Man this forum rocks, thanks all you sticky dudes, Im new to the diesel world and this website has helped me soooo much! SO Here i go!When i first start my 91 and get going the temp guage rises to roughly 1/8th of an inch to the "H" then I can tell the thermostat opens and the needle rushes down to normal opperating temp range. Thats the first temp issue. Then when Ive got a load on her she gets to roughly the same high guage reading and wont cool off going down hill with no throtle untill the clutch fan kicks in? I know it sounds weird! Cleaned radiator still no change.

 

welcom to the world of a non innercooled Cummins. they will run warm. you should put a new t-stat in it though.

 

Thanks for the input but Ive already replaced the t-stat I just dont understand the having to get hot to activate the t-stat

 

Agree with 2stroke... that thermostat is sticking....

 

should i get a lower temp t-stat

 

That would be a good question for wannadiesel... I would trust him on this one.... I am sure that it would depend on what your current T-Stat is rated at. I don't think I would go over about 175-180....

 

But the thing is that you could have a faulty 165 that is waiting till 200 to open!

 

thanks for your time rockfoot, im just gonna have to crack her open again and check out the temp and mabee make an adjustment if nothing was wrong but for some reason I think that orileys oem temp setting in thier computer for that truck was 195 that seems wrong

 

Thats why I referred to wannadiesel cause he is a lot more familiar with the CTD than I am. 195 is not a real high temp... as long as that is where it (the T-Stat) opens... If it sticks, there could be a problem

 

Get a mechanical gauge and test the Factory gauge against the mechanical one. The Dode gauges are not known to be accurate at all.

 

If it's not a genuine Cummins thermostat, get one and put it in.

 

another thing to look out for with the T-Stat is where you position it in the housing. There was a tech bulliten out about having the jingle pins properly aligned to prevent them from being blocked and not opening, causing a warm or over heat condition.