Radiator not working properly? sw20 mr2

[Al]

My car overheated just after xmas coming back from Blenheim, thought it may have just been out of water or bad thermostat. Replaced thermostat, radiator cap and changed coolant (50/50 mix). All seemed well for 100kms of 5th gear 100km/h driving, then the needle just started to rise so I put the heater on full and it went back to halfway, everything seemed fine with the heater on until I had to stop for roadworks for about 30 seconds and the temp needle started to climb again with the heater on full got moving and it stopped.

Now I don't think it has a BHG because the car still performs well, theres no white smoke from the exhaust, theres no water in the oil and theres no mayo around the oil filler.

It seems to consume water, but It doesnt leak onto my garage floor

[fivebob]

Are you 100% absolutely positively sure you've bled all the air out of the system, including the heater core. If you have then it might be time to replace the radiator, but that would only be if it was overheating all the time and losing water.

*edit have you had the system pressure tested?

[Al]

We just put the service hoses up, opened the valves, drained the water from the front with the car jacked up from the rear and filled it up and ran it with the heater on and the rad cap off until it got to temp.

I've been driving around today and it just sits on halfway Yet open road driving makes it rise up.

No haven't had the system pressure tested, should have done that when we replaced the clutch two weekends ago...there was a pressure tester hanging on the wall

[fivebob]

Well that's the correct way to do it, so you should have got all the air out.

Sounds like it may be a clogged radiator causing overheat and dumping fluid out the overflow bottle, is the bottle full when you stop from a hard run?

[Al]

Haven't done any hard runs in it, still got the silencer in the tail pipe since WOF last week and im paranoid something will pop if I give it too much with a 1" exhaust outlet

[Caveman]

You might have a small crack in the head gasket? Maybe when your car overheated it warped the head a little enough the create a small void. I know its not what you want to hear but if the waters not leaking onto the floor, its going through the engine This can happen without having the tell tale signs with the milky looking oil if it only cracks through to the water jacket.

I think all_fours had this problem last mega meet.

[85AW20v]

In Targa a couple of years ago, we had problems with a car overheating in stages but OK when touring. Radiator was pulled out, top and bottom tanks removed and core cleaned out. End of problems.

[Malcolm]

I had similar problems with mine, didn't have many of the usual BHG type problems, but it seemed that it was leaking only under the higher cylinder pressures caused by boosting. 100km of hardish driving caused it to overheat and use most of the water in the system! The return trip without any boost caused it to use no water at all.

[mr2_t]

Al,

I had exactly your symptoms, sporadic overheating. I suspected a dodgy thermostat, as it would only do it on initial warm up, and then only a couple of times in a two week period. Enough to worry me none the less...

Took it into a radiator shop, they pressure tested it and could find any leaks, but the radiator was "30% blocked". They flushed it and put new coolant in, no problems since.

[Al]

Cool I'll get it pressure tested and go from there, thanks

[Meadzy]

sounds like you could have a hole in your radiaitor, our commodore was overheating exactly the same, one time it went right off the clock!!

[Punter]

It seems to consume water, but It doesnt leak onto my garage floor

sounds like you could have a hole in your radiaitor

A hole would probably leak.

[Meadzy]

oh yer didnt read that bit

[RomanV]

I had a split in one of the coolant lines under the car.

It would only leak when the pipe was under pressure, (highish RPMs) and it would drip onto the top side of the cars undertray, making it hard to find where it was leaking from.

It also meant that it didnt leave a coolant puddle on the driveway.

Perhaps this would be worth investigating? It took a bit of head scratching to work out why I was losing coolant at such a rate, without it dripping everywhere.

Park your car on a hill, and see if any coolant drips off the back of the trays.