engine temp fluctuating radiclly

DieselFanatic87

DieselFanatic87

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May 13, 2009
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hey guys im stumped on anissue im having with my truck. Ive look in the search and couldnt find anything. Anyways i have a 1995 dodge 2500 reg cab 2wd. i have takin the stock tranny cooler off the side if the bolck and and replaced the water pump, thermostat and hoses. I capped off the the two ports that went to the tranny cooler. the side of the block and the tee right above the ac compressor. now my temp doesnt stay where it supposed to. it heats up to around 210 then instantly drops to 140 or so then heats back up and keeps repaeting that. sorry for the long thread but trying to give as much info so i can get an answer. thank you for your input.
 
did you bleed all the air out of the coolant system? often an air pocket would cause a similar issue
 
Isn't that normal?... Mine always did that.

But I guess mine would go around the middle and then drop back off and repeat.
 
Last edited:
cummins part #3928499
its a updated thermostat thats is suppose to fix it but it is totally normal for it to heat up then cool down. Put some weight behind it (5,000 or more)and it will not do it anymore.
 
I say normal as well. I have a video of mine too and I was told it's normal.

Garrett

Probably getting paid at work to post this from my D1
 
As everyone has said, its normal. I've been through quite a few T-Stats and they all do it. I have a 180° in now so the swings in temp aren't so extreme, but got still drives me crazy. When you think about what you've always heard about rapid, significant temp swings and the effect they have on different materials, it seems like it can't be good.

What really gets me is the fact that my 1st Gen 12V never did that.

The new Cummins T-Stat should fix it, but I just don't want to spend fiddy bucks on a T-Stat right now.

Sent from my DROIDX using Tapatalk
 
i have been told that some trucks have a dummy guage so you dont see it do this but that it does it anyway. my truck does not show this on the temp gauge, but i doubt that means its not happening.
 
If its a air bubble you wont have heat either all the time or at a stop light lol (low rpm). Mine was like that. What I did was take the heater line with the 90* hose to the head off and turned the 90 up and put a funnel in it then held it up and put antifreeze in and it worked. If your temp gauge is just moving welcome to cummins power!
 
Sry guys I've been pretty busy with work but thank you for all your input. So im gonna guess that thus is normal LOL. Thank you again.

Sent from my PC36100 using Tapatalk
 
Does that not seem like an overly large swing in temps? My original 12v t-stat would go from 170-190 and bounce back and forth. My new one stays between 180 and 190, and rarely moves after that. 70 degree swings seems outside of normal.
 
Mine wouldn't fluctuate at all on my 12v. It would climb to 180-190 and stay there, and thats without a fan at all. I could see it moving some when the fan would kick in.
 
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