my car overheats?

Heater valve I guess behind the dash or on engine baulk head. Follow back from heater hot cold switching.

Circulation ,yes you will have some as water heats up, as hot water will always circulate in the rad via convection.

One basic test for the water pump is check temp top to bottom hose, there should be a v noticeable diff. Top hot bottom cold if pump working.

Maurice
January 2010

i havnt checked the water pump as i do have water circulation,so i assumed it to be working correctly re the heater valve where would i locate this ?.
regards geoff

geoff
January 2010

Did we forget the water pump !!!!!

Maurice
January 2010

I know you say that the rad and heater matrix is not blocked but have you tried fushing the system through.
Perhaps use special flushing liquid from spares shop?
Also worth checking the thermostat and see if it opens fully in boiling water. I have come across them before and they sit in parts dept for years b4 being sold. Boil it up in hot water---
Heater valve may also be a problem not allowing water through the matrix / trapping air
There has to be a reason!

Maurice
January 2010

yes mate i have and it still overheats,and the heater still fails to work i have bled it properly too after adding the anti-freeze ?.its a strang one this.

geoff.
January 2010

i have bled the cooling system several times to no avail,wether the header tank cap is on or off the engine still overheats,the cooling fan is working fine,the heater only blows cold air wether the engine is glowing hot or not.the heater fan is working but only blows cold air ?.could this be causing the problem ?.the heater rad is not blocked either,i am at a loss mate,geoff.

geoff.
January 2010

Based on the additional information it may well be an air lock in the system hence heater not working. Have you recently drained the cooling system to add anti freeze?

I dont know the engine well enough but there may be an air bleed screw at the higest point in the cooling system.
If not from cold start the engine with the heater valve open (ie as if to warm up the car) and the expansion tank pressure cap removed -top up water to marked level- no more.
Run the engine and as it warms up -taking care on moving parts- see if you can flex /compress the bottom hose ,encouraging water to displace any air, this may overcome problem.
Also might be worth checking the seal on the expansion tank cap maybe replace cap .
Is cooling fan operating okay

Maurice
January 2010

i have changed the thermostat,re.the head gasket failure answer it starts up first time every time,it runs perfect, it will do 100 mph so no lack of compression anywhere, there is no oil in the water,or no water in the oil,( could it still be a head gasket fault ) ???.
it doesnt loose water or oil,

geoff (the owner)
January 2010

Sound like a head gasket failure

Maurice
January 2010