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T-Bone

Auto Insights Needed (NF)

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Sorry for the non-fishing thread, but I know there's a lot of activity on this board and a lot of insightful and resourceful members to this great community. With it being very cold lately, this issue has become more pressing.

 

I have a 2001 Subaru Outback. When the car is warmed up and I have the heat temp to 'full heat' and the fan blowing (on any speed, I only get warm heated air when the car is moving. When the car is stopped, like at a traffic light, the air still blows, but is obviously not heated as it is cool again. Once I start moving...boom....warm air again. I've already checked the coolant level and it's fine.

 

Any insights on what may be causing this? I'd hate to take it to the dealer, as I'm sure they'll say it's the timing belt, head gasket, thermostat, heater core, and every hose on the cart. "That'll be $4,200...thank you very much."

 

Thanks for you insights and opinions...I really appreciate the help. And again, sorry for the non-fishing thread.

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Ditto on the thermostat. Not familiar with the Subaru lay out but thermostats are usually easy to do yourself and not too costly. Good luck!

 

 

bly

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I don't think it's the tstat, you'd have the opposite problem.

 

Does it blow hot if you rev the engine standing still? Maybe something is restricting the flow to the heater core (bad hose)? Sorry I dont have anything better for you.

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I'm think the belt to the water pump too loose or the pump is wearing out....or a dirty cooling line/system and when the car is idling not enough water is getting through

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Hey T-Bone,

 

cold air blowing while idling may be due to an air pocket in the cooling system, while moving the water pump is working the current of the coolant.

 

My wife's van had a similar problem a little back. Found out it was due to low coolant level, be VERY careful as it may overheat while in use. Found out the van had a broken gasket (repaired under courtesy warranty as it was a known problem and had a silent recall on it).

 

look around the engine edges to see if there is any sign of coolant leakage, check the hoses to make sure they're not punchured or too soft (weak).

 

If the there is no leakage, it may be the waterpump malfunctioning.

 

I know a mechanic who may be helpful, pm me if you want an opinion.

 

Stan

Edited by HearingFish

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If you get a cooling system flush it could correct the problem if it's a clog, but if you do that be prepared to replace your water pump in the near future. I like to call it waking the sleeping ghost. Best bet is obviousluy to take it to a licensed mechanic istead of troubleshooting with new parts. Get's expensive replacing parts that aren't broken.

Edited by Castmaster

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Its possible you may have air in the cooling system but I think the first thing I would check is the temperature difference in the 2 hoses at the heater core. Not sure how accessible the hoses are but if there is significant difference in temperature (5-10 F) between the 2 hoses with the heater on full would suspect a partially plugged heater core. If they are easy to get to undo the 2 hoses and add some rad flush. Let it sit in there for a while(15 minutes) and flush out with a garden hose both directions.

Edited by Nipissing

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I've heard others say "you probably have a bubble or air in your system". I've also consistently heard "fuel pump".

 

Just so I know, how do you get an "air pocket" or bubble in your system?

 

Thanks.

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If this is cooling system or head gasket related the temperature guage should detect such a sudden and drastic fluctuation. If the temp guage is stable it sounds like ventilation. Does this car have a "fresh air/recirculate" button or switch?

-Brian

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This may sound stupid but have you really checked to see if your fan blades are moving?

It sounds like as you move warm air is being forced in. :dunno:

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Yes SlowPoke, it does have a fresh/reciculate switch...but I couldn't tell any real difference from on to off on that. It's been so dang cold here though that I'm not sure my test environment was secure enough to detect the difference.

 

And Davew3, there are no stupid statements when it comes to me managing an auto engine related issue. And no, I haven't checked to be sure the fans were circulating, but I will...great suggestion. You see, something so 'common sense' slips right by me.

 

I'm going to check all these items when I get out of the office this evening. I'll let you know what I find out tomorrow.

 

Thanks for the insights...I really appreciate the help.

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Your themostat is stuck open.

When siting the water pump is not circulating as much water. Engine runs cooler.

Driving conditions the engine is under load, more heat.

 

You will not have air in you system . the only way air can get in,If you have

drained the system or you needed to add coolent. That would mean a leek

some where.

 

If it's not you themostat, It's you muffer bearing.

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Hi Tybo. T-bone said he had heat when moving. In gasoline engines when you are moving the air flow through the radiator would actually cool it down even more if the thermostat was stuck. Diesel engines tend too cool at idle due to no engine load. As he is increasing his RPM it increases coolant current flow which increases the flow through the heater core. Air can get into cooling systems in a few different ways. Low coolant levels is most common but headgasket leaks can also introduce gases into cooling systems. I checked for technical service bulletins in Alldata today and I didnt find any pertaining to poor heat. In my experience and from what he has explained I still suspect partially plugged heater core.

Edited by Nipissing

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I would have to surmize that if the heater core was plugged, then regardless if he was at idle or Warp 9, coolant would no longer go through the heater core if it was plugged. I would lean to a partially opened and stuck thermostat.

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could be a t-stat that opens a little to soon, a plugged heater(or partially plugged) core could be a malfuntioning water valve if equipped, possibly even the fins came off on the water pump, but with my expierence with subys i would say you most likely have a issue with your t-stat, is your vehicle equipped with a temp guage and is it reading lower than normal? check your heater hoses for temp differences.

And if your in the scarborough area you can bring it by my shop it will take me all of 10 minutes to check this out for you and give you a proper answer.

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Is it possible that this problem is vacuum related? I always thought the vacuum system had some control over the ventilation system. If he has a minor leak, maybe the higher revs when moving compensates for some vacuum loss?

 

Anyways, just a thought. You folks are the auto specialists, so I'm really just guessing.

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i gonna say a couple things first thing get it pressure tested for leaks bleed the bleed screw . when u are pressure testing it u will see leaks in your cooling system is there is not leaks that's good. check your oil see if there is green stuff in it and check your oil cap if u see kinda like white mixture that's not good if u see coolant in the middle of the car ( means your heatcore is leaking . i think it's a air pocket bleed it let it get hot and full pressure and bleed it with the bleed screw/valve. i doudt it's the head gasket cause it would prob overheat.

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Tybo's got it right, try this, with engine warm and heating system turned on and the fan blowing, try tapping on the thermostat housing, sometimes this will unstick the stat, don't hammer it, just a light tap with the handle of a screwdriver, hold the hose with one hand, you should feel the coolant flowing. If everything else is working and there are no leaks the stat is bad. PS, where are you and what's the temp in your area, the stat could be lower temp unit and with the temp's out there now it will make a differance

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I agree with Tybo ( and others ) drain some that other site off and take off the thermostat housing and simply look at the thermostat. If it's open that's your problem, not that hard to do ( usually depending on the vehicle ) and cheaper than $60+ an hour if you do it. If it's open replace the thermostat and gasket and you all set to go.

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Yes SlowPoke, it does have a fresh/reciculate switch...but I couldn't tell any real difference from on to off on that. It's been so dang cold here though that I'm not sure my test environment was secure enough to detect the difference.

 

Okay, the symptom you are having perfectly describes a fresh air vent stuck open.

The fresh/recirc control...If it is lever;

Does it move freely or does it stick?

Does it move too freely as if there is nothing attached to it?

If it is a button it should have a light on it... light on usually represents recirculation

If you don't see a light, check for blown fuses. I don't think it would have its own fuse but check anyway. If you are able, test the switch with a circuit tester.

If you do see a light, listen for a vacuum leak (very slight hiss under the dash). Also listen for the sound of a plastic flap opening and closing (ffffffffffff....fwap) LOL

 

I'm not willing to bet that the fresh/recirc. vent is the problem but I am willing to bet all of Tybo's tackle that it isn't a thermostat stuck open. Easy to check. With the engine cold remove the rad cap. Have someone start the engine and watch for coolent flow. If the t-stat is stuck open it will flow, if it is working properly it should just sit there.

 

You didn't mention what your temp. gauge was doing... is it stable, pulsating or cycling warm when driving or cool when sitting?

 

-Brian

Edited by SlowPoke

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Okay....here's what I can tell you from your suggestions of diagnosis I did last night.

 

 

If sitting at a light and the car is idleing and I can feel the heat coming out of the vents getting cooler, I revved the engine and it definitely warmed up right away.

 

This morning, I was traveling about 75 mph for about 15-miles and looked down to see my temp gauge at the red line. I hadn't noticed that before this morning. So, I let off the accellerator and coasted for about 1/4 mile, and the temp fell back to normal in about 5-seconds. It rose again about 5-minutes later, then as I kept the RPM lower, the temp went down to normal quickly.

 

I put a piece of cardboard under the engine last night to check for leaks...this AM I noticec 3 drops of something on it...not oil, but couldn't tell if it was coolant/anti-freeze...nearer the back of the engine toward to firewall.

 

So, there you go. Any insights are greatly appreciated.

 

Thanks.

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:( that doesn't sounds good head might be leaking i would take it to get it a compression test. orless u have a air compresser. if so ill tell u how to check to see if the head it leaking if u have a air compresser send me a PM let me on sounds like a head gasket if u drive it temp goes in the red meaning over heating. i had the same problem with my buddies bmw e34 at idle everything was fine and when he drove i it overheated. but the thing is you not getting warm air so iam gonna toss it up and say thermostat or headgasket Edited by E30Nigel

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