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galaxy mk2 1.9 tdi cabin heat

Car used to get to normal temp (90) and stick there until turned off, after the water pump failed last winter and the temp got to 100 (no higher) the pump was replaced and now the engine temp gets to 90 and stays there but with no cabin heat at all, if I ease off and drive at 55mph (much better fuel economy)the engine temp drops and we get warm air from the cabin heater.

Ps water pump failed by impeller spinning on its shaft which apparently is a common failure mode but no debris went into the system.

Reply to
Ghostrecon
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oops forgot to ask ... any ideas what could cause this behaviour?

Reply to
Ghostrecon

Thermostat stuck open maybe, or an airlock?

Reply to
Chris Bartram

Airlock would be first port of call for your symptoms, then head gasket.

Reply to
Mrcheerful

there is also a secondary electric water pump and apparently the little hose to the water tank can block. lots of people with the same fault here:

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Reply to
Mrcheerful

thanks - unlike many of the peeps there we have no overheating, the secondry water pump works fine and the water circulates back to the expansion bottle. No real sign of head gasket failure (gas over water test) system doesnt overpressurise (hoses are not hard) no oil i water or vice versa :-(

Reply to
Ghostrecon

I was assuming that since it got up to temperature (90) and never went any higher that the thermostat was ok - just wondering if the fans on the radiator are set to come on at that temp so that when it gets up to temp its cooled quickly leaving little or no heat for vthe cabin heater/

Reply to
Ghostrecon

The thermostat is supposed to stop the coolant going to the radiator until it's got up to temperature, this includes the coolant to the heater since that should be circulated through the engine. Sounds like thermostat to me, since the heater gets warmer when you go slower, but there could be an airlock as well.

Reply to
rp

then it is down to airlocks. The temperature gauge should remain at the same point whether you are doing 90 or 50.

Reply to
Mrcheerful

yup, airlocks, or you've fitted a duff thermostat. You could try a vacuum fill.

Reply to
Duncan Wood

on this model the cabin heaters are in circuit whatever the thermostat is doing - according to the garage, and they have checked that the thermostat is opening at the correct temp. pparently they have bled the system at different points to ensure there are no airlocks and its still the same

Reply to
Ghostrecon

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