Stoopid car Stop blowing cold air

[Pengwuino]

Stoopid car! Stop blowing cold air :(

So, since this is a forum full of people who knows mechanics so I figure this is the perfect place to ask this question! giggle.

My car has been a pain in the butt lately. The heater blows cold air until I get the car to go over about 3k rpm. When I say over 3k rpm, I literally mean it will only work beyond around that range, no matter how long the car has been on. Apparently my car uses this Dexcool coolant which has made people sue GM like crazy over corrosion and clogging issues. The thing I've been wondering is, in a regular modernish car, how is the coolant pump powered? Is it directly off the engine? I figure if there's clogging, that maybe the high rpm is giving the pump enough torque to push the coolant through to transfer the heat to the heater.

I'm skeptical though, as the car never overheats... unless there's a pump for both the heater core and the main radiator for the car. Anyone have any ideas? :D

DISCUSS!

ps. my car is a 2001 Pontiac grandprix if anyone is curious :P

 

[my_wan]

The water pump on your car is belt driven. Your problem is almost certainly a thermostat. The thermostat is not powered by anything but the temperature and designed to prevent water flow when the car starts up cold to warm it up faster. It is place directly in the water flow line, about a 3 inch black rubber hose, right where it connects to the top front of your engine. Two bolts is generally all it takes to get to it, but you need to replace the gasket once removed.

What appears to be happening is that the hot water is no longer opening up the thermostat as it should. Since the water pump is belt driven the higher the engine RPM the higher the pump pressure. When you reach a high enough RPM, increasing the water pressure enough, this pressure opens the thermostat that should have opened itself when it got hot. You might even need a lower temperature thermostat if your car is running very cool. The lower temp thermostats open up at lower temps. More likely it simply is not working properly so go with a new thermostat rated for your car.

 

[turbo]

Your car has a water pump which is driven off the engine. Your cab heater operates off the same coolant loop that feeds your radiator, and shunts the coolant to coils that it uses to heat the air in the cab. The need for high rpm suggests to me that your coolant lines/valve are badly restricted. If this coolant problem is wide-spread, hopefully there is some universal fix available so that you can have the coolant system (including your heater) flushed and cleared out. Ask the garage to guarantee their work - it will do nothing for you to have the radiator/main coolant lines flushed if the heater coil remains plugged.

 

[micromass]

So, since this is a forum full of people who knows mechanics so I figure this is the perfect place to ask this question! giggle.

My car has been a pain in the butt lately. The heater blows cold air until I get the car to go over about 3k rpm. When I say over 3k rpm, I literally mean it will only work beyond around that range, no matter how long the car has been on. Apparently my car uses this Dexcool coolant which has made people sue GM like crazy over corrosion and clogging issues. The thing I've been wondering is, in a regular modernish car, how is the coolant pump powered? Is it directly off the engine? I figure if there's clogging, that maybe the high rpm is giving the pump enough torque to push the coolant through to transfer the heat to the heater.

I'm skeptical though, as the car never overheats... unless there's a pump for both the heater core and the main radiator for the car. Anyone have any ideas? :D

DISCUSS!

ps. my car is a 2001 Pontiac grandprix if anyone is curious :P

 

[MrsLorinda]

The heater core could be broken or there might not be enough anti-freeze in the radiator. Also, your heater fuse may be blown.

 

[rhody]

Peng,

Had this happen, exact symptoms on a long ride from a ski area in a blizzard in Vermont.
Since you car is a 2001 Pontiac, in my case it was a 98 Chrysler ... box, my heat would not get more than luke warm, and then only if the engine was spinning fairly fast, in your case 3K rpms. Pop open the hood and look very carefully around the neck of your radiator near the radiator cap. In my case, the spring tension, normally 12 - 14 pounds was weak and as the pressure built, a small amount of coolant leaked by it. The coolant from the top of your radiator goes out through a small hose to the heater core (like a radiator with fins) in your dash, if the radiator is not FULL air goes with it and as well and as we all know air is NOT a good conductor of heat. Once you pressure test the radiator cap and radiator for leaks and they are good and you fill to the proper level with fluid you should be good to go. All I needed was a new radiator cap and a little anti-freeze, problem solved. You could have a broken impeller fin on your water pump too, but I would only check this if the radiator and cap check out good. Don't burn your flippers when you check the radiator too. I am willing to bet one of those three things is the root of your car heat problem:

weak radiator cap spring (replace the cap)
leaky radiator (recore or replace radiator)
damaged water pump impeller (replace water pump)

or (rare) leaking heater core (lets hope this isn't the case, I have replaced them and they took me over 5 hours to do, they are a royal PITA to remove and replace, you have to disassemble part of the dash to get at it). You will curse many times, trust me, unless you pay someone big dollars to replace it.

One more thing, have you ever replaced the radiator fluid in the 10 year history of the car? If not then you may have a leaky radiator or heater core. The nasty radiator fluid turns acidic and damages them from the inside out. Don't ask me how I know this because I won't tell you. If that is the case, and the fluid is old, get it replaced with fresh fluid ASAP.

Good luck, oily Bird...

Rhody...

 

[KrisOhn]

HAHAHAHAHAHAHAHA

 

[turbo]

Let's rule out the thermostat right away. Pengy lives in a warm climate with lots of traffic. No overheating means that the cooling system/radiator are still working OK. The problem is most likely due to sludge in the heater core, especially since the heater is probably not used all that often. Hopefully, this can be addressed without replacing the heater, since the cost of parts and labor may end up being ~$1000.

 

[S_Happens]

Well, you can rule out the thermostat being stuck closed, not that it isn't the source of the problem. I've dealt with thermostats that didn't close enough to allow proper heating. You'd probably see lower temps on the dash gauge if it's not simply a dummy gauge. (not arguing, I've simply wasted too much time on problems to rule out something when it technically shouldn't be)

I agree it's most likely that the heater core or lines to it are fouled/plugged. Typically it's quite easy to backflush. It's up to you whether you want to try it yourself or seek a professional. It probably wouldn't cost much. I'd look up specific info for you, but I'm pressed for time.

 

[rhody]

Let's rule out the thermostat right away. Pengy lives in a warm climate with lots of traffic. No overheating means that the cooling system/radiator are still working OK. The problem is most likely due to sludge in the heater core, especially since the heater is probably not used all that often. Hopefully, this can be addressed without replacing the heater, since the cost of parts and labor may end up being ~$1000.

Turbo,

In my POS Chrysler, the coolant dropped less than an inch in the top of the radiator, the line from the radiator to the heater core and back was a little bit above that one inch line, this means that normally when the radiator is full to the neck of where the radiator cap screws on, no problem, but because of the weak cap spring small amounts of coolant were escaping over time. Does this make sense to you ? Not all the coolant was circulating to the heater core and back, most of it was just air with a small amount of fluid at the bottom of the radiator core hose.

Rhody...

 

[Pengwuino]

So we brought it in today and apparently the radiator is corroded to hell and clogged so we're getting it replaced along with the thermostat. GM has put in this Dexcool coolant into certain models and apparently, they have been sued in the past because of corrosion problems related to dexcool. Now that I read all these posts, I'm hoping it's just this.

We had it flushed twice in as many years because this has been a persistent problem. Hopefully this fixes the problem or else I'm guessing, based off the posts, that there might be clogging in the heater core.

 

[xxChrisxx]

Let's rule out the thermostat right away. Pengy lives in a warm climate with lots of traffic. No overheating means that the cooling system/radiator are still working OK. The problem is most likely due to sludge in the heater core, especially since the heater is probably not used all that often. Hopefully, this can be addressed without replacing the heater, since the cost of parts and labor may end up being ~$1000.

Thermostats can fail in the open position allowing over cooling. As S happens said, it'll cause the gauge to drop.

I was actually going to suggest this earlier, but an radiator/coolant flush is more likely the best solution.

Also if it's poor coolant, why not just use something else?

 

[AlephZero]

Hopefully, this can be addressed without replacing the heater, since the cost of parts and labor may end up being ~$1000.

You remind me of a heater problem with the first car I ever owned (a Ford, FWIW).

The heater core sprang a slight leak. Actually, it only leaked during the transition period while it was warming up and cooling down, and only a thimbleful of coolant, so that wasn't a big deal...

Except that the core was surrounded by some foam rubber material, the leaked water soaked into the foam, and when the heater warmed up it filled the inside of the car with "steam" for a few minutes as it dried out. That was kind of amusing driving to work in the morning rush hour, because the peak steam generation happened every day when I hit one of the regular traffic jams. On a typical damp UK morning, there were clouds of "steam" coming out of everywhere when the car wasn't moving. A couple of times, a "helpful" driver in another car let loose with a fire extinguisher and/or tried to pull me out of the car thinking I had been overcome by the "smoke".

So I got a replacement and spent several "happy" hours fitting it myself. After finishing the job I discovered that the replacement part had a bigger hole in it that the first one, carefully positioned to aim a stream of hot antifreeze straight at the driver's legs.

At least the second replacement was watertight.

That was first and last Ford I've ever owned. There are some things you never "forgive and forget"...

 

[Ivan Seeking]

You should be able to turn off your fan for a time with the engine up to temp and running below 3KRPM, and coolant flow enabled to the heater core, and then turn the fan on low. If the air is hot at first and then gets cool, this is a pretty good sign that you don't have the coolant flow to the core that you should.

 

[rhody]

You should be able to turn off your fan for a time with the engine up to temp and running below 3KRPM, and coolant flow enabled to the heater core, and then turn the fan on low. If the air is hot at first and then gets cool, this is a pretty good sign that you don't have the coolant flow to the core that you should.

Yeah, and if the core is clogged, get it replaced, I found mine in junkyard in good condition, mine was only 6 years old, on another car toyota tercel. I am glad you found the problem, because winter is near impossible without heat/defrost. If the core is not original and been replaced you can have them flush it for you, then pressure test it, and reinstall with new c clamps, then you should be good to go.

Rhody...

 

[Ivan Seeking]

Before pulling the core, I would just want to rule out the possibility that there is a control valve inline that isn't opening properly. I would also check to be sure that 3KRPM isn't the minimum RPM for the alternator to kick in - with the possibility of a voltage related problem in mind.

 

[Ivan Seeking]

Does the linkage for the manual control valve [hot/cold] feel solid? Perhaps this isn't opening completely.

 

[AlephZero]

Before pulling the core, I would just want to rule out the possibility that there is a control valve inline that isn't opening properly. I would also check to be sure that 3KRPM isn't the minimum RPM for the alternator to kick in - with the possibility of a voltage related problem in mind.

I agree those are all possible causes, but I would take the simpler minded view. You know the radiator is clogged. The grot wll be spread around everywhere in the system, not just in the radiator. With luck you will be able to disconnect the heater core hoses and flush it without taking the car apart. You want to do that anyway to flush the system properly, because there is usually a low point somewhere in the heater where the fluid can't be drained completely.

If the car is 10 years old, almost everything will be "out of spec" one way or another. The trick is to ignore all the "faults" that don't matter and fix the one that does. If flushing the system doesn't work, then you know you have to look for something else.

 

[256bits]

You remind me of a heater problem with the first car I ever owned (a Ford, FWIW).

The heater core sprang a slight leak. Actually, it only leaked during the transition period while it was warming up and cooling down, and only a thimbleful of coolant, so that wasn't a big deal...

Except that the core was surrounded by some foam rubber material, the leaked water soaked into the foam, and when the heater warmed up it filled the inside of the car with "steam" for a few minutes as it dried out. That was kind of amusing driving to work in the morning rush hour, because the peak steam generation happened every day when I hit one of the regular traffic jams. On a typical damp UK morning, there were clouds of "steam" coming out of everywhere when the car wasn't moving. A couple of times, a "helpful" driver in another car let loose with a fire extinguisher and/or tried to pull me out of the car thinking I had been overcome by the "smoke".

So I got a replacement and spent several "happy" hours fitting it myself. After finishing the job I discovered that the replacement part had a bigger hole in it that the first one, carefully positioned to aim a stream of hot antifreeze straight at the driver's legs.

At least the second replacement was watertight.

That was first and last Ford I've ever owned. There are some things you never "forgive and forget"...

Now THAT is a hilarious story!

 

[Hepth]

Whats weird is this JUST started happening in my 2007 Mazda 6 (60k miles). I'm thinking thermostat (it IS cold here in detroit). I can't imagine I have something more serious this soon in the car's life.

 

[S_Happens]

Before pulling the core, I would just want to rule out the possibility that there is a control valve inline that isn't opening properly. I would also check to be sure that 3KRPM isn't the minimum RPM for the alternator to kick in - with the possibility of a voltage related problem in mind.

Not that it isn't possible, but none of the newer Chevrolet or Pontiac vehicles I have worked on used any inline valve (coolant side). I skipped the blend door and HVAC controls when he said it works over 3k rpm.

You really caught me for a second with the alternator comment. The alternator itself might need 3k rpm (realistic), but it's pretty far reduced from the crankshaft rpm. I'd consider that a little far out of normal operating range to be useful. Although this entire response is based on the accuracy of a Penguin...


I just replaced the heater core in my 94 Oldsmobile daily driver this winter. I got in it one day, could smell it, and knew what had to be leaking. She replied "oh yeah, I'd been wondering what that was." Getting to it through the dash was quite easy. It was the hose clamps at the firewall, tucked up under the AC dryer that were the biggest problem.

I've had 3 camaros and had to backflush the heater cores on all of them at least once. The last two I had were still two years before they started using Dexcool.

 

[Ivan Seeking]

I agree those are all possible causes, but I would take the simpler minded view.

They are simple tests that take few minutes. We aren't talking rocket science here.

 

[Ivan Seeking]

You really caught me for a second with the alternator comment. The alternator itself might need 3k rpm (realistic), but it's pretty far reduced from the crankshaft rpm. I'd consider that a little far out of normal operating range to be useful. Although this entire response is based on the accuracy of a Penguin...

Voltage regulator failures can cause this to happen. I have seen similar problems [rpm related] that turned out to be voltage related.

It only takes a voltmeter and a minute. In fact, you can just watch the headlights to see when the alternator kicks in. Just start the car at idle and watch for the lights to brighten as you slowiy increase the rpm. If you see the lights change intensity at any RPM below 3K, it's not an electrical problem. As S_Happens mentions, the alternator should kick in at a much lower RPM.

If there is a charge gauge, that's even easier.

 

[zoobyshoe]

We had it flushed twice in as many years because this has been a persistent problem. Hopefully this fixes the problem or else I'm guessing, based off the posts, that there might be clogging in the heater core.

Way things are going, I wouldn't worry about it. You'll be warm and toasty in that volcano.

 

[turbo]

Way things are going, I wouldn't worry about it. You'll be warm and toasty in that volcano.

Nice segue!

 

[zoobyshoe]

Nice segue!

Yep. He's going to wish he'd asked for Air Conditioning advice.

 

[Ivan Seeking]

Besides, the obvious fix is to get a Toyota.

 

[xxChrisxx]

Besides, the obvious fix is to get a Toyota.

Sure, it may have decent build quality and work properly, but you'll forever be driving round in a dull car.

 

[turbo]

Sure, it may have decent build quality and work properly, but you'll forever be driving round in a dull car.

A dull car that takes you everywhere that you want to go, and takes you home safe and sound. Hmm...that car might be dull, but it ain't bad! Give it a rad paint-job if you can't stand dull - I'd rather have something that starts, runs, and acts predictably.

 

[snowghost]

A couple of (not so) quick comments, A plugged radiator will not stop you from the heat but will overheat the engine, The high rpm before feeling the heat is a typical sign of a water pump going bad. two quick checks for that is to get a mirror or look from under the vehicle (or if you can see from above) and see if there is any coolant leaking from a small hole at the bottom of the pump. Its call a weep hole and shows when the bearing in the pump is giving out. The other is to remove the drive belt and try to move the fan or pulley on the pump by hand. Any movement indicates a failed (or soon to fail) bearing. The heater core valve is usually in under the dash and hard to get to and rarely fails and when it does it is usually wide open or closed . If you try to flush the core from the engine compartment, first determine which way the flow is coming from the pump and use a garden hose and flush it BACKwards . Flushing forward can jam it even harder. As for flushing the radiator, it is best to take it out (a coupe of hoses and bolts is all) and take it to a radiator shop for a core flush and rebuild. As for Dexcool (the antifreeze) the fact that it states that it is good for 100,000 miles is THE problem. All coolant should be changed every two years no matter the mileage despite what the label states. This is where GM messed up. Also DO NOT mix coolants unless the container specificly states that they can be mixed! Mixing two of the wrong types in the correct ratios turn it into a jello like substance. There are inexpensive coolant testers that you can use to test your coolant for PH, freeze point, or additive loss. Without the engine running and the coolant NOT hot, a quick (and cool) way to tell if your coolant is any good is to use a volt meter and drop one probe down into the radiator (it has to be the radiator itself not the overflow tank) and then ground the other probe to the engine on a good ground. The alternator housing is a good spot. Remember the engine is off and cool. If you get more than .4 - .5 volts, then the coolant is shot and you need to replace. I think I got carried away! Any questions please ask!

 

[TurtleMeister]

Over the past 20 years or so I've had this exact same problem with two different vehicles. The culprit in both cases was trapped air. This happens sometimes when the system is not bled properly after a coolant flush. Have you had the cooling system serviced or flushed recently? One common point where air becomes trapped is where the line goes through the firewall to the heater core. There is usually a bleeder at that location and it's the first thing I would try since it is usually easy to get to. But I have heard that there are other points in the cooling system of some vehicles where air can become trapped.

 

[snowghost]

Trapped air usually happens when the heater core is higher than the fill on the radiator. Minivans and some SUV's have this as a common problem. The vehicle here is a grand prix and this should not be a problem. If they have been driving the car without leaks (so no air gets into the system) this shouldn't be the problem. If they had changed coolant or replaced a component recently then air could have been introduced. One quick test you can try is to open the radiator cap (WHEN COOL!) and start the engine and while some one revs the engine, look for swirling or movement in the radiator. Its a down and dirty test but you should see quite a bit of movement. A bad pump may still move it some not just as much. Once again, make sure the engine is COOL. Sometimes there is a bleeder on the head near a rear coolant passage or near the thermostat housing but i don't think the grand prixs had them. Least I don't remember seeing any there.

 

[FtlIsAwesome]

Stoopid car! Stop blowing cold air :(

Um... why would cold air bother you?

You're from the Antarctic, right?

 

[edward]

Try to grab both heater hoses in you hands when the engine is hot and heater turned on.

They should both feel hot. If one is much cooler than the other there is nothing or very little flowing through your heater core. The extra engine speed 3000 rpm, forces more water through.

I think someone already mentioned the blend door.

 

[rhody]

For the record the OP, Peng has told me that:

They replaced the radiator, hose, thermostats, and something else, and it's working fine for now.

His original issue has been addressed. So, where do we go from here ?

Rhody...

 

[Ivan Seeking]

For the record the OP, Peng has told me that:

His original issue has been addressed. So, where do we go from here ?

Rhody...

Replace the engine, body, drivetrain, and chassis, with Toyota parts?

Sell it before it breaks again?

Burn it and report it stolen?

 

[Proton Soup]

Try to grab both heater hoses in you hands when the engine is hot and heater turned on.

They should both feel hot. If one is much cooler than the other there is nothing or very little flowing through your heater core. The extra engine speed 3000 rpm, forces more water through.

I think someone already mentioned the blend door.

hmm, if there were a leaky vacuum, might the extra engine speed help there?

when I've had vacuum problems though, it always screws up my A/C.

 

[snowghost]

water pump
The high rpm before feeling the heat is a typical sign of a water pump going bad.