Before I even begin to type up the actual issue, I just want to make it clear, that it 100% not a head gasket! I've had every test and nothing..

So, my car can drive absolutely fine - has done all week (par wednesday), but occasionally (3/5 times in the last 2 weeks) the temperature can rise right up - not all the way to red, but it gets above the second line. At which point, I quickly flip the ignition and the fans kick in.

Today, I fit a new temp sensor along with a new thermostat. I found the existing thermostat seal had snapped (not the housing one, the spring side) and believed that was the problem, as it could hold the thermostat open.

Started it up, fine held temp. Then it rose up to the second line (normally sits mid way) and held that temperature relatively stable the entire test drive. I gave it a boot then cruised/ even stopped to let it idle expecting to see the temp rise up, but it didn't really go up a lot.

When I got back 5 mins ago - it appears that the fans still aren't coming on when they should be.

I've already checked the entire fan system and nothing appeared to be wrong there. I'm now thinking it's to do with the ECU, am I right in thinking this?? It's the only thing I can see is the issue. Obviously the ECU is the centre part of the system that regulates and tells the fans when to come on.

Worth noting that I have an aluminium rad.

Also, the fans - they are 2 speed, 2 wires for each speed?

 

I dont want to sound negative but i think you are clutching at straws thinking the ECU is a fault for an overheating issue,

Have you changed the caps on the header tank and radiator yet as these can also give similar symptoms if faulty ?

 

Yeah, I've changed the rad caps too! I thought the ECU idea wasn't the answer, but it's the only thing between the instrumentation and the actual temperature.

I'm going to try burp the system again, but I'm very confused as of now.

 

The fans will trigger at 94-95c on stage 1 stage 2 only triggers at way over 100c.

 

Anyone got anything else on this?

 

1. You can't bleed the system properly unless you are VERY lucky. Drain and refill. Properly...do a search on here for how to.

2. If the thermostat goes, the engine doesn't overheat 99.99% of the time, it never gets up to temperature.

 

Any coolant loss ??

Mick

 

No coolant loss at all.

I'm now starting to think it's the water pump?

Very inconsistent temperature. Drives fine for a day, goes off the charts the next.

 

Is it actually overheating or just a gauge fault??

Be worthwhile to beg,steal or borrow an infrared 'red dot' thermometer and checking the cooling system temps when the 'fault' occurs to see if it is actually overheating.


Mick