Help with heating

[captinsho]

I am getting very little heat in my car. It is a 93 ATX that I recently purchased and put a new tranny in. The gauge takes forever to rise and only hits the "L" on normal when it is at it's highest. I know the gauges are not accurate but I have a 94 MTX and it reads much higher. My assumption is that my heater core is bad but I am wondering if anyone has suggestions on how to troubleshooting the heating/cooling system. I know the water pump is good, I just had it out and inspected it a week ago so that should not be stopping coolant from flowing through my system. Also does anyone have a "how to" on how to replace the heater core in a 93 ATX. I am not sure how to get to the thing!

 

[NoSlo]

I am getting very little heat in my car. It is a 93 ATX that I recently purchased and put a new tranny in. The gauge takes forever to rise and only hits the "L" on normal when it is at it's highest.

I can't see how your problem would be the heater core - You'll know the core is bad when you have coolant dripping from under your dash!

The most likely cause of your always-cold car is a stuck open thermostat. The engine coolant would be going through the radiator even when the coolant hasn't reached operating temperature and the engine would never warm up. Replace it with a new one. You can also replace it with a higher temperature rated one - 195 degrees - if you want your engine to stay even warmer.

After that's done, you will most likely have no problems. If you live somewhere where the temperature is less than zero, you might try the old-skool trick of putting a piece of cardboard in front of the radiator to keep air from blowing through the radiator and engine compartment. If you live somewhere warm where you don't need super anti-freezing or boil-over protection, you can get better thermal transfer by reducing the amount of antifreeze in your cooling system, since water is more effective than x-glycol coolant at moving heat. Try closer to 25% antifreeze and 75% distilled water mixture with some water wetter and your engine will stay cooler and your heater core will stay warmer.

Also set the EATC to 'auto' 90 degrees, it will use the most efficient fan speed to warm up the car.

 

[HopefulSHO]

Could be a plugged heater core.

I've had two stats in my ATX and both of them will keep the needle at the bottom line on the tempature gauge, and the cooling fan comes on at the bottom of the A. Pretty low on the gauge itself, but the sytem itself is working fine.
For comparison, my MTX ran between the bottom of the N and the bottom of the M.

In other words Don't take that gauge as gospel. Perhaps try changing your t-stat as NoSlo has suggested, and backflushing your heater-core.

 

[ckinart]

Could be a plugged heater core.

Ditto on that. There are two coolant lines in the engine bay that run up to the firewall on the drivers side. When the engine is at temperature (i.e. has been running for more than say 15 minutes), both of those coolant lines should be rather hot to the touch (be careful, they may be very hot). If one hose is considerably cooler than the other, your heater core is likely clogged. Don't quote me on this, but I think the hose closest to the drivers side is the inlet and the other is the outlet, so if the drivers side line is hot and the other isn't so hot, that may be a clue. I went through this about a year ago, had my heater core flushed, and now I've got great heat.

Good luck!

 

[captinsho]

Thank you so much. I try to put all the info in my threads but I forgot to mention that I bought a new T-stat but did not put it in because the one already in the housing was still good so I know it is not the T-stat. Also when I have the car in the garage running for 20 minutes I still get very little heat which rules out the outside temp being the main factor. I will check the heater core lines.

 

[Cobraii976]

ever thought about bleeding the air out of the cooling system?

 

[captinsho]

How do I bleed the system? I mean when I filled it I allowed it to "burp" and then I added more coolant to top it off. Then after running it for two days I topped it off again. I checked it a couple of days later after the second top off and it was completely full. Is there another way to bleed it?

 

[1black89mtx]

I had the same problem, the car was running very cold, put a new stat in and it seemed to help a little...I cold feel some warmth, but mostly cold, so I pulled out the ps dash and reached in...turns out my blend door was stuck open... as soon as I shut it, I got the best heat i could ever hope for...maybe thats your problem....did you do the self test for the eatc

 

[captinsho]

No I have not. How do I do the test and what might it tell me? Also have you heard of bleeding the system? I know that some GMs have a coolant system bleeder valve like you would have on you fuel system (fuel rails) but I am unaware of such a bleeder on the SHO. I will attemp the checking the blend door. You got to it by pulling out what?

 

[captinsho]

Can you explain what you mean by bleeding the system?

 

[Mr Anonymous]

There is almost never a need to bleed a SHO cooling system unless it has become airbound (again, very rare on a SHO -- you almost have to try to intentionally do this). You burped it so you should be fine.

Your problem as mentioned is most likely a heater core problem, although you could have a blend door problem also. Read this SHOTimes article on how to perform the EATC self-test to see if it gives you any trouble codes. You still haven't mentioned feeling the heater core lines. That's the first test you should do. If one's hot and ones not (or significantly "less hot"), there's your problem.

Also, the "L" in Normal on your temp gauge is just about where it should be. Even on a motor with a completly stuck-open thermostat, you'll still get a fair amount of heat.

 

[captinsho]

You still haven't mentioned feeling the heater core lines. That's the first test you should do. If one's hot and ones not (or significantly "less hot"), there's your problem.

Thanks for the info. Sorry that I did not mention that I drove the car home from work today (15 minute 75 mph highway drive in 28 degree temps) and then immediately parked the vehicle outside, still running, for 1/2 hour. Then I felt the two lines one at a time. I noticed that the left (passenger side) was cooler than the right, but not by much. I tested it sever times while the car was still running to make sure and each time I found the same thing. My brother also tested, for a second oppinion, and he said the same thing as me that the lines were close in temp but the left was cooler.

 

[Slo-Sho]

I am getting very little heat in my car. The gauge takes forever to rise and only hits the "L" on normal when it is at it's highest.

I forgot to mention that I bought a new T-stat but did not put it in because the one already in the housing was still good so I know it is not the T-stat.

How did you test the old one? These symptoms are indicative of a faulty T-stat. They are only a few $ and should've been replaced anyways while you were in there. Luckily when they fail, they more often than not fail to the cold side (stuck open).

 

[1black89mtx]

I had to pull out the passenger side dash....if you let you glove box go down all the way by squeezing in the little tabs that keep it from falling all the way down you can reach the blend door better through the glove box...when you reach in turn your heat on and you should feel air coming into the cabin towards the middle, in mine i could feel some warm air and mostly cold air....try feeling around for a bit until you find the blend door and if its open close it..if that was the problem you should now feel all hot air, being that your car is warmed up enough to do so...then do something to keep it shut until you get another. And also in some tutorials you might read on how to remove the dash it says that you have to take the steering column out but you do not have to if you're going for the blend door, just the three screws up front by the winshield, the knee panel, there are two bolts on the side near the parking brake release and the same on the passenger side...also it is better if you remove the black dash panel, and the EATC in the dash, you will then have to reconnect to check your heat when feeling around the blend door. But before you do any of this as it is sort of a pain, do the test in the article...I think the code for blend door failure is 02 if i remember correctly...good luck, hope this helps.

PS...I might have sounded as if I had removed the whole ps dash but i didnt i just pulled it enough (about 6-8 inches) to get my hand back there...there should be two black ridged tubes you have to put your hand behind to get to it....

 

[Rockledge]

I had to pull out the passenger side dash....if you let you glove box go down all the way by squeezing in the little tabs that keep it from falling all the way down you can reach the blend door better through the glove box...when you reach in turn your heat on and you should feel air coming into the cabin towards the middle, in mine i could feel some warm air and mostly cold air....try feeling around for a bit until you find the blend door and if its open close it..if that was the problem you should now feel all hot air, being that your car is warmed up enough to do so...then do something to keep it shut until you get another. And also in some tutorials you might read on how to remove the dash it says that you have to take the steering column out but you do not have to if you're going for the blend door, just the three screws up front by the winshield, the knee panel, there are two bolts on the side near the parking brake release and the same on the passenger side...also it is better if you remove the black dash panel, and the EATC in the dash, you will then have to reconnect to check your heat when feeling around the blend door. But before you do any of this as it is sort of a pain, do the test in the article...I think the code for blend door failure is 02 if i remember correctly...good luck, hope this helps.

PS...I might have sounded as if I had removed the whole ps dash but i didnt i just pulled it enough (about 6-8 inches) to get my hand back there...there should be two black ridged tubes you have to put your hand behind to get to it....

Your blend door actuator (BDA) is what is broken, and the tutorials properly point out that in order to to replace the BDA, you have to pull the dash back a few feet in order to get in there and have sufficent access to get at the BDA screws, and to do that the steering column has to be dropped.

What you are recommending is to pull the dash back just enough to reach in and force the blend door into a certain postion and then rig it to stay in that same positon so it keeps blowing warm air out. This is not quite the same fix as replacing the BDA, and IMO, it's not only a temporary fix, but a little bit risky, as well. By forcing the door into a new positon against the will of the BDA, and/or if the BDA does decide to activate and trys to open/close the door with it being mechanically held in one position, this will place great stress on the "hinge" portion of the door where the BDA stem inserts and controls the door movement. In fact, when I went in and replaced the BDA on my own SHO, the blend door's hinge was broken, so they are succeptible to that.

Also, I would think that stopping the door in one spot (for the winter months) could be accomplished by pulling out the fuse dedicated to the AC/EATC circuits (on my SHO it's fuse #17). I suppose you'd still have to force the door into the preferable postion before pulling the fuse, though.

 

[1black89mtx]

Yes, I realize the blend door actuator is what is broken, some people just dont feel like typing every word out all the time,(do you) know what i mean? ya see....I thought I made it clear that I was not trying to permanently fix it, just have heat until the new one came. This is why i said you do not have to drop the steering column to do this "temporary" fix, but when I do replace it i believe I will have to...also the BD moves easily back and forth so I dont see why it would matter if you moved it being that the motor is already shot....but I guess you do have a point, removing the fuse would be a smart idea if you're going to do this. It may not matter though if the door can be easily fixed or replaced.

PS..Sorry for any misinterpretations of my previous post
TEMPORARY fix...

 

[captinsho]

Thank you very much for the ideas. I may not be able to get this done until after Christmas becuase of my schedule being so busy (haven't even started shopping yet) but I will let you know how it all goes. Once again I do appreciate the help!