Engine/Transmission (1994 - 1998) thermostat housing leak

[JRS]

About a month ago, under preventative maintenance, I changed out the water pump, thermostat, hoses, belts, and flushed the radiator. I drove the truck about 1200 miles, including a stint in South Texas in 100°F+ weather. no problems. then last week, I was pulling a 12,500 lb. trailer to New York State and noticed that the engine temp. going up the hills in Virginia/Pennsylvania was rising to 205/210°F. I wasn't too cocerned because I had the A/C on, a lot of trailer weight, there was traffic, ambient air temp. was warm and the truck was pulling at 65 mph. And in the flat areas, it was running 175°F. I have a TST #11 plate, but my boost never went over 30 psi and my EGT was about 1100°F going uphill. However, I noticed at the next fill up that the thermostat housing had weeped some antifreeze an sprayed it onto the No. 1 exhaust manifold runner. (it's right behind the thermostat housing) I watched the situation the rest of the trip. there is a light blue dried crust on the exhaust manifold, but the overflow resevoir never dipped in level. I have new gaskets for the housing, but would imagine it would be prudent to change the housing bolts too. Is this something to be expected while pulling heavy loads?

 

[CumminsPower98]

No, this shouldn't be leaking no matter what. Take it back apart and make sure all surfaces are completely clean and smooth with wire wheel and or emery cloth then reassemble with new gaskets. Make sure the engine lift bracket is also clean and smooth.

 

[JRS]

thanks. l always use a 3M ro-loc pad on a die-grinder to clean up the surfaces. I must have missed some rust or a piece of old gasket before. I went ahead and ordered some more parts from Cummins this morning. more gaskets and for grins, three new thermostat housing bolts.

 

[GAmes]

That is right in the area that a lot of engines develop a small weep from the head gasket. A Cummins mech told me not to worry about it, but I changed the head gasket anyway since I spend so much time far from home. I was losing about a pint of coolant every 3000 miles. Once I had the head off I saw that, in fact, it was nothing to worry about, there was no coolant going into the cylinder... ... but by then I was committed. So if replacing the gaskets doesn't fix it, you know where to look next.

 

[JRS]

thanks. I'll check it out once I get all the parts from Cummins. did yours spray coolant on the No. 1 exhaust manifold runner?

 

[GAmes]

did yours spray coolant on the No. 1 exhaust manifold runner?

No, just a constant ooze under the thermostat housing, and it was so slow that it dried immediately when the engine was idling and I was looking for the source.

 

[JRS]

I checked mine again this afternoon, I'm fairly certain it's leaking from the housing and around the lifting eye.



noticed on your tag line you have an exhaust brake. have you been happy with it? around here in Houston I don't really need it, but this past week I was hauling 12K lbs. up and down Virginia/Pennsylvania and really felt I could use one.



how high does your water temp rise when you are towing?

 

[GAmes]

I can't think of one mod that was more worth the price than the E/B. I've had it on for about 340k. I changed out the stock front disc pads at 107k, am still working on the 2nd set. The rear shoes are the originals. About 70% of my miles are towing, mostly out west.



Engine temps rise while towing up hills, as you would expect. As long as the fan clutch is working I rarely see anything over 210 tho. If I do, I shift into 3rd, turn off the A/C and pull the hill at 2000 rpm. Usually I'm back below 190 by the time I reach the top.