cooling problem, overheating... please help!! somebody knows

[pccalloutservice]

recently my rev 1 tubby has been heating up, but it is very strange, sometimes the hand will rise up quickly and back down again.
then no problems for a while.
with the help of another forum member changed the coolant and thought this may cure my trouble but to no avail.
while drivin with full heat on, it would be warm one second and cool the next??
then the other night the temp went right to the top and wouldnt come down, stopped the car and went to the radiator, opened bleedscrew and the water was cold.

?? could the thermostat be sticking?
?? would radiator need replaced?

help appreciated

[terminater2_uk]

I'd say a blockage or an air lock

[Mr Two]

Sounds like an airlock in the coolant system to me and when it moves around you will get all sorts of temp readings. Just " might " be a slight blockage somewhere but i think i would go for an airlock first

[pccalloutservice]

thanks for the help, took thermo out and sometimes it opens and sometimes not.

hopefully it is it, but i think i'll replace radiator as well cause i had it tested recently and told there would be no harm replacing it.

[pccalloutservice]

ran the car without the thermostat and it is still overheating, the water doesn't seem to be circulating, is this starting to look like the water pump?


does water pump mean engine out?

[terminater2_uk]

I think the water pump is run by the cam belt in which case, although it can be done by partially dropping the engine, its much easier to do completely out.
If the waterpumps gone then the car will keep warming and getting hotter conyinuously until it overheats as theres nothing cooling it whatsoever

[steve b]

1. Hope its an airlock and you didn't bleed it properly
2. Hope its your thermostat
3. Hope its a simple leak from a pipe
4. hope its a hole in your radiator
5. Hope its a leak around your water pump/the metal non stainless on rev1 pipes
5. Hope its your head gasket
6. Your blocks cracked

The way the water pump works means its highly unlikely/ impossible for it not to work, a bearing could fail and cause horrible noises etc but it'll still pump.

Whilst owing MR2's i've suffered 3,5 & 6