I have a 98 forester, just changed the head gaskets with the engine removed. And now the fans run constantly. The temperature guage seems to work properly. anyone have any ideas? Also if I let the car sit overnight it is reluctant to start, like it is not getting fuel. If I put the key to the on position and try restarting it catches a little, I have to repeat it 20x then she will start. Any help would be great, Thanks

Sounds kinda like the coolant temp switch to me. See what everyone else thinks though.

Sounds kinda like the coolant temp switch to me. See what everyone else thinks though.

 

 

+1, I was thinking the same thing, coolant temp switch, before reading your reply.

I'm also thinking along the same lines.

 

The engine coolant temperature sensor is what the ECU uses to determine how hot the engine is. (It's not the same sensor as the one that operates the gauge.) If the ECTS gets damaged or misconnected, it can cause the ECU to "think" the engine is hotter than it is, causing the starting mixture to be too lean and both fans to run.

 

The ECTS is on the coolant pipe, kind of buried in the area under the intake manifold cylinder #3 runner. It would be easy to miss the electrical connection not being good, or a damaged wire.

Edited February 5, 201016 yr by OB99W

X2 on make sure you plugged the CTS in.

Glad we all agree That's the only time I've had the cooling fans run constantly is when there is an issue with the CTS. As the other guys said, that would explain the hard starting if the sensor is giving a false reading, or is disconnected and not giving an input to the ECU at all.

Is that the single wire sending unit on the flat pipe under the manifold? I had forgot to plug it in originally, but corrected it after I noticed that the temp guage was not working at all. But the fans stay on, thanks for the help...

Is that the single wire sending unit on the flat pipe under the manifold? [...]

There is a second sensor, with two wire contacts. It's slightly further back and harder to see or get to.

Is that located on that flat pipe or is it elsewhere?

It's (1) in the diagram. Unfortunately, it's not that easy to get to with hoses and wiring harness in the way.

will I need to loosen the manifold bolts to get at this?

You might also want to try this: disconnect the positive terminal to your battery. Leave disconnected for 15-20 minutes, then reconnect. Maybe the reboot of the ECU will fix the problem. It is worth a try!

will I need to loosen the manifold bolts to get at this?

That shouldn't be necessary, although a couple of PCV hoses might have to come off, etc.

(Not that it isn't a lot easier to get to without the manifold in the way!)

 

See the following links for some previous discussion and pictures:

http://www.ultimatesubaru.org/forum/showthread.php?t=75009

http://www.ultimatesubaru.org/forum/showthread.php?t=52053

OK guys thanks for the help, you were dead on about the ECTS! Cooling fans are off and smooth cold starts. Once I finally spotted the (un)connection it only took 20min to plug that sucker in! I could just barely see it and barely get my finger(s) on it. Again thanks tons, and what a great forum!! USMB forever!

 

Dave

Congrats!

Good! Glad to hear it fixed your problem! And they are def a pain to get to,haha. Good job.

Ahh the sweet smell of success!

 

 

Or is that my dessert?

Thanks again, i used the car to deliver pizzas last night in the snow storm. Added bonus-- CEL is out wohoo!!

I'm having the same problem, and so glad to be popping into this forum once in a while. Never even thought about it too much, was kind of like, old car, whatever, until I came across this thread.

 

This seems like an easy fix, and I was looking for parts on RockAuto. They have two items along these lines:

 

1. colant temp sensor with two wires

2. the other is radiator fan with switch that has one wire, looks like oil pressure switch.

 

Which one is it to fix the fan issue?

The two-wire sensor is the one that tells the ECU what temp the coolant is at. However, there's no guarantee that the part is definitely what's wrong. If you can get access to an OBD-II scan tool (not just a code reader), find out what the ECU "thinks" the temp is and see if it makes sense. If not, the ECTS could be bad, or the connection to it might be corroded. If what the ECU sees seems correct, then the ECTS is probably okay.