engine problem again overheating this time !!!!

[filh]

I was rallying this sunday with my newly rebuild engine (600km done before race) .
Everything went well and the engine was really pleasant BUT......
2 stages before end of race, The heating gauge went in the red area , and oil was near 120°C as I was on the start line .
I started ans stop 500m further . The coolant in the expansion bottle was boiling and both up and down hoses were hard as concrete.

I manage to get the pressure out of cooling system , wait a little and poured about 2 1/2 liter of water in radiator . I restarted the engine and finished the stage without any overheating problem . I also achieved the last stage (14km) without any problem.

So what do you think : could a blocked thermostat be the cause ?
The cooling ventilator is well functional .
I forget to mention I stopped near a cemetary, and the water I added came from there Holy water ????? : :idea:

Phil

[Ivan141]

Drain the holy water and look for signs of oil. No one wants to believe it's a cracked head/block or faulty headgasket on a newly rebuilt block, but it sure does sound like that is the case.

[jondee86]

Cooling system capacity (with heater) is 6 litres. If you were missing
2-1/2 litres, the level was well down, and it was boiling pretty good

Water pump not working (broken belt), thermostat jammed closed,
engine working hard in low gears without much airflow (especially at
high altitude), blown head gasket pressurising cooling system, radiator
blocked with mud ??

But strange that it did not blow more water out after you filled it up

Cheers... jondee86

[cvrle]

I have blown two head gaskets when I rebuild my first engine in 1000km and have same things with overheating, boiling, and when I put some 1-2lit water everything going good some 50km when its cold, but when oil warm up start overhithing again. Try to look does you have white (oil- water mixed) under the oil cap after 10-15 min of idle. If you have its probobly head gaskets blown.

[filh]

no sign of oil or water leak .
I of course checked the water pump before reassembling the engine .

Radiator is clean .
I ran a 14km rally stage at high revs , and there was no sign of overheating.

The water i refilled came out of radiator when I let the pressure out .

I'll change the thermostat, eventhough it's a new one , but not a Toyota genuine .And I'll try it hard .
Thanks for your advices
Phil

[JonnyAE86]

NEVER heard of a jammed closed thermostat, afaik when they jamm they always jamm open, its just the way they are built.

Are you running viscous fan? If so, the greese inside could be old enough not to make the fan work in regular condition.

[jondee86]

There are complicated thermodynamic explanations/theories that can
explain what happened. At high speed the effect of the fan is negligible.
All the airflow for cooling comes from the airflow generated by the
forward motion of the car. I have removed my viscous fan for circuit
racing (every little bit helps ) without any sign of overheating.

What can happen is that the cooling system is operating very close to
maximum heat transfer capacity, with high airflow thru the radiator.
When you stop the vehicle/reduce the engine speed to an idle, a type
of "heat-soak" occurs. There is heat stored in the metal of the engine
that continues to enter the cooling fluid for a few minutes after the car
stops. If the heat gain to the fluid is greater than the heat loss thru
the radiator, the engine can boil.

This is the purpose of the cool-down lap for racing cars... to allow the
stored heat in brakes and cooling system to be passed out to the air
without overheating.

Cheers... jondee86

[Jan Pedersen]

My old engine did the same thing. The fuel pump died and took the engine with it. So check your fuel pressure!

Hmm, maybe we all should add holy water

[filh]

Fuel pressure is 2kg at idle and 2,6kg at higher revs . Went on Dynobench
last week , and fuel mixture was ok at each revs level !Stock injectors and fuel pressure. 141 hp at 6800rpm
I spoke today with my machinist , and he had the same thing with another ae86 , while on dyno bench . a new thermostat , and everything was ok again.

[totta Crolla]

Air lock in the system maybe ?
Make sure, if it's fitted, the heater is set to 'hot' when filling water system.
Could also be the water pump if it is continuously turning at a high speed.