Solving a cooling issue

zurbfoundation

HI guys - looking to get some ideas on what might be at play in the cooling system

Basically engine has been running hot if driven above 60mph - I have diagnosed a problem with the coolant temp switch that powers the relay that turns on the fan - so that's one thing I have to change. But disconnecting it runs the fan constantly so its still getting hot even when the fan runs on.

Thermostat was replaced last year so i don't think its that. However the blower is only sending warm air into the cabin when then car is full up to temp. So dunno - maybe its sticking half way?

Could be the waterpump as no idea when last changed. However the rad is getting hot so i think water is being circulated and i cant see leaks etc.

Could it be an air blockage? Should i try running it with the rad cap off for a while see if it burps anything out?

Thanks

ZF

two wheels good

I'd try running it without the thermostat.
Does it need a coolant flush -does the rad or exp. bottle look gunged-up?

zurbfoundation

two wheels good wrote: »

I'd try running it without the thermostat.
Does it need a coolant flush -does the rad or exp. bottle look gunged-up?

yeah good shout on the flush - would be no harm. would you just use a few rounds of water or get one of the flush products?

Alanstrainor

Coolant flush wont help things at all, even if you were running pure water through the system it should be enough to keep it cool. A failed water pump would cause the engine temperature to rise at any speed surely, and not just at 60mph+? I would think this is related to the thermostat and it is worth investigating there first.

As for air in the system, I would doubt it, I would expect this to produce different symptoms. Usually you will get low coolant warnings in that case, and I wouldn't expect air in the system to only cause issue at speed/engine stress.

All that being said, there's no harm popping open the expansion tank cap and checking your coolant level when the car is cold. What car is it? Make, model, year, engine.

zurbfoundation

Good points - don't forget the fan is running full time at the moment. Its like it can disapate enough heat under that stress level but any more (speed, hills) and it cant cool itself anymore. So if there was a large pocket of air (there have been coolant top ups of late) its like that amount of coolant can cope with that amount of heat - anymore and it cant cool itself.

If water pump was borked I would not expect rad to be getting much hot coolant pumped into it to cool. If i am going to drain it and flush it, then a thermostat change would be easy and cheap to try so i may do a combination of both.

1996 Toyota Carina e 1.6 petrol

BrianD3

When you say it is running hot - are you basing this on the temperature gauge. Gauges/the gauge sender can become faulty and read erratically or much hotter than the actual temp.

From what I've seen, thermostats rarely give trouble and cooling system issues I've come across have generally been due to bad water pumps. I've also seen a case where everything seemed ok and the system appeared clean and the rad and heater got hot. However when the radiator was changed for a new one, the symptoms went away. Over time a radiator might have deposits restricting (but not blocking) the tubes resulting in it not properly dissipating the heat generated at high revs/speed.

zurbfoundation

blocked cores in the rad have crossed my mind also - its 21 years old after all

zurbfoundation

theres 220k miles on it and i know its had a water pump in that time - its possible that it needs another, however i would have expected the rad not to heat if the water was not circulating

Cerebrum

Go ahead and burp it with the rad cap open is a must. If there's no air present, you can expect that you're losing coolant due to excess heat and the coolant making its way out of the expansion tank overflow pipe.

Simple check for starters;

After a spin where the engine has got up to temp, put your hand on the hose that goes to the radiator (after the thermostat valve). This should be very warm if the thermostat valve has been opening without issue. You can feel the return hose and use it as a reference. If the thermostat to rad pipe is cooler, then you've a blocked/failed/faulty thermostat valve.

If the thermostat valve is blocked, as mentioned, a coolant flush may be required. In order to do this without further issues down the line, you'll need to remove the thermostat so any debris can exit. Even though it was changed, residual debris can easily block it up again as it makes its way through the coolant system. You'll need to push it through the system under pressure.

Check under the rad cap when cool also- any sign of rust on the underside of a rad cap is a sign you'll need to flush it thoroughly.

CJhaughey

I had this before on a landcruiser, rad was the problem. At 60 the cooling should be working well due to increased airflow, overheating at that speed would indicate the cooling system can't cope with the increased heat.
Don't forget that Toyota Gauges are stabilised and once it starts to move the engine is getting quite hot.
I'd get a new rad for the small cost of one.

zurbfoundation

Giving it a flush out now - it's pretty manky. Thermostat and pump seem to be functional - went ahead and ordered a rad and will fit that when it arrives -

It doesn't loose coolant as far as I can tell - so reduced capacity in the Rad could be the issue. Rad was cheap so worth a go

zurbfoundation

new rad in a the weekend and today gave it a good 70 mile blast this morning - good periods sitting at 70 mph and she stayed at normal temp.

To recap on the work done - new rad, coolant and a flush, new thermostatic switch (unconnected to the high temp but wasn't enabling the fan when required so needed changing), left existing thermostat as it was changed only last year but tested it in some boiling water while i had it out and seems to open fine.

I am thinking it was the rad as i was able to get more coolant into the system after its replacement.

Thanks all for y'all input!