Hey, I am new to this site but I am hoping to find some advice with my 94 Dodge 12 valve 5-speed 3/4 ton 4x4. I have a 30 foot triple axle toyhauler and I have noticed that when I pull it on long hills the engine has been overheating. I have a fuel plate and gauges. My pyrometer runs cool but my water temp is around 220 on a long hill. Is there a different thermostat I can try?

 

do you have any trouble with losing water or anything like that? does your water look brown-rusty or even oily in the radiator? how fast does it cool down after climbing a long hill? what does it run for temps normally? have you tried downshifting a gear or just slowing down even 5 mph when temps get to 220? could be fan clutch or dirty radiator. could be rusty chunky stuff in the water jackets not letting it cool right. what are the outside temps when you pull this trailer. give us a scenario kinda so we can tell if it is a normal, or kinda or not so normal thing. and welcome to dtr. there are a lot of nice people with a lot of good information here. i have learned a LOT from these people. i am fairly new to dodge-cummins 5.9 myself.

 

My 95 as many others suffer from the cycling thermostat delima. I have yet to see mine hold out at 190 where it opens.It always bounces between 140 to 190. The early thermos did this and in revised one will not cycle, but hold at a even temp. I hear it just takes longer to warm up fully however. It seems anything other than a Cummins one will perform less than optimum. You should hear a loud roar when the fan clutch engages also at those temps. As you will learn there is no correlation between high H2O temps and high EGTs. Hows the radiator? what EGTs are you hitting? pre or post turbo?

 

First thing I would look to is the rad and how much gunk u have in the fins and so forth. That's the most common culprit and the easitst to check

Clean it thorouly and you will be amamzed at the difference

 

Yep. Check for stuff between the rad and the intercooler.

 

Either your radiator is plugged up or your fan clutch is shot.

 

Had the same problem last summer, it was the fan clutch. When temp gets up there you should hear a loud roar from under the hood. If you dont its the fan clutch. You can check it also by turning the fan by hand. It should be really stiff when the engine is cold. Hope this helps.

 

I don't think I have ever heard my fan start up on this truck. Not even while towing, temp seems to always stay normal too.

 

It's quite possible it never has come on. The fan on my 2500 has only come on a couple dozen times in ten years. Half of that was due to leaving the winter front on when it was too warm.

 

My EGT's are pre turbo and on a long hill I pull about 1000-1200 degrees up a hill. It will happen at any outside temp. I changed the thermostat with a Cummins one because my old one fluxuated. Radiator and antifreeze are clean. The only thing I haven't checked is the clutch fan. It sounds like that might be it. Thanks for your help.
Smokey94

 

Yeah I have a fluctuation in the -30 bitter cold. I think most of them do. When that T-stat opens the water that has been in the rad has cooled off in a hurry!