had the truck in the shop for some front end work. while it there i had them change the antifreeze and put on new radiator hoses. everuthing worked great for a month and then suddenly overheated while going down the road. I installed a new autozone t-stat, but it still acts like its not opening. I guess im gonna have to pull it back out and put it in some boiling water to see if it opens. my friend said its not unusual for a new t-stat to behave kind of funny right at first. the last time it overheated was when i was backing up my 5er trying to get it lined up just right. i looked down and the thing was hotter than two mice making love in a wool sock. I released the pressure and added some hose water to get the temps down. SOmetimes the t-stat works, sometimes it dont.

 

It's not unusual for T-Stats to be bad out of the box either.

 

thats what im thinking too. maybe ill just have to get another, or find a cummins dealer and get a good one

 

The first thing I always do when I get a new T-stat is put it in a pan of water with a thermometer and heat until it opens. I have had more than a one of them not work at all out of the box. Cheap insurance.

 

Same here ...Then I went and put a factory cummins Thermostat and never had a problem !

Greg

 

One thing to think about as well is the antifreeze they put in it. If they put straight antifreeze in it thinking it was pre mixed 50/50 it might not cool as well.

Just a thought, it wouldn't hurt to test it to see what the level of protection is.

 

.


Along with that, I hope they put the right anti-freeze in it to begin with. We're supposed to use a diesel rated low silicate anti-freeze.

 

well, it seems to have fixed itself. i havent had an overheating problem lately. maybe the new t-stat just had to get broken in. As far as wat anit freeze got put in it, i dont even know. Maybe I'll call the shop and find out.

 

Another little tip if you want to call it that. I had a truck come in once, where the guy put new hoses and all that on, and then the truck kept overheating. There is supposed to be a spring in some of the intake hoses to the water pump, if this isnt installed, the water pump can collapse the hose and cause overheating. Not sure if the cummins has a sping built into the hose or if its a seperate piece, but just figured I'd throw it out there anyway

 

probably didnt have all of the air purged from the system with all of those components changed. the air will go to the highest point(which is the thermostat housing) air is a poor conductor of heat, so the thermostat was never seeing the actual temp of the coolant. after a few times of overheating, the air will eventually be blown out of the coolant system. the industrial b and c series cummins we have here at work, all have a petcock(vent valve) on top of the aftercooler assembly(if equipped) if not there, behind the thermostat housing.

 

Agreed. I always drill a tiny bypass hole in the bod of the thermostat to help bleed off any residual air pockets. And adding a bleeder screw or pit **** to the housing should be a snap.

 

Yup, they do. Don't use a lower hose without spring inside!

I'm with Greguw - Cummins T-stats in a Cummins engine!! Wrong place to go cheap, IMO!

RJ

 

Ill have to check out that lower hose and see if its got a spring. I think the problem was just a big air pocket. I just changed the gasket on the engine oil cooler and a bunch of coolant drained out. I drove the truck and it overheated so i put more water in the radiator then kept opening the pressure reliefe valve on top of the radiotor cap. this seemed to let quite a bit of air out. my next step is to go get the radiator flushed (Again) and have all new antifreeze put in (again) then it will be a trial by fire cause as soon as i get back, im gonna be towing the 5er for about 3 hours up to the lake.