Overheating - no fans kicking on

[dunbray]

Sorry this is going to be a bit wordy, but I want to provide all the info I have in case anything trips an idea for whoever might have had a similar problem.

 

I just spent all day trying to fix an overheating problem. My daughter is primary driver on my 2000 Legacy GT. We have had this car (used) since last Aug 2016 approx. Over 150,000 Have had no problems with cooling. Check engine light was on, with a reading for exhaust gas.

 

The other night she was out driving when it shot steam from under the hood. When I got there, I could see it had come out the nozzle on the side of the place the radiator cap screws on, and that the tube and overflow tank were missing.

 

I drove the car a few blocks home and during that time the temp gauge went pinned on hot.

 

Filled the radiator and couldn't get it to overheat at idle, so took it up some hills, and it spurted. Fans never kicked on. When I turn on the A/C they run whenever the compressor engages, which is intermittent. It isn't very hot here yet.

 

Took it to a shop and they said the head gasket was blown. Purchased a tester (combustion gas in coolant tester), and I got a negative. No other symptoms of blown gasket either. I think they lied. On way home check engine light was flashing.

 

Today I replaced the temp sensor, and the thermostat. I also found my O2 sensor was unplugged, so plugged it back in. I also removed the big tube to the PCV valve, removed the valve and cleaned it, then replaced it. The big tube was cracked and brittle at the end. When I started the car it was clearly missing, and ran worse than ever. I bought a fill funnel to burp the coolant, and a OBD2 reader. reader threw codes 0500, 1514, 1101, 1121, p0303. Those codes relate to speed sensor, Idle air control solenoid, neutral position switch, miss on cylinder 3. The speedo works fine. The engine stopped missing and idles ok now. I cleared the codes, but the check engine light is still flashing. The fans will still not come on, even at temp. When I simply turn the key to run, but don't start it, the fans cycle on and off, both together, then one at a time.

 

My best guess is the ECU thinks the car is going fast enough it doesn't need the fans? But if it's the speed sensor, why is the speedo working?

[dunbray]

Also, tranny working fine. I just unplugged the plug to the coolant temp sensor by the carburetor, and as soon as I did the fans kicked on and stayed on until I plugged it back in.

[RumbleRumble]

It's overheating cause you have a carburetor. The heat riser for the choke is probably stuck. Try some 3-1 oil.

[dunbray]

This is a useful idea potentially. I hope it isn't right, since I have the engine out of the car now, changing the head gaskets and having the heads machined, which from the looks of the head gasket and the oil and coolant passages was not the problem. I'll see if I can find out what the heat riser is. Thanks

 

My search indicated it might be some form of riser tube coming up from the exhaust manifold. However on this car it appears there is a water jacket around the throttle body which routes warm coolant around the intake to warm it up.

[Ottocolororange]

New to the forum but would like to give some insight on subaru overheating issues which might help you. I bought a 2000 Subi legacy non-turbo about a year ago from a shady shop who keeps the stop leak chemical companies alive, but since I needed a car I really didnt check everything. About 6 months after i bought the car i noticed oil drips and using a quart every 2-3 days I finally had enough and pulled to motor for a full rebuild. Since i work for a dealership parts come pretty cheap minus the water pump which had to be shipped and i didnt have that time so i just went to AutoZone to get one. After I installed the motor did the coolant bleed everything ran as it should. 2 weeks ago my car overheated and had to be towed to my house. Put a new thermostat in it as i thought that was the problem car would over heat and then not over heat finally having enough of watching the gauge I diagnose everything starting from scratch. Cooling system held 25PSI so no cooling leaks, next I checked the new thermostat it tested good after 20 boils and cooling off so thermostat wasn't the problem. Did a head gasket test system tested fine (WTF). Did a complete back flush no clogs so that was fine. Last thing I pulled off the new water pump and tested it, failed the outside pulley was not matching the inside propeller speed so even through the New water pump was somewhat working it was not working efficiently to cool the car off. Put on a oem subaru water pump for 39.99 (again dealership discount) bled the cooling system and that car has been fine since. I don't quite understand how a new water pump can fail at under 10k miles but it did. Moral of my story is to check everything even new parts you put on and do not if you can avoid it never buy from AutoZone.

[dunbray]

I finished re-assembling the motor yesterday, and dropped it in the car. Spent the morning putting everything back together. NO check engine light! Bummer though, is that the **&&&@@ fans still won't come on. Essentially I spent 2500 bucks fixing and replacing everything that was wrong with the car, except the problem that caused the overheat in the first place. I checked every single fuse, relay etc in the circuit, and even the ones that aren't in the circuit. I also again replaced the sensor, which I temperature tested first. No fans. I have given up. It has got to be electrical, and might be the ECU. I took it to Tunex so they can have their electrical guy try to figure it out. Chances are it will be something simple, and I'll be happy to feel stupid, just so I can hear those fans kick on when the engine warms up. Never thought I would be so anxious to hear that noise!

[dunbray]

Here is the end to the saga! Just in case anyone is interested, I found the answer to my Subaru problem. It is a long story, but the bottom line is: my repairs were flawless. The car was not overheating after the overhaul. The gauge on the instrument cluster went bad, and reads overheat when the temp is really fine. Ran it way past the gauge redline in the shop where we could monitor the actual engine temp, and when it got to the temp where the fans should kick on, they did so. As Spock said: "when you have eliminated the possible, all that is left is the impossible." Moral of the story, if your car shouldn't be overheating, but says it is, get a second opinion!