Water temp guage movement. CAT?Fleetwood DP

[Big_Katuna]

I recently had a full service performed, including new coolant.

I have to admit I rarely glance at my analog guages knowing I have idiot lights, at least on level ground. In the mountains I watch temp like a hawk.

SO after the service, I started paying close attention in case there was a air pocket, etc.

I noticed that sometimes the gauge was in between cold and straight up and five minutes later, just left of straight up. I keep watching it and it cycles back down.

It does this on a 3-5 minute cycle; goes down, slowly climbs back up, then slowly goes back down. All on flat ground.

I checked coolant level and its full. It acts like the fan clutch kicking in but I never noticed it before.

Anybody elses do that? Its about 70 out today when it was doing it.

[RCtime]

last time I had a wandering temp gauge it was faulty thermostats.
I replaced both thermostats and it solved the problem.
One or both of your thermostats could be faulty.
They should be replaced every 3 years.
My gauge dropped to cold as yours do, They were sticking open, then recover and repeat.

[EdNdonna]

my direct drive fan did the same thing. when I went with a clutch drivin fan my temps pretty much stay the same unless I'm climbing.

[w4phj]

My fixed fan C7 coolant temp rises quickly from cold
to 180, Then another rise to 190 about 10 minutes later
where it stays regardless of load. Cat ELC installed last
year w/o thermostats being changed.

[randallb]

My 6.7 Cummins acted like that from day one. After I replaced the thermostat the temp dropped slightly and the cycle time actually shortened. I attributed the shorter cycle to a slightly smaller center hole in the replacement Stant thermostat which required a quicker cycle to maintain the correct temperature. In response to Wolfe this is an engine with a fixed fan. With a fixed fan the only temp regulation comes from the thermostat and they are not instantaneous.
Randy

[Big_Katuna]

It's a rear radiater. Not sure about clutch. I'm guessing it has one.
I'll call CAT and or the mechanic that serviced it. He put a new belt on too.

It may have always done it and I never noticed.

[wolfe10]

First, a question-- do you have a solid-drive rear radiator fan, clutched rear radiator fan or side radiator?

Fluctuating within a safe operating temperature is NOT reasonable with solid drive fans. It IS reasonable with either of the latter two. Actually, more than reasonable-- DESIRABLE. Desirable because that means you are not paying for the fan to run at 100% all the time which would cost you HP and MPG.

[Big_Katuna]

Two hours.

[dakdave]

thermostat opening and closing.how far did u drive it ?