Help with CAT C15 on Peterbilt 387

Is the fan kicking in? Maybe thermostats jammed.
seems strange no logged codes tho, compare the coolant temp in ET to the gauge on the dash.

 

I agree sounds like ar flow problem, is the fan coming on? If so it should be on about 225* and cool it off enough to turn the fan off. Also check for an excessive fuel temp code. If you have the fuel temp wire on it it might have broke a solder joint, if your not using the wire it might have a bad fuel temp sensor, or connection.

 

I had the same problems on my 05 w900. If its none of the obvious eg coolant level is good, fan comes on , T stats are good etc it may be that you need a new rad core. That's what I ended up doing. I went with a 4 row core and haven't had any trouble since. A 6 to 7 year old rad has done its job and probably is in need of re-coreing. Just double check the tell tale on the water pump isn't leaking as it would contribute to the problem if it was on its way out.All up it cost me just under three grand for a new core, new stainless pipes and the coolant to fill it , that includes the labour cost as well.

 

I do believe the gauge gets it's info from a sending unit in the top of thermostat housing.

 

heres something else to throw at you, when was the last time the rad/air2air was blown/washed out? if it has a substatial amount of dirt/dust/bugs in it, it wont pull enough air across it when the fan kicks on. we pulled the a/c condensor to the side, pulled air2air off and washed all 3 separately with dawn until it was just water then took a blow gun and blew through them before re-assembling them.

 

i think it could be your radiator ,have you blown r washed it out?