Cooling fan running continuously- coolant temp sensor?

I've noticed that when I shut off my wagon ('98 Legacy L with 2.2 liter & automatic) I can hear the cooling fan shutting off as well. Sure enough the fan on the passenger's side is running any time the engine has warmed up, even on a cold day. It's been doing this for a few months now.

 

I'm thinking the coolant temperature sensor is causing the fan to kick in at too low a coolant temperature. Otherwise the cooling system is in good shape- the engine temperature is right where it should be and doesn't fluctuate, no coolant leaks, etc...

 

My problem is that I can't find the sensor. I've read up on it and seen some pictures online, but none of the pics look like what's on my car. I know it's on or beneath the intake manifold, near the IACV and the sensor for the temp gauge is next to it. Does anyone have a better way to locate it on an EJ22, or have some pictures showing it's location?

WHen you are looking into the engine bay put your finger at the top of the curve for the front intake runner on the passenger side. That's slightly closer to centerline than the power steering cap. From that point on the intake point straight down through it. Now you are pointing at the two sensors.

 

Another reference is the metal neck that the upper radiator hose connects to on top of the engine. Follow that metal tube back to where we were talking about before. The sensors are on the rear face of that tube.

 

It's pretty hard to get a look at it, and I doubt it would be possible to change it without taking the intake and related stuff off.

 

It's not such a huge job, but it involves a number of things that would scare away most parts changers who don't have some experience. EDIT: (NM, at first I didn't read who posted.)

 

The only slightly serious things to watch out for doing this job is 1) don't shoot high pressure gas in your eye and 2) don't drop anything down the intake ports in the head once the intake is off.

 

The rest is just being gentle enough with old plastic bits and remembering everything so you can put it back together.

 

If you have some experience or if you have a Factory Service Manual you can do it. Just no dropping anything down those holes!

 

And we can help as well if you have time to stop in here for info during the job.

Edited February 1, 2020 by doublechaz

Also, it would be useful to know if the ECU is commanding the fans on or if there is a stuck relay. It's probably not a stuck relay or I think it would just stay on forever until your battery died, but before ripping in, more testing is always good. And also, if one fan is on low, the other should be on low as well, so once you get the one to turn off you'll want to find out why the other isn't coming on.

My mechanic went over the electricals and found the ECU is not switching the fans on and off. Also the fans seems to cycle normally if the car is idling, but once it's driven even a short distance the fan stays on.

 

He did a coolant flush and fill and was certain her got all the air out but was still seeing bubbles. He is concerned about headgasket leak (as that's one of the signs) but he also thinks the radiator is fairly clogged up so i'm thinking there is trapped air in the system even his suction device couldn't get out. I'm going to taker it back over with both of my spare radiators and see if that solves both the bubbling issue and the cooling fan issue.

Fans running without the ECU commanding them sounds like a stuck relay.

Our motors are a pain to get all the bubbles out of. One of the easiest ways to do it is jack the front end up a foot or two and start the car, letting it get up to temp. You will then get all the bubbles out of everything. It still takes time that way, but it works.

 

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I then returned with one of my spare radiators which he installed. He reported the fans are now cycling properly, but the air bubbles still remain.

 

The car has never overheated and no oily gunk in overflow tank or anything like that. He is thinking early signs of headgasket failure. I know it's rare on phase 1 EJ22's, but not unheard of.

 

Are there any other ways to better identify if it's headgaskets? (I plan to drive it some to see if the air bubbles are still coming up to make sure it's not just trapped air- really hoping this is ti). It's getting close to needing the timing belt done anyway, so I'm thinking it may make sense to do headgaskets too.

 

If so, what are recommendations for good MLS headgaskets? Did Subaru ever produce them, or are OEM EJ22 gaskets all single layer?

There is a chemical test you can do. Take a fresh sample from the radiator, add the reagent and look for the color change. Simples.