Sudden Engine Overheating

[oz_subie]

Recently I went on a driving trip from Sydney to New England. Day 1 fine as we reached Armidale. Next day, as we were heading out of Armidale in the morning (with outside temperature about 3 degrees) , suddenly noticed thermo needle past 3/4 mark and climbed up to nearly red zone within a few seconds.

This was barely after 20-30kms from Armidale and a cool winter morning. Switched engine off and could actually hear boiling from radiator. Got worried, rang NRMA roadside assist and they promptly came in half hour. Noticed radiator coolant was much below normal level.

I have MY07 Forester with 30K . The car was serviced barely a week before the trip.

What puzzles me is nothing happened on day 1 when i did about 500k. Why would the temp shoot up the next day after barely 30k, that too when out temp was so low ? The NRMA guy topped up the radiator with plain water - no leaks detected and no dramas thereafter (1500 ks since then).

I am now worried that the radiator might freeze when I head to snowies next month as he used plain water instead of the coolant.

THoughts appreciated. cheers

 

[El_Freddo]

The thermostat position on the EJ engines are "upside down" to a traditional position - its on the inlet side of the engine - heated by the heater core circuit. I recently froze my cooling system when I mistakenly put coolant in without antifreeze - the cooling system held up well while trying to thaw it out.

Anyway, I've experienced a sudden cooling of the radiator that closes the thermostat and heats the engine really quickly... Now I'm used to it and I've seen my thermometre hit 115 degrees C on a decent hill climb and hold steady there without a problem. It'll usually sit on about 108 or there abouts when going for it without a load.

What I'm thinking is that you A) didn't warm up the engine a great deal before you headed off and B) you're head gaskets might be a little suspect. You mention that your 2007 foz has barely 30k km on the clock. Is it a 2.5 litre by any chance? There was a batch quite a while back that had factory head gasket issues but I'm sure these were with the Outbacks rather than the Foresters, something to do with the new head design and a dodgy batch of gaskets...

Hope its not head issues for your foz, but I reckon you need to take it out more often - and get it dirty once in a while - It'll love you for it!

Cheers

Bennie

 

[El_Freddo]

Or you have a dodgy thermostat/temp sensor for the ECU...

Have a dealer do a diagnostics on the ECU and see what comes up.

Cheers

Bennie

 

[jonbob]

The head gasket issue on the EJ25s was supposedly resolved late 2002 out of the factory, but did affect some of the early Foresters (delivery until about mid 2003).

I experience similar problems (although not to the point of boiling) where the temperature gauge rises in cold weather to about 2/3 (it usually sits just above 1/3, even in 45°C heat with the air-con on full blast).

The explanation of the thermostat not opening would be my best guess - the radiator is staying cold, the cold water at the base of the radiator is keeping the thermostat closed. It is worse when the windscreen demister is on, which switches on air-con, which switches on the radiator fan and cools the radiator further. I notice the temperature comes back really quickly when I slow down, switch off the demister and give the radiator a chance to warm back up.

The solution might be to change the thermostat to one that opens at a lower temperature. It might also be faulty, sticking closed.

Jonbob

 

[eden]

I am now worried that the radiator might freeze when I head to snowies next month as he used plain water instead of the coolant.

just drain it by undoing the hose. put the hose back on and refill. if its still under warrenty i think you have to use the subaru made coolant.