Hey Guys,

I've been looking around the forum for a while and haven't sound anything that really sounds like my issue unless I'm blind- very likely
Its about -37C here in Canada and my heater does this amazing thing where while I drive I get heat, but when i stop (at a red light or park) it drifts to cold air quite abruptly. This makes starting my car even more annoying because I get in and it's just cold.
I changed my thermostat last year and the issue persisted. The entire heating system just doesn't seem to have the same "umph" it once did. Even when its "hot" it feels lukewarm at best.
Any advice or suggestions on where to look?
I will sit here in 3 parkas till this issue can be resolve, and due to hyper-hydrosis this greatly causes discomfort in the armpit area. LOL

Thanks peeps

 

Check to see the heater control valve is working, it's in the engine bay on passenger side.

 

To check if the HCV is working. having someone in the car increasing and decreasing heat would cause a visible movement in the valves various "open states" to achieve desired temps, right?
I actually have no idea that was my logical thought on how to troubleshoot that.

 

Did you bleed the cooling system and get all the air out?

 

All good ides to check. Just want to add, check the fluid in the radiator.

 

If your coolant levels are okay and you've given it time to get air out of the system, other possibilities would include a bad heater control valve, a bad thermostat, or even a failing water pump.

I would definitely inspect the heater control valve and thermostat itself.

 

So this morning i went ahead and and "burped" the air out of my coolant system. I left the radiator cap off and ran the car till it was at temperature and even went ahead and let it run for 15 mins more. While the car was warming up i was squeezing the inlet and outlet hoses to the rad and didnt see much in the way of bubbles. i also got in the car and moved my heater setting to low and the HCV was closed off (in the up position) and when i went ahead and turned it back to high the HCV opened up (parallel to the tubing). I let the coolant rise to the brim of the radiator and put the cap back on to even ensure there was no air between the cap and seal. So i took the car out in my cool -40C weather and still the same issue with the heat turning cold when i come to a stop or idle.

Does the waterpump pass coolant? would it be leaking? How do i tell if my waterpump is actually failing.
This is the most mystifying issue I've ever experienced.

 

Shoot, i should have mentioned to check (physically feel) the inlet and output hoses on the heater core. These should all be warm or hot to the touch once the car is sufficiently warmed up, and it will be a sign of hot coolant being moved through the core. If only one of the hoses is warm/hot, and the other is cold, you could have an obstruction in the core or in the hoses, or a problem with the heater control valve.

Here's some dumb questions. Are you using OEM coolant? Did you check the coolant level when the car was cold/off? Is your cabin air filter dirtied/plugged up beyond belief?

As for the water pump....have you noticed any abnormality in your temperature gauge? There is a possibility that your WP is simply not moving enough coolant through the engine and the core, it could be weak or failing, but I feel like another symptom would be noticing high engine temps if that was the case....

 

Am I using OEM coolant? I'm using Prestone 50/50 - supposedly its good for all makes and vehicles. Should I be using something else?
Coolant level when the car is cold/off? - The coolant level is right at the brim when the radiator cap is taken off and 1/4" below the "max" line on the reservoir
Cabin filter filth? - Haven't looked at that, although I did change the filter just under 6 months ago.

The temp gauge in my car has never done anything drastic and has remained just below half throughout this entire ordeal.

When i get home today I will remove the strut bar? - I think that's what its called- and physically feel both sides of the HCV, and report back.

Appreciate all the help with this guys

 

your eyes can deceive you, the water valve actually made from plastic and over time it could be brittle and broke off. From the outside looking in the valve seem to be working normal but the actual connection between the flap and handle is long gone. This actually happened to me in my accord and yes it does suck with barely warm air when its 15F outside.

 

+1 on replacing the HCV. Had the same problem on my 06 TL couple years back. Replaced the HCV and it fixed the problem.