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[BenjieH]

Hi Everyone, having some issues with the miggy (again!) this time the heater will start blowing hot air, (Climate on Hi and not auto,) then 5 seconds later will blow almost cold air, i've checked the fan and everything i can see under the bonnet but no change, it has just had a coolant change and flush.

Any help would be most grateful as always. 

Ben

[martin42]

Was it ok before coolant change?

[BenjieH]

Yep no issues before the change

[RobG]

Airlock

[JamesV6CDX]

PM sent.

It's had a head gasket and water pump too and has been run up to temp with cap off and heater on

Can you a) see if both matrix pipes are hot and B) do a climate reset as per info on here?

[BenjieH]

James PM answered 

Have done the reset, auto and off held

[BenjieH]

Hey everyone,

Some more info on this one, the rear blowers are blowing hot air, but the front ones are still blowing cold, i have completed the reset and 'burped' the system, i've taken her on a run and she's running at 85-90C until i turn on the heater then she drops down slightly, i am trying up upload a picture to show the engine bay and which pipes are hot and cold.

Thanks Ben

[BenjieH]

Blue are pipes that are cold, and red are pipes that are hot

[cd 2.2]

Well the blue pipes are your aircon pipes iirc

The top hose you have in red is your top radiator hose coming from your thermostat .... Does that get warm gradually or all at once while your getting it up to temp?? It could be a dodgy thermostat causing your  problems 

Sounds like a blocked / air locked matrix to me ... the hose on the very bottom left of your picture may have an airlock in it, I found mine got the airlocks out of it's own accord and I just had to top up a couple of times before it was fully cleared!

Failing that as I mentioned the heater matrix could be blocked, You mentioned it's had a head gasket ... did it take a crap in the coolant system (a technical term for put oil in the water)?? If it did you may have to flush it through big time! Soda crystals into clean water in the expansion tank does work better than most bio flushes (in my own experiences), but be warned if anyone has added leak stopper for the radiator the soda crystals will break it down bringing any leaks to the surface

[Bigron]

I'm NOT an expert, but surely if there is heat to the rear seats, that suggests not an air lock but a problem with the flaps?

Ron.

[Bigron]

cd 2.2, I just re-read your comments and in particular the bit about clearing old sealant additives.
A few months back I added K-Seal (I know, not a good plan and I'll get my arse kicked for admitting it) in an attempt to stop the HBV leaking. It failed to do so, but some of the K-Seal is still in the system; is this a problem, because it didn't actually seal anything and obviously the new HBV doesn't leak, so nothing to break down?

Ron.

[BenjieH]

thanks for the comments so far everyone, the rad pipe heats up gradually, the system had a full flush after the head gasket was changed, the blowers are still giving me that initial blast of hot air then going cold? very odd one!

[05omegav6]

Did you change the thermostat

If it's getting lazy, it won't warm the coolant fully. That initial blast of heat is all you will get because the heater fan draws cold air over the heater matrix. If the coolant isn't up to temp then that air flow won't take long to cool it down. Heater matrix works just like the radiator... The key difference is that it sits in a box rather than behind the grill

[Entwood]

thanks for the comments so far everyone, the rad pipe heats up gradually, the system had a full flush after the head gasket was changed, the blowers are still giving me that initial blast of hot air then going cold? very odd one!

Thermostat needs replacing .. so insufficient heat in the circuit.

[BenjieH]

starting to sound like the thermostat then!    thanks everyone.