32 replies to this topic

[john2502]

I had the same issue in another thread on my MPI too.

Did all of the same things (except my thermostat was KNACKERED too), and i just happened across the fact that my alternator belt was a bit loose. Since it does also spin the water pump it was possible that under load it was slipping and not spinning the pump correctly to give a decent water flow. Other cars you hear it squealing, but i never noticed it with the mini.

My tensioner was basically seized and took a load of effort to get it off and adjusted. But once i got it back on and the tension back to how it should be, the car has been fine since.
So definitely worth checking.

Oh really? Did yours also go the middle, settle for a while, then steadily climb after fn came on.

Funnily enough I do have a replacement belt as when I replaced the alternator a couple of years ago I misplaced the belt at the time so had to fit the old one back again. It looks to be spinning fine but definitely worth a check along with the check on the header tank for exhaust gases. Cheers.

[john2502]

Hi,

you say your radiator is hot all over, should it be ? shouldn't it be cooler down the bottom where the coolant has been cooled ?

Sorry should have been clearer. Yes I mean radiator felt as I'd expect basically. If it was blocked I think it would have been much colder than I felt basically. I still won't rule it out 100%. At tia point I am just hoping it isn't the head gasket but sadly it's the front runner at the moment.

Plan is test on the header tank for emissions as no other signs of gasket, replace belt, maybe remove and inspect water pump, then head gasket is all that's left really.

Bloody cars eh! Haha

[dan1zo]

 

I had the same issue in another thread on my MPI too.

Did all of the same things (except my thermostat was KNACKERED too), and i just happened across the fact that my alternator belt was a bit loose. Since it does also spin the water pump it was possible that under load it was slipping and not spinning the pump correctly to give a decent water flow. Other cars you hear it squealing, but i never noticed it with the mini.

My tensioner was basically seized and took a load of effort to get it off and adjusted. But once i got it back on and the tension back to how it should be, the car has been fine since.
So definitely worth checking.

Oh really? Did yours also go the middle, settle for a while, then steadily climb after fn came on.

Funnily enough I do have a replacement belt as when I replaced the alternator a couple of years ago I misplaced the belt at the time so had to fit the old one back again. It looks to be spinning fine but definitely worth a check along with the check on the header tank for exhaust gases. Cheers.

 

Hey, so yes similar. It would idle on the driveway from cold start perfectly fine, it could get to temperature and stay there in the middle, fan would kick in around the right time and it all be fine.

 

For me also the same, the water pump looked to be spinning ok, but you can't tell if its slipping when driving! haha

 

But if i drove for more than 5-10 minutes, the gauge would spike and coolant would boil and release through the pressure valve in the header tank cap.

 

I tightened the belt so it had about 10mm deflection when pressed and so far so good.  I replaced the water pump about 10 years ago, when the original one failed, with a minispares replacement for the mpi that had a larger impeller.

Edited by dan1zo, 05 August 2026 - 08:29 AM.