legacycentral bbs

A few days ago I ran into my first coolant issue. I was driving on the freeway got to a friends house and heard some noise. Coolant was bubbling and rising in the overflow tank. I checked my temp and it was about 230*. I noticed the fans weren't kicking on. Checked the fuses, started the car, noticed the fans turn on at 220*~225*. Thought all was fine. Got in the taco bell drive thru, temp went up real quick. Turned on the defrost so the fans would turn on, then the temp dropped back to normal.
Now where I'm stuck is where the problem lies. I am going to replace the thermostat but what if that's not the issue? I must note, no CEL and that the coolant is only bout two months old and was full. Any help on this would be greatly appreciated.

Joe

My stab in the dark: it kind of sounds like it might be the water pump. When the water pump starts to go, you often get overheating at idle. The problem goes away when you're moving or the fans are on because the extra airflow past the radiator masks the problem (and also when you're moving the water pump is spinning faster usually).

It's odd that the ECU isn't turning on the fans though, unless there are air bubbles that are keeping the temperature sensor from properly sensing engine coolant temperature.

How are you checking the temperature?

I disconnected the stock gauge to put in an aftermarket gauge. But I don't think it could be the water pump tho I could be wrong of course, but just for the fact that I thought first sign of a dying water pump was the dripping from the pump itself. I did put a new water pump in at the begining of 2010.
I wonder if it could be the temp sensor. Maybe time for a change, giving off wrong readings, I dunno but just another thought.
Thanks for your quick input.

Joe

Sounds like a thermostat issue for sure....all the symptoms I had at least, fixes by the thermostat replacement and tranny flush of course, if not the water pump theory doesn't sound too far off... Especially if u didn't get an oem or aftermarket pump

Sent from my PC36100 using Tapatalk 2

You disconnected the stock gauge? You mean you removed the stock temperature sender and installed an aftermarket one in its place?

Leaking out the weep hole is one way in which the water pump can fail, but it's possible for an old water pump to just slowly have its vanes wear down so it doesn't move enough fluid. If your pump isn't old that's unlikely though.

So, actually, yes, a bad temperature sensor could do this. That'd explain why the fans aren't turning on. And without airflow, the radiator won't actually be able to do any cooling. If you have the means to use my scantool, you could verify whether the ECU's temperature readings match your aftermarket probe's.

alexandermf might be right about the thermostat, but I'd do the sensor first. It's pretty easy to replace and not too expensive.

How old is the t-stat, or do you not know?

I'm kind of also leaning towards the coolant temp sensor.


Just an FYI, the coolant temp sensor reading shouldn't really rise above 202 deg F before the ECU kicks the fans on. So either your aftermarket gauge is not correct with it's readings, or the factory coolant temp sensor is definitely bad.

You disconnected the stock gauge? You mean you removed the stock temperature sender and installed an aftermarket one in its place?

-Yes, under the throttle body. There's two there, one for the stock dash gauge and the other is to the ecu. This has been hooked up like this for almost two years with no issues.

How old is the t-stat, or do you not know?

-I don't remember if I replaced it when I did the water pump, but I'll point towards no.

Just an FYI, the coolant temp sensor reading shouldn't really rise above 202 deg F before the ECU kicks the fans on. So either your aftermarket gauge is not correct with it's readings, or the factory coolant temp sensor is definitely bad.

-I did not know this. Since I put in the aftermarket gauge, I've always noticed the fans kicking on at 215* - 220* range.
-Would it be best to get the coolant temp. sensor, radiator cap and thermostat from Subaru or would any basic auto parts store be fine? I'm in the process of taking the front end apart to go fmic so the coolant will get changed, again, for about the 4-5th time in the last two years, just cause of things I have been doing to it. Thanks again guys.

-Joe

Yeah, the coolant temp should not be getting that high. The factory manual specifies 176-203 deg F. I usually see the fans cycle on and off between 189-203. Are you 100% certain the aftermarket gauge you installed is accurate? A lot of those gauges will ground through the engine, and if the grounding isn't right, the value won't be correct.

Personally, I'd suggest getting the coolant temp, tstat, & cap from Subaru. You can get them from one of the online Subaru dealers. www.subarugenuineparts.com www.1stsubaruparts.com www.subaruparts.com

Are you 100% certain the aftermarket gauge you installed is accurate?

-Its pretty straight forward. I Have the red wire running to the gauge and the ground wire, grounded to the stock grounding location from the battery, refer to pic:


-Hooked into stock temp. location:


-The gauge is a (cheap) nitrous brand, picked up from harbor freight tool, for only 25 bucks:


-I will pick up those three items within the next day or two. But, is there a big difference between a regular auto parts store and the stealership? I ask cause I'm not rich and want to use the dealership as a last resort.

-Joe

Coolant temp & rad cap you could get at the auto parts store. As for the tstat, I'd only suggest getting a Subaru one.

Check out Rockauto.com They've got pretty good prices on stuff, so you could try getting the temp sensor & cap there.

-Well so far, I got the radiator cap and temp. coolant sensor from napa. I just finished my front mount install so today was the first day starting the car in a week. I ran out of daylight this evening, so I've only put on the radiator cap and I still have my coolant issue after test driving the car. Tomorrow I plan on putting the new coolant temp. sensor in and see if that cures the problem.

-Joe

-Is a 13lb cap correct for this car? Just curious cause my old cap is all in Japanese and cant read none of it so I have no reference.

-Joe

Yes, 13 psi is correct.

-Thanks vrg3.
-So I just installed the new coolant temp. sensor and based on my gauge, this is where exactly the fans turned on, just letting the car warm up to this temp. without touching or doing anything to the car:


-I still have yet to put in a new thermostat.

-Joe

Hm. That's irritating. It looks like the ECU is still misreading coolant temperature.

If you can run my scantool -- http://surrealmirage.com/vrg3/b10scan/ -- you can verify that by asking the ECU what temperature it thinks it's reading.

But in the meantime, I'd switch my attention to the coolant temperature sensor wiring. Unplug the sensor and the ECU and check the resistance of the whole harness with an ohmmeter. The red-with-green-stripe wire goes to the ECU's "Sensor Ground" pin and the black-with-yellow-stripe wire goes to the ECU's "Water Temperature Sensor" pin. Both should read zero ohms. Here's an ECU pin reference: http://surrealmirage.com/vrg3/ecupins/

If you have around 100 or 200 ohms of resistance in the circuit, that could cause the ECU to read 220 degrees as 200 instead.

^Thanks for all that info vrg3.
-So I put in a new thermostat, coolant temp. sensor and radiator cap. Drove around in the car for a while and noticed nothing had changed. Subaru even told me that it could be possible that the head gaskets could be going out... dunno bout that.

Are you 100% certain the aftermarket gauge you installed is accurate? A lot of those gauges will ground through the engine, and if the grounding isn't right, the value won't be correct.

-Turns out, Josh, that you were correct here. I went to the local Goodyear and checked the temp with a infrared gun (I think its called) So my gauge was reading 210°-230° -ish when the fans would kick on. When the temp was checked with the infrared gun, between upper and lower radiator hoses, there was bout a 10° difference, 180°-195° give or take. (valve covers were about 210°-215°)
-Seems like I don't have a problem after all. Next I'm going to try grounding my gauge to the chassis instead of the block and if that doesn't give me a correct temp reading, I'll just have to invest in better quality gauges.

-Joe

Where am I able to buy one of these scan tools so that I can see where my temp range is?

Joe - It is possible for an overheated engine to blow a headgasket, which would make the engine overheat again and again after that. But it sounds like one of the things you replaced resolved the problem. Cool. If you're curious, you can test the old thermostat in the kitchen. Put it in a pot of water with a thermometer in it and see what temperature it opens at. You should see it move at around 180 to 190 degrees.

Thesubielover - My scantool software is free. You just need a PC laptop with a parallel port and a simple cable you can make yourself. Follow the link in my post.

CAV3MAN227 wrote:Turns out, Josh, that you were correct here. I went to the local Goodyear and checked the temp with a infrared gun (I think its called) So my gauge was reading 210°-230° -ish when the fans would kick on. When the temp was checked with the infrared gun, between upper and lower radiator hoses, there was bout a 10° difference, 180°-195° give or take. (valve covers were about 210°-215°)
-Seems like I don't have a problem after all. Next I'm going to try grounding my gauge to the chassis instead of the block and if that doesn't give me a correct temp reading, I'll just have to invest in better quality gauges.

-Joe

Glad to hear that there wasn't a problem, and just a gauge reading issue. Yeah try different grounding spots and see if that affects things. If not, yeah you'll need to try a different gauge.

I did try grounding the gauge to the chassis instead of the block and the results were the same. So I will soon need to upgrade to name brand gauges.

Thanks for all the help on this. A lot of stress is off my back now.

Vrg3: the only time the car may have gotten anywhere close to an over heating state was back in jan. of 2009 when the water pump blew up on me but haven't had an issue since with the cooling. I'll try the thermostat in hot water and see what happens but I'm thinking it was the radiator cap causing the problem, just for the fact of see the coolant bubbling and coming out of the over flow bottle.

Joe

Well, bubbling out of the overflow tank is either a sign of overheating (if the bubbles are boiling coolant) or a leaking head gasket (if the bubbles are combustion gases).

If the bubbling has stopped, I'd say you're okay though.

With whatever gauge you end up using, I would say to definitely run a ground wire from the body of the probe to the gauge itself. That's what the ECU's probe has.

Im having you symptoms, only at idle though. When I drive the car or have it at idel with the air on 3 or 4 on defrost theres no issue, but at idel with my cab air totally turned off the fans dont turn off or will go through one cycle of turning off then click back on again and while sitting at idle, the temp gauge slowly rises. When im driving though, with can air off there are no issues. Angy thoughts?

What type of thermostat do you have in the car?