Overheating in winter on a 6.0L? help needed

[doktorek]

I have a 2008 Burb 2500 with 6.0L with clutch fan and huge AUX transmission cooler (tranny running 100 degrees in winter - no problem there - not causing temp issues).

In 30 degrees outside or 50 degrees outside - I seem to run 10-15 degrees hotter (220-225 degrees) while driving when I let go of the gas (say going down the hill) or when pulling up to the light and waiting until it changes. Once I give gas while driving or from a dead stop - temp goes back to 210. Once I stop it goes 10 degrees higher - I give gas it goes back to 210 - back and forth. Then while parked and when I give gas - it comes back to 210 and it stays there.

I dont know what it is!!?? I already changed few things in the summer when it was almost the same issue. That is when MY AC started blowing warm air pass 210. What I did was changed: New radiator (aftermarket), New thermostat (aftermarket), new clutch fan (dealer). Water pump doesnt seem to be leaking anywhere.
What the heck is it? Why is the temp going back and forth when I give gas? Is it thermostat opening and closing too late? crappy thermostat? Is the water pump dying? Or are the coolant passages in aftermarket radiator too small and I need new radiator? Or perhaps 40GVW tranny cooler covers the condenser and radiator not letting enough air? Im clueless. I need help or ideas. I dont want to just keep throwing money at this car.

See pic attached. This is as far as it goes. It doesnt go anywhere pass that. It just hits 220 and it either stays there or goes back

Thank you in Advance

 

[about20ninj45]

Couple things it could be....
for starters, is you fans working correctly?;@ what temp do they go on high? Have you measured your hose temp with an temp gun? Is your coolant low? Did you replace the upper and lower radiator hose when you purchase a new radiator? Is a hose collapsing? Have you had a flush recently?

Id turn on the heat in the vehicle on high (front and rear) and top of your radiator fluid. You may also have a air bubble which could be a pain to get out. What type of coolant are you running?

 

[doktorek]

Coolant is at correct level. Fan has a new clutch so its working fine (no electric fans) . I have not check the temp of the hoses but heat works well in the car. Hose is not collapsing. I have never replaced the hoses (60K miles on the car)...But its hard to check because its going over the correct temperature only when I drive mostly. System was flushed when radiator was replaced.
I used dex coolant. I was thinking about the bubble. I will try to park up the hill somehow and run the car for 20 min...or I have to google how to get rid of air pocket. Im also thinking either pump is ready to give up and impeller needs to turn harder to cool it - or - thermostat issue.

 

[TheAutumnWind]

What makes you say its overheating?

 

[ta07hoe]

How do you know the actual temp and why do you think it's overheating. Possible water pump issue since it goes away with more rpm

 

[doktorek]

Not really overheating, but look at the temp gauge. That should stay at 210 all the time just like on cars with electric fans. Instead it keeps jumping 201-225-21-225-210-225 depending if I give gas or not. Makes me nervous that I will get stock somewhere at some time. So I probably need to address this.

 

[doktorek]

Anybody else - any ideas?

 

[ta07hoe]

Do you have any way to watch coolant temp with a scanner? I'm guessing your just estimating the temp

 

[doktorek]

No way to watch via the scanner without going to mechanic... im trying to avoid that trip unless necessary. Thanks.

 

[ta07hoe]

Will it do it in neutral or park

 

[doktorek]

Once I drive and then stop, pull over an stay parked with that temp already up higher (as pictured) - it will stay there. Once I give a litttle gas it comes back to normal and it just stays normal at 210. I can just stay parked for 1 hr idling - it will stay there. Doesnt go up any more. It doesnt climb up unless I start driving. Slow driving (stop and go traffic) or 60 mph. Same story. Just back and forth 210 - 225 - 210 - 225. If Im not pressing gas while driving (going down the stope or whatever) - it goes back up after about 1 min - i give gas (it comes down after 15 sec) - I let go of gas (it climbs up within 60 sec). NEVER pass the point on the picture above. It seems that only when driving that happens. It seems to be dependent on me putting car under load

 

[doktorek]

I have a feeling that my flow is restrictive by aftermarket radiator having small passages. Because its not overheating enough to engauge the clutch so as the fan gets more speed it just cools it .

 

[bottomline2000]

Anybody else - any ideas?

Your water pump is failing.. the blades inside wear down and it loses some of its ability to move coolant, hence why the temp drops when u Rev it because u are forcing the pump to flow more coolant..it doesn't have to leak to fail.

Your ac is blowing warm because the heat from the radiator is warming up your condesensor and causing your ac pressure to go up..

Just a guess[emoji12]

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[doktorek]

I was thinking about the water pump...but I have no leak of any kind and I heard that is the main sign of it failing. I know that overheating is another sign but Im just going slightly over - not overheating. But Maybe that is a sign? I dont know. I would hate to throw parts at this thing unnecessarily.
I figure maybe someone ran into this situation.

 

[bottomline2000]

I was thinking about the water pump...but I have no leak of any kind and I heard that is the main sign of it failing. I know that overheating is another sign but Im just going slightly over - not overheating. But Maybe that is a sign? I dont know. I would hate to throw parts at this thing unnecessarily.
I figure maybe someone ran into this situation.

I probably shouldn't have said just a guess. Sarcasim doesnt always show itself. This scenario happened to me. Maybe there is a seal that breaks after the pump gets too to let you know it's bad.

The only thing I can think of is to check the heater hoses and see if the pump is sending hot fluid thru them.

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[Russ]

You can buy an OBD2 dongle that will wirelessly stream ecu data to a smartphone or tablet for less than $50. I would not read too much into the accuracy of the dash gauge. Seeing that it does not seem to be overheating, it sounds like you may have a thermostat that is slow to respond causing the fluctuation. If you buy aftermarket parts on a regular basis, you will get bit, the only unknown is how long it will take.