Heater Sometimes Blows Cold, No Reasone

[89llx]

Sometimes my heater will blow cold, if I mess with the switch I can get it to throw heat.

I have already looked at the small vac line on the firewall---ok

I have already checked the fluid leavel----ok



thanks

 

[jcgafford]

Is the upper radiator hose firm at temp or can you easily squeeze it closed? Also, if it is firm at temp you might try flushing the heater core.

 

[89llx]

I will check,

but it does blow hot air, just sometimes not---[ when it should],

like it is low on antifreez, but its not

 

[jcgafford]

If the cooling system is not making pressure due to a leak it will lack the ability to push coolant through the heater core. The guages may not show a temp problem and it may show an acceptable coolant level but it also needs to make pressure to operate properly.

 

[jcgafford]

Usually when it idles it will cool off but while driving the rpms will circulate enough coolant to allow it to heat the passenger compartment. Granted there could be other things wrong. I would pressure test the cooling system.

 

[89llx]

it also kinda acts like, if the heater is on to high, it cools down the coolant and shuts off the thermostat.

I will check somemore latter

 

[89llx]

Update, I put my pressure tester on it, and DID NOT SEE any LEAK, or drip under the car.
So I tightened the hose clamps and put a new thermostate in and rad cap.

I will try it out

 

[jcgafford]

When i did the pressure test i did it wrong initially. I thought it was only supposed to be pressurized to the capacity of the radiator cap. Did it again later following directions i found online(i forget the psi) and found my leak then. Good luck.

 

[89llx]

I think I found it, and you were right, [leak]---
Press test again and found a small leak at the water pump gasket ,and timing cover gasket.

All seems good now on first test drive after the fix, we will see

 

[jcgafford]

That is exactly where mine leaked. Drivers side and only pissed coolant when i upped the pressure.