what is the most likely problem? I am suspecting control valve, but can't find it on a parts list at autoparts stores on line. It is my son's minivan, and he is bringing it to me, says he can't see a valve anywhere....
I am in northern Utah, its very cold here.....he is driving up from Phoenix with no heat, and apparently no brains. He knew it was acting up a month ago.
thanks...
he just got here, says if he takes it out of overdrive and gets the RPMs over 3500, he can get heat....

 

Model year?

 

You won't find a control valve on these vans from at least the 3rd generation (96-00) vans forward and probably even earlier than that. Coolant flows through the heater core all the time. An electrically actuated door in the HVAC unit controls how much hot air enters the cabin.

Bad thermostat? Are you seeing a slower than normal temperature gauge increase as the engine warms? Is the upper rad hose cool or only warm 10 minutes after starting?

I only learned of this restricter from this recent thread (linked below). This is all I know about it. No idea if your van has one. The last post on the second page may say it all.
https://dodgeforum.com/forum/dodge-c...rol-valve.html

 

2005 dodge grand caravan....

 

Think easier before you go to harder. Thermostat before something like a control valve. Cougar is probably on the right track. Had my thermostat go out. When I got it out it wasn't just stuck but had actually come apart.

Anyway, if your thermostat stays open all the time, then the coolant runs through your engine and back to the radiator so fast that it doesn't have time to heat up. Especially in cold weather, your thermostat needs to close periodically to stop the flow of coolant and to allow the coolant that is then stuck in the engine channels to warm up. When that coolant gets hot enough, the thermostat opens allowing cooler liquid into the engine and allowing the warmer liquid to move out. The hot liquid then moves out to your heater core under the dash where your a/c system blows air across it to heat the cabin before it moves back to the radiator to be cooled back off.

With a thermostat stuck open, the cooling system is basically free flowing, and in cold weather the coolant will simply stay chilled all the time. Cold liquid in your heater core means no heat in the cabin. Sometimes you'll notice a difference if the car is moving vs. not moving. While it's moving, there is air blowing across the radiator meaning the radiator works better and cools everything completely. But, if you've the engine is warm and the car is stationary, then no wind across the radiator and less cooling. In other words, if you start to get a little heat when you're stopped at a long red light, but it goes away when you start moving again, then that's another sign of a bad thermostat.

Pull your thermostat and take a look at it. Shouldn't take you 5 minutes even if you don't really know what you're doing. If that's your problem it's a cheap fix.

Good luck and merry Christmas.

 

thanks, new thermostat will go in soon, will let you know how it turns out.

I forget which car, but a few years ago I did find a thermostat had come apart completely...

 

well, no water in the overflow, and only about half in the radiator.....
there must be a leak somewhere, but we see no dripping on the floor...hope it isn't the water pump. I hate replacing water pumps on front wheel drive cars....thanks for the help....

 

They are not that really that bad. Thats why you join this forum, everyone helps everyone.

 

Our thermo went out 2 hours away from home when it was 6 degrees out side. That may have been the coldest I ever was in my life, and for sure was the coldest drive ever. That had to have been 3 or 4 years ago, and was in our 2001 GC. It has 144K on it now.

 

My son's minivan has given him a lot of little problems, egr system failing several times, and failing emissions, power door locks won't work for very long, have to keep resetting the computer by lifting battery terminals, leaking power steering fluid, a water pump, etc. but the engine and tranny keep on truckin'. A lot of the miles on the van are city miles from taking their oldest child to Phoenix Children's Hospital once a week for over 5 years for chemo, due to an inoperable brain tumor. She is hanging in there, tho, and is on a trial drug now that has been proven good at killing other kinds of tumors.
At 127K miles, their van is about due for replacement, but he hopes to get 2 more years out of it. By then he should have gotten a promotion to Asst. Principal and will be making enough money to get a new family car or truck or van. His other car is a 95 dakota and it has been very reliable considering its age. I am advising him to get a quad cab dakota. With 3 kids, it is just big enough for them to travel in...and a lot easier to work on after the warranty expires. I am getting too old for the hard repairs....