MK 2 running warm to hot on a run..

[Hammerhead]

Hi all,

Mrs Hammerheads MK2 1.8 seems to having issues with its cooling system currently. The car gets up to normal temperature and stays there for a while but will then run warm to hot (temp needle swings to the right) whilst out on the road. Turning the heater up to warm then brings the temp dial back to where it should be. It only seems to overheat when the heater is set to cool.

The car doesn't seem to be loosing coolant and it doesn't overheat whilst stationanary, both fans kicking in (UK car with a/c).

Any ideas with what might be wrong? It's only just been serviced by Mazda and this didn't happen prior to the service. Guess this could be coincidental though!

Cheers,

Steve

[Munter]

Have you got a grid in front of the rad?

My guess is the Rad is not doing it's job well enough. Either part of it's blocked (does it all get hot?) or air is not getting to it fast enough on the move.

[DennisTheMenace]

Could be the rads got gunk in it , mine was doing the same after i changed the engine , ended up fitting a new radiator .

oh and the rad was ok before the swap so god knows what happened as it just sat in the garage ??

[Hammerhead]

No, no grid in front of the rad. Will have a feel of it tomorrow and see if it has any warm spots.

Thanks

[NiceCupOfTea]

Might be worth ordering a (genuine) rad cap from MX5parts. They are dirt cheap, and fail regularly.

[OnlyMX5ives]

If it isn't loosing coolant the cap should be fine.

You are checking the RAD not the exp tank though ?

I'd guess a blocked rad fairly common on MK1's and MK2's are catching up now.

[Hammerhead]

Fitted a new (gen Mazda) rad cap and it's still doing it albeit a bit less than before. Do you reckon it's worth flusing the original rad out or just getting a new one and being done with it?

Thanks again,

Steve

[DennisTheMenace]

NiceCupOfTea said:

Might be worth ordering a (genuine) rad cap from MX5parts. They are dirt cheap, and fail regularly.

AFAIK mine is still on the original rad cap , 14 years and working fine ,

[odyssey2200]

Could be a dodgy Thermostat.

[DennisTheMenace]

Hammerhead said:

Fitted a new (gen Mazda) rad cap and it's still doing it albeit a bit less than before. Do you reckon it's worth flusing the original rad out or just getting a new one and being done with it?

Thanks again,

Steve

I would go stright for a replacement radiator and a refill with fresh antifreeze/deionised water

[odyssey2200]

DennisTheMenace said:

Hammerhead said:

Fitted a new (gen Mazda) rad cap and it's still doing it albeit a bit less than before. Do you reckon it's worth flusing the original rad out or just getting a new one and being done with it?

Thanks again,

Steve

I would go stright for a replacement radiator and a refill with fresh antifreeze/deionised water

Worth flushing the thing out before replacing it.

[DennisTheMenace]

I cleaned mine out , ran ok for a bit then clogged up again , new rad is the best way.

[odyssey2200]

DennisTheMenace said:

I cleaned mine out , ran ok for a bit then clogged up again , new rad is the best way.

What did it clog up with?

If you had flushed it properly there would have been nothing to cause a blockage.

[DennisTheMenace]

havent a clue , the water ways in the rad arent very big , and i kept getting hot spots .
Replaced teh rad (had larger waterways) flushed the system and the coolant is still a lovely blue colour and clear.