Hey guys. I'm hoping you help me diagnose some symptoms I've been experiencing with lately. I have a 2003 3500 with 217k on the ticker.

As I'm sure you all know it's been unusually cold here in the Midwest recently. The past couple of days my truck has been erratic when the engine has been warming up. Usually it warms up pretty consistently til about 190* and then doesn't move. Recently it will heat up to about 140-150*, then drop back down to 130*, then take forever to warm up. Sometimes it will hit 210* then drop back down to 190*. It's just kind of all over the board.

I usually wait until the truck gets above 140* to turn the heat on so I'm not blasting cold air on myself and the wife but with this new turn of events, no warm air will come out at all. I'm guessing these are related somehow.

The cooling system is not leaking anything and antifreeze levels look good. Could this be a bad/stuck thermostat?

Thanks for any help.

 

when was your last coolant flush? anything 'erratic' has some nasties plugging up ports....

you can test engine load simply by start, idle in the driveway, then turn on the a/c. yup. see if the engine warms up without the dancing temp AND it should warm up faster. you don't have to turn on the fan and freeze your begonias but the routing is a different draw, what we do with our tractors to get them up to temp quickly when not by driving.

also check the middle door of the heat vents, see if that is stuck. common with the 3rd gens....

quick checks.

 

It's been a while since a true flush. I've had the truck for about 50k and had to replace the water pump so it got all new fluids then but was not "flushed" per say.

I'll give the A/C-style warm up a try next time I go out. Thanks for the tip.

I am 99% sure that the actuators in my HVAC are stripped but that is a problem for another day!

Thanks.

 

That's about normal in real cold weather. I would recommend a cold air front or some cardboard to block some of the cold air. Just make sure you pull the radiator cap with a cold engine and ensure the antifreeze is up to the top of the filler neck. If not, you may have an air pocket.

 

Normal, eh? I don't like this new normal. We just moved up here from Georgia so this whole sub-zero temperature is new to me. Hopefully there won't be any more cold weather surprises.

 

Wait till January.

 

Is your coolant low? Could be a sticking stat. I have had an issue like that on my old 74 Dodge where it cant decide what to do. Its not a normal thing to happen.







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Please replace the 190F thermostat and make sure the coolant system is FULL of coolant.

 

The coolant was a little low but I topped it off before made this post. I thought I had solved the issue but it has snuck back up on me.

I drove the truck about 600 miles to Thanksgiving. I had some time today so I popped the hood to make sure everything looked kosher still and the coolant is low again. I have been checking the garage floor and been keeping an eye on it when I am out and am very confident that it is not leaking anywhere.

I did a little more research on here and found this thread: https://www.dieseltruckresource.com/...w-t302169.html

It sounds like what's happening to my truck. I'm not sure where to go from here. I'm keeping it topped off but I don't want to do any long term damage to the engine. Any suggestions?

Thanks guys.

 

Keep looking harder for leak, not just looking at the floor!
Loss of coolant = Leak somewhere
If you cannot find the leak under the hood then your engine burns coolant.
Try pressure test the coolant system and check for leak.