Frontera Temperature

I have a '99 Frontera Sport with the 2.2 Ecotec engine and it has a strange
cooling system problem. The car has just had the head gasket done and I
don't think it is blown again.

The temperature gauge will sit happily at 85 degrees all day while the car
is moving, but if it is idling for a sustained period, it will jump suddenly
jump up to 100 within a couple of seconds and if you drive off it will jump
down just as quickly.

Normally I would think this is an electrical fault but the heater also goes
cold when the temperarture jumps up and it goes warm again when the
temperature goes down.

When climbing a hill at around 1500rpm in 3rd will cause the temperature to
jump up, but climbing at 3000rpm in 2nd will cause the gauge to drop even
though the car is going at the same speed

I thought it was maybe the heater matrix hoses reversed but changing them
made no difference.

TIA

 

Water pump not pumping coolant around quickly enough?

 

That's certainly would explain the symptoms, but how could that occur? The
car has done 60k with FSH and the engine is generally in very good condition
with nice lear blue coolant.

 

I would go with the water pump. I had the same symptoms with my omega (with
100K on the clock). When I came to change the cam belt the pump bearings
were clapped and you could move the pulley 5-10mm but with no leaks. Changed
pump and problem went away.