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my heater doesnt blow hot

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bcrosby

20+ Year Contributor
75
0
Jul 11, 2002
Des_Moines_Iowa
What would make my heater not blow hot? Now that its getting cold out ive noticed that my heater just doesnt blow hot. Could it be the thermostat? Any ideas would be appriciated.
 
I am experiencing similar problems as many of the people above. Does anyone have a picture of the hoses i need to check that go in to the heater core? I think mine is clogged, but i am going to run all of the tests, i just need to find the heater core! Thanks in advance.
 
There are two hoses entering the firewall from the engine bay, those are the ones for the heater core.
It's not usually the hose than plugs up but the core itself. It's a small radiator in the passenger compartment inside the heater/AC duct behind and a little to the right of the center console.
 
I'm going to beat a dead horse....
So I was driving around yesterday and all of the sudden my car started smoking...
A coolant line from the throttle body to the side of the engine literally broke off.. coolant everywhere..
No big deal, replaced it, ran sweet this morning.
At a stop sign this morning car is smoking, heat doesn't work, and the car is overheating like crazy.
Pull over and there is coolant all over the engine, but the line is on good.
Will replace the thermostat (cheap like $12 at autozone) and let every one know!
 
If one hose broke, it's common to fix it and have another leak right away. Best to replace all the old hoses at the same time. Sometimes it's a pinhole leak which under pressure sprays everywhere. You have to run the car to see or get a coolant pressure tester and pressurize the system with the engine off to find the leak.

I've never had any luck with the autoparts store thermostats. Everytime I try one the car overheats and I have to replace it with a OEM thermostat. The OEM passage seems much larger than aftermarket. I haven't tried using one in a long time now so there may be good ones. It isn't worth the hassle of changing it twice so I just go to the dealer for the factory part.
 
The hose that "broke" off was connected to the thermostat housing. I'm assuming it blew off because the thermostat has been stuck shut...? Oh well, hopefully I make it home with out doing damage to anything so I can take my other car to the shop to get a thermostat. Luckily it's a little cool in Colorado
 
Replacing the thermostat was probably the easiest thing I've ever done.
Had to get a 195 degree instead of 180... hoping that it won't be much difference.
Haven't had a chance to run it yet.. will do it tomorrow

So I took it for a little test run. Was going great and I decided to test the heater. Turned it on and it was still blowing cold, looked at the temp gauge and it blasted to overheating temperatures.
I'm guessing there is a clog?? I am going to try and check the lines, but I have no idea where they are located.
I have the Chilton guide, but it is no help.
 
I attempted to, don't know if I did it right.
I just got really frustrated and took it to Mitsubishi. He was telling me if it wasn't a clog or excess air that it might be the head gasket. Which I hope it isn't, but if it is I'm I've found some ones from $45/$98/$125 and up.
 
So the problem.... it was a big ass air pocket in the coolant system, so much for burping it myself.
It's ok though, I needed an oil change and since it sits like 1" from the ground its kinda hard to do it myself with out a jack.
 
1995 gst, 2.4l hybrid with forged internals.
big 16g from cx racing, fmic, speed density dsmlink v3

i let the car warm up to normal, turn on the heat, get a blast of hot air and then it goes cold.
i pulled the heater hoses and flushed them with a garden hose both directions until the water ran clear, hooked up and topped off coolant.
no change.
and suggestions before i pull the dash to get to the heater box?
also, i seem to have good resistance and whatnot on the temp knob and i can see the stuff actuating.
 
When it turns cold are both heater hoses are cold to touch or hot? Because it one is cold and one is hot than the core is clogged but if both are hot then I would check blend door operation. If both hoses are cold then you need to inspect the rest of the cooling system. First you need to bleed it really good, then you need to check if you building pressure.
 
Looks like this thread has already been revived, so I'll chime in as well.

I know it varies from model to model and car manufacturer, but I feel as if the 2G DSM heater doesn't get as hot as some other cars (like a Mercedes or a Focus). It's just around freezing in my area and even though I get lukewarm air quite early on (when engine temp is around 40-50 C) [104-122 F], by the time my coolant reaches full operating temp (88-90 C) [190-194 F] the heater on full blast (setting 4), set to outside air + torso direction and full hot, I would describe the air as warm. Like maybe about 25 C or 77 F. Would that be the usual full hot temp that comes out of the blowers on our cars? Or does it get much much hotter?

I also just finished flushing out just the heater core with tap water + garden hose, and it didn't really look all that dirty or stained. I also have a new-ish stock thermostat.
 
Put cardboard in front of 1/2 of the radiator (on side the fan does NOT come on first which is driver's side in the USA. You want the side the fan normally comes on to still be able to draw air through it's side). Standard procedure here in Minnesota. When it's below -10*F I cover the entire radiator.
 
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Looks like this thread has already been revived, so I'll chime in as well.

I know it varies from model to model and car manufacturer, but I feel as if the 2G DSM heater doesn't get as hot as some other cars (like a Mercedes or a Focus). It's just around freezing in my area and even though I get lukewarm air quite early on (when engine temp is around 40-50 C) [104-122 F], by the time my coolant reaches full operating temp (88-90 C) [190-194 F] the heater on full blast (setting 4), set to outside air + torso direction and full hot, I would describe the air as warm. Like maybe about 25 C or 77 F. Would that be the usual full hot temp that comes out of the blowers on our cars? Or does it get much much hotter?

I also just finished flushing out just the heater core with tap water + garden hose, and it didn't really look all that dirty or stained. I also have a new-ish stock thermostat.

Nope, my stock virgin 96 gst has the best heater and ac of any car I've ever owned

If your cooling system has ever had stop leak in it, it will partially clogue the core. You can blow as much water and cleaning solution as you want through it, but it's not going to get enough out to heat up like it should. My 98 is partially clogged, I would say only 1/3 of the fins inside the core actually circulate the coolant so all I get is Luke warm heat

When you flush the core it just moves water through the path of least resistance, so it may seem like the coolant flows through it quickly and cleanly but it's only going through half of what it needs to clear out of the core

Replace the core, these cars are at least 20 years old now
 
Steam at atmosphere will not go above 212*F, but if he had a leak large enough to bleed off all possible system pressure, chances are he would not be asking why he is overheating. That is usually a case where a radiator hose has completely burst and spewed out enough coolant for almost any motorist to see.

My stock gauge will begin to rise on my car at anything past 225-230*F or so, meaning that as long as he has over 6psi of pressure the gauge will pick up steam temperature as overheating. I don't mean to say that his cooling system is FULL of steam, I'm just saying its more than likely an ingredient in it.

If his problem is more complex such as a headgasket failure, the burst in the gasket will cause cylinder pressure to leak into the cooling system causing more pressure. I ran into this problem when my headgasket went. All of my little coolant lines began to burst every time I drove it causing massive headaches and many purchases of rubber hosing and coolant until I could fix the problem.

But yes, when he posts back more information we can solve the problem better.
if it was a head gasket then you would see white smoke comeing out the exhaust and you would be losing coolant.
 
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