heater..

If there’s hot water getting round when revs are up perhaps the water pump impeller is loose.

I need to be more scientific about the water usage. So far I had attributed slight drops with getting air out but that is looking less likely now. Expansion tank is new, genuine, cap also . Radiator is aluminium, i'm not aware of any leaks, but I will check again. But surely if it had a leak then it would still blow hot, just losse coolant over time?

I've driven it to work all this week so will check coolant etc this weekend when I get some daylight.

I did wonder about the water pump, it's the one item i've not changed. Has anyone used the Circoli ones from Euro? They are cheap as chips and not that hard to change.

[LSG]

Id been losing coolant for some time and stupid as it sounds its hard to pin point them some times. Mine was the water pump. So it had a new Audi one fitted along with the belts ect. I don't know circoli to be fair although Id be careful with what brand water pump you get coz they maybe cheap as chips, but could cost you a lot off money and grief if it did fail. Hope you get to the problem soon fella best wishes Lynn

[newsh]

If you’re doing the water pump get one with a metal impeller, IIRC the plastic ones don’t last

[montyrs2]

If you’re doing the water pump get one with a metal impeller, IIRC the plastic ones don’t last

Any suggestions for places to get a new pump. TPS can supply a genuine but they think it has a plastic impeller.

[montyrs2]

Hi all, so I have done a water pump and new thermostat. It isn't leaking water. I bleed it through, it warmed up blew hot air and worked a treat on my drive. I've used it for work today and it blew hot the whole way until I stopped at a junction and the revs dropped at which point it blows cold air?

Any ideas, its driving me nuts.

PS i flushed the whole system out with the hose, everything ran clear and free.

[rynaqui]

I have the same problem with mine so I am going to gather and change the pump, thermostat, belts and the interior heater matrix. Going to be a massive job but hopefully will solve it.

It's a pain to locate the problem for sure.

[M2ki]

Expansion tank cap?

[montyrs2]

Expansion tank cap?

Changed, new expansion tank, heater matrix is only a few years old. The odd thing is how it runs so perfectly when the rpm is above idle. In other good news the air con worked well yesterday.

[Greg_S]

Could it be a faulty thermostat if it’s only doing it when the engine is cooler?