my truck has no heat, antifreeze is full, changed thermostat, heater core is not plugged, i put a garden hose on and it flows both ways just fine, not leaking and i have the grille covered to prevent air at high speeds in eng. comp. any help would be great it is pretty cold in WI, thanks

 

The problem is the blend door. If you have a newer truck the blend door act is elect, if older truck it's boden cable driven. Either way look up at the heater plenum close to the hump on the pax side. When you move the hot/cold **** you should see the door arm move. You will need the key on if it's electric, truck doesn't need to be running. My guess is it's not moving. If boden cable , the cable has likely come off at one end or the other, if elect then it's probably the elect rotary actuator either defective or broken off the blend door arm.

 

the arm moves and i can feel the heat difference, but just barley. i wonder if the thermostat i put in is no good

 

If you are getting full travel on the blend door then I would suspect the thermostat is either not the hottest rated (190?) or is defective. I have read on here (DTR) that the ones from Cummins are best. Does the eng temp come up on the gauge?

 

it is usually at 190 but sometimes a lil higher only when it gets over 40 outside and i still have the grill covers on, it is an aftermarket thermostat so maybe

 

busboy: thanks for the info. i will get a cummins therm. and try it tomorow

 

Did the cummins therm. fix your heater? I am in Wisconsin and having the same problem. I am topping off coolant since it is low. But my heat comes on after I drive the truck at highway speeds. My engine temp guage is jumping to redline and then settles back down after the heater starts working. I saw above a comment about "cooking the trans oil". Is that relevant?

 

You guys have it wrong.

To fill the radiator after any service to the system you have to use the reservoir bottle., never top the radiator.
By manual instructions you fill up radiator cold, close cap and NEVER open it again, then fill reservoir bottle to the full (or a little above). Run truck to normal temperature then shut off, fill reservoir to add line, run truck again.
Do this until bottle stays to the full level and never drops.
Done.

What happens now every time you open the rad cap you create an air bubble in the system and pump cannot operate.

Guess how I found out ? I even replaced water pump. Now I have a spare good used

 

Those are classic air in the system symptoms. Heed Valv's advice and see if that doesn't fix it. If you still have problems, inspect the radiator cap, tubing between the radiator and the reservoir bottle, and the reservoir bottle itself for a leak.

 

Your manual is different than the Dodge manual for my 97. Perhaps yours doesn't have a one way check valve (jiggle pin) on the the thermostat housing. It is the thing that the very small hose is attached to.

"The check valve is used as a servicing feature and will vent air when the system is being filled." It goes on to say, "Due to the use of this valve, the engine must not be operating when refilling the cooling system"

No where does it say NOT to refill the radiator thru the filler neck, other than the standard warnings of removing the cap when the engine is hot.

One of the troubleshooting charts states that both heater hoses should be hot when at operating temp. If not the pump could be weak. The temps to test the thermostat in hot water. It should start to open at 181 and should be fully open at 203. If it opens at a lower temp (or not at all) or is not fully open at 203 it should be replaced.

 

I don't read the owners manual I use the OEM Technical Service Manual.
You should be able to see what's my truck from below signature.

Here's what the manual say

STANDARD PROCEDURE—REFILLING
COOLING SYSTEM 5.9L DIESEL ENGINE
Clean cooling system prior to refilling (Refer to 7 -
COOLING - STANDARD PROCEDURE).
(1) Close radiator drain plug.
CAUTION: Due to the use of the one-way check
valve, the engine must not be operating when refilling
the cooling system.
NOTE: The diesel engine is equipped with a oneway
check valve (jiggle pin). The check valve is
used as a servicing feature and will vent air when
the system is being filled. Water pressure (or flow)
will hold the valve closed.
(2) Fill the cooling system with a 50/50 mixture of
water and antifreeze.
(3) Fill coolant reserve/overflow tank to the FULL
mark
(4) Start and operate engine until thermostat
opens. Upper radiator hose should be warm to touch.
(5) If necessary, add 50/50 water and antifreeze
mixture to the coolant reserve/overflow tank to maintain
coolant level. This level should be between the
ADD and FULL marks. The level in the reserve/overflow
tank may drop below the ADD mark after three
or four warm-up and cool-down cycles.

STANDARD PROCEDURE—ADDING
ADDITIONAL COOLANT
Do not remove radiator cap to add coolant to
system.When adding coolant to maintain correct
level, do so at coolant reserve/overflow tank. Use a
50/50 mixture of ethylene glycol antifreeze containing
Alugard 340-2 y and low mineral content water.
Remove radiator cap only for testing or when refilling
system after service. Removing cap unnecessarily
can cause loss of coolant and allow air to enter system,
which produces corrosion.

STANDARD PROCEDURE—COOLANT LEVEL
CHECK
NOTE: Do not remove radiator cap for routine coolant
level inspections. The coolant level can be
checked at coolant recovery bottle .
The coolant reserve/overflow system provides a
quick method for determining coolant level without
removing radiator pressure cap. With engine not running,
open the coolant recovery bottle cap and
remove coolant level indicator dipstick to observe
coolant level in coolant recovery bottle. The coolant
level should be between ADD and FULL marks. If
the coolant level is at or below the ADD mark, fill
the recovery bottle with a 50/50 mixture of antifreeze
and water ONE QUART AT A TIME. Repeat this procedure
until the coolant level is at the FULL mark
-------------

Do you still think it's not the correct procedure ?

 

I'm quoting from my Dodge service manual, I've never seen an owners manual with that kind of info. I never said it wasn't correct, just not necessary. The caution for air isn't for pump cavitation, it is for corrosion. Plus there is this, directly from your post

"Remove radiator cap only for testing or when refilling
system after service."

So where is the smilie for having a beer?

 

That may be what it says but a smart guy would take the cap off every now and then to see if there really is coolant there. A bad rad cap or a leak enough to bleed off pressure and its game over. You may also notice that he hasn't reposted since installing the Cummings thermostat which leads me to believe that fixed his problem.

It would be interesting to see just how many people fill the cooling system in that way, I have never done it that way and never had a problem. Comments?

 

I've never done this way myself, except I replaced radiator and never had great heat.
I drove all the way to N.Carolina and towed a 11,000lbs trailer and I had to wear a coat and gloves. Figured was the water pump and replaced it.
Same issue until I read the manual.
Followed instructions and now I can be at -45* outside and you will sweat inside. Temperature does not fluctuate, and truck runs great.
Manual says NOT to remove cap while truck is running.
Many newer vehicles don't even have the cap anymore, through the tank is the only way to fill.

I don't understand why arguing about it. Before replacing parts it's easier, more convenient, and common sense trying the simple things.
I have here a $ 90 perfectly good Cummins water pump that I didn't need if I followed.... my own advise

 

I agree about removing the capwhile running. For one thing you are liable
to get scaulded, plus there is the jiggle pin. My wife's car has no radiator cap, but it has no jiggle pin either. I'm also a fan of the KISS method. I do have a very difficult time believing that trapped air would not be purged from the system during operation causing a loss of heater efficiency. The design of any cooling system wouldn't support that theory. A radiator low on fluid with an empty tank could cause it, but that isn't the same thing. That is the only fact that addresses the OPs problem. My money is on a bad thermostat or radiator cap.