[QUOTE]Originally posted by cheshire_carper

 

I would check the cooling system carefully, it could be a head gasket problem.

Below fan setting #3, there is only ram effect, so the heater only puts out as the speed increases. Above that, it should be fairly consistent.

VTEC will warm up the water, but the effect should be load-dependent, not rev-dependent.

 

This heater thing happened to me once, I realised what it was a few miles down the road when the water pump exploded ...

 

This is getting worse and worse I'll be checking everything tonight

 

Chris,
FWIW, I just had my head gasket replaced and I wasn't experiencing any cooling/heating probs. Mind you it was a little strange as the fulid exchange seemed to be in the wrong direction.

 

Does the heater route through the pollen filter ? Might be worth checking that out as well. It's located passenger side near the base of the bonnet under the black plastic cover, and is a B**** to remove & replace.

 

It was interesting having the head problem in the MR2, got down to 30 miles between coolant (water) refills before i had a replacement engine.

 

Water coolant was just below the low mark so I topped it up then took her for a test and found that:

. heat started coming though after 300 yds then went cold again.
. rolling @ 2k - cold.
. up to 3k - warmish
. up to 4k - hot
. down to 3k - warmish
. down to 2k - cold

Sod it and roasting. All ok after that. I hope that topping it up sorted the problem but I am concerned as to where the fluid went I was up to max a couple of weeks ago. The dip stick is clear so hopefully not head gasket. I'll just keep an eye on the water level and take it from there.

 

I'd keep an eye on it.

Check the inside of the oil cap for mayonnaise.

I would recommend a cylinder pressure test, if you are at all suspicious the problem has returned.

 

Chris.
Wait until the engines completely cold and check the level in the radiator.
If you've got air into the system, there's a possibility that it wont flow in from the topup tank.
Keep a towel handy as the system may still be under pressure even though it's cold.

The symptoms of higher temps at higher revs is definitely showing a possibility of lack of coolant in the engine. The higher the revs, the faster the remaining collant goes through, the better the heat exchange. Slow revs, very little manages to get into the heater matrix, therefor colder.

Anybody know if there's a bleed valve on the coolant system?