I recently bought a Zafira B 1.7 diesel 2011.
I have a problem with my heater.
When the engine is hot (it does take a fair while to get hot), the heater is blowing hot air but only for 10 seconds and slowly goes back to cold.
I have changed the thermostat, flushed the heater core, and checked the motor that controls the hot to cold air flap just to make sure, and it all functions.
I imagine the coolant warms up the heater core, but heat is not replenished fast enough from the coolant to keep the heating blowing hot.
When I flushed the heater core, no "dirt" seemed to have come out of it and the flow of water was coming out of the core as fast as it would from my hose.
Also, the coolant in the expansion vessel is still dead cold after 20 miles drive. The engine is hot, showing around 90⁰ on the ob2 reader (not overheating then) but the coolant in the vessel stays cold. It will eventually warm up after quite a long drive, way more than on my ford transit or the golf I had previously.
The expansion vessel seems to empty fast enough when opening the drain plug, indicating that it shouldn't be a clogged pipe.
I am going to try a coolant system cleaner just to make sure all residues are dissolved and disposed of but I doubt it will work as it does not seem to come from a restricted flow of coolant.
I believe the water pump is working as the engine is running at 90⁰ and staying at this temperature while driving, unless the engine cools itself down only by convection, but unlikely.
I have the Haynes book for it and it doesn't say anything about bleeding the system on the 1.7l engine (only the 1.9l has a bleeding screw on the exhaust manifold apparently).
I am running out of ideas on what it could be.
Your help would be greatly appreciated.
Many thanks,
Alban
Friday, February 7th, 2025 AT 1:13 PM
