thermostat symptoms?

marvella · #1 04/02/09, 10:09 AM

i drive a 1996 subaru legacy outback AWD wagon as a commuter car/ light duty hauler.

about once a week lately it will overheat slightly. when i fill the radiator it's taking a gallon or two so it's clearly leaking out somewhere. It does not lose coolant until it is heading for the red line. once the water is back it's fine for another week or so.

is this a symptom of needing a new thermostat or a more serious problem??

TIA!!

Wis Bang · #2 04/02/09, 10:28 AM

Something is leaking.

T Stats stick open [no heat] or closed [overheat] but should still have a full system unless you open the rad cap while it is hot & let coolant spray/burp out, not something you should do!

Get the system pressure tested to reveal the leak.

**Cabin Fever** · #3 04/02/09, 10:30 AM

I'm thinking it may need a new intake manifold gasket.

marvella · #4 04/02/09, 10:58 AM

shoot. oh well, i'll take it to the mechanic tomorrow.

i've noticed the heater/ defroster isn't working well lately. i'd say that's part of it.

thanks for all the prompt replies!

Wis Bang · #5 04/02/09, 11:18 AM

Do you smell coolant inside? Does the defroster fog the windows? These are signs of a leaking heater core along w/ a wet passenger floormat. The Subaru 'boxer' engine might not have the intake mainfold problems that a GM v-6 has but any leaking rad or heater hose or a bad rad core would cause overheating.

Continued overheating will kill an engine quickly...

Curtis B · #6 04/02/09, 11:35 AM

Check your rad cap, they go bad quite a bit and is not a leak until you get up to operating temp.

Hooligan · #7 04/02/09, 11:46 AM

Google "subaru 2.5L head gasket".

Head gasket failure is a very common problem on the old 2.5s. It acts just like a faulty t-stat.

I bet if you start the engine and leave it idling as you look into the coolant overflow tank you will see a layer of scum (oil) in the coolant and you will see a stream of bubbles entering the tank.

Should cost about a grand if you have it done and assuming there is no further damage. Make sure they use the new and improved gaskets if it turns out to be this and you have it fixed.

agmantoo · #8 04/02/09, 11:48 AM

It could be a more serious problem. You need to determine where the coolant is being lost. It could be as simple as the water pump seal is weeping coolant. It could be as bad as a head gasket blown. Until you get the problem identified and fixed you need to top up the coolant daily. Park the vehicle on concrete and see if you see any evidence of even a tiny drip. Check the oil to see if it is milky color. With the coolant topped up and the radiator cap off let the engine run for at least 5 minutes by the clock and observe for bubbles. Report your findings back here and someone will further assist.

marvella · #9 04/02/09, 12:18 PM

to be clear- it's a 2.0 liter engine 5 speed.

the water in the rad bubbles out a bit when full but not foamy or discolored.

oil looks like oil, no milky color etc. no oil in coolant.

no smell of coolant or wet floors.

just overheating a bit and not all the time. not enough to do damage. (done that before and now know to pull over!! when it overheats instead of trying to make it home.)

i kept a close eye on the guage so i could pull over if i needed to. to beat it all once i pulled off the highway and hit the back roads the temp went right back down and stayed there. my son wondered if the thermostat could be intermittently sticking open or closed.

agmantoo · #10 04/02/09, 12:27 PM

Redo the radiator for bubbles test. Give the system time for all the bubbles created from topping up to dispense. You should have no bubbles coming out the fill hole with the radiator cap off and the engine warm. How many miles are on this engine? PS...the symptoms observes with the defroster/heater are a result of low coolant.

marvella · #11 04/02/09, 01:49 PM

Quote:

Originally Posted by agmantoo

Redo the radiator for bubbles test. Give the system time for all the bubbles created from topping up to dispense. You should have no bubbles coming out the fill hole with the radiator cap off and the engine warm. How many miles are on this engine? PS...the symptoms observes with the defroster/heater are a result of low coolant.

hm, there was coolant in the box thingy next to the rad, only down about half from full.

145K.

what will ongoing bubbles tell me? i never have waited for them to stop fully stop. as long as the water level stayed at the top i just capped it off.

Wis Bang · #12 04/02/09, 02:52 PM

Any combustion gsses getting from the combustion chambers into the coolant passages via a blown head gasket would cause bubbles on a continous basis. I just experienced a cracked head on the car my DD has at college and it would overheat while climbing a grade and the temp would drop down if you pulled over. The head gasket could act the same way.

A shop could test the coolant for Hydrocarbons that would be lefft over frrom the combustion process...get this car into a shop. The longer you wait, the more it may cost...

I ended up spending $500.00 & change for a junkyard pull out engine & $500.00 and change getting it installed plus tax [she is at school in Gettysburg about 170 miles away] for a bill off $1280.00 as we needed it fixed quickly as she is doing her student teaching. I could have done it for alot less if it was here and my neighbor [auto tech] had the time to do it...

marvella · #13 04/03/09, 07:52 AM

thank you to all. it's still running fine and i don't think there is any damage. i learned a long time ago with a subaru do not overheat their engines. i can see there is a problem on the horizon and want to get to it before it breaks.

it may be a blown head gasket then. i'm leaving work early today to see my mechanic.