Scenic mk3 heater not working

[wrinklet1]

Hi everyone , l have a scenic mk3 1.5dci and the climate control isnt working. The fans blow okay but no warm.air. The expansion tank keeps overflowing water when the engine gets hot. I am wondering if it could be the thermostat that is faulty?
Any ideas?

[myglaren]

Your suspicions sound correct - does the top hose get hot or stay cold?

On second thoughts, the heater supply bypasses the thermostat so there may well be another problem - a failed water pump perhaps.

[wrinklet1]

Recently had a water pump and timing belt replacement

[xantia_v6]

Perhaps the system was not bled correctly and there is an airlock preventing circulation?

[wrinklet1]

I have opened the heater matrix and the thermostat vent plugs......

[Peter.N.]

Worst case scenario would be a failed head gasket causing the system to be pressurised, the combustion gas escaping can fill the heater matrix and stop the water from circulating.

Peter

[wrinklet1]

No bubbles in the expansion tank though which l would have expected if it was the head gasket

[wrinklet1]

Well, it seems like the head gasket has failed, so you right Peter N.
£500+ of a job. I may as well have the glow plugs changed too.