Yet another overheating question (this is a long one)

[Arty]

Ok, I'm more than sure you're all tired of hearing this question, but I think mine may be a bit different than normal.

 

And like I said, this is a long post...

 

My 96 Legacy GT randomly overheats. And when I say randomly, I mean there's no real rhyme or reason, no pattern, and it will sometimes overheat in two minutes, other times, 4 hours. And sometimes it will stay hot, others, it will just come down in a matter of seconds.

 

Obviously, any time it happens, I stop immediately. This car is a real problem child, but I need it to run. I know most people are automatically going to think "Head gasket", but I seriously don't think it is................... yet. Whenever I tell most people anything about this car, they blame the head gasket and won't give me a word in edgewise (mechanics, that is). I swear I could tell these guys that my headlights are out, and they'd blame the head gaskets. This is from 5 different places, one of them being a Subaru dealership, not one of them seeing my car, only hearing the word "overheating".

 

 

My reason for not thinking it's a head gasket-

When it "overheats", nothing gets hot to the touch. Well, not hotter than normal, I should say. The engine is warm, but it feels like it's at a perfectly normal temperature. No steam, the reservoir tank doesn't bubble, no smoke from anything, it runs smooth, so on and so on. The other cars I've had with blown gaskets did all the above and then some.

 

I've recently had the radiator checked, nothing was wrong. The water pump was replaced, but I never checked the belt after that. I also had the t-stat replaced, but not with an OEM subaru one. I also had the car burped a couple days ago, ran like a champ all day, then the next day, overheated after about 20 miles of normal driving. Then cooled back down after a but, ran for a while again. Same thing tonight (I don't drive it every day)... I ran it pretty hard to test it. It did FANTASTIC for a very long time. Then, I got off the freeway, only after going all over every kind of surface imaginable, up hills, down hills, turns, stop and go, everything... it overheated. For a bit. I hit the gas lightly, it went back down. Again... no steam, smoke, hot to the touch... all normal. Ran fine. I just turned it off.

 

Another symptom worth mentioning if the heater worked like a champ the first few days after replacing the t-stat, and the car didn't overheat for a couple months of super light driving. Now, the heater blows cold air unless it "overheats", then goes back to cool when it cools back down.

 

 

I could go on and on. Like I said, I really don't think it's a bad head gasket, not yet at least. My question is as follows-

 

Might I need to get the t-stat replaced with an OEM part, might there still be an air bubble somewhere by the water pump, and, as is the case with my 95 Outback... could the ECTS possibly be sending incorrect readings all over the place?

 

 

Again- no coolant leaks, no oil burning, no smoke, no steam, no hot engine, runs smooth, but gets terrible gas mileage, is a 2.5, and oh yeah-

Two mechanics have looked at it and said "Not the head gasket". They simply told me something was wrong with the coolant system, wanted lots of money, I didn't spend it because I didn't need the car every day like I do now.

 

 

 

HELP? PLEASE?!?!?!!?

 

 

Sorry for the super long, repetitive post, and thanks for any help.

[Suzam]

Replace the t-stat with Subaru part and burp the system.

 

When you say overheats, except for the temp gauge what other symptoms lead you to that conclusion?

 

Any hot fluid in the reservoir or is it consistent? Both top and bottom hoses hot?

 

I'd also check the wire connection for the temp sensor and gauge to make sure it's not giving false readings.

[Olnick]

Might I need to get the t-stat replaced with an OEM part, might there still be an air bubble somewhere by the water pump, and, as is the case with my 95 Outback... could the ECTS possibly be sending incorrect readings all over the place?

 

Definitely replace the t-stat with an OEM one. Yes, it could be an air bubble--drain the coolant, replace the t-stat and do the whole burp drill again. Not sure about the ECTS--when I did mine it sure cleared up a lot of running problems, but overheating wasn't one of them.

 

Good luck.

[Arty]

Replace the t-stat with Subaru part and burp the system.

 

When you say overheats, except for the temp gauge what other symptoms lead you to that conclusion?

 

Any hot fluid in the reservoir or is it consistent? Both top and bottom hoses hot?

 

I'd also check the wire connection for the temp sensor and gauge to make sure it's not giving false readings.

 

Honestly, I'm going by the temp gauge only. I have a really hard time believing it's the entire engine, since it's "cool" to the touch (just feels like it's at normal operating temp all over... block, headers, hoses, so on). The t-stat is going to be replaced Tuesday, and I may also go crazy and replace the ECTS while I'm at it. The wires all seem to be fine, and there doesn't seem to be any hot fluid... all temps seem to be normal to the touch all across the board.

 

 

Could a blown HG cause isolated heating issues I wouldn't be able to see, smell, feel, etc? Or am I right in thinking the ECTS/t-stat/sender may be bad? All three, or any combination thereof?

 

 

 

It may also be important to note that this poor car sat for over a year, never turned on or so much as touched, and I used to only drive it once a month, after I bought it when it had sat there for so long?

[Suzam]

Typical headgasket overheats at speed or under load and spews steam and coolant out the overflow tank. Look at some of the post on the board and you'll see the symptoms.

 

You could have a bad sensor or connection that is causing the problem, I believe there are 2 sensors- one that goes to the ECU and one that signals the gauge.

 

Others here can confirm this and give you their locations.

[hankosolder2]

A thought- it's definitely possible that you have a faulty coolant temp sensor for the gauge. I have seen the failure mode (in BMWs) where 2 degrees of temperature difference determines if the gauge is in the middle or pegged!

 

Here's an idea. Since the temp sensor for the engine control computer and the gauge are separate, if you can, borrow a scan gauge and drive around with it attached. You can read out what the ECM's temp sensor is saying (in degrees) and compare it to what your dash gauge is reading out.

 

Or, you could just change the temp sensor for the gauge and see what happens.

[Olnick]

There are 2 sensors as Suzam said. Look at the engine from the passenger's side--they are towards the rear, under the IACV below the intake/throttle body. The brick red one is the ECTS.

 

Here's a link that includes one of porcupine73's excellent pics:

http://www.ultimatesubaru.org/forum/showthread.php?t=75009&highlight=temp+sensor

[Gloyale]

Heater blowing cold is a HUGE sign that the system is getting air in it. If you burp it properly (nose up, filler plug open, run it till lower hose feels warm and you get no more bubbles) and then it loses coolant, overheats, and starts blowing cold in a few days...........you are losing coolant from somewhere, and if it ain't leaking.....it's burning.....

 

but ruling out the gauge would be a good start. I like the drive while watching the CTS data streaming on the scan tool. that will tell you if the car is actually running hot.

 

 

However, in truth I'd bet it's the Headgaskets. They can be really "random" in subies with how they present symtoms.

[MilesFox]

i second the loos of coolant. cold heat is definately a sighn of LOW coolant, since it is being lost somehwere.

 

i guesss the only way to be confident in diagnosing a head gasket is to have several of them go bad and therefore know what to compare to.

 

if you cannot source a leak, you could try a can of K&W block sealer. if that does not work, then schedule for a head gasket. the K&W just might be a permanent fix. i have had good luck with the stuff. it worked in my toyota sealing up the bubbles in the radiator

Edited March 2, 2010 by MilesFox

[Mike104]

Since yours is a 96 it has a Phase I motor. Best way to diagnose a HG leak is to use a chemical Block Tester (sold at NAPA) or if you know someone that has one, an Automobile Gas Analyzer. If there is CO in the cooling system=HG leak. It often starts off slowly and gets worse.

 

First thing is to change the thermostat to a Subaru OEM one and make sure you get all the air out of the cooling system. Radiator issues and/or cooling fans could also create overheating issues. Clogged heater core can also cause overheating issues (reduced coolant system flow). You can bypass the heater core with a fitting to eliminate that as a possibility.

[Arty]

Since yours is a 96 it has a Phase I motor. Best way to diagnose a HG leak is to use a chemical Block Tester (sold at NAPA) or if you know someone that has one, an Automobile Gas Analyzer. If there is CO in the cooling system=HG leak. It often starts off slowly and gets worse.

 

First thing is to change the thermostat to a Subaru OEM one and make sure you get all the air out of the cooling system. Radiator issues and/or cooling fans could also create overheating issues. Clogged heater core can also cause overheating issues (reduced coolant system flow). You can bypass the heater core with a fitting to eliminate that as a possibility.

 

Mike, you're in Northern Kentucky??

[Arty]

So everyone knows-

 

 

it loses no coolant.

[montana105]

Did you replace your t-stat since posting with Subaru OEM? Installed correct side up? This does sound more like restrictive coolant flow, if you honestly aren't adding any coolant and have no black crap in your overflow.Who is burping the system?

[Mike104]

Mike, you're in Northern Kentucky??

 

Yes I am

[Arty]

Just following up-

 

The OEM T-stat seems to only have made things worse. The part auto-zone originally gave me, and the part Subaru gave me were two completely different pieces.

[Arty]

Yes I am

 

Which city?

[Olnick]

The part auto-zone originally gave me, and the part Subaru gave me were two completely different pieces.

 

Can you clarify? What do you mean by "two completely different pieces"?

[Arty]

Can you clarify? What do you mean by "two completely different pieces"?

 

The one from AZ was much, much shorter than the one from Subaru. The one from Subaru fit just fine, but it is probably half an inch longer than the other.

[Arty]

In hind sight, it probably would've been a good idea to take a picture of the two t-stats.

[Olnick]

In hind sight, it probably would've been a good idea to take a picture of the two t-stats.

 

No, that's okay. What you pointed out is exactly why we always recommend a Subaru OEM t-stat.

[Suzam]

The one from AZ was much, much shorter than the one from Subaru. The one from Subaru fit just fine, but it is probably half an inch longer than the other.

 

That's the reason for OEM, the T-Stat is made to open up at the proper time. The biggest problem with aftermarket is a wide variation in the temp of the coolant. The OEM keeps it at a much more constant temp and opens up sooner to avoid high spikes when heat is building up..

 

Just following up-

 

The OEM T-stat seems to only have made things worse. The part auto-zone originally gave me, and the part Subaru gave me were two completely different pieces.

 

So what is going on now? Do you did get it burped properly?

[Arty]

That's the reason for OEM, the T-Stat is made to open up at the proper time. The biggest problem with aftermarket is a wide variation in the temp of the coolant. The OEM keeps it at a much more constant temp and opens up sooner to avoid high spikes when heat is building up..

 

 

 

So what is going on now? Do you did get it burped properly?

 

It just overheats in no time flat. The heater didn't work for a very, very, very long time of me just letting it sit there and idle. I tried burping it, and after I had let it cool down (engine off) for a while, I went back out to let it idle, and I kept my foot on the gas to about 2k RPM. All of a sudden, the temp gauge went just a bit below half (where my other car always sits), and the heater started working beautifully. Things looked like they were just fine, I thought maybe I'd finally taken care of it. I took it around the block, heated up again, heater went ice cold again.

 

Can you please tell me the BEST way, step by simple step, to burp it?

 

 

Like I said, I let it cool down with the engine off before trying anything.

[Olnick]

Can you please tell me the BEST way, step by simple step, to burp it?

 

Arty, "search" is one of the most powerful things on this board. Took me 10 seconds to find the following:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=106500&highlight=coolant+burp

 

Good luck. Hope it solves your problem.

[Arty]

I have searched, but man... there's so many different ways I've found. It confuses me.

[Olnick]

It can be frustrating at times but there's so much info available here that it's sure worth learning.

 

Try "Advanced Search"--put in your "Keyword" then click on "New Gen" forum. If it's a 3 letter word or term (like ECU) add an asterisk (ECU*).

 

Good luck.