radiator fans won't turn off

[Arek]

A small introduction to my problem: I had a small leak from the radiator, this has been taken care of. Then I was driving a while (a wk or so) with de-mineralised water in the colling system to give it a good flush, then I put antifreeze in it. Next day water pump gave up (leak), car got slightly overheated. After replacing water pump everything seems ok (no leaks) apart from one small problem: no matter where the car is driven (highway or town), when engine reaches normal temperature, the rad fans will turn on and will keep working forever.

As a result, the heating temperature is different, i.e. air is warm, but not very warm, as it was before. Slightly disappointing, given that winter just began

The temp gauge shows permanently the same, normal level. It is not hard to squeeze the upper rad hose, but I figure this is normal if the fans are working all the time - the pressure in the system does not go up.

What I did:

- replaced temp sensor twice (the one that operates fan, obviously ),
- there are 4 A/C relays - interchanged each of them,
- read ECU codes (by connectng the wires, not Subaru Select Monitor or anything) - no codes
- checked coolant in expansion tank a few times - maintains the same level.

I also checked the fans on motor started and warming up when parked - when motor gets hot, the fans would turn on and then turn off after a while! Like normal. But while driving, the fans would stay on. Even when parked after a drive, they would not stop.

This would suggest something related to speed. Is fan operation depandent somehow on speed sensor? I read sth like this in the shop manual for a WRX (but much newer than my car). My car is Legacy '95 EU version.

Any suggestions where to look for next?

Much appreciated!

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[Legacy777]

May be a stupid question....but did you replace the thermostat?

If not, I'd suggest replacing it.

If you did, did you replace it with a subaru thermostat?

Myself as well as others have had lots of weird issues with non-subaru thermostats.

[Arek]

Thanks for your input.

Thermostat was not replaced. So I still have a genuine Subaru thermostat in there

Correct me if I am messing up something: if the termostat would not fully open the cooling circuit, then the fans would kick in, but at least I would feel hot air inside the cabin. On the other hand, if it would be open all the time, the fan would not start working while I am driving highway.

[Charlie-III]

Arek, I agree with your comments.

What troubles me is your comment regarding, "It is not hard to squeeze the upper rad hose, but I figure this is normal if the fans are working all the time - the pressure in the system does not go up."

If the cooling system is full (no air) and the engine is hot, the hoses should be fairly hard (all that non-compressability of fluids and all). So.....the fact that they are easy to squeeze leads me to believe you have air in the system.
Thus, the heater issues.
Also, if the fans see hot coolant, they will run trying to cool it off.

[Arek]

If there is air in the system, it should go out as a bubble in the expansion tank, I guess. Did not notice anything like this (except from usual bubbling just after a coolant refill), but will check tonight and report back.

I will also take off the A/C (fan) relays and see what happens when temperature goes up.

[mariuzs]

You got air in cooling system

[Charlie-III]

Originally Posted by Arek

If there is air in the system, it should go out as a bubble in the expansion tank, I guess. Did not notice anything like this (except from usual bubbling just after a coolant refill), but will check tonight and report back.

Arek....there is no such thing as, "Usual bubbling."

If it does, there is air in the system (from an improper refill) or you have a leak (Maybe) or a blown HG (Likely).

[Arek]

Thanks for all suggestions.

BHG would be surprising to me - normally one would expect increase in the coolant pressure, not the opposite. Movements of the expansion tank are also normal - from min when cold to a finger above max when hot. Can this be a BHG in these circumstances?

As to the bubbles, I always have them in the expansion tank for a couple of minutes after a refill. I would love to learn how to fill the system and not to have any bubbles after starting the engine for the first time.

I have covered approx. 400 kilometres since the refill. Do you think air (from improper refill) may be trapped in the system for that long? I heard that EJ25 had some design faults with this respect, but not EJ22 nor EJ20

[Arek]

An update on some further testing.

Started the engine, let it warm up, put accelerator at 2krpm and kept this way. Fan turned on for 30 secs and turned off. Repeated 2 times more. IMO this is the way it should be.

Then I drove a little under extremely low load - not exceeding 2krpm. When stopped, fans were working. Waited 2 minutes or so, but would not stop. No pressure in the upper rad hose.

Then I put accelerator at 3krpm+ and kept it for some time. Pressure steadily increased, hose got hot and level in the expansion tank increased form half way to max level (btw, when cold it was at min level). Then suddenly the pressure in the hose got very low and subsequently the system sucked some of the coolant from the expansion tank (level dropped from max to half). Then fans turned off.

When they turned on again, I put increased rpms again and after a while the fans turned off. Repeated several times. The only difference compared to the first time was that sucking from the expansion tank never repeated.

Under high rpms the pressure in the hose was very high so as the temp - I could hardly keep it in hand for loger while. At idle (and fans working), the pressure was dropping to almost nothing and also the temperature dropped considerably.

During whole process no single air bubble appeared in the expansion tank.

My guess is that at idle, when there is no pressure, water has high temp around the sensor and the fans are on all the time.

I suspect my new water pump is not doing the work properly. Cannot easily imagine how it is possible though. Did anyone have bad experience with water pump not giving enough pressure?

Any thoughts would be much apreciated!

PS. Thanks for pointing me in the right direction. Before posting here I would bet it is an electronic problem. And I did not know I am doing my refills not properly - still hoping to get advice on this, Charlie-III

[Legacy777]

When cold take the cap off the radiator and check the level, if it's low, fill it. Start the car with the cap off, and see if the level goes down. If it does add coolant until it's full.

Leave the cap off until the fluid starts going up and down and almost coming out. Then put the cap back on. Also make sure that the level in the overflow tanks is at least in the middle. If the level gets below min, it'll suck air into the cooling system.

Where is your filler neck? On the right side or center (standing in front of the car) The older legacies had a bleed screw on the left side of the radiator. If you didn't take that out, it was a bitch trying to get the air out.

[Texas25RS]

ARG! I read this thread earlier today.... and I have been noticing the same problems with my car... same situation, same work having been done on the car.

Where is the temp sensor for the fans to turn on located?

[Arek]

Legacy777, thanks for all suggestions.

I have a filler neck on the right (when standing in the front of the car) and I also have bleeder screw on the left. I always open it when refilling the coolant. Not sure though whether the guys who changed my water pump did this too.

I will check the levels as you described and get back.

Texas25RS, the temp sensor is screwed into an alumnium water pipe, which goes across the engine under intake manifold, starting from the upper rad hose. The exact place to look at is the passenger side of the engine, under the intake manifold, looking from the rear side of the engine. The sensor is screwed horizontally in the forward direction. There are actually 2 sensors, the one with one pin gives info to the gauge in the istrument panel. The other one is 2 pin with brown connector on it. Suggest 19 mm open/closed end wrench and a bit of patience (not too much place to turn the sensor). If you are lucky, you do not have to unplug any of the hoses and connections, which are around. If you do not want to spill your coolant, you may want to get the coolant level lower by draining the radiator by 1-2 litres (with a rad cap open). When removing the sensor take care not to loose the sensor's copper washer - sometimes it easily slides down from the sensor onto the block.

What are the exact symptoms with your car?

[Texas25RS]

Originally Posted by Arek

What are the exact symptoms with your car?

I have no issues with anything near overheat or getting hot... but my radiator fans run more often/longer than they use to (before having my headgaskets replaced the second time which also included the WP, TB, t-stat, radiator hoses, accessory belts, etc)... I think maybe the sensor could have been messed up during one of my car's many trips into "danger" territory on my trip home from Missouri while nursing a blown HG...

I will look tomorrow to see if there are test procedures for the sensor in the FSM.

[theicewall]

Have you since rechecked the fluid levels in your radiator. I changed my radiator hose back a year ago and didnt tighten the hose clamp enough and it came loose and I had to both stop in a gas station for more coolant and clean up the mess it made under my hood. Smelt for a few days upon driving and I felt really stupid, but that isnt the point. I had to keep adding more coolant a few times throughout the week to eliminate air bubbles and keep the fluid level at the mark where it was supposed to be. Then I think I added slightly too much and the car was driving below optimal water temperatures so I added a small amount of distilled water to the mix and then everything was perfect. It took a little time, but definitely change the thermostat, check to make sure that your fluid levels are still correct and that due to air bubbles being eliminated into the overflow chamber that you arent low on coolant causing the fan to remain on cooling the engine.

[Arek]

Legacy777, following up on your suggestions: I opened the cap and the rad was full of coolant. Started the engine and the level started to raise. After 30 secs turned off the engine, as the coolant started to come out from the rad.

Level in overfill was at min when cold. Added to reach the middle.

Any other suggestions?

Did anyone seen/heard of a water pump that was not producing pressure at idle? Cannot imagine this myself, but you never know...

[Legacy777]

Originally Posted by Arek

Legacy777, following up on your suggestions: I opened the cap and the rad was full of coolant. Started the engine and the level started to raise. After 30 secs turned off the engine, as the coolant started to come out from the rad.

Level in overfill was at min when cold. Added to reach the middle.

Any other suggestions?

Did anyone seen/heard of a water pump that was not producing pressure at idle? Cannot imagine this myself, but you never know...

If the coolant came out when it was idling, the pump is doing its job.

Have you driven the car around since you added coolant in the overflow tank?

[Arek]

Yes, I drove the car since then. No change, unfortunately. Fans running at idle, upper rad hose v. soft, same story.

[Legacy777]

Have the coolant sniffed for hydrocarbons. That should tell you definitively whether you have a headgasket issue.

[Texas25RS]

Originally Posted by Legacy777

Have the coolant sniffed for hydrocarbons. That should tell you definitively whether you have a headgasket issue.

With my second set of HGs, it took the mechanic some 1.5 hours of trying the hydrocarbon test to get a "positive-positive" result on the two chamber system... he would have given up had the car not been able to overheat so reliably... there was just so small of a HG leak that very few HCs escaped.