[Ol' blue]

This seemed like it happened after i changed my head gasket, my temperature gauge fluctuates all day long whether im goin up, down, flat, any kind of ground. it never stops, and it goes back and forth constantly. It goes from bout 175-180 to 200-210, and you can tell a huge power difference when it dumps the cool coolant in, then it runs normal when it heats back up. You can even hear and engine noise level difference. Have no idea why its doing this or even what would cause it. I also changed my thermostat to try that, still didnt help. Need some help with this one:S:

 

[Ol' blue]

C'mon fellars need some help on this one still can't figure out what it is

 

[whenpigsfly514]

Did you put it in upside down?

 

[jakesclark08]

did you put the right ammount in? did you use 50/50? and is you thermostat bad? sometimes it can not let it flow freeley bc your thermostat is messed up or stuck in one spot.

 

[1stgen3rdgendodge]

^^^^^^^^^My water temp use to jump up and down all day. It would run up clear to 215 before the thermostat would open up then run back down to 180 and then do it all over again. Did a coolant flush and put a new thermostat in and I run a constant 190 now.

 

[paulb]

Did you put a Cummins 24v head gasket on? I know you said that you changed the thermostat, but I would use a Cummins thermostat if you haven't already.

The water temp gauge is not an actual water temp reading. It is a calculated value. On a 24v, VP44 truck it uses both the water temp sensor reading, and the intake air temp (IAT) senor. When you can hear the change in the engine, that makes me think that you are hearing a timing change. This is most often related to the IAT. I would remove the IAT, and clean it with some brake clean. Also make sure that both the IAT and water temp sensor have good connections. While the engine is idling, wiggle the connectors at the sensors, and see if you hear the engine change.

Does the wait-to-start light seem to be working normally? Does the check gauges light every come on? Do you ever get a couple extra "dings" from the dash after starting?

Paul

This seemed like it happened after i changed my head gasket, my temperature gauge fluctuates all day long whether im goin up, down, flat, any kind of ground. it never stops, and it goes back and forth constantly. It goes from bout 175-180 to 200-210, and you can tell a huge power difference when it dumps the cool coolant in, then it runs normal when it heats back up. You can even hear and engine noise level difference. Have no idea why its doing this or even what would cause it. I also changed my thermostat to try that, still didnt help. Need some help with this one:S:

 

[98whitelightnin]

Mine does the same thing. Before it started I did a coolant flush and put in a new napa 190 t stat. When I flushed the coolant I pulled the water pump and it leaked from the weep hole when I put it back on so I put a new one on and thats when it started. So i have new water pump, t stat and coolant and it fluctuates just about the same s yours, 186-210 usually but did get ip to 222 last time I drove it. I used a bosch water pump with the little dome piece over the impeller and its a little harder to turn than the old one was but thats to be expected with a new part. Im gonna pull the water pump and replace it with a different brand and might get a new radiator cap too. I have never changed my headgasket but its not leaking either. I did get the engine a little hot (246)when I was running the flush before the new coolant, thankfully I dont have a 53 block.

 

[SmokeyAussie]

i just did mine and it fluctuates more than i would have thought it did, when i had my old t stat in it stuck to 181-183 constant even with my winter front.

now yesterdat was 10 degC here and i put the new one it and it ran under normal driving load at 190-195 and then once the coolant dumped in dropped down to 185 ish

is this normal?

the one on the left is the new one (190) from Autoparts who have always been better than napa to deal with, and the right is the old 180

 

[Shainer]

The water temp gauge is not an actual water temp reading. It is a calculated value. On a 24v, VP44 truck it uses both the water temp sensor reading, and the intake air temp (IAT)

Paul

Incredibly inaccurate information there Paul. The coolant temp gauge reads... coolant temp. I've built enough manual high idle setups on different trucks to verify this. I can set the IAT to 30 degrees and the ECT to 190 and the gauge reads 190. Now the ECM does use all available parameters to determine correct injection timing, but the coolant gauge reads actual coolant temps.

 

[Hendrenj2]

Did you put a Cummins 24v head gasket on? I know you said that you changed the thermostat, but I would use a Cummins thermostat if you haven't already.

The water temp gauge is not an actual water temp reading. It is a calculated value. On a 24v, VP44 truck it uses both the water temp sensor reading, and the intake air temp (IAT) senor. When you can hear the change in the engine, that makes me think that you are hearing a timing change. This is most often related to the IAT. I would remove the IAT, and clean it with some brake clean. Also make sure that both the IAT and water temp sensor have good connections. While the engine is idling, wiggle the connectors at the sensors, and see if you hear the engine change.

Does the wait-to-start light seem to be working normally? Does the check gauges light every come on? Do you ever get a couple extra "dings" from the dash after starting?

Paul

What happens when the wait to start light don't come on and a couple extra dings?

 

[bigfish95971]

Thank you Shainer.
High coolant temp variation usually comes from a few things.
Air in the radiator, usually due to poor filling procedure after work or a leak somewhere that sucks air back in when cooling on shut off.
Bad Thermostat.
Dirty clogged radiator on back side in front of fan from oil and dirt clogging fins. Often cools fine down hill or no load. Add any load or city driving and temps go up.
Trans no going into lockup when it should.

 

[5.7 Hemi]

This is a Cummins 200* thermostat that was in my truck. Temps used to be very stable 199-203 no matter what. 2 weeks ago, coolant temp got to 191 and would hit 199 then yo yo back and forth. Replaced it with one from Geno’s, rock steady again. See how the rubber is deformed??