2002 Dodge Cummins blows lukewarm air

[Andy]

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My 2002 Dodge diesel pickup has been blowing lukewarm air lately. Like, just enough to melt some of the ice on the lower windshield, and definitely not warm enough to ever take your jacket off while in the truck.

Any ideas? Someone mentioned either an air bubble in my coolant, or that I might need a thermostat change...

Andy

[blue7.3]

Originally Posted by Andy

My 2002 Dodge diesel pickup has been blowing lukewarm air lately. Like, just enough to melt some of the ice on the lower windshield, and definitely not warm enough to ever take your jacket off while in the truck.

Any ideas? Someone mentioned either an air bubble in my coolant, or that I might need a thermostat change...

Andy

Hey Dude!
Diesel coolant tends to get acidic, which plays havoc with thermostats, water valves, and heater cores. Air bubbles are kinda rare in pickups since there is plenty of room for proper plumbing geometry to prevent it. If idling fully warmed up you can't hold on to the radiator, and/or your temp gauge works, then it's not the theromstat. Generally, American thermostats tend to fail closed, leading to over heating. Those on most foreign cars/trucks tend to fail open (way smarter in my book) leading to never heating, or luke-warm heating. I've had both happen to me.
The water valve (if your truck has one, my '98 gas-Ram did) is generally located on the intake hose to the heater core (sometimes outlet side) and may be either spliced into place or part of the core or another part. Essentially it blocks coolant flow to the radiator when AC is called for by the HVAC control (it is defeated when the defroster comes on). They can clog or sieze internally, or, if vacuum controlled you could have a bad hose or vacuum source. If electric the solenoid could be bad.
Internal to the duct work, you might have a bad door flapper motor or solenoid.
Then again, you could have a mouse-house in the heater ducting (it happens whether is the city or country, trust me).

Give me some more detail and I might be able to help further the diagnosis. That, and maybe check The Diesel Garage. Tons of smart fellas in there!

-pete

[ack]

Pete covered the stuff I was going to mention and a lot more!

Samurais have a bad habit of disconnecting the heater valve cable from the heater flow valve.

The underlying concept is that if it moves, it will break - or come loose.

That's where I would start my diagnosing...

[Andy]

Wow, thank you both... I'm going to turn my truck on and see if I can hold on to that radiator... I'll get you some more information soon

[blue7.3]

Originally Posted by Andy

Wow, thank you both... I'm going to turn my truck on and see if I can hold on to that radiator... I'll get you some more information soon

Just don't hold on to the part swept by the fan. But I guess that goes without saying...
Oh, umm, latching onto the upper radiator hose should work just as well unless the Cummins is a reverse-flow like the old GM LTX engines. But I doubt it.

Ack, you're not kidding. Everything attached comes loose or breaks. The corollary is:
"Everything Leaks".

-pete

[stove warrior]

It's a boy people. He came early from the great white north. year of the tiger. Second grandson. Anything new in the mahindra world while I was gone. Everyone take care for now.

[Andy]

Originally Posted by stove warrior

It's a boy people. He came early from the great white north. year of the tiger. Second grandson. Anything new in the mahindra world while I was gone. Everyone take care for now.

Congrats! Good for you!

[howam00]

Originally Posted by stove warrior

It's a boy people. He came early from the great white north. year of the tiger. Second grandson. Anything new in the mahindra world while I was gone. Everyone take care for now.

Maybe you'll finally be able to buy one when the grandson is old enough to drive

Congrats!