heater hot/cold

Hi, when first started car's heater lovely and warm eventually it goes cold, had a pressure test on exspansion tank it seems ok, so I dont think its a head gasket problem but on releasing exsp tank lid it does seem to surge air out of tank as though its pressureised but there's no smell of exhaust or fuel fumes, also just had air con system regassed, I must be missing something any ideas? ta.

what engine ???

Sorry its the 2.5 bmw 6

Air in the system, duff thermostat, blend motor playing up, matrix temperature sensor. Have you checked the heater pipes stay hot?

Hi, not checked pipes, thermo is new, not got kit to check blend motors or matrix sensor, any ideas? ta

bleed it first , every thing else cost money !!

New thermo is the clue, lots of duff ones about.

What's your engine temperature gauge doing?
Have you got the check book symbol on the HEVAC display?

Hi, temp gauge not working, but landy dealer can force it to work, text book was on but after regass not now.

drkwack said:

Hi, temp gauge not working, but landy dealer can force it to work, text book was on but after regass not now.

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Never ignore things that don't work on a P38.