Lets try this again!

[beecho2]

Hello everyone I am posting this as a follow up to a post I had on here about 2 months ago, I will try to make it as short as possible. I have a 2004 Pilot EX-L that i am having trouble keeping the car to maintain heat. I have replaced the timing belt, water pump, thermostat and radiator cap. it looks like whoever owned it before me used some sort of stop leak in the cooling system. I backflushed the system and cleaned out and replaced some of the hoses that i could. It seems that the upper rad hose gets nice and hot but the lower one takes forever to get hot. Does the coolant have to travel through the radiator then go thru lower hose to open thermostat (which could be the reason for lack of heat)! I dont want to replace radiator without ruling other things out first. I am open to any and all suggestions.

[carguy07]

Could easily be the heater control valve. Try tightening the screw on it and see if that fixed it.

[mclairmo]

Why do you say it will not maintain heat? I do not understand? Are you saying that the engine runs too cool? Or, does the heater not work?

[beecho2]

No the heater control valve works, its just the heat that doesnt get hot. the upper hose gets real hot but the lower one takes really long to get hot. Plus the radiator cap isnt hot when you put your hand on it. I am thinking it is possible the thermostat is stuck open and not allowing the coolant to get hot enough which would make the heat feel very cool

[rocky]

By making the heat feel very cool, assume you are talking about the air coming out the vents.

I suspect that the fault is in the air vent flap control system. Engine coolant circulates all the time regardless of the position of the interior controller.

Sorry but I think you are going to have to take the dash apart.

[beecho2]

So are you saying it needs a new heater core?

[rocky]

The heater matrix may be fine. Failure of one of those is very rare, and is usually revealed by puddle of coolant inside the car or excess humidity on the windshield.
But the control flaps for the air movement or their controls may have failed. Or even the controller itself. Very expensive in terms of labor.

[beecho2]

Can I ask where it is located? I have verified the blend door is functioning properly but I am not familiar with the control flaps. do you have or know whereI can get pics of that

[krazykarguy]

The stop leak stuff is NOTORIOUS for clogging and destroying heater cores as the passages are smaller than in a radiator.

I suggest a super thorough flush at the heater inlet and outlet hoses at the firewall first. If that does not produce a mess that looks like sawdust and coolant when you flush it out, I'll eat my hat.

If, after the hat eating, you still have no heat, I would replace the thermostat - it kind of sounds like it's stuck closed. When the thermostat is stuck in this position, it will not allow any warm coolant through the lower hose.

[beecho2]

I am going to pull the thermostat this weekend and put it in boiling water to see if it functions then replace with new one, I will post if it works or not. By the way i did flush the heater core and it did clean out as there was clear water coming from both ends so I hope the thermstat is the problem.

[krazykarguy]

Keep in mind that boiling water is 212 degrees F, most thermostats are designed to open at 170-180 degrees. Boiling water can open a "stuck closed" thermostat.

A digital thermometer will be a great aid in this test.

[beecho2]

Ok...I pulled the t-stat today and i am a little unsure what to do. In my past experience with t-stats, whenever i put them in hot water they popped open fast this one however seems to drag open very slow and it doesnt look to open very far (maybe 1/4"at most). Is that normal for this t-stat or is it suppose to pop open fast to allow the coolant through faster.

[carguy07]

I think a new one is under $30, if I already had the old one in my hand and there was any question at all, I would just pop a new one in.

[beecho2]

Well the new thermostat didn't do it.. Now i noticed after driving the car the lower hose which has the thermostat in it is barely warm and the radiator cap is cold. Now i did replace the water pump, thermostat (twice), and radiator cap, I don't know where else to look other than to drop it off a cliff

[Acura2g]

replace the radiator. You probably have a clogged radiator. That explains the cool lower hose and a hot top.

With the stop leak used, I wouldn't be surprised. Stop leak just sits in the bottom of the radiator and F's up your cooling system. Mainly small passages like your radiator core.