Folks,
I live near the Rockies. When I travel up to the hills, my Subaru tends to overheat when the car shifts into overdrive and back. If I back off, the guage goes back down to the normal range. I also see this problem around town, again if I go into overdrive.
I took it to a repair shop. They said they tested it and said everything looked normal. Unfortunately, I was in to get something else repaired and am not sure what "tests" were done.
Any thoughts?
Why don't you get a mechanic to fix it? ASE certified, BBB Approved.
A lot of things can cause this overheating. Electric fan switch, temperature sensors, malfunctioning ECU, Blow-By, cracked cylinder head, leaking/ blown head gasket, old radiator fluid, clogged radiator, bad water pump, etc etc.
Because you live in high altitudes and drive around in severe heat in middle America, your car is put under exceptional additional stresses that it otherwise would not by under if you lived on the West Coast for instance.
The high altitude/low pressure puts additional strain on the radiator/cooling system. The difference between inside and outside pressure on the radiator is drastically increased due to the high altitude. Result? Shorter cooling system lifespan. Shortened engine life. All of which is further exasperated by the freezing winters and hot summers of the rockies.
East-
Hi,
If I got this right, your overheating occurs in overdrive, then it cools down in drive? That sounds to me like a lack of coolant flow at the lower rpm of overdrive is a "first thing to look at" problem, followed by poor air flow.
Possibilities for poor coolant flow:
Partially clogged radiator. If you have been using coolant mixed with regular tap water instead of distilled, it's possible you're starting to develop some scale in your radiator that allows enough flow for "low demand" cooling, but not enough for "high demand" situations. At five years, you're close to halfway thru the average life of most radiators, even when properly cared for, according to several sources. New radiators aren't that expensive compared to the damage you may be avoiding. Two online sources I've used are
Slipping drive belt, IF your water pump's driven by an adjustable belt. I don't know how yours works on the 2000.
Grumpy thermostat: it's open, but not flowing enough coolant. While my experience w/ t-stats says they USUALLY work or they don't, I HAVE had some that didn't quite get all the way open when they needed to be or acted very slowly. This is especially a problem if the car's been seriously overheated and the t-stat wasn't replaced after that incident. The t-stat could be damaged. Most folks recommend using Subie OEM stats--some aftermarket units don't seem to flow as well. If you don't go OEM, I've had good luck with Stant Superstats (also sold under the NAPA brand as Superstats.)
Possibly wrong temp thermostat. In today's engines, it's not so likely you'll have one that's too high a temp, since so many are running in the
190-195 deg F (88-90 deg C) range, but there ARE still apps that call for a 180 (82 deg C), so if someone put a hotter one in, there COULD be some flow problems.Possibilities for poor air flow:
Fan clutch dying, IF you have a fan clutch. The fluid in fan clutches does degrade over time, and the fan ends up turning slower and slower by the year. You COULD have a clutch that still turns fast enough at higher engine rpms but drops off when the engine slows. Just replaced one like that last week!
Bad thermoswitch for an electric fan, or even a dead fan motor (check fuses first.)
Radiator clogged w/ bugs or debris. Get out the garden hose or air hose if you've got a compressor and clean it out. Doesn't have to be perfect, but get as much crud out of the fins as you can without going crazy.
And one oddball possibility:
Wrong coolant mix. Most mfrs recommend 50-50 to 70-30 mixes. Pure water cools best, and the cooling ability (not boiling point--actual heat rejection capacity) drops as you raise the anti-freeze percentage. Contrary to some people's opinion, a 100% anti-freeze level can cause overheating! You can get testers at the auto parts store to test the mixture level.
Lots of things to look at, no? Hope you find the problem easily!
Rick
superb post.
Carl
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