Overheating problem - at slow speed.

[TC]

Have an issue where the car seems to overheat when in heavy traffic.
I commute 25 miles to the station and its mainly motor way. Temp gauge just sits below half all the way until I hit traffic the last 2 miles or so.
Gauge rocks from half way to off the scale depending on how the traffic is flowing. But basically if I am moving it will head back to around the half way mark.
After parking, the expansion bottle is full and boiling like a kettle. Returned to the car in the evening with plenty of water to top it up but did not need a drop.
As it had cooled down all the coolant had been drawn back out of the expansion tank.

Drove home fine so hopped it was just a blip. But again this morning hit the traffic and up went the temp again.
Thinking maybe its the fans not kicking in ? any other ideas?
Is there an easy way I can check the radiator fans to make sure they are working correctly?

[010on1986]

this needs attention urgently before you cook your engine. (you may have already done so, they really don't like getting too hot).

the fans seldom come on if ever so ignore the fans. Edit : test fans by unplugging sensor on radiator (right hand side above bottom pipe?) when engine running, fans come on when circuit broken

I would wonder if you have coolent circulating at low revs. So maybe its your waterpump. Sounds a bit like heatsoak.

[blue2]

Does it go down quickly when you rev it? Sounds like an air lock.

[TC]

Just drove the 25 miles home and not a problem.
Let it run on the spot for 5 mins and I could hear the fans cut in every so often so I know they work now !
Also felt the pipes in and out of the radiator and they are both hot so I know coolent s getting round.
Possibly could be an air lock then?
Should I drain the system altogether or is there a way I could flush out the lock??

[jon_st205]

My money is on the water pump if there's no sign of it having been done, the impellor corrodes and loses effectiveness.

[widster]

My friend had a problem like this which it turned out was due to a leak in the plastic header tank.

[SuperRedMR2]

the cap on the coolant reservoir, is it see through? these can break down through old age and perish. Get a black one - these can be taken from a Yaris or toyota sell them for £12. This may be the reason if you have an air problem.

[010on1986]

if it were the reservoir cap I don't think it would refill itself via vacuum on cooldown.

How old is your waterpump?

I suspect it is inadequate refill (insuficient coolent), airlock, or maybe headgasket failure (again?).

[TC]

Water pump looked ok when I took it off, the impeller was complete and not warn down. It has let out a squeel once and a while though so the bearing is probably on its way out. I plan to swap the pump and then bleed and flush the system before refilling again. Hopefully that will sort it. Its strange that its intermittent though as I do 50 miles a day and it does not always overheat. When it does happen its after a long run and then when I hit the heavy traffic. If I rev then engine when the temp guage is rising you can see it fall again ?

I have a posting in the wanted section for a water pump, but if I have no luck by the w/e I will get one from the local motor shop.

If it is the head gasket again - oil is still nice and clear and I have no smoke (yet) from the exhaust. Would a sniff test be the only way to confirm its shot ? ( lets hope thats not the problem as changing that was a pain in the ass

[010on1986]

You have inspected the water pump condition which seems okay and we know that it does circulate the coolent, probably not the culprit.

HG failure is not definately confirmed by water in the oil or oil in the water on these cars.

I have had the HG fail and been able to use the car daily for about a year....with no steam and no oil in the water symptoms. In my case the only thing you could not do was give it beans on the motorway. You could use it every day on a and b roads without overheat, why, because it was all to do with the amount of exhaust gases placed into the coolant. It was RPM and time dependant. In my case a tiny pin leak between the HG and the coolent passage was placing tiny amounts of gas into the coolant. (hence no steam or oil contamination)........on a short journey it will not gass up the coolent sufficiently to displace alot of coolent back into the overflow reservoir and not lead to an overheat. At motorway revs it would displace the coolent and guarantee a overheat in about 20 minutes.

I would definately sniff test to eliminate HG failure, why? Because it is essential to eliminate it from the list of problems FIRST as you cannot solve a bad HG by the replacement of other parts of the system such as the radiator, waterpump , neither is it solved by refilling the system, bleeding, burping, flushing or going to your local toyota dealer xxxx.. etc etc, your engine also has a history of HG failure.

If not the HG then you can proceed to query other system parts replace/check bits and pieces such as water pump, thermostat, radiator cap, radiator etc etc and also have the joy of draining, flushing and refilling the sytem with the correct amount of coolant.

At the end of the day the cause is going to be

The HG or
a leak in the system/ insufficient coolent
the radiator cap not holding pressure or
a fault with another part ( thermostat, radiator, water pump)