Zootal Posted April 19, 2014 Share Posted April 19, 2014 1994 Subaru Legacy. 4 door, auto trans, no turbo. Symptom: check engine light came on, engine over heats. Happened suddenly with no warning. No history of over heating or even running hot. Get car in garage, find it is two quarts low on coolant and the water pipe on top of engine leaks. No problem says I, easy money, just replace the water pipe and we are good to go. While I was at it I replaced the belts and hoses and replaced the timing belt. New water pump. New thermostat. Put it all back together. Start engine. Check engine light comes on. Engine overheats. Now I'm going, wtf wtf wtf? Did I put the thermostat in backwards (no, I pulled the radiator hose and looked - the pointy end points towards the hose, the temp sensor plug end goes towards the waterpump/engine. It's a no brainer, I'm not even sure it can fit in backwards.) While I had the radiator out, I ran water in one end and out the other, and it seemed to flow good. So....engine cooling is mechanical. Water pump pumps water, thermostat opens up and closes to maintain minimum temp. I'm thinking these are the things that can or have gone wrong: Defective thermostat is not opening. I'll pull it and give it the boil test just to be sure. Radiator is plugged (never mind that this happened suddenly, no gradually heating problem) Engine is ... what? What in the engine could cause this? Unless the thermostat is defective, I'm stumped, and I've never seen a defective brand new thermostat. Any suggestions would be very welcome. (PS: The engine light gave me code 24, air control valve, unrelated to the overheating problem, you would think. Valve is bad, I put the gasket on wrong, or left it unplugged) Edit: Engine runs fine. Started right up, purr like a kitten. No sign of timing problem. Link to comment Share on other sites More sharing options...
cal71919 Posted April 19, 2014 Share Posted April 19, 2014 Did you make sure and "burp" all the air out of the cooling system when you refilled it? Seems like you remedied the leak so air in the system would be my guess. I refilled my radiator with the front wheels up in the air to help get the air out. Does your radiator have the bleeder screw on the passenger side near the upper hose? Link to comment Share on other sites More sharing options...
Zootal Posted April 19, 2014 Author Share Posted April 19, 2014 There is a bleeder screw on the passenger side, I opened it to let air out. I did this before a few years ago, it seemed a no brainer at the time. Put water in, bled out air, worked fine. Come to think of it, the driveway did slope to the back a bit, but the radiator cap is well above the engine position, you would not think that would make a difference (?). But it over heated *fast*. And I could only get a gallon of coolant into it, it is supposed to hold six quarts. I pulled the thermostat and boiled it, it opened right up before the water came to boiling. Crude, but at this time I have no reason to suspect the thermostat is defective. For the price of a thermostat I think I'll just go buy another one just to be safe. I suppose the water pump could be defective, but how likely is that? The empeller could have come loose, but I have to pull off the timing belt (sigh) to get to it to see. I'm going to put it all back together again with a new thermostat. If it still over heats, then what? Pull the water pump and if it is good, cry and contemplate a blown head gasket? Link to comment Share on other sites More sharing options...
Idaho subaru Posted April 19, 2014 Share Posted April 19, 2014 Air in the system, simply taking the bleeder screw out while filling is not sufficient. It is usually a more complicated, and more user involved process. With the engine running, cap off, filling, squeezing hoses, repeat, repeat, repeat, repeat...........repeat.... Link to comment Share on other sites More sharing options...
cal71919 Posted April 19, 2014 Share Posted April 19, 2014 Run the heater as well. I wouldn't tear it down just yet. Get the front end up in the air and repeat the process several times, adding coolant as necessary. It takes a few heat cycles to get it all out. Link to comment Share on other sites More sharing options...
Zootal Posted April 19, 2014 Author Share Posted April 19, 2014 Thermostat did not fix it - didn't think it would, but I had to do it to be sure. Put it back together. Run it. Temp went slowly up to redline, at which point I shut it off. Let it cool. Will repeat as y'all have said to do. Link to comment Share on other sites More sharing options...
WhoUtink Posted April 19, 2014 Share Posted April 19, 2014 Go grab one of the rental head gasket liquid testers from advance auto parts. If forget what it's really called. I'd be a little worried if it hit the temperature redline. But like the guys said bleed and bleed and bleed some more. Heck if it don't work leave the thermostat out for testing purposes. Link to comment Share on other sites More sharing options...
Zootal Posted April 19, 2014 Author Share Posted April 19, 2014 Annnddddd...I let it cool. It sucked everything out of the overflow reservoir. Add more coolant. Start up. Run. Hits midpoint. Fans come on. And it sits there. And sits there. And sits there. Drive a few miles around the neighborhood. No overheat. Do you mean to tell me that all this overheat and panic was simply because it needed to burp??? Link to comment Share on other sites More sharing options...
Zootal Posted April 19, 2014 Author Share Posted April 19, 2014 180,000 on the engine. New timing belt, water pump, all new belts, all new hoses even the crossover hoses (subaru hoses - made by Fuji Heavy Industries, Japan, not the made in china junk autozone hoses). Checked throttle body gasket (cause I took the throttle body off), checked iac valve connector. Reset check engine light. Engine purrs like a kitten, check engine light stayed off this time. Can't believe how smooth it runs. Now that I'm done with the drama, I'm good for another 60,000 miles. Panic averted. And once again I owe you guys a cold one....or two or three....I never would have guessed that this engine just needed to burp to get the air bubbles out.... Link to comment Share on other sites More sharing options...
Idaho subaru Posted April 20, 2014 Share Posted April 20, 2014 Glad to hear its up and running! No guarantee that your done yet though, so keep your guard up for for a little while, and keep the coolant tank full. I noticed you said it sucked all the coolant out of the tank.....that causes people a lot of grief, because when it sucks the coolant tank dry.....it sucks in more air into the system, it's a vicious cycle! Subarus are very picky when it comes their cooling system. Link to comment Share on other sites More sharing options...
Zootal Posted April 21, 2014 Author Share Posted April 21, 2014 Glad to hear its up and running! No guarantee that your done yet though, so keep your guard up for for a little while, and keep the coolant tank full. I noticed you said it sucked all the coolant out of the tank.....that causes people a lot of grief, because when it sucks the coolant tank dry.....it sucks in more air into the system, it's a vicious cycle! Subarus are very picky when it comes their cooling system. The next run/cool cycle it sucked out half the coolant in the overflow. Drove about 15 miles, now it seems to be stable. What fun Link to comment Share on other sites More sharing options...
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