need help diagnosing cooling system stuff

[davidv]

new to this board... any help would be appreciated... 91 subaru legacy (recent purchase) has been leaking coolant out of the reservoir. temp guage says temp is ok. happened three times in the last week. each time i refill radiator and a day or two later it backs up into the reservoir and leaks out. temp guage seems to work. only noticed it getting close to too hot once- the morning after it first happened, before i refilled the system. since then it goes to just below halfway.

what could cause this to system to back-up like this? the check engine light also goes on and off, seemingly in no relation to the overflow times. any ideas ?

[Frank B]

Will it continue to pump out the coolant untill there is no more? Or will it only pump out a little then stabalize?

 

Is your overflow tank overfilled?

Does it do it only when it's hot, or does it begin at start up?

 

The system is designed to allow for expansion of the coolant, the rad cap releases pressure at a set psi(usually written on the cap), and excess coolant will flow into the overflow, or expansion tank. Usually, if the system is overfilled, the coolant level will stabilize. It will usually look as if you need some coolant because the rad isn't completely full. But that space)air) left in the top of the rad by not filling it completly up, allows room for expansion.

 

Hopefully this is all that is happening.

 

 

 

new to this board... any help would be appreciated... 91 subaru legacy (recent purchase) has been leaking coolant out of the reservoir. temp guage says temp is ok. happened three times in the last week. each time i refill radiator and a day or two later it backs up into the reservoir and leaks out. temp guage seems to work. only noticed it getting close to too hot once- the morning after it first happened, before i refilled the system. since then it goes to just below halfway.

what could cause this to system to back-up like this? the check engine light also goes on and off, seemingly in no relation to the overflow times. any ideas ?

[Roundeye]

I would look at replacing the radiator cap. A bad cap will allow coolant to overflow at a lower than normal pressure. A bad side effect of this is that it lowers the boiling point of your coolant which only adds to the problem.

[davidv]

Thank You. Seemed like not all the fluid but way too much to be just stabilizing. I replaced the cap yesterday so we will see... Also, this first occurrence was during a drive from sea level to the near top of 10,000' haleakala volcano on maui (full moon too) wondering if elevation/air press change may have contributed to this situation?

[Roundeye]

Thank You. Seemed like not all the fluid but way too much to be just stabilizing. I replaced the cap yesterday so we will see... Also, this first occurrence was during a drive from sea level to the near top of 10,000' haleakala volcano on maui (full moon too) wondering if elevation/air press change may have contributed to this situation?

Yes, altitude does affect boiling point. High altitude=low ambient pressure. The lower the ambient pressure, the lower the temperature is that water will boil.

 

This may be a reach, but higher altitudes (meaning lower ambient pressures) would mean less force on the top side of the radiator cap seat, which aids the spring in keeping correct pressure on the radiator opening. I don't know how much of an affect it would have, but it would surely have some. Think about what would happen if you put your car in a huge sealed chamber and pulled a vacuum on it. You would eventually reach a point where you would off seat the radiator cap and suck the air/fluid out of the radiator.

 

I think you need to make a sacrifice and throw your old cap into the volcano:cool: That should fix it.

[Frank B]

You didn't mention a 10,000 ft volcano!

 

 

 

Yes, altitude does affect boiling point. High altitude=low ambient pressure. The lower the ambient pressure, the lower the temperature is that water will boil.

 

This may be a reach, but higher altitudes (meaning lower ambient pressures) would mean less force on the top side of the radiator cap seat, which aids the spring in keeping correct pressure on the radiator opening. I don't know how much of an affect it would have, but it would surely have some. Think about what would happen if you put your car in a huge sealed chamber and pulled a vacuum on it. You would eventually reach a point where you would off seat the radiator cap and suck the air/fluid out of the radiator.

 

I think you need to make a sacrifice and throw your old cap into the volcano:cool: That should fix it.

[davidv]

Mahalo from maui for the advice! sacrificed the $7.89 for a cap, reluctant to drive to the top again without a few days of test driving at sea level first... and then there is the randomness of the check engine warning light...

[Frank B]

Does it flicker at sea level, or only in the high elevations?

 

I had an 86 3 door that would flicker a bit when I went to the top of the mountains here in VA, and it was only 1500, maybe 1800 ft!! Only on the mountains too.

 

Mahalo from maui for the advice! sacrificed the $7.89 for a cap, reluctant to drive to the top again without a few days of test driving at sea level first... and then there is the randomness of the check engine warning light...

[davidv]

not really a flicker... more of either on or off when the car is started. maybe 1 in 3 starts it will come on. have not noticed it change (from on to off, or off to on) when the car is out and about.