Jeffro Posted July 7, 2013 Share Posted July 7, 2013 I think that I have a temperature gauge problem. The dash says that it has been running hot lately (up near the red sometimes). I don't think that I have a cooling problem. Here is what I'm seeing and have done: 1) Checked the radiator "in" hose with an IR thermometer when the gauge says it is hot. The hottest I've seen it at is 200F. I think that tells me I'm not overheating? I'm not sure what normal is, but 200F doesn't sound that bad. It was driving up a pass on a hot day. 2) Both fans work. I can see them cycle on and off. They will cycle off even when the dash says it is hot. 3) I replaced the temperature sensor (Subaru p/n 22630AA11A, I used an aftermarket). This seems to make it worse if anything. I think this is essentially 2 sensors, one for the dash gauge and one for the ECU. Is this correct? My understanding is the sensor for the dash gauge is a thermistor. Can I put a resistor betwenn on the the pins and ground to test the dash gauge end of things? What resistance value would I use? Last fall I had the head gaskets done. They also put in a new water pump and tstat, so I wouldn't suspect those. I've also put in a radiator, but it was used so maybe it is clogged. From what I've observed I don't suspect a cooling problem though. Thanks for any suggestions! I'm new to this so I'm probably going down the wrong path. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 7, 2013 Share Posted July 7, 2013 You need to confirm that the thermostat used was OEM-style. do you lose coolant or is the overflow bottle getting filled up? Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 7, 2013 Author Share Posted July 7, 2013 I will try to find out on the thermostat. What will that tell me? Forgive me for asking, but it seems that the thermostat is opening if I'm getting 200F at the radiator? The overflow bottle was empty when this started. I put aprx. 1 quarts of water in, and it has held steady sense then, but it could be slowly loosing coolant. I guess that would be a HG issue agian or a bad radiator cap? I've put about 3-400 miles on it after adding the water. Quote Link to comment Share on other sites More sharing options...
Caboobaroo Posted July 7, 2013 Share Posted July 7, 2013 I would check the lower radiator hose for the temp and see how it compares to the upper hose temp. If the lower hose stays cold, this means the thermostat isn't opening and should be replaced. I would also use your infrared just to double check the radiator for cold spots. This could pinpoint a partially restricted radiator which I have seen happen, more often on aftermarket brass radiators. I have also seen the thermistor for the gauge cause a similar issue but the car was overheated prior causing damage to the thermistor. If you have anyway to see what temp the ECU sees, that would help significantly. It will help determine if the gauge/thermistor are accurate. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 7, 2013 Author Share Posted July 7, 2013 Lower hose was hot too. I'll have to take it out again for specific numbers. I didn't see much cooling if I remember correct (maybe 10F). I ordered a cheap OBDII bluetooth scanner yesterday; it will let me see what temp the ECU is seeing. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 8, 2013 Author Share Posted July 8, 2013 (edited) Ok, definitely seems worse. It happens driving around town now, not just on passes or going 70+ mph. Gauge 7/8 of the way to red on the dash. 150F top radiator hose 141 bottom radiator hose 165 top of radiator (the EPDM rubber hoses read a bit lower, I assume because they insulate more) 137 left top front of radiator 107 right top front of radiator This points to better flow through the drivers side of the radiator I suppose. The water pipe (where the temp sensor mounts) was reading about 10 degrees higher than the top of the radiator. Edited July 8, 2013 by Jeffro Quote Link to comment Share on other sites More sharing options...
luko Posted July 9, 2013 Share Posted July 9, 2013 Did you do a test for resistance on the temp sensor wires? I know on the 3 gen legacy's if you either unhook or if there is a break in the wires the gauge will go up all the way and the fans will turn on. So there could be a slight break in the wires causing high resistance which causes your temp gauge to go up Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted July 9, 2013 Share Posted July 9, 2013 even wiggling the wires, harness and grounds while someone observes the gauge for changes might point to a problem area. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 15, 2013 Author Share Posted July 15, 2013 I received my OBDII scanner. Does well for less than $10! "Redline" on the dash gauge happens at about 205F. That seems a low temp to me for a redline. I was able to get the ECU to read as high as 228F pushing up a hill. That seems high? Maybe I have temp gauge issue and a cooling issue? RE: Loose wires or a break: A wire break causes the ECU to turn on the fans and the temp gauge reads all the way down on my car. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 15, 2013 Share Posted July 15, 2013 did you add the subaru coolant conditioner when the head gaskets were done? this is required. i have been driving subarus since 1994 and on this forum since 05, and i have NEVER heard of a bad temp gauge single wire sensor. the other sensor, ECTS, can go bad and cause issues, but those are usuallt ''starting'' issues, not overheating issues. it is a cooling system or head gasket (hopefully not) issue, not the gauge. Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 15, 2013 Share Posted July 15, 2013 I suggest you have the coolant checked for exhaust gases to see if there is a head gasket leak. If that test shows no problem there then I suggest you replace the used radiator with a new one. I don't think you have a gauge problem. You also might try replacing the radiator cap as a first step. That has helped some folks with this kind of problem and is fairly cheap and very easy to do. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 16, 2013 Author Share Posted July 16, 2013 I suggest you have the coolant checked for exhaust gases to see if there is a head gasket leak. If that test shows no problem there then I suggest you replace the used radiator with a new one. I will do just that. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 16, 2013 Share Posted July 16, 2013 that is a pretty good idea, but the usual head gasket leak in the 00 - 04 engines is external. so if the test is positive you have learned you have an internal leak. but if the test is negative, you have not ruled out an external leak. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 16, 2013 Author Share Posted July 16, 2013 An external leak would cause overheating, yes? Oil has been disappearing, but I haven't found it on the outside of the engine (yet). As I mentioned, it was low on coolant when this started. It has held steady since then, but I've only driven it a little. Maybe I've got a head gasket leak and I'm losing oil and coolant. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 16, 2013 Share Posted July 16, 2013 Maybe I've got a head gasket leak and I'm losing oil and coolant. there is a very good chance of this. Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 16, 2013 Share Posted July 16, 2013 Don't rule out the radiator cap either. A faulty cap can cause this kind of problem also, at least with the coolant. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 16, 2013 Author Share Posted July 16, 2013 What should I do? Replace the radiator cap and take it to a shop for a coolant pressure test? Is there a definitive test for a head gasket leak? Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 17, 2013 Author Share Posted July 17, 2013 I grabbed a radiator test kit from O'Reilly. With the engine cold I pressurized the coolant system to 15PSI. It was dropping (say 1/2 PSI over 5 minutes). I didn't see an obvious coolant leak. I then started it and hit the throttle a few times. It pressurized to 7-15 PSI pretty quickly. My radiator cap is rated at 15.7 PSI. I haven't tested it yet. Is that a definitive head gasket failure? Quote Link to comment Share on other sites More sharing options...
Cougar Posted July 17, 2013 Share Posted July 17, 2013 I would have to say it appear to be a gasket failure to me. Quote Link to comment Share on other sites More sharing options...
Jeffro Posted July 17, 2013 Author Share Posted July 17, 2013 Sounds about right. I'll have to see what the guys says that did the work for me last fall. My understanding was that he would warranty for 1 year. Once the engine cooled off I pressurized it again to 15PSI. It dropped to 10PSI overnight. Not sure why the HG didn't last longer. I really don't think that I ran the engine hot before this. He didn't machine the heads because they were within Subaru's specs. Maybe I should have them machined? Thanks for help. I was obviously looking down the wrong path when this started. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted July 17, 2013 Share Posted July 17, 2013 A reading of 205 temp and the dash gauge is at the red? That does sound wrong to me. You can test the gauge calibration by using a resisitor in place of the sensor. Need to identify which wire of the 3 is for the gauge, and connect it through a resitor to ground. Gotta get a spec for what ohms=temps....but those are ussually in the FSM as a chart for testing just this excact problem. Redline should be more like 230-240 Try refilling it through the upper radiator hose, with the car parked on a slant so the nose is above the heater core. Take the upper hose off the radiator, fill the block with coolant. then hook up the hose and fill the radiator the rest of the way. Quote Link to comment Share on other sites More sharing options...
Gloyale Posted July 17, 2013 Share Posted July 17, 2013 specs for first gen legacy temps. Newer models should be the same 135F = 135.4 ohms resistance 248F = 19 ohms resistance Additionally, the fans should come on when the ECU sees a temp of 205....so if the fans come on and go off......then the ECU is seeing temps around 200-205......which should be right about at the halfway or just above halfway mark on the temp gauge. I think you should test the gauge using a 100 ohm resistor. If that pushes the gauge over halfway, then the problem may be with the gauge, or the voltage regulator inside the gauge. Quote Link to comment Share on other sites More sharing options...
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