Overheating

[Flying U]

2003 mack granite cv 713 oil temp getting up over 250 which is bringing water temp up causing trk to over  heat on bigger hills. Literally just did oil change on it and went out monday trk overheated about mid day. Fan seems to be wrkn can hear it come on and off. Trk cools down at an idol or when engine not under a load. Blew radiator out. Any thoughts? I was leaning towards stuck t- stat but shouldn't oil temp be kinda close to water temp seeing it gets cooled by it?

 

 

[br549]

Water helps keep oil cooled down,  you say you don't hear fan kick in. From what I have seen if it has the Horton air fan & if you can turn it with the engine off  it is slipping and not turning at full speed.  On the ones I have seen it takes air to release it and should be locked in with the truck turned off.    If the fan is not slipping there is a screen in the bottom radiator hose between the transmission cooler that goes into the oil cooler.  Ck and make sure it is not stopped up. 

[RedBullDog]

The oil temps should run about 20 to 30 degrees over water temp.  Sometimes the radiator needs a little more than blown out.  Pull the charge air cooler and fan shroud for better access and really hose it out good with water.  In the past I've used foaminator  condenser coil cleaner to clean up really plugged fins.  You can get it at plumbing supply places, or probably the internet too.  It sprays on and foams up and pushes out dirt and bugs and stuff that can really hang in there.  Cooler water = cooler oil.

 

[Mackpro]

Oil temp being 250 or alittle higher is no big deal. There is a Mack service bulletin about that but I still cant attach any files on here after the site format change. whats the water temp doing is the real question?  As others have said , slipping fan clutch  or clogged radiator is my guess.