Advice needed please

[jamGTT]

Right so I bought a gt, on 75,000 miles and completely standard apart from a back box! On the way home she started to overheat! Driving normally it's fine, sat at idle it's fine, driving a bit spiritedly and up the temp goes and then will overheat while normally driving! Changed the thermostat and flushed the rad today but does the same, it's also now spewed a load of coolant out the top of the rad, any ideas??

 

[garry goodall]

Could be a faulty water pump? Give it a rev when cold with the rad cap off and see if the coolant rises up

 

[jamGTT]

It does fella, raises up just like it should! Had a new water pump about 3 months ago! any other ideas??

 

[turbominicooper]

is your fan kicking in when it should or at all?

 

[jamGTT]

Yep, fan kicks in when it should!

 

[turbominicooper]

how much boost you running?

have you checked your timing?

hows your knock sensor?

 

[dac69er]

sounds like the headgasket has gone

 

[Guye]

it could be a weak coolant hose. Rev the car and check to see if the raditor hose "collapses". This happened to me a few years back. The hose would collapse with revs blocking the flow of coolant and causing the car to overheat while driving.

 

[jamGTT]

Standard boost not checked the timing and how do I check the knock censor? Gonna check the hoses and get sniff and comp tests done on Friday

 

[garry goodall]

Alternator belt slip when under load? Tis a strange one, if it was head gasket could it be pressuring the cooling system causing the coolant to blow passed the rad cap? Clutching at straws though now

 

[jamGTT]

Ahh the rad cap hadn't been secured proper for that one!! The water pump has been changed a few months ago could the belt be over tight?

 

[garry goodall]

Over tight belt would hum but wouldn't slip it wouldn't do the pulley bearings any good though, belt should have about half inch deflection across the longest distance between pulleys

 

[jamGTT]

Cool, That's about the right play in the belt then! I would of thought a HG would cause it to over heat all the time??

 

[dac69er]

Cool, That's about the right play in the belt then! I would of thought a HG would cause it to over heat all the time??

Not if it's just started to go. It holds ok under normal driving, but add some boost and the pressure is too much and it pushes exhaust gas into the cooling system making it overheat.

 

[jamGTT]

I'm guessing a compression test and a sniff test would point the finger??

 

[dac69er]

Compression test would most likely be fine. The sniffer test would be the one that proves it either way

 

[jamGTT]

Ok, had the sniff check done, no colour change!! However unplugged the rad fan and the rad behind it was stone cold! Left it for 5-10 minutes and still stone cold!! Could all this be caused by half the rad being blocked??
Helpppp!!

 

[garry goodall]

Doubt the radiator would be blocked that badly, i know you said thermostat is new but could this be restricting somehow and not opening? Might be worth taking the thermostat out and running see if starts warming up?

 

[jamGTT]

I checked, double checked and triple checked the stat before fitment, I may jus do it to see what happens!!

 

[mork]

Could easily be a blockage somewhere. I'd flush the whole system with a hose pipe until it runs nice and clear. Then fresh coolant and see what happens.