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Car heater issue

dukebound85

dukebound85

macrumors Core
Original poster
Jul 17, 2005
19,218
4,342
5045 feet above sea level
Effect
Does not blow hot air at idle

Symptoms

The car temp gage will point to slightly less than half way and at idle, blows cold air

Will blow warm air (not as hot as it should be though, just warm) when the engine is under load

Coolant leaks from under car

Cause?

Could it be a bad thermostat stuck wide open? Would that cause these symptoms? Any car buffs out there?

The hoses looked fine from when I checked them recently, no corrosion stains, no wetness, no dry rot type stuff as far as I can tell

Any other possible causes?
 
If the engine temp is where it normally is (thermostat should be okay), then I'd venture to say the heater core is most likely shot. These can be a pain to replace as they are sometimes only accessible from the behind the dash on the passenger's side.
 
belvdr said:
If the engine temp is where it normally is (thermostat should be okay), then I'd venture to say the heater core is most likely shot. These can be a pain to replace as they are sometimes only accessible from the behind the dash on the passenger's side.
Click to expand...

Thanks. That had crossed my mind too but I heard that sympoms of a bad heater core would be that your passenger compartment would be wet from leakage in a sense as its just a heat exchanger as well

Also, the leak isnt that far back (wouldnt it be back there?), its near the front/center of my wheels on passenger side. Assuming the leak and no heat are interrelated that is

I will say that it was working fine before

1) I added more coolant after I saw the reservoir was dry.....how long no idea but wasnt having any issues till i added some
 
dukebound85 said:
Thanks. That had crossed my mind too but I heard that sympoms of a bad heater core would be that your passenger compartment would be wet from leakage in a sense as its just a heat exchanger as well

Also, the leak isnt that far back, its near the front/center of my wheels on passenger side
Click to expand...

The leak may be another issue. On some of the heater cores, they have a drain that brings it outside as well.

Check your coolant level as well. If you don't have enough coolant, that could cause the issue too. Start with the engine cold, and remove the radiator cap (some newer models don't have this). Fill it while the engine is running. This will circulate coolant and assist in removing air gaps from the chambers in the engine block. Once it is full and stays full, put the cap back on.
 
dukebound85 said:
besides an expensive heater core fix, would any other issue cause these sympoms?
Click to expand...

I don't think so. It's simple really. The coolant that circulates through the engine gets circulated through the heater core. The heater core is just like your engine radiator, except the heat gets driven into the passenger cabin. If this gets plugged up, then the heater core doesn't heat up, thus your cabin doesn't heat either. However, the engine radiator (and thermostat) are working to keep the engine cool.
 
Another symptom...

Steam comes out of radiator cap when I shut car off (may have been doing this awhile and just now notice)

However....

Temp gauge in car is still fine
Coolant reservoir tank is still adequate


I had replaced the radiator cap recently
 
Most analog temperature gauges are crude devices but if your gage is staying at below 1/2 after the vehicle has been run long enough to warm up then I'd suspect your thermostat isn't closing properly. Thermostats are usually very cheap and easy to replace on most vehicles. If you suspect leaks then take it to a shop that has a pressure tester.
 
I've owned several dozens of vehicles with analog temp gauges and all of them registered well above 1/2 when they achieved normal operating temps or about 190-195 degrees (F). A stuck thermostat that never allows your engine to achieve optimum temps will cause premature engine wear. Again, they're cheap as hell and easy to replace.

The following is a bit of advice from: My heater isn't putting out much hot air. What's wrong?

One way to tell if the thermostat is stuck open is to start a cold engine and feel the upper radiator hose. You should feel no coolant moving inside the hose until the engine starts to get warm. After several minutes, you should feel a sudden surge of hot coolant when the thermostat opens.
 
The heater controls on most cars today use engine vacuum to function. If there is a broken vacuum line somewhere between your engine and control panel you would experience this sort of problem. Maybe something has been knocked loose. If the engine gets hot then it wouldn't be your thermostat. I didn't see what type of car it was. My vote is a vacuum hose
 
If the heater core was leaking inside the car, you would have moisture buildup on the windows. If it is the heater core, get ready to pay a lot of ducketts. Most shops dont like doing them since if takes up a huge amount of time, thus not allowing them to make quick money on some other car. The whole entire dashboard has to come out on most cars to repair the heater core. If this does happen I would replace every possible part that is in the dashboard, this way you get the satisfaction of knowing everything is new inside and you wont pay twice to do the same job again. Hope you find out whats wrong. Lloyd
 
update

I changed spark plugs

Next day, I get a check engine light

Now my car idles way hard and is hesitant to accelerate

Is this a sign of bad ignition cables? I hadnt replaced the plugs or cables since 2001

my car is giving me trouble lol
 
dukebound85 said:
update

I changed spark plugs

Next day, I get a check engine light

Now my car idles way hard and is hesitant to accelerate

Is this a sign of bad ignition cables? I hadnt replaced the plugs or cables since 2001

my car is giving me trouble lol
Click to expand...

It could be bad cables. It's usually a good idea to replace cables every now and then. It could also be bad gaps on the plugs. Did you measure the gaps on the plugs before putting them in?
 
steve2112 said:
It could be bad cables. It's usually a good idea to replace cables every now and then. It could also be bad gaps on the plugs. Did you measure the gaps on the plugs before putting them in?
Click to expand...

yup, gaps were good

think its bad cables?

i feel its unlikely its the distributer as it was working fine before i changed plugs

Maybe I bent, pulled the wire accidentally on the ignition cables
 
dukebound85 said:
yup, gaps were good

think its bad cables?

i feel its unlikely its the distributer as it was working fine before i changed plugs

Maybe I bent, pulled the wire accidentally on the ignition cables
Click to expand...

It's very possible. New plug wires usually aren't that expensive, so it may be worth it to change 'em out. In my old Protege, I had to change the wires every time I changed the plugs. That thing ate plug wires for some reason. If you can get a timing light, you may want to check the timing. Also, go back and check all your vacuum hoses. It's easy to accidently disconnect one while poking around under the hood. Your symptoms sound kind of like a loose or disconnected vacuum hose.
 
dukebound85 said:
update

I changed spark plugs

Next day, I get a check engine light

Now my car idles way hard and is hesitant to accelerate

Is this a sign of bad ignition cables? I hadnt replaced the plugs or cables since 2001

my car is giving me trouble lol
Click to expand...

I just asked my roommate and the spark plug wires ****ed him.
 
dukebound85 said:
Could it be a bad thermostat stuck wide open? Would that cause these symptoms? Any car buffs out there?

The hoses looked fine from when I checked them recently, no corrosion stains, no wetness, no dry rot type stuff as far as I can tell

Any other possible causes?
Click to expand...

That's one possibility, another is that you have crud in the coils of your heater core. Running the engine under load increases the pressure output from your water pump, forcing more water through the system. If the pipes or coils are starting to gum up from crap in the lines, it could be enough to force some hot water through the core under load but not under idle.

dukebound85 said:
update

I changed spark plugs

Next day, I get a check engine light

Now my car idles way hard and is hesitant to accelerate

Is this a sign of bad ignition cables? I hadnt replaced the plugs or cables since 2001
Click to expand...

Or a bad spark plug, or distributor, or distributor cap.

Could it be that the wires got put on the plugs out of order?

The mechanic wasn't able to pull the codes and detect whether there was a miss, and on which cylinder?
 
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