Erratic Idle Temps

[specops1526]

Been having a weird issue lately. Idle temps have been jumping around lately. Not sure what could be causing it. Hasn't been overheating or anything like that, but I'm just curious as to what could be causing this.

Currently have a PEL500110 180* t-stat and just had my waterpump replaced. Before the waterpump was replaced temps were between 188-190 driving and probably 193 at idle, very, very occasionally hitting 195-197.

With the new waterpump, I'm still driving at 188-190 (sometimes even down to 184-186) but idle temps are all over the place. Most often it's 197-198 and occasionally it's at these various temps: 190, 193 or 200.

I noticed my Throttle Body Heater plate has a small leak again...Could this small leak be messing with the idle temps? Does any leak in the system cause temps to fluctuate like this?

thanks

 

[K-rover]

This doesn't answer your question, but for what its worth I have the same T-stat. Your driving temps are spot on to what i get. and your new idle temps are what I see normally at idle.
Ill see 201 after letting idle for 10 minutes, but that's as high as it goes, and it usually goes down to 198 after 12 or so minutes.

I would address your leak regardless, but not worry about those temps. The electric fan doesnt even kick in until 210.

 

[KyleT]

Weak fan clutch is my guess. Does the ac seem to lag at idle too?

 

[specops1526]

This doesn't answer your question, but for what its worth I have the same T-stat. Your driving temps are spot on to what i get. and your new idle temps are what I see normally at idle.
Ill see 201 after letting idle for 10 minutes, but that's as high as it goes, and it usually goes down to 198 after 12 or so minutes.

I would address your leak regardless, but not worry about those temps. The electric fan doesnt even kick in until 210.

Yeah, I'm glad it's not overheating and good to hear these are the same temps as yours. However, my other 04 DII seems to never go above 193, occasionally hits 195, so I figured something must be off, right?

 

[specops1526]

Weak fan clutch is my guess. Does the ac seem to lag at idle too?

I just replaced my fan not too long ago plus just about everything else in the cooling system. But it's definitely possible as the Waterpump bearing shit the bed and the fan was wobbling like crazy. That could have messed something up.

In terms of the A/C, I hardly ever use it but it doesn't seem to lag. I'll need to give it a try. In terms of lag, would I just be checking to see if the temps don't stay cool at idle?

 

[K-rover]

Yeah, I'm glad it's not overheating and good to hear these are the same temps as yours. However, my other 04 DII seems to never go above 193, occasionally hits 195, so I figured something must be off, right?

Not necessarily. You could have 10 trucks with the same setup and all would read a little bit different. These trucks are hardly precision engineered.

 

[specops1526]

Not necessarily. You could have 10 trucks with the same setup and all would read a little bit different. These trucks are hardly precision engineered.

Ha. That is true. My issue is that I assume they should all be the same...

 

[dcarr1971]

FWIW, My D2 exhibits the same temp fluctuations with a very similar setup. The only difference is that my throttle body heater isn't leaking, and the temps do jump to 208 occasionally (for no obvious reason).

 

[robisonservice]

Are these temps you measure from a consistent spot with a tool, or indicated temps on the dashboard gauge? Be sure you measure in the same way, and if you are relying on the dash gauge, the problem may be voltage stabilization in the dash

 

[K-rover]

Are these temps you measure from a consistent spot with a tool, or indicated temps on the dashboard gauge? Be sure you measure in the same way, and if you are relying on the dash gauge, the problem may be voltage stabilization in the dash

I use a after market OBD2 adapter and app for my phone. Same principal as an scan gauge..etc.. The dash gauge doesnt show actual temps.

 

[dcarr1971]

Are these temps you measure from a consistent spot with a tool, or indicated temps on the dashboard gauge? Be sure you measure in the same way, and if you are relying on the dash gauge, the problem may be voltage stabilization in the dash

I'm using an Ultragauge.

The fluctuations don't worry me too much anymore. I'm used to the them at this point. I suspect that I may need to tighten something up on the top end to seal up a leak of some sort. The truck has consistently used a little coolant all the time for the past 25k miles. In the summer it uses very little (i.e.- a pint every 3000 miles), but in the winter it uses a lot more. (In the winter, it leaks off the back of the motor on the passenger side...not at all when the weather is warm though.)

I've just concluded that I'll try to tighten the intake manifold up, but that if that doesn't help it might be something a lot worse. If that's the case, I'll drop a whole new motor in, or maybe a whole other D2 under all my off-road stuff. Either way, I'm not sweating it.

 

[specops1526]

Are these temps you measure from a consistent spot with a tool, or indicated temps on the dashboard gauge? Be sure you measure in the same way, and if you are relying on the dash gauge, the problem may be voltage stabilization in the dash

I'm using a ScanGauge II to monitor these temps. I presume it's pretty accurate.