Heating Issue: Moves up from 40% to 75%, but then back down.

[PhoenixDownVII]

So Riddle me this:

I've had my fair share of heating issues before. I've owned 2 high mileage integra's that needed t-stats and radiators...and well..I've owned an Rx7.

Anyways. I'm driving the subaru today and while on the highway on a cool day here in NY (50 degrees, no humidity) the temp. gauge moves north, but slows at 75%. I turn on the heat full blast and in less than a minute it returns to 40% and stays there, even with the heat off....still on the highway.

Figured it was a burp/bubble in the coolant system.

When car was cool I checked the Radiator- Full of Coolant. Looks green. Normal. Car doesn't eat/leak any coolant, and much oil for that matter. Never had an issue outside of this in regards to temperature.

So it happened again and I'm just wondering what else I should diagnose. If the Pump or T-Stat was failing I'd imagine it'd want to stay hot or stay cold. Not return to normal after wiggin' out for a sec.

I did unscrew the plastic screw on top of the radiator but the car was sitting for 15 minutes so it wasn't near it's Normal operating temp. I'll try that again later I suppose.

It's a 2.2L Motor with only 95k miles on it. :)

[PhoenixDownVII]

Bump for more Xposure.

[PhoenixDownVII]

Bump.

It's happening again.

I got a CEL for Temp Sensor and replaced it.

Now it's doing it again. From 40% (Normal) to 70% or so.

Turning on the heat fixes it back to 40%.

So I have full coolant in the radiator, new temp sensor, both top and bottom rad hoses are hot (shouldn't be a thermostat problem then, or could it?)...

Not sure if it's just massive bubbles in coolant or perhaps the fans not coming on? Should they come on on the highway on a cool day? It happens at any point, not necessarily when under load or sitting still for a while...

[AkumaMax]

Bump.

It's happening again.

I got a CEL for Temp Sensor and replaced it.

Now it's doing it again. From 40% (Normal) to 70% or so.

Turning on the heat fixes it back to 40%.

So I have full coolant in the radiator, new temp sensor, both top and bottom rad hoses are hot (shouldn't be a thermostat problem then, or could it?)...

Not sure if it's just massive bubbles in coolant or perhaps the fans not coming on? Should they come on on the highway on a cool day? It happens at any point, not necessarily when under load or sitting still for a while...

Sounds like a faulty thermostat! Replace and all will be well.

[Huffer]

Fans should come on if there's insufficient flow.

You've already replaced the thermostat, did you notice any blockages when you replaced the coolant?

[PhoenixDownVII]

Fans should come on if there's insufficient flow.

You've already replaced the thermostat, did you notice any blockages when you replaced the coolant?

No, I've replaced the Temp Sensor, not the thermostat.

Should I go with an OEM thermostat? keep reading here how the autozone/advanced auto parts is insufficient....or has that been corrected? i hope it's easy to assess.

[AkumaMax]

any non OEM part will last about 25% of the life an OEM part! So yes go with OEM!

[PhoenixDownVII]

Is there a dealer website online that offers better prices?

A lot of car clubs (I'm thinking of the Rx7 club specifically) know and post of a dealer/website that offers OEM parts but at a cheaper rate than most local dealers...

:)

Is the Thermostat in the engine housing from the Upper Rad hose? Or lower?

[Huffer]

any non OEM part will last about 25% of the life an OEM part! So yes go with OEM!

Not necessarily true, and you should be shot for saying so. However, with the thermostat you want one that has a fail-safe that will stay open, not one that shuts when it breaks. The OEM part is good.

Phoenix - the t-stat is really cheap, and isn't worth messing around with websites if it's the ONLY part you need and there's a Subaru dealer nearby. I'd just run up there, buy the part.

Although, Rockauto.com does stock a LOT of parts in the cooling system like the water pump which could be failing too.

The thermostat is in the lower section and is very easy to replace once the coolant is drained.

[AkumaMax]

I've owned 2 integras at one time and both had the same problems(not at same time) one I wanted to keep all OEM and the other was my backup car. I replaced the thermostat, Hoses, and radiators on both one OEM and one Autozone I think it was duralast or one of the el chepos! Anyway 2 years down the road mind you both cars were driven about the same. I would switch off cars each day to keep my milage down. The OEM car did take one trip that was like 600miles extra. anyway back on topic, 2 years pass and the Autozone car started to not heat up all the way replaced the thermostat and all was well. 2 weeks later the seals on the autozone radiator went. I just recently had the same problem with my distributor the OEM works like a champ but the Ausin healey or however you say it Autzone one mad the car run like crap! All of the autozone parts have now been swapped out with used OEM parts and the car runs better than before. This is the reason for me not going with anything less than OEM unless it's to upgrade for road race!

[Plays_with_Toys]

Get the OEM subaru T-stat. It has a check valve in it that non-OEM units don't. Not to mention that the shape and size of store bought t-stats was no right (including napa). T-stat was like $20, but I was told $14 earlier in the week, so they knocked the price down. It was two clicks of the mouse, so you might try it as well.

[PhoenixDownVII]

Wow.

I must be confusing T-Stat with Coil Packs or something....I was recalling an OEM price of like $90-100 for a T-Stat...but it must have been something else.

I'll go with an OEM replacement, thanks guys!

[PhoenixDownVII]

What the hell!!!!

Okay, so I just spent my friday evening doing a bit to the Legacy (Oil change, brake pads/rotors ALL around...) and I replaced the thermostat with a new OEM one.

Refilled the radiator and topped it off and squeezed the upper rad hose several times to top it off...


....and it's still happening! At random! The needle moves up from 40% to 70% and comes down either on its own or when I blast the heat.

So here's what I've done to the cooling system thus far:

Fans (Main one had a blown fuse)
Radiator Flush (while I did the t-stat)
New Thermostat

What else could it be? How best could I remove air in the system? Could it be the radiator cap?

How about the pump itself, is this a symptom of a bad pump? How about Headgaskets? (Didn't notice any coolant in the oil when I did the change though...)

Thanks!

[AkumaMax]

My guess is make sure there is no air in the coolant system. Pressing on the hoses to make the coolant go down could have caused this. Just open your radiator cap turn the car on and let it sit. It may bubble but not sure.

[racermcphee]

it could be a blown head gasket. i had the exact same problem... i replaced the thermostat (twice), the water pump, and i can't even begin to count how many times i flushed the radiator. it still kept doing it. turns out i had ... what else? ... a blown head gasket. upon further inspection, the head gasket issue lead to other issues, like all my internals being baked to SHIT. the entire motor was rebuilt, and I never had the problem again. hell, the car made it across country, and still no problem!! check the head gasket. it might be worth your while.

[J.McDonald Knives]

it could be a blown head gasket. i had the exact same problem... i replaced the thermostat (twice), the water pump, and i can't even begin to count how many times i flushed the radiator. it still kept doing it. turns out i had ... what else? ... a blown head gasket. upon further inspection, the head gasket issue lead to other issues, like all my internals being baked to SHIT. the entire motor was rebuilt, and I never had the problem again. hell, the car made it across country, and still no problem!! check the head gasket. it might be worth your while.I second that. I had the same problem but mine would not cool off after turning on the heater. I had also noticed a slight sweet smell coming from the vents which turned out to be antifreeze. Its an expensive fix unless you know how to do it yourself and have a way to pull the motor.

[racermcphee]

yeah pulling the motor is NO BUENO!!! Can't wait til i do a motor swap... i get to pull it again!!! WHEEEE

[J.McDonald Knives]

yeah pulling the motor is NO BUENO!!! Can't wait til i do a motor swap... i get to pull it again!!! WHEEEEAnd you wonder why I want to just mod this motor. Not to mention I already have new head gaskets and they were installed by the Subaru mechanics at the dealership. If anyone happens to be in the San Antonio, TX area and needs to take it to the dealership you can count on those guys there. Its hard to find a good Subaru mechanic.

[racermcphee]

yeah i was giving that some thought, too. just modding the original ej25. i'm racing my roommate either this weekend or next, and i know the OBW is not gonna stack up to his truck. he's pushin 500 hp versus my guesstimated 165. If I could get an STI motor or even a WRX motor, I could possibly give him a run for his money.

So, what do you have done to your car? what's it pushin out?

[J.McDonald Knives]

yeah i was giving that some thought, too. just modding the original ej25. i'm racing my roommate either this weekend or next, and i know the OBW is not gonna stack up to his truck. he's pushin 500 hp versus my guesstimated 165. If I could get an STI motor or even a WRX motor, I could possibly give him a run for his money.

So, what do you have done to your car? what's it pushin out?Nothing yet but remove the silencer. Check out my webpage for updates and info. When I'm finally done I hope to push 200hp with motor only. Don't need a turbo for what mine will be used for. Put it this way, when I'm finally done with it and I am in the area and you need a tow truck you can call me and I will be more than able to tow your subie anywhere.