808Legacy Posted April 27, 2012 Share Posted April 27, 2012 (edited) New user here, my 5th Subaru. Just got this '94 Legacy Fwd and have barely driven it. Bought it from an elderly couple, original owners, who seemed to take care of it (needed new struts, a new CV axle, might need a new muffler: making hoarse, throaty sound in back, but exhaust all looks ok) So, the check engine light has been on and off, engine runs good and strong, but I noticed that it runs a wee bit warm: needle is usually in middle. It was a little low on coolant, so I added 60/40 yesterday, but needle stays in middle. Then, last night, I was driving home, I decided to run the heater full blast to see if that cooled it any, and it did the opposite! The needle went almost to the top, then came back to middle when I turned heat OFF. Then, it kind of went up for a little, then back to middle. Wondering if it's a sensor related to check engine light, thermostat, air pocket? All of the above? Radiator is very new, btw, maybe a year old max. Any ideas are greatly appreciated! Edited April 27, 2012 by 808Legacy Quote Link to comment Share on other sites More sharing options...
Recian Posted April 27, 2012 Share Posted April 27, 2012 Thats odd seeing as these dont have a cut valve for the heater core. If it rose to hot quickly then back down that sounds like an air pocket or faulty sensor. The gauge sensor isnt the same as the ecm one so its likely to do that and not throw a code. The fact that it was low worries me. Has it dropped any since you topped it off? Quote Link to comment Share on other sites More sharing options...
808Legacy Posted April 27, 2012 Author Share Posted April 27, 2012 (edited) It did that after I topped it off. I just checked the hose leading to the thermostat, and it has a small leak when I squeeze it, so I guess I ought to start there, replacing that hose, right? Would that be causing an air pocket? Also, would the check engine light be affected by that, or I guess there is no way of knowing? Edited April 27, 2012 by 808Legacy needed to Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted April 27, 2012 Share Posted April 27, 2012 does it have a ''subaru'' t-stat. after market t-stats are really squirrely in a subaru. if the older couple didn't drive it much it may not have been an issue for them. i would look for more leaks and replace any hose in question. drain and save the coolant. check the t-stat, replace if not a subaru part. search for pics to see. and then refill and burp correctly. this is just about the only way you are going to know if it is right. once this is done, you can look for other causes if it still over heats. Quote Link to comment Share on other sites More sharing options...
808Legacy Posted April 27, 2012 Author Share Posted April 27, 2012 (edited) I guess I'll need to study up on burping it. Just drove it to get hose, gauge stayed where it's usually been, just below midway, which I know is a little hot. I didn't play with heater, though, I'm scared to. I did call a reputable shop on the island and he said it could be a sensor for the gauge. Going to start with the hose first. This is a (hopefully minor) project car. Needs left CV axle, and I'd love to find out why it makes this throaty, hoarse sound toward the rear when I give it gas. Needs a driver's side lock cylinder replacement (I guess I need a locksmith?), new wiper sprayers... Edited April 27, 2012 by 808Legacy Quote Link to comment Share on other sites More sharing options...
Rooster2 Posted April 27, 2012 Share Posted April 27, 2012 I guess I'll need to study up on burping it. Just drove it to get hose, gauge stayed where it's usually been, just below midway, which I know is a little hot. I didn't play with heater, though, I'm scared to. I did call a reputable shop on the island and he said it could be a sensor for the gauge. Going to start with the hose first. This is a (hopefully minor) project car. Needs left CV axle, and I'd love to find out why it makes this throaty, hoarse sound toward the rear when I give it gas. Needs a driver's side lock cylinder replacement (I guess I need a locksmith?), new wiper sprayers... The gauge staying just below midway is normal, and not a little hot. All 3 Subarus that I have owned, the temp gauge read midway on the dial, as normal operating temperature. Yea, first things first, replace the hose, and burp out any air in the cooling system. I, too, would be concerned that a cheap thermostat could cause your problem. I remember someone posting on this forum a picture of a good thermostat, and a cheap one. The cheap one was rather flat, with minimal coil winding on the thermostat. Check the archives here in the "search" mode to retrieve the pictures. There is also a possibility that you may have a bad head gasket. Classic symptom of a bad head gasket, is quick spike of the temp gauge to hot after driving for a while. If that happens, turn off the motor pronto. Also, look in the radiator over flow container to see if bubbles are blowing to the surface in the container with the motor still running after it is at operating temp. Quote Link to comment Share on other sites More sharing options...
MilesFox Posted April 27, 2012 Share Posted April 27, 2012 Run the heat while adding coolant. Quote Link to comment Share on other sites More sharing options...
808Legacy Posted April 27, 2012 Author Share Posted April 27, 2012 Ok, thanks all of you for your tips! Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted April 28, 2012 Share Posted April 28, 2012 Get a new thermostat from Subaru, not a cheapo aftermarket, replace all the hoses, and refill with 50/50. The thermostat isn't opening all the way and likely has too high of a temperature rating. The heater core is part of the bypass circuit which keeps hot coolant flowing to the thermostat. This is because the thermostat is on the inlet side of the water pump, meaning COLD coolant (in a relative sense) is flowing across the thermostat at all times. This will cause the thermostat to close, generally only in cold weather but it can happen other times as well, particularly when the thermostat is clogged or partially jammed. The flow through the bypass circuit keeps the thermostat open by keeping warm coolant flowing over it. This keeps it from closing and blocking the flow of coolant through the block. Obviously blocked flow means the coolant in the block will overheat. Quote Link to comment Share on other sites More sharing options...
pamike Posted April 28, 2012 Share Posted April 28, 2012 There is also a possibility that you may have a bad head gasket. Classic symptom of a bad head gasket, is quick spike of the temp gauge to hot after driving for a while. If that happens, turn off the motor pronto. Also, look in the radiator over flow container to see if bubbles are blowing to the surface in the container with the motor still running after it is at operating temp. this is the problem i had. the temp spiked and then would be good for a while. eventually it got to the point where it would be ok on nice easy cruses but any up hill or heavy throttle and it would over heat. Quote Link to comment Share on other sites More sharing options...
808Legacy Posted April 30, 2012 Author Share Posted April 30, 2012 Get a new thermostat from Subaru, not a cheapo aftermarket, replace all the hoses, and refill with 50/50. The thermostat isn't opening all the way and likely has too high of a temperature rating. The heater core is part of the bypass circuit which keeps hot coolant flowing to the thermostat. This is because the thermostat is on the inlet side of the water pump, meaning COLD coolant (in a relative sense) is flowing across the thermostat at all times. This will cause the thermostat to close, generally only in cold weather but it can happen other times as well, particularly when the thermostat is clogged or partially jammed. The flow through the bypass circuit keeps the thermostat open by keeping warm coolant flowing over it. This keeps it from closing and blocking the flow of coolant through the block. Obviously blocked flow means the coolant in the block will overheat. Someone local here told me to just take the thermostat out, as it's not really needed in a tropical climate. Coldest it ever gets here is 70 degrees. That would preclude me from driving it up Haleakela, however (10,000 ft). I winced at that notion. I finally got the hex socket to unscrew the engine coolant reservoir. Something tells me this is going to be messy. I'll look at the thermostat and compare it to the pics I've seen on here. Napa sells a Tama for $21, which I'm told is OEM. Quote Link to comment Share on other sites More sharing options...
808Legacy Posted May 1, 2012 Author Share Posted May 1, 2012 Ok, replaced hose and voila! NO thermostat. so, mechanic must have taken it out. Asked local Napa guy about it and he said a lot of people in Hawaii with older cars take out the thermostat. So, I'll leave it out. Flushed cooling system, now about to start 'er back up! Wish me luck! Quote Link to comment Share on other sites More sharing options...
808Legacy Posted May 1, 2012 Author Share Posted May 1, 2012 Needle started rising again, burped it again tonight, twice with heater on full blast outside Walmart. Ran fine for rest of night, until, when almost home, I decided to test the heater again after climbing hill. Heat came on, then, turned lukewarm and needle started to rise, though not as high as the other night. Is this a heater core issue? I guess I need to flush the heater core now? Is this an air pocket in the heater core line? Quote Link to comment Share on other sites More sharing options...
808Legacy Posted May 1, 2012 Author Share Posted May 1, 2012 Get a new thermostat from Subaru, not a cheapo aftermarket, replace all the hoses, and refill with 50/50. The thermostat isn't opening all the way and likely has too high of a temperature rating. The heater core is part of the bypass circuit which keeps hot coolant flowing to the thermostat. This is because the thermostat is on the inlet side of the water pump, meaning COLD coolant (in a relative sense) is flowing across the thermostat at all times. This will cause the thermostat to close, generally only in cold weather but it can happen other times as well, particularly when the thermostat is clogged or partially jammed. The flow through the bypass circuit keeps the thermostat open by keeping warm coolant flowing over it. This keeps it from closing and blocking the flow of coolant through the block. Obviously blocked flow means the coolant in the block will overheat. So, no thermostat. It's Hawaii. Replaced bottom radiator hose and trimmed off cracked part of the small hose right above thermostat housing. Ran pretty good rest of today until tonight when I tested the heater again. Why would heater be causing this overheating thing (per my last post)? A side note: I swear too, that my past Subarus (an 83 GL, a 92 Legacy LS, then two subsequent 91 and 93 Legacys) normal temp level was at about 1/3 on the gauge. This one seems to like halfway, but others here are saying that is normal. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted May 1, 2012 Share Posted May 1, 2012 And you have NO thermostat in right now correct? Halfway on the guage is pretty much normal. One of my cars it sits at halfway all the time, the other just a hair below, but they never move once the engine is warm, even when it's 100 degrees out. Losing the heat after only a few minutes could be a plugged core, but that shouldn't cause it to overheat or run hot when there is no thermostat. The only affect that running the blower fan will have is cooling the liquid that is in the heater core. Regardless if the heat is on or off, coolant moves through the core at all times. You can try flushing the hearer core and radiator, also wouldn't hurt to put a new radiator cap on if that hasn't been done. If none of that helps it's time for a block test. Quote Link to comment Share on other sites More sharing options...
808Legacy Posted May 1, 2012 Author Share Posted May 1, 2012 Ok, time to flush heater core. Radiator was flushed yesterday (it's basically brand new anyway). There was minimal sediment in flush. Wish Haynes was more clear about flsuhing heater core, but I guess that's why I'm here! Quote Link to comment Share on other sites More sharing options...
Ricearu Posted May 1, 2012 Share Posted May 1, 2012 the thermostat may not be opening all the way, not allowing for enough coolant flow under load here is the pic of the difference. the meaty manly awesome looking one on the right is a "subaru" fuji heavy industries made one Quote Link to comment Share on other sites More sharing options...
Rooster2 Posted May 1, 2012 Share Posted May 1, 2012 When burping and T-Stat attention fails to correct over heating, it most likely is a bad head gasket. Subie head gaskets go bad, by allowing hot exhaust gas to enter the cooling system, causing the motor to over heat. Not what you want to hear, but it is what I think you are facing. Quote Link to comment Share on other sites More sharing options...
pamike Posted May 1, 2012 Share Posted May 1, 2012 When burping and T-Stat attention fails to correct over heating, it most likely is a bad head gasket. Subie head gaskets go bad, by allowing hot exhaust gas to enter the cooling system, causing the motor to over heat. Not what you want to hear, but it is what I think you are facing. yup this is exactly what happened to mine. and when it would heat up and i turned the heat on it would blow cold. Quote Link to comment Share on other sites More sharing options...
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