Hi all just recently got an 89 4x4 sierra saph cos. it seems to have a problem overheating. The car does not overheat on tickover and the fan kicks in and keeps it at running temp only when on a run ie; in boost. the temperature still remains hi even during a run down the dular as in the middle of N verging the top line. the car never done this when i first purchased it. have recently done a cambelt and replaced the bottom pulley wonderd if the ignition timing could cause this problem? have checked the usual stat ok blead the air out the system, pump appears to be operating fine. there is no oil in water water in oil. should mention that the expansion bottle cap was leaking till i replaced it seemed new one seems fine now. also thot that the head gasket might be on its way out as in it is only letting pressure into the coolant when there is more pressure in the cylinder from the turbo. perhaps a leak in the gasket acting as a 1 way valve when the pressure inreased causing the csr to over heat. any ideas or help would be greatly appreciated. phill

 

is she loosing any water???do the fans run all the time?how is she on a cold start after a night of driving?does she mis-fire for a while?

 

no shes not using any water. seems to start fine the next day without any splutters doesnt appear to use any water. i have wire the fans to an overide switch to the relay

 

I'm sorry to say that I suspect the head gasket - had very similar problems with my saff years back and it ran slightly worse (hotter) time after time for about 18 months. In the end I took the head off and the sealing ring around No. 3 was cracked. New gasket sorted it fine... I used a grp A item.

 

i second that

hope you get it sorted soon

 

cheers probably gonna whip the head of and have a look gonna try a compression test on it though i suspect that it might not be apparent with this either. the car has low comp pistons any idea what sort of pressure reading should get wet/dry?

 

had the same on my saff mate changed the head gasket and it was no better,the problem was the radiator it was blocked with shit put a new 1 on and it was perfect not saying this is your problem but i was a bit gutted that i went the long way round,and dont want u to do the same

 

is there any way to check if the radiator is getting blocked? did urz over heat at idle? the problem does seem to be gettin progressively worse.

 

suspect head gasket - get the coolant checked for combustion gases

 

could just be a dodgy temp sensor?

 

mine would sit there all day ticking over,fans would cut in then go off all as should do but as soon as i went down the road it would get hot,i changed all the simple things first ie thermostat etc didnt think 2 replace the rad as i had only recently put it on seconhand,changed the head gasket and the car was no different,pulled the pipes off the bottom of rad and the water that came out of one side of the rad seemed dirtyer than the other changed the rad and no problems, maybe your pipes will be hotter one side of the rad than the other but mine seemed ok but it was deffinatly the rad on mine fr the price of a rad its prob worth a try hope i have been of help cheeRS

 

different engine but this happened to my missus's golf 1.8t i thought the worst too , turned out the water pump was fooked ! still a pain in the arse cos i'd just had timing belts done and all that had to come off again to do pump , 3weeks after . doh !

 

I've had radiators that have been partially blocked and always seem the same symptom - OK at idle, hot when driving, too hot when motorway driving. Get the rad flow tested.

Charlie

 

Or simply drop it out and try reverse flushing it mate - though I initially thought it had solved mine but it was the head gasket as said unfortunately. As said above, a quick header tank gas check at your local garage will confirm it or not.