Weak Heat in subzero weather - 01 Mazda Protege ES

[wetcat007]

I have a 01 Mazda Protege with the 2 liter engine and the heat will work fine if it's 20-30 degree outside, but when it gets to zero(which is often here in MN 🙂 ) and below outside the heat in the car never really seems to get above blowing 50ish degree air out even after an hour of highway driving.

The engine temp gauge gets to the center like normal but the heat really never seems to kick in much, I can eventually warm the car up by having it on internal circulation(which then fogs windows).

Anyone have any ideas?

 

[Vette73]

If the engine temp is fine then the thermostat is probably doing its job.

The 2 other most common problems is low coolant and a bad radiator cap. So top off the coolant and replace the radiator cap.
If that does not work then some other not so common issues are a clogged heater core, clogged up cabin filter, bad blend door, etc?

So try the easy stuff first then write back.

 

[Gillbot]

Originally posted by: Marlin1975
If the engine temp is fine then the thermostat is probably doing its job.

The 2 other most common problems is low coolant and a bad radiator cap. So top off the coolant and replace the radiator cap.
If that does not work then some other not so common issues are a clogged heater core, clogged up cabin filter, bad blend door, etc?

So try the easy stuff first then write back.

Not always true. Most temp guages are a dumb device and are not accurate with temperature. Start by changing the thermostat and move forward from there. I used to run many cars without a thermostat and the temperature on the guage always read "ok".

You also can have restriction in your heater core so a good radiator flush might help.

 

[desy]

mould buildup HVAC system as well

 

[nakedfrog]

I'd definitely start with checking the coolant level.

 

[JulesMaximus]

Check your coolant level and if you haven't done a cooling system flush in a few years I'd recommend that too, it is good preventative maintenance.

How many miles do you have on this car?

 

[wetcat007]

Coolant level is fine, mileage is 88k. I've had the car for 4 years, the heat has never been very good in very cold weather it seems to have gotten progressively worse, coolant was flushed about a year ago.

 

[Vette73]

Originally posted by: wetcat007
Coolant level is fine, mileage is 88k. I've had the car for 4 years, the heat has never been very good in very cold weather it seems to have gotten progressively worse, coolant was flushed about a year ago.

Rad. Cap?

 

[wetcat007]

Originally posted by: Marlin1975

Originally posted by: wetcat007
Coolant level is fine, mileage is 88k. I've had the car for 4 years, the heat has never been very good in very cold weather it seems to have gotten progressively worse, coolant was flushed about a year ago.

Rad. Cap?

How do I go about checking the radiator cap, what would be wrong with it that I need to look for?

 

[Vette73]

Originally posted by: wetcat007

Originally posted by: Marlin1975

Originally posted by: wetcat007
Coolant level is fine, mileage is 88k. I've had the car for 4 years, the heat has never been very good in very cold weather it seems to have gotten progressively worse, coolant was flushed about a year ago.

Rad. Cap?

How do I go about checking the radiator cap, what would be wrong with it that I need to look for?

If you have over 80k and never changed then just spend the $5-10 for a new one. Just don't remove until it has cooled.