1999 Olds Bravada Heater Problem

[thetopdoor]

I have a 1999 Olds Bravada that has a heater problem. I have replaced the thermostat twice thinking that the first one was bad. That was not the case, the engine temp rises to normal operatating tempatrue. If I rev the engines RPM's to 2 1/2 it gives a little heat but not enought to bairly defog the windows. If I am going down the interstate at 65mph I get heat just fine. But when I am off the gas it blows cold. I have checked the HVAC fuse thinking it was something with the climate control. That wasnt it. My next step is to flush the rad. If anyone else has any suggestions Im all ears.
Thanks

[ericn1300]

sounds like a vacuum problem. the climate control is operated by vacuum operated motors, ever notice the hissing sound when you move the control from floor to defrost. check your hoses for cracking or splitting. vacuum diagrams can be found here:

http://www.autozone.com/servlet/UiBr...3d8018bb17.jsp

vacuum changes with throttle postion and rpm. my 1950 GMC has vacuum operated winshield wipers, when i step on the gas hard they slow to a stop.

[thetopdoor]

I will check the vacume system like you suggested. Also I think I am going to do a rad flush just for fun. It cant hurt it has 100,000+ miles on it and Im sure it has never been done. All I know is if it dont warm up here in Wisconsin I will have to find a different car to drive. (listen to me its been one of the warmist winters on record and Im complaining about a cold spell)

[Chris Stewart]

Does the heater fan blow plenty of air..even cold air?

[thetopdoor]

Yup it blows plenty of air, a little warm at first then completely cold. I even attempted to unplug the airconditioning unit thinking that maybe for what ever reason (computer issues) it was running. That didnt change anything. It doesnt change anthing if I turn the fan speed dial to Climate control or on full speed. It also doesnt change anything if I turn the air flow location dial to climate control or from the dash to the floor to an in between settings. It blows cold no matter what.

[ericn1300]

do a search in the forum for radiator flush, i've seen some good links on how to. also you might have it done by a shop that can also do a pressure test on the cooling system to check for leaks. shouldn't cost to much and they dispose of the old stuff safely.

[boldsmobile]

its not a vaccum operated heater door, its operated by an electric motor. to know if it is the motor drop the glove box door all the way down and look for a little motor enclosure sitting on the heater box - about 2" x 2" if i remember correctly. pull the electrical plug and remove the two screws holding this gear box on. they are really really hard to get at but you can do it. once the assy is off move the door flap by hand and start it and see if you get heat. you wont be able to move it after the fan is on high due to the vacuum it creates on the low side. also try the door in the other position too.

there are other threads on here about this. i found on mine the gear was cracked - happened when i went to turn the heat on after the coldest morning of the year last year. open the housing and see if yours is cracked too. if you know someone who has access to a lathe you can have an aluminum insert machined, press it in the gear face recess and use it to the hold the cracked gear together. sounds strange but trust me it works. or buy a motor for about 60.

thats what i found in my 98 and others here have had the same pro as well. this is assuming all coolant and engine related things check out.

good luck

[thetopdoor]

I noticed today that the radiator was low with fluid and the overflow reservoir was empty. I know I had them both up to a full level when I changed the thermostat (for the second time) so maybe I have a leak. But it must leak when its traveling down the road because it doesn't leak when its sitting in one spot. I will try all of your suggestions and post my findings when I figure it out. Or maybe I could just sell the hunk of junk. Just kidding, its a great vehicle.

[Chris Stewart]

Keep a close check on your oil in case the intake manifold gasket has developed a leak and leaking coolant to the inside of the motor.

[thetopdoor]

Well I think I figured out what the problem was. I noticed that the input hose to the heater core was hot and the out back to the engine was cold. (weird I know) so we took both hoses off and blew them with a aircompressor first fluid flow direction then back the other way, you wouldnt believe the junk that came out of it. Long story short its heating now not as well as it should but it has heat. I think the next step is to do a flush. The only other thing that I noticed is that when you have the radiator cap off and rev the engine the fluid level drops in the radiator so you cant even see fluid. Im guessing thats normal? I checked the oil and thats clear no sign of water getting into the oil. (THANK GOD) There is to many gagets on that engine to have to pull it to fix the intake manafold gasket. Thanks for all of your help everyone!!

[Chris Stewart]

Way to go TopDoor!
Since you've changed the coolant and disloged some sediment from your heater core, your heater core may clear up even better as you drive it.

[thetopdoor]

Here is an update and question. Well I figured out the cause of the heating issue thanks to your guy's help. Well it blowing back the heater core fixed the heat issue but more problems occured over the next few days. I noticed that the coolant wasnt staying full in the radiator so I crawled under the vehicle to find that it was leaking from above the crank pully area. Being that I couldnt see exactly from where I figrued that I would change the water pump just to be safe. I went and pulled the dealer recipts to see that it had an intake gasket replacement just before I bought it. I replaced the water pump which by the way was really easy, GM really made it easy to get at.
Now it doesnt leak coolant but here is my question when I accelerate I hear a rushing noise sorta like a turning the water on in your sink coming from the heater core what could this be? It happens every time I accelerate.

Also I had my check engine lite on so I had a friend figure out what the code was and its P0410 which from what I can find tells me that the air pump has water in it. Where is the air pump? Is it that pump below the radiator? Is it something that I need to be conserned about? The vehicle has 100,000 + miles on it. Is it expensive to repair?
Thanks in advance for your help.

[Chris Stewart]

Your water sound is likely a leaky radiator cap, clean it under a stream of water and under the rubber seal ring. It may have to be replaced. Recheck your coolant levels as air gets trapped on water pump replacement.

Regarding your airpump code:
http://www.automotiveforums.com/vbul...ighlight=PO410

[ericn1300]

Originally Posted by Chris Stewart

Your water sound is likely a leaky radiator cap, clean it under a stream of water and under the rubber seal ring. It may have to be replaced. Recheck your coolant levels as air gets trapped on water pump replacement.

Oh man Chris, and i thought i was cheap, but cleaning and reusing a critical cooling system part with over a hundred thousand miles when you suspect a problem with it? i'd say go ahead and splurge. spend the whole 6 to 8 bucks to get a new one.

[thetopdoor]

Originally Posted by ericn1300

Oh man Chris, and i thought i was cheap, but cleaning and reusing a critical cooling system part with over a hundred thousand miles when you suspect a problem with it? i'd say go ahead and splurge. spend the whole 6 to 8 bucks to get a new one.

Actually I was thinking of looking for one on ebay Maybe a used one from a bravada with less than 100,000 on it. Washing it with soap and water isnt to far fetched for me, I come from a long line of duct tape users.

All humor aside, so its a lack of preasure in the cooling system? Maybe air in the system because I changed the water pump. That would make sense.