[HTi]Johnson Posted June 15, 2007 Share Posted June 15, 2007 Hello all. I don't have much time. My 1998 Outback (2.5 DOHC) is overheating. I just did the HGs, waterpump, thermostat, rear main, oil pan and the works. I filled the engine up with coolant through the upper coolant hose and then topped off the radiator with the bleeder screw out. It even has a new radiator cap. Then I "burped it". It'll be ok for a while, then over heats, I pull over, let it cool. Top off the coolant (doesn't take much) then go for 3 minutes, it over heats again. I'm not getting warm air out of the heater and the radiator is cool to the touch until I open the cap and release the pressure, then it gets hot. I used all Subaru parts for the recent HG job. What could this be? Do these blocks tend to crack from overheating (it was overheated before, that's why I did the HG job. I couldn't find any problems with the heads (pressure tested) and visual inspection of the block didn't warrant any worries) Could this be a clogged radiator? and if so, where could I find a dual core? Thanks for your time, Justin Johnson. Link to comment Share on other sites More sharing options...
cookie Posted June 15, 2007 Share Posted June 15, 2007 it sounds like an air lock to me. I dirvie it around the block and put the front up on ramps and open the bleeder with the engine running. Then I let it cool down and refill. sometimes it can be a bear to get air out. Warm air out of the heater is key. The heater is higher and often holds air. Link to comment Share on other sites More sharing options...
porcupine73 Posted June 15, 2007 Share Posted June 15, 2007 Hm, yes maybe air pocket or for some other reason the water pump is not circulating....I don't think it would be a radiator issue because you would still get warm air out the heater. Link to comment Share on other sites More sharing options...
nipper Posted June 15, 2007 Share Posted June 15, 2007 i too vote for an air bubble. Start the car and let it idel with the cap off. When the t stat opens top off the cooling system. No car should ever be filled up cold, they all need to be filled up running. Drive around the block and check the level. nipper Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted June 16, 2007 Author Share Posted June 16, 2007 Well, I elevated it and gave it water as needed. Then drove it around, still overheated. I've done every way of filling this thing up. Even what the owner's manual said to do...fill it up with the bleed screw out, put it together then start it and rev it at 2-3k for 5 mins. Then top off once cooled. Could it be the thermostat? It's only 3 months old, but it was in the car when it overheated the first time (leading to the HG replacement)? Could the extreme heat cause it to fail? Thanks, Justin. Link to comment Share on other sites More sharing options...
porcupine73 Posted June 16, 2007 Share Posted June 16, 2007 Are you still not getting any warmth out the heater? If the coolant is circulating, you get at least some warmth out of there unless it's totally plugged or there is some heating system problem. Even if the thermostat is failed or radiator is plugged heater should work. Did you replace the thermostat? The first post says you did the HGs, waterpump, thermostat. If it is failed closed or in backwards or something that can definitely cause overheating, though with heat out the heater... Can you see if the water pump is pumping and it's making it through the system? Like maybe pull the hot hose going to the heater core and then crank it and make sure you get a good garden hose like stream out of there. Obviously you can't do this for more than a couple seconds. Was the timing belt and tensioner in good condition and not oily or anything? Link to comment Share on other sites More sharing options...
MDW25gt Posted June 16, 2007 Share Posted June 16, 2007 I fill through the air bleed hole while running. Link to comment Share on other sites More sharing options...
nipper Posted June 16, 2007 Share Posted June 16, 2007 Let me goto the dark side.... DId you have the heads machined when you replaced the head gaskets. Was the engine previously repeatedly over heated? nipper Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted June 17, 2007 Author Share Posted June 17, 2007 Let me goto the dark side.... DId you have the heads machined when you replaced the head gaskets. Was the engine previously repeatedly over heated? nipper It was overheated a couple times, that I know of. THe heads were flat when straight edged with a machinist's straight edge. I'm thinking it popped a HG again. Because when I would drive it cold and as it warmed up then started to overheat, the temp would climbed with how much I push the throttle in. Is there an easy way to do a comp test on these 2.5's? I know it was a pain to replace the spark plugs months back? Thanks for you time. Justin Link to comment Share on other sites More sharing options...
nipper Posted June 17, 2007 Share Posted June 17, 2007 Dead flat is not the only issue. The surface finish also has to be a very tight tolerance. If the surface finish is not to spec, you will blow a head gasket. nipper Link to comment Share on other sites More sharing options...
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