2010 Subaru Outback overheats
Vehicle idles up to temp fine. Fan relays kick on @ ~210F. Holding idle a 2k no leaking, no overheating.
During road test with RPMS … for 2-5 min, return car to shop with the radiator cap bypassing into the expansion tank, filling the expansion tank, and overflowing. Upper radiator hose is hot and pressurized to the touch, lower hose also pressurized, and somewhat cooler, though still warm.
I conducted a combustion gas leak test and results were inconclusive.
Any suggestions would be appreciated!
Thank you all!
Driving creates much more heat than idling and this heat needs to be shed at a much greater quantity. I'd look into reduced water pump flow due to failed impeller, an inefficient radiator, or crap in radiator fins (or even condenser fins). You can also measure temps across the radiator to see if the thermostat is opening. Then again, with Subaru I'd imagine the chance for head gasket failure is…
Classic symptoms of Subaru head gasket failure. Been there many times. Had one the other day, bled the cooling system, customer drove it 3 days before the symptoms returned .
How were you were able to confirm the failure?
Head gaskets. How do you know?… it's a Subaru. Only three givens in this world-Death, Taxes, and Subarus blowing head gaskets. Only kidding around, but it is common and they are the common clues. Subaru used a MLS (Multi Layered Steel) head gasket, and they will leak between plies. You can try charging the cylinders @ TDC with shop air to see if signs show up in coolant, and check underneath to…
Pull thermostat and can inspect water pump impeller through opening for t-stat. Replace t-stat and retest. Had multiple t-stats fix this issue before.
Thank you. A blocked heater core can also cause a t-stat to not open.
The Tstat is on the bottom of teh motor at the lower rad hose. Hottest water is at the top of the motor. The tstat gets warmed by the coolant flowing from the top of the motor thru the heater core and dumping onto the back of the tstat, which also the intake to the pump. No flow thru the heater puts no hot coolant on the tstat pellet.
Agree with the likelihood of a Subaru head gasket failure. But before you pull the trigger, lets check a couple of things. - Is the car overhating? Sorry, but have to ask since you don't specify temps when driving. If it is getting hot, you might want to check for a cracked water pump impeller. Some were plastic and would crack around the shaft and the impeller wouldn't spin fast enough or at…
I worked for a Subaru Dealer years ago, one of the engine class instructors said a sure way to know head gasket failure was to perform cylinder leak down test on cold engine while monitoring for bubbles in radiator. That has always worked perfectly for me.
You described the symptoms of a cracked head. Possibly a blown out head gasket. I've had a lot of them that wouldn't turn the blue solution to yellow when testing for combustion gases. In fact, I've had so many I don't even bother with using the test kit anymore. It's almost useless I'd bet good money if you pull the heads you will find a head with a crack in it small enough it only leaks when…
Never saw cracked heads in a Subie, but maybe. Not much space between water jacket passages and cyls. on this one, and forget about oil drainback slots and edge on bottom of engine- ‘bout 3/8" to leak. Don’t get too many of the newer ones that are chain driven so can't vouch for longevity, but with timing belts? For years, during the evolution of these engines you would be like “well, maybe…
Jordan, It's a head gasket failure - how do I know; You have verified the coolant is full, you drove the car … for 2 to 5 minutes = and you observe an unreasonable excess of heat that overwhelms the cooling system pressure limiting cap. You confirm that both hoses are “at temp”. It can't be a thermostat, because one hose would be cold. It can't be the pressure cap, because you didn't…
Jordan - we have gone in circles with theses too usually a cracked or warped cylinder head in our experience. Often the color changing fluid is not able to prove anything. If you end up pulling the heads absolutely get them checked and surfaced by a machinist! Dont forget to replace the head bolts either.
I had a similar issue a few years ago, it was the tension the timing belt over the water pump pulley was not enough to keep the water pump turning at the same rpm as motor. It would be ok at idle etc but once you were driving under load it would over heat. This vehicle was diagnosed as a blown head gasket and owner had sold the car all due to a loose belt and lack of water flow through cooling…
Would a 5 gas confirm a head gasket issue? In theory? Especially knowing the gas test was inconclusive…..
Thank you everyone, I am going to try a Leakdown test on Monday and if that is still inconclusive I'll take a peak at the impeller. Will reply with results.
Performed Leakdown Test. During test of Cylinder 3, coolant began to rise and eventually bubble as I held ~70psi. Thank you gentlemen! J.