http://www.1stsubarudealer.com/subaru-thermostat-problems/
why does my subaru keep overheating?
hiya… i have a 1998 subaru outback with 2.5l engine… i had some problems overheating… i had a radiator hose leak… i replaced the hoses and thermostat… and i drove it today for 2 miles… and it the temp gauge goes up all the way to hot…
i think its the waterpump.. but i am not sure… anybody have any ideas… and cost of this repair…
Starting from simplest to most complex and costly!
#1 did you actually get the system full of water to begin with? It is possible to pour “water” in till it runs over, “cap it” and run engine a minute or two, – when removing cap you will see that the water went down and can not be seen at all! I always start engine and fill till no more water goes in , and most of “bubbling” stops, – then put on cap! You also can run for 5 minutes or so, and then shut off and let cool down, remove cap and see if it went down (sometimes heater core won’t take water till it us under pressure (from heating up engine), – and thermostat opens! #2 pressure cap, –is it pressureizing properly, or “leaking” pressure? #3 is the bottom radiator hose collapsing ? Sometimes hoses are known to collapse from “vaccuum like” negative pressure and will ‘suck flat,– if they are sucked flat not much water can pass through, – most replacemnet lower hoses have a coil of “spring wire” inside to hold them open! #4 waterpump? Usually this is not caused by waterpump on Subarus, unless the water is leaking out so fast that the water in radiator is depleted very quickly.. To do this the pump has to be really bad for some time, – and will sound like “ballbearings in a blender” when the engine runs!
#5 (expensive) possibly blown headgsket, – which allows compression pressure to be pumped in the water jacket,- and air pushes all the water out of engine on to the ground through overflow on “reserve water tank”! There are many jobs easier than changing head gaskets on a Subaru engine!! Run engine with radiator cap off, let idle ,- if a continueous flow of bubbles continues to come up after the engine has run for a minute or two, – and especially if the thermostat has opened (by now all the “normal” bubbles shoud have been purged out)! The more bubbles and faster they come, – the worse the “compression leak” is. Blown head gasket doesn’t nescessarily put oil in water, – or water in oil , – which depends on just where it is leaking!
Are you sure the thermostat is good / I have seen new parts from box that were bad form factory! Check in a pan of boiling water to see if it opens and closes! I of course am assuming that you put the thermostat in”right side up”, — however if you didn’t it shouldn’t overheat this quick Unless the water didn’t get all the way down in engine when you filled it . Note- that if you stopped immediately, waited for engine to cool down, and then drove again, repeating sequence, – after about the 3rd or 4th time it should then open from “backflow water so that the engine would run near normal, — unless the weather is too cold (below freezing), – in which case it might cool water enough so that “hot water” would never get the thermostat from “back”.
I have had a little experience with them (as a Subaru mechanic 35 years ago!)
Subaru Alliance #21
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