hi guys,
i got my coolant temp running @180 but it's not steady. climbs up and down in a few seconds(180-185).
it went close to 200 when i hit the hills in PA, fan never comes on. it was up in the 40s last week.
2000 miles on new rebilt with new thermostats.

whats wrong with it?

thanks G

 

What type engine?

I have a C-15, with 190 degree thermo-stats. Cat told me that I will see my best fuel mileage at 1450 rpm and 205 degrees....that the engine itself is designed to run on the hot side.

When I was up in OH and PA ther last 2 weeks of Dec and first 2 weeks of this months...my fuel mileage was down 3/4 mpg, because I seldom say 200 degrees on the coolant.

 

Over the years I've seen a few posts about "why their truck is running (hot)".

It must be a regional thing, north, south... And the fact I run around in the mountains with 140,000 lbs.

Why wouldn't your temperature rise and fall with the demand on the engine? It's normal, relax.

You might be shocked to know that it's normal to see my coolant temp rise from 180 up to 230 and then the fan would blow it down to maintain it...just climbing one short hill.

I've had trucks where the fan would come on at 205 and trucks that wouldn't blow till 230...

The only problem I ever had was an 07 ISX 565 and it was the oil getting hot (250) on long hard pulls, all the bells and whistles would go off and it would de-rate.

 

it's a 14l ditrot.

 

normal.

 

my truck at work runs 180-200. fan normally goes on after 200... sometimes 220.. i drove another one yesterday didnt get any hotter then 170.

 

Nothing!