Hi all,

I have a 2007 Hawk, 2.5 STI. Usual basic mods recently mapped at 363hp. 26k on the clock.

I just want to explain my symptoms to everyone to see what people's opinions are...

So a few weeks ago after driving it fairly hard for about 15 mins I pull up on my drive way and I'm say there on idle sending a few texts and notice the temp start to raise above usual.

Took the car to get mapped a couple weeks ago by Duncan Graham at Surrey Rolling Road so was obviously driven hard on the dyno, drove a few miles to the town centre and the temp started raising again when I came to a stop. Car was fine whilst driving home.

Couple days ago I hadn't driven the car in a couple of days, left the car on tickover on the drive for 10 mins to warm up, drove less than a mile, come to a junction waiting to pull out and temp starts to raise. Drove 4 miles down the motorway, stopped the car in a car park and left on tickover for 10 mins but temp stayed normal.

On the motorway yesterday and temp started to go up and down whilst cruising at 70... Eventually settled and did not raise again on a 40 mile drive.

As you can tell the temp issue is very intermittent, some times it over heats, sometimes not. Had thermostat and coolant replaced today and after a few mile hard drive is again started intermittently overheating... If you feel the top rad hose you can feel air pulsating through it.

No oil in coolant and no cream in oil or around oil cap. Heaters blow hot no problem.

Opinions welcome.

 

Id lean towards temp sensor or thermostat- im not a mechanic but thats my two pennys worth.

 

Changed thermostat today mate.

 

Flush and refill the coolant. Easy and doesn't cost a lot. As said above, not a mechanic but is an easy thing to do

 

Just for future reference, sitting idling in the drive to "warm up" doesn't actually do much aparently. Better driving a mile or two off boost to "warm up" .

 

Duff thermostat usually leads to UNDER-heating, ie not getting warm, rather than overheating.

I'd reckon you have an air lock.

 

Did that yesterday with thermostat change too.

 

How did you refill?

As you'd expect, or followed a thread on here?

 

I didn't do it but a friend who runs a garage did. Pretty sure he drained the system, changed the thermostat and filled the rad and the header tank to the top.

 

Are you actually having to top the coolant up or is it just the gauge fluctuating ?
Can you hear coolant moving through the heater matrix/ gurgling noise when starting from cold from behind the glovebox ?

Mick

 

Full coolant change yesterday so it's brimmed. Gauge goes up and comes down intermittently, yes I do hear a gurgling noise from behind the glove box mate.

 

Tbh you will be chasing this until the inevitable HG rebuild

The heads lift under boost and cause airlocks and random overheating. If you have ever seen little black particles in the coolant that's your HG's

 

Does the old...pull the expansion pipe out and extend it under your wiper blade and then go and hit some boost, if it pumps it all over the windscreen there is a problem actually work?

 

If you can hear a gurgling from the heater matrix, then you have air in the system - as the engine cool's overnight,the air will tend to end up at the highest point of the cooling system which is the heater and get pushed around the system when you start the engine.
You need to get rid of the air-lock to eliminate this before looking for possible head gasket issue's with a sniff test.

Mick

 

Would be its the hg too, hard driving pushes air/boost into the coolant. Enough air causes an air lock and over heating. Driving like a granny wont bring on the symptoms and you can also bleed the air out

 

Does your coolant go a murky brown colour with a slightly greasy feel? That is what happened to mine when the HG went on my Hawkeye. I also had to keep topping the water up between drives as the increased pressure in the system forced it out.
Good luck

 

Did you buy genuine thermostat or aftermarket

 

Yes, but HOW you fill it can have a dire effect. You can't just pour coolant into the header tank and hope for the best with a Scoob