A plea for help! Impreza 2006 non-turbo.

I have an intermittent overheating problem which only happens every 2 or 3 weeks. It can happen when travelling on a freeway or standing in the traffic. The temp very quickly rises to 110C and may then go up and down.

I had the exact same problem 2 1/2 years ago. At the time they replaced the following: 3 X thermostats, 2 x fan relays, radiator, temp sensor and water pump. My garage said they couldn't find the problem and told me to take it to an auto-electrician. At the end of a full day's work (charged for a day's labor) they said it was the thermostat! Anyhow, it behaved fine until 2 months ago.

I've just replaced: thermostat, radiator cap, and fan relays with no improvement. The system has been "burped" following the regular recommendations.

There are no bubbles that might indicate a head gasket failure but I have ordered a kit to test for this just in case. The level in the header tank isn't dropping.

Please guys, I'm desperate for ideas.

 

Has the water been flushed out and replaced? Sounds a head scratcher. What's a freeway?

 

Antifreeze replaced twice.
Freeway = British for highway!

 

You do realise this is a UK based forum ?? and that we Brits would use Motorway - Freeway is more US..........

 

Sorry!

 

There's another thread with similar issues, but with a WRX might have same issue.

 

Thanks Jaygsi, I'll look for it.

 

How are you proving the temp you are seeing on the dash, sounds like a it could be a erroneous reading if you have changed the whole cooling system
Id be tempted to run it up to temp and compare what the ECU is actually seeing and using a infra red thermometer see if they tally, the dash is rather vague so find a cheap OBD lead, grab some free software like Romraider and see if they tally up,
It could be a faulty CTS sending random info to the dash, I know a few that have had this, as Ive changed a few CTS`s for members on here when this happened,
Hope this helps.

 

Thanks JDM Stig.

I have an OBDC reader and it shows the same occasional jumps to 115C. It normally runs between 91 and 102.

I have narrowed it down to usually happening after travelling for 5 to 10 minutes at 100kph and then stopping the car. If I jump out and check I see that the radiator fan is running, top and bottom hoses are hot, and that there's some pressure in the hoses but they're not hard.

If I turn the engine off for 2 minutes and restart, the temp is back at normal.

I'm ripping my hair out.