No heat, but then heat, no heat, then heat.. grrr

[warrior]

So I started this thread (https://sl-i.net/FORUM/viewtopic.php?f=10&t=12343) thinking there was something wrong with my heat slider

I don't believe that's the problem at all anymore. The problem never resurfaced until today. I just finished my timing belt, waterpump, t-stat this past weekend and all has been well. This morning, on the way to work, I pulled at a red light and no heat, blower was working, but no heat. Temp gauge was at normal as well. I revved it a bit and light turned green, then heat started coming out so all is well again, until I pull up to a red light again.

After that, it seemed to stay on so I pulled into work, parked, popped the hood and the reservoir tank was above full.. no oily residue or anything like that.

What is exactly going on? I'm thinking the termostat is sticking and not letting coolant pass through my heater core, but that doesn't make sense why the reservoir would get filled up? :smt017

[Stang70Fastback]

I don't know much about this kind of stuff, but when we had the head gasket problem with our car, the first ever indication was no heat on the highway because air was being forced into the coolant lines. Car didn't overheat because it was being driven fast enough that it kept cool. But if you stopped, the temp needle would creep up. And it caused the coolant reservoir to overflow, which we discovered when we stopped and popped the hood.

But you said your engine wasn't overheating so maybe that's not it.

[warrior]

I'm sure it's not the head gasket because I already replaced mine with a Cometic one about 50,000km ago :smt023

I hope to god it's not or else I'm gonna be pissed :smt013

[jey]

Heater core could be clogged.

[Huffer]

Probably air bubbles in the system after you refilled the cooling system.

Jack the car up, take the rad cap off and run the car, squeezing the top rad hose a little...it should burp and the coolant level should drop...

[impreza_GC8]

This same thing has been happening to me but I did disconnect the rad hose twice because I was measuring for a water temp adapter. So if air gets in the line then the heat could stop blowing hot off and on? Didn't know that, guess I should burp the system in mine as well.

[2.5GT]

Probably air bubbles in the system after you refilled the cooling system.

Jack the car up, take the rad cap off and run the car, squeezing the top rad hose a little...it should burp and the coolant level should drop...

I'm going with this. You have to burp out the air bubbles.

[Plays_with_Toys]

Burp the system.

Bring it up to temperature, shut off car, then open the plastic screw at the top of the radiator (passenger side, right by where the top hose is). Once fluid starts coming out screw it back in. Repeat as necessary. Oh. And make sure you are topped off with fluid.

EDIT: I hope you replaced your t-stat with a subaru one? I've heard of several problems with aftermarket t-stats.

[Huffer]

I like the Crucial t-stats... if they fail they stay open, allowing coolant to circulate. Subaru ones fail, they shut, preventing coolant from circulating (hence the rapidly peaking temp gauge).

[warrior]

Burp the system.

Bring it up to temperature, shut off car, then open the plastic screw at the top of the radiator (passenger side, right by where the top hose is). Once fluid starts coming out screw it back in. Repeat as necessary. Oh. And make sure you are topped off with fluid.

EDIT: I hope you replaced your t-stat with a subaru one? I've heard of several problems with aftermarket t-stats.

Sweet, I will do this and yes I did replace with OEM everything!

I never knew the proper way to bleed it, I just let the car warm up with the rad cap off, squeezed the upper rad hose a few times and yea.. that's the way I've always done it but I will try your method. Thanks!