CattleKev

Strange problem.
Start truck and drive to work. Engine temp increases and cab heat is available. Continue to drive and loose cab heat (only cold air blows) temperature guage increases almost to the red warning temp. Pull over, pop hood to find that upper rad hose is pressurized and hot and the two heater core lines are cold? What's up with that?
What would stop the flow of coolant throught the heater core lines, a valve? Why does the coolant flow through heater core occasionally?

I put a new t-stat in last night and nothing changed.
Got any idea's? Is there a valve in the heater core lines somewhere?

Kevin

TIMMY22

I'm not sure if we have a valve that closes when you turn the heat to "off"
maybe someone else can help on that.

1. could be a bad core.
try connecting the two core lines together (a loop eliminating the core) then see if they heat up.

2.you say almost red? is it over the temp of your t-stat 190, 195?

you could have bad circulation, like a bad water pump or a restriction somewhere.

ccmckee

Is your coolant level correct? If it is low maybe an air lock in the system.

CattleKev

The coolant level is correct.
Could the thrmostat be in backwards?

TIMMY22

well, by your descriptions, it sounds like you had the problem before you changed the t-stat?

CattleKev

I did have the problem before changing the t-stat.
I tested the old stat by boiling it in a pot of water.
The old stat would not open until the water was at a very rapid boil.
I suspected that it was not opening soon enough so I replaced it.
I'm quite certain that the new one's in correctly but the wife was complaining and I rushed the job to get to a b-day party.

Is it possible that the water pump could be spinning freely part of the time??
Maybe the heater core is being plugged part of the time?

TIMMY22

10-4 on the wife b-day party thing.....sounds so familiar.

anytime you have the t-stat out, just replace it, it's not worth the few bucks to fool with the boiling thing.just my opinion.

um, I've never had my water pump out on the cummins but i've worked on alot of other ones (mainly JD). usually the impellers wear out. (the distance between the fins on the impellar and the cast water pump housing becomes greater and greater) When this happens you press the impeller off the shaft, replace the impeller, bearing, and seal and your good for another 15 years.

I'm told these cummins water pumps last a long time so it's unlikely your problem.

are you actually overheating?

remember water boils at 212f -sea level-

http://www.biggreenegg.com/boilingPoint.htm

CattleKev

I'm not sure if I'm overheating but the antifreeze has bypassed the rad cap, filled the reservoir and run out the overflow once before I changed the stat.
That's part of reason why I suspected the stat was not opening.
Tonight I am going to double check my stat install and also run water with a garden hose through heater core in both directions.

Garnet Kid

What was your coolant good to temp wise?? And what was the outside temp. Possibly your rad core was freezing up.

TIMMY22

you should be able to start up, and watch your temp gauge slowy (usually very slowly) come up to 190 ish. then if youre going up the road, it should dive down to 150 ish then repeat.

this means your t-stat's workin.

TRCM

if your are filling the overflow that bad, you may have a cracked head or a head gasket leak.

that has been the cause every time I had that problem.

And a bad t stat (your old one) can cause that.

it sounds to me like you are fine cold, but as it heats up, the coolant is being replaced by combustion gases. the first place this gas bubble will show up is the heater core, since it is the highest spot inthe system...hence the loss of heat.

Sadly I'd say you have a major problem on your hands. Stop driving it until you can fix it before it gets worse.

gerry

If it is an earlier truck you could have oil debris in the radiator fins from the vent breather thus no air moving across the radiator.. between thae radiator and coolers to see it is is full of debris/old oil that has turn hard causing bad flow through the radiator...

Just a thought that is free to check..

CattleKev

Update - still no heat.

1) Replaced aftermarket t-stat with correct Dodge part.
2) Checked water pump and it's perfect.
3) Replaced rad cap.
4) Flushed HTR core again.
5) Replaced coolant (correct mix/qty) and removed any air locks.
6) Found that my hot/cold control moves a cable that moves an arm near HTR core. The Arm does not move, connection must be broken so I put vise grips on door shaft and moved the door to the heat position manually.

Truck does not overheat anymore, must have been the aftermarket t-stat, I noticed that it was a standard looking stat and did not have the big rubber plunger like the original dodge part so I replaced it.

Still no heat.
Engine comes up to temp but heater core lines stay cold. I have flushed cor twice and even blown out the lines.

Got any new idea's???????

Kevin

TIMMY22

try moving that valve back the other way.