Troubleshooting cooling system help

[lostinthe202]

2000 Legacy wagon

224k

 

Hiya folks!  How's everybody's evening?

 

So, I've been slightly overheating every so often, like about every two months.  I'll check coolant and it's about a quart low, so I add, no more overheating.  Did this twice.  In prep for taking into the shop for an unrelated reason I thought I'd have my cooling system pressure tested to see if a leak could be identified.  The HGs were done around 150k with the updated gaskets and coolant additive so I don't really suspect them, but to be safe, I bought a new coolant overflow and checked for black sludge and exhaust smell after about a few days (this was just a few days ago) and it's free and clear.

 

So today on my way home today, driving residential speeds, I saw the gauge start to creep up again.  I had topped off the coolant when I changed the bottle so my first thought is that wherever the leak is, it's gotten worse.  But when I get home and let the car cool, the level is still at the top, so not a leak, something else.  I know the thermostat is opening and the water pump is pumping because I was able to bring the temp back to normal by turning on the heat full blast, so coolant is flowing through the system. 

 

This suggests to me something with the fans.  I know they work because I got them to cycle on, but I've had intermittent fan behavior in the past with different vehicles, so I know it's possible.

 

Question,

 

Can the fans themselves be intermittent?  My thought is that the fan is just an electric motor, it either works or it doesn't.  I know there's a relay involved somewhere and that could be intermittent.  I don't know what tells the relay to relay, some temp sensor someplace, could that be intermittent?

 

Thanks!

 

Will-

[Fairtax4me]

The low coolant level is the issue here. Either you find a leak somewhere, (hose clamps, thermostat housing, common places for leaks)

or your head gaskets aren't holding up to their end of the deal.

[lostinthe202]

The low coolant level is the issue here. Either you find a leak somewhere, (hose clamps, thermostat housing, common places for leaks)

or your head gaskets aren't holding up to their end of the deal.

 

Heya Fairtax!  How ya been?

 

That's just it tho, I'm overheating, but this time the coolant level was fine.  But the other two times this happened, the coolant was low.  So can the coolant appear full, but still be low?  I can't imagine an air bubble as the system hasn't been cracked by anyone in over a year

[1 Lucky Texan]

I have read of intermittent fans - if the temp only creeps up when you are stopped or at extremely low speed - there's no air going thru the rad. At normal speeds of course, the fans are secondary to the air from forward movement.

 

if the overflow stays at the same level, but the rad is partly empty - that means that during cooling, air is getting in.

 

I'd say a leak of some type is possible, including HGs of course. But, you don't seem to be pushing fluid into the overflow?

 

I dunno, pressure test seems like a good idea. You might consider a new rad cap and put a tiny clamp or a coupla small zip-ties on the o'flow hose at it's connection to the nipple on the rad neck. I've done that on both my soobs - the hose is stiff now and that seal seemed poor. On one of my cars, I had coolant stains under it.

Edited February 1, 2017 by 1 Lucky Texan

[DaveT]

Checking coolant level is not just the level in the recovery tank.

 

I was tricked by this once, many years ago, and learned the hard way, blowing headgaskets due to low coolant.

 

Sharply pinch the upper radiator hose, listen for gurgles and the jiggle pin. There should be very little to no air in the upper hose.

[lostinthe202]

@1LuckyTexan

 

The temp has crept up at highway speed and 25mph speeds.

 

The overflow level drops along with the tank level, that is, I have to add to both when I add. But again, this last time it overheated, levels in both the overflow and the tank were fine. I didn't check for an air bubble at the bleeder, but again the system hasn't been cracked open for a couple of years

 

The cap is fairly recent, but good idea on the zip ties

 

@DaveT

 

I never check the level by the coolant tank, I always pull the rad cap and add if I don't see anything.

 

I did squeeze the upper and lower hoses to see if I got/heard bubbles to no effect. Not sure what you mean by "the jiggle pin"

 

Thanks fellas!

[pontoontodd]

Second the small hose clamp or zip ties on the overflow hose, that seems to help.

You could check with an OBDII scanner that the ECU is getting a proper temperature reading.  The gauge and ECU use different sensors.

You should be able to hear if the fans are running if the car is just ignition on, especially with the window rolled down.

I think the easiest and most definite way to check for head gasket leaks is to look in the overflow bottle when the engine is warmed up and running.  If you see any air bubbles coming out of the overflow hose, even small ones every few seconds, you probably have bad head gasket(s).

You can also get a head gasket leak check kit that you put special fluid in, warm up the engine, stick it in place of the radiator cap, pump a squeeze bulb, and if the fluid changes color from the air going through it you have hydrocarbons in the coolant.

Hate to say it but if you have to add coolant but don't see any leaking onto the ground you probably have bad head gaskets. 

Maybe you're lucky and the fans aren't coming on when they should and then the engine boils some coolant out.

How high does the gauge get?  Does it rise rapidly or slowly creep up?

[DaveT]

The jiggle pins is part of an oem or high quality aftermarket thermostat. It is loose, and will make a noise when the hose is pinched - If there is coolant in the upper hose.

 

I'm not sure on the geometry of your particular car, as different models vary, but opening the Cap on my radiator lets air in, so I don't open that just to check the level. If the system is 100% full of coolant, you should hear the jiggle pin. Note, it isn't loud. If the coolant is low, the hose feels softer and very little sound. In between , you should hear gurgles & jiggle pin. Best to do this check cold.

[keith3267]

Fans can be intermittent.  That is usually the result of one or more brushes sticking in their holder or a dirty section on the commutator.  In either case, the fan only stops working when commanded on, it will not stop if the motor is in motion.  Sometimes vibration will eventually turn on a fan that did not turn on when power was first applied.

[lostinthe202]

Second the small hose clamp or zip ties on the overflow hose, that seems to help.

You could check with an OBDII scanner that the ECU is getting a proper temperature reading.  The gauge and ECU use different sensors.

You should be able to hear if the fans are running if the car is just ignition on, especially with the window rolled down.

I think the easiest and most definite way to check for head gasket leaks is to look in the overflow bottle when the engine is warmed up and running.  If you see any air bubbles coming out of the overflow hose, even small ones every few seconds, you probably have bad head gasket(s).

You can also get a head gasket leak check kit that you put special fluid in, warm up the engine, stick it in place of the radiator cap, pump a squeeze bulb, and if the fluid changes color from the air going through it you have hydrocarbons in the coolant.

Hate to say it but if you have to add coolant but don't see any leaking onto the ground you probably have bad head gaskets. 

Maybe you're lucky and the fans aren't coming on when they should and then the engine boils some coolant out.

How high does the gauge get?  Does it rise rapidly or slowly creep up?

 

I'll see if I can get my hands on a scanner and take a peak.  Zero bubbles in the overflow tank, no black sludge, no exhaust smell.  The gauge usually sits at about eight o'clock.  When it starts to overheat it creeps up to about 9:30.  I haven't waited to see if it would keep going, I turn on the heater full blast to bring it back down.

 

The jiggle pins is part of an oem or high quality aftermarket thermostat. It is loose, and will make a noise when the hose is pinched - If there is coolant in the upper hose.

 

I'm not sure on the geometry of your particular car, as different models vary, but opening the Cap on my radiator lets air in, so I don't open that just to check the level. If the system is 100% full of coolant, you should hear the jiggle pin. Note, it isn't loud. If the coolant is low, the hose feels softer and very little sound. In between , you should hear gurgles & jiggle pin. Best to do this check cold.

 

I tried this, but I didn't hear anything, but the wind was howling pretty good so I could have easily missed it.  I'll try again when things quiet down

 

Fans can be intermittent.  That is usually the result of one or more brushes sticking in their holder or a dirty section on the commutator.  In either case, the fan only stops working when commanded on, it will not stop if the motor is in motion.  Sometimes vibration will eventually turn on a fan that did not turn on when power was first applied.

 

This is my strongest suspicion.  Today, I saw the gauge going up, but I'm not sure for how long it had been rising.  I was on a 25mph road and I pulled over as soon as I saw it and killed the radio to listen for the fans.  They were running, but immediately the temp dropped to normal, so I don't know if they were slow to come on and I just happened to come on before I was able to pull over and listen or if they were running the whole time and it's something else.

 

Are the motors serviceable?  Can I just get new brushes and put them in like I do on my router?

 

Thanks for the help everyone!

[pontoontodd]

There is a big difference on these cars between 8 o clock and 9 30 as you put it.  The temp gauge sits at about 8 o clock from about 150F to 190F and then starts climbing again over 190F (which is about where the fans come on).

 

I don't know if the motors are serviceable, but you can easily just replace the motor itself by unbolting the motor from the shroud and removing the fan.  It might be worth replacing the relay(s) too.

 

Good to hear it's probably not the engine itself.

[lostinthe202]

There is a big difference on these cars between 8 o clock and 9 30 as you put it.  The temp gauge sits at about 8 o clock from about 150F to 190F and then starts climbing again over 190F (which is about where the fans come on).

 

I don't know if the motors are serviceable, but you can easily just replace the motor itself by unbolting the motor from the shroud and removing the fan.  It might be worth replacing the relay(s) too.

 

Good to hear it's probably not the engine itself.

 

Good info on the temp range, I figured it had something like that behavior since it normally never moves once warmed up, at least not under casual perception, dame as any car/truck I've ever owned.  I know the fan replacement is easy, just if I can replace the brushes and dust the commutator with some scotch-brite, cheaper solution, keeps from buying something I wouldn't have to, etc.

 

When I get replacements, I"ll tear the old ones apart, see what they look like, cause that what kids that used to take apart VCRs for fun do,

 

Thanks!

[Fairtax4me]

This is my strongest suspicion. Today, I saw the gauge going up, but I'm not sure for how long it had been rising. I was on a 25mph road and I pulled over as soon as I saw it and killed the radio to listen for the fans. They were running, but immediately the temp dropped to normal, so I don't know if they were slow to come on and I just happened to come on before I was able to pull over and listen or if they were running the whole time and it's something else.

This sounds more like a sticking thermostat. But is also typical behavior of a bad head gasket > Air pockets causing a false temp reading.

 

Radiator fans should come on at 204°F and turn off at 194°F. Ideally when moving even at 15 mph the engine should run around 195° without the fans. If the fans have to run while the car is moving, that's a problem.

[lostinthe202]

This sounds more like a sticking thermostat. But is also typical behavior of a bad head gasket > Air pockets causing a false temp reading.

 

Radiator fans should come on at 204°F and turn off at 194°F. Ideally when moving even at 15 mph the engine should run around 195° without the fans. If the fans have to run while the car is moving, that's a problem.

Hmm.  I'm not sure on the history of the thermostat, I know the HGs were done at around 150-175k or so and that the system hasn't been cracked for about two years.  But the fans come on at idle and low speeds all the time, my '96 OBW was like that, so was my '99 forester, just figured that was normal.

 

Well, the thermostat is a cheap fix, so I'll do that first.  I guess also bleed the system to make sure air isn't a factor.  What's that procedure again?  Park on a slope, run until the fans cycle with the rad cap off?  Something along those lines.

[lostinthe202]

I do have an infrared heat gun, maybe I'll let the soob idle while I work on the bike and see what temp the exhaust manifold gets up to

[Fairtax4me]

Lol at your avatar!

 

Check the coolant level in the radiator with the engine cold.

What kind of coolant is in there? The Subaru blue stuff lasts a long time. Green stuff needs to be changed about every two years so it's probably due for that.

Thermostat is possible if it's a non-Subaru stat or non- similar design to the Subaru OE type. That design is very important because it prevents constant opening/closing of the t-stat.

 

The other consideration would be that maybe the heater core is partially clogged. A back-flush of the core could help with an overheating issue if it's happening in cool or cold weather.

[lostinthe202]

Lol at your avatar!

 

Check the coolant level in the radiator with the engine cold.

What kind of coolant is in there? The Subaru blue stuff lasts a long time. Green stuff needs to be changed about every two years so it's probably due for that.

Thermostat is possible if it's a non-Subaru stat or non- similar design to the Subaru OE type. That design is very important because it prevents constant opening/closing of the t-stat.

 

The other consideration would be that maybe the heater core is partially clogged. A back-flush of the core could help with an overheating issue if it's happening in cool or cold weather.

 

I'll check it when I next head out.  It's got green coolant in there now, no idea what kind, or the last time it was changed, so probably due.  So the subaru stuff eh?  On the heater core, I'm not sure what to think, I get immediate heat and it drops the engine temp immediately if I turn it on full blast, does that tell me that it's not clogged?

 

As for the stat, I'll return this one I got from Napa, no jiggle pin, and just get one from the dealer which I was hoping to avoid since it's 80 miles round trip to get it, maybe just get one online and wait it out.

 

On the avatar, yep, cracks me up too.  As a machinist, I do trig all the time and I sometimes soooo want to give that answer!

[rocketman]

Exacstat from stant is the same if don't want drive 80 miles.

[lostinthe202]

Exacstat from stant is the same if don't want drive 80 miles.

I'll check it out, thanks!

 

Will-

 

bowie fan?  Er, wait, Costello?

Edited February 6, 2017 by lostinthe202

[Fairtax4me]

There's also rockauto. I've used a couple of Gates thermostats with good results. 34012

about $10 compared to $30ish for the dealer part.

[lostinthe202]

There's also rockauto. I've used a couple of Gates thermostats with good results. 34012

about $10 compared to $30ish for the dealer part.

Yeah, Rockauto stuff gets to me in a couple of days, but I have a hard time distinguishing quality parts from expensive parts.  I subscribe to the "you get what you pay for rule" but I don't really know how to tell the difference

[1 Lucky Texan]

I guess I 'really' can't tell either - I try to ask here, stay with OEM or 'name brands' or , at RA get something with the 'heart' symbol - or read reviews if buying from Amazon.

 

but some of the above just comes from word-of-mouth when I was younger, and reading on the Forums nowadays.

 

if it's a 'consumable' item like brake pads or fan belts - I stay away from the 'economy' items. Been burned in the past on those.

[Numbchux]

My '04 Outback H6 has had a failed primary radiator fan, I suspect since I started driving it about a year ago. The only time I noticed was offroading on a tight and technical trail, so about an hour of driving with zero airflow other than the secondary fan, under a load, in 80* weather.

 

 

I bet you have a tiny coolant leak, causing the water pump to cavitate under certain conditions. Could easily be the overflow tank.

 

I would put a UV dye in the coolant, that would make it pretty easy to pinpoint the exact leak point.

[lostinthe202]

I guess I 'really' can't tell either - I try to ask here, stay with OEM or 'name brands' or , at RA get something with the 'heart' symbol - or read reviews if buying from Amazon.

 

but some of the above just comes from word-of-mouth when I was younger, and reading on the Forums nowadays.

 

if it's a 'consumable' item like brake pads or fan belts - I stay away from the 'economy' items. Been burned in the past on those.

Huh, hadn't thought about reviews for products, sorta assumed that's a game that's rigged.  On the brands, that's hard to tell also as any given brand will shift around their production, so who really knows where it's being made and under what tolerances.

 

My '04 Outback H6 has had a failed primary radiator fan, I suspect since I started driving it about a year ago. The only time I noticed was offroading on a tight and technical trail, so about an hour of driving with zero airflow other than the secondary fan, under a load, in 80* weather.

 

 

I bet you have a tiny coolant leak, causing the water pump to cavitate under certain conditions. Could easily be the overflow tank.

 

I would put a UV dye in the coolant, that would make it pretty easy to pinpoint the exact leak point.

It's totally possible I have a coolant leak.  I've zip-tied the overflow tank hose, but haven't driven it enough to know if it made a difference.  I'll look into the UV die, don't know anything about that

 

Will-

[1 Lucky Texan]

no question there are some reviews that are less-than-legit, but it's a datapoint even if not 100% reliable. Even car manufacturers shift sources. The Roki filters Subaru sold in the past were good. Then they changed to a supplier that had crimp joints that leaked.

 

moving targets......