No Heat, Heat Gauge shows HOT!

We are stumped here. There is no heat, just blowing cold air. We replaced the Thermostat. Still no heat and now the gauge goes to hot after 10 minutes on the road although No signs of blown head gasket or clogging. Hoses feel fine but noticed water not flowing so replaced water pump/timing belt. Still no heat and gauge going to hot. Could it be the module under the dash that controls the heater? If not, we are stumped! Please Help... Thanks:

Sounds like an air pocket in the cooling system. try bleeding it.

if you had the symptoms before you did any work there is a good chance that you have bad head gaskets. what model, trans, miles, year are we talking about?

 

if you did some cooling system work and then got these symptoms you probably have an air bubble in the system and need to burp it. search for ''burp'' in this forum, i posted this week how to.

 

the reason you don't have heat is because there is an air pocket in the system , not enough coolant, and it is not circulating. burp the system, top it off and drive the car. if it happens again in a few hours / days / weeks, then it is head gaskets.

 

repeated and/or severe overheating can lead to rod knock. change the oil, do not drive on oil that has been over heated.

It's a 95 Legacy LS.. 4 cylinder. 2.2L 205,000 miles

I am going to try Burping it .... Again...for about 40 minutes like we did after we replaced the Thermostat the other day and the water pump last night. We are starting to think it's a clogged heater core tho...

Otherwise, bad Heater Valve? (not thermostat) BTW... when we burped it last night, the gauge stayed normal and there was still no heat... I drove it home and on the way, the gauge rose to Hot again... lucky I don't live very far from where we worked on it. What's weird is that there is not the normal over-heating issue.. smell, smoke, all that. This is what make us think it's a bad sensor under the dash or clogged heater core. thoughts?

the clogged heater core could cause no heat, but i doubt it would cause it to run hot. i've known folks to disconnect the heater core altogether and run without and not over heat. the hoses to the heater core are a secondary branch line of the main cooling system. ( the supply takes off from the water pump at the t-stat housing goes to the core and returns to the cross over pipe undr the intake on the rear driver's side. )

 

it is open all the time, unless it is clogged. there is not a valve to open or close which would limit or stop the flow of coolant. the core is always hot, when you call for heat, air is routed through the core.

 

what kind of t-stat did you buy? lots of folks say subaru only.

 

did you install it with the spring side ''up'' in the water pump?

 

as you probably know, 2.2L engines are NOT known for bad head gaskets like the 2.5L engines are. it can and does happen, but i would look somewhere else first. at 200k you could have a clogged radiator.

 

have you tried flushing the radiator? (might try back flushing the heater core while you are at it.) disconnect the hoses, and run water in the rad cap from a garden hose. it should pour out the bottom as fast as it goes in the top.

 

have you ever put any ''stop leak'' or coolant ''conditioner'' in your radiator?

 

how long have you had the car?

 

do you know it's history?

 

subaru head gaskets fail differently than most engines, or so i hear, i only know subaru. they do not produce white smoke out the tail pipe and very rarely mix coolant in the oil. (i've never heard of it.) the most telling indicators are bubbles in the overflow bottle when running hot and ''black gunk'' in the overflow bottle. but if you have changed the coolant this week, you probably will not see any floating black gunk. there may be ''a lot'' of gunk on the inside of the bottle. if you don't see either of these things, your head gaskets are probably good.

 

 

i'm thinking clogged radiator. but check your cap if you haven't already and everything else mentioned.

 

edit: what prompted you to change the t-stat?

I have had the car for about a 1 1/2 years. We got a new thermostat (Subaru) because we thought we would try the most obvious solution first. Next step was water pump... Burped, Burped and Burped again... excuse me... lol... anyhow...

 

Before we spend money on a heater core, I am gonna try back flushing it tomarrow. Also, I hope the Subaru mechanic I know is working tomarrow at his shop. No answer today... He would definately know the answer to the puzzle. Dang we can't even figure out where the radiator fluid is disappearing to! When I went to burp it today, it was empty...again.

Air Bubble.

 

According to my Subaru friend and mechanic of over 35 years, that I couldn't get ahold of until today...

 

Heater cores rarely get plugged on these cars. We didn't get that air bubble out because we didn't pop the bleeder screw on the passenger side of the radiator. Soooo... did that with engine off, filled radiator 50/50 until it came out that hole.... then, replaced screw... ran engine with radiator cap off and filled accordingly. Spent 120.00 and that's really all that needed to be done.

another air bubble happened 4 days later... lol... I realized the bleeder screw needed an o-ring to seal. Sooo... the original problem happened because it had no seal left and air kept coming in/coolant leaked out. I realize most of you know this but there may be those that don't. Just make sure that it's tight but not "real" tight! Happy trails!!

It happened to me a couple winters ago. Everything was fine 'til I went down a steep hill. The rest of my trip was 5 miles at a time and no heat on a super cold morning. Luckily the engine did not fry. I did not let it get critical so didn't notice the signs of extreme over heating. I replaced the thermostat which helped enough to get home slowly. The problem slowly faded w. no harm done. Was a bubble being absorbed? It was not plugged anything because plugging is generally cumulative and not sudden.

 

An engine temp. sensor under the right intake manifold needed to be replaced shortly after it returned to normal temp. The sensor seemingly only made starting difficult if one barely touched the gas pedal first.