D4d Cooling System Problem

[Turbun]

Hi all

My parents own a 2000 Avensis D4D. Yesterday the vehicle overheated (through no fault of its own, stuck in mud) and lost a fair amount of its cooant through the cap blowing off. Once the vehicle had returned to a cold state, I drained the coolant from the radiator and engine block, and very carefully refilled the system with correct mixture of coolant. The system only took half of its capacity (around 3.5 litres). I assumed that it had a air lock and went through the normal routine of trying to exhaust the air from the system (squeezing pipes, blowing down degass pipe etc) but with no luck. Also the heater was blowing cold confirming no circulation to matrix. I again drained the system and very very slowly refilled. Again the system only took exactly the same amount as previously taken (3.5 litres). I have checked the operation of the thermosat off the car and it opens and closes perfectly. I then removed the 2 pipes that feed/return coolant from the cylinder head to heater matrix (at cylinder head) and ran the engine. There was no flow of coolant from either of the 2 stubs on the cylinder head. I then blew into both stubs suspecting an air lock somewhere in water jacket, but the air I blow passes freely into expansion tank. So to summarise the coolant is not being circulated around the system and the system is only taking half its capacity. I previously have changed the coolant in this vehicle as part of routine servicing and it took its full capacity with no problems or or manual bleeding required. Anyone have specific knowledge about the cooling system on these engines that can help?

Thanks in advance

[johnd4d]

I take it you have tried refilling wth hot engine and thermostat fully open ,

heater controls to hot ,

with the rad cap on you will notice when the stat opens as the top hose will pressurise slightly only then will you get flow.

[Fat Slob]

When you refilled the radiator did you run the engine until hot with the cap off for a while and top it up as necessary?

Also you could try backflushing the entire system and then refill.

[Turbun]

I take it you have tried refilling wth hot engine and thermostat fully open ,

heater controls to hot ,

with the rad cap on you will notice when the stat opens as the top hose will pressurise slightly only then will you get flow.

Thanks for getting back johnd4d. Yes engine was left to run until hot when refilled both times. Dont think stat had opened as top hose was cold whist ngine was very hot. IMO cylinder head should still flow coolant to the matrix regardless of stat status. What you think?

When you refilled the radiator did you run the engine until hot with the cap off for a while and top it up as necessary?

Also you could try backflushing the entire system and then refill.

Thanks for reply Fat Slob. Cap has been left off for the whole time whilst heating up until warm.

[gazza1286]

Is it possible that the water pump has failed?

Try filling the system direct into the block with the hoses diconnected. Briefly restart the engine in order to prove the water pump is working. It could be a bit messy but it's the simplest method of checking pump that I can think of??

[johnd4d]

Ok turbun here`s what you do , don`t start your engine with the hoses off even for a short time it will cook for sure !!!

But do get yourself a new stat and refit that,they can easily stick in the open or closed position . and hopefully that will be your problem ,

NO flow with engine hot this would be the first thing to try ,and it could also be the cause of the air lock stopping fluid gatting to heater matrix, hope this help`s mate...

[Turbun]

Thanks fo reply/advice guys

Johnd4d, I checked operaton of stat by placing in boiling water off the car, functioned correctly.

gazza186, yes was thinking water pump could be at fault and not an air lock as have never struuggled with an air lock such as this before and work on engines of a particular make for a living.

Is anyone aware of problems with water pumps on these engines or failures after overheat situations? Also does anyone know of the water pump drive arrangement?

Once again advice very much appreciated.

[Turbun]

Now sorted guys.

Turned out to be a very stubborn air lock. Leaving it for a few days (whils I got engaged)! seemed to get rid of the air.

Thanks for your help guys