6-71 operating temp question

[Casper4104]

Ok, here's the deal.

I've had my 4104 for about 4 months now.  Driven it about 2500 miles.  It uses a little oil (leaks – no smoke) and runs pretty decent.  The hill climbng performance is acceptable but not great.  I've never had a ride in another, so I don't know if it's normal.  Fuel mileage on my last run (1000 miles, OH to VA & back) was 11.4mpg.

From the day I picked up the bus the water temp has read cold on the gage, rarely getting above 150 degrees F.  I believe the gage is pretty close, because even after a long run I can comfortably put my hand on the side of the block, the R-stat housing, or just about anywhere else.  I had planned to shoot the thermostat housing with an Infra gun to see if my gage is accurate, and upgrade the thermostat if necessary to get it up to the usual 180 degrees.

After this last run I'm rethinking that.  If I'm satisfied with the performance and economy I'm seeing now, would it be wise to just leave it alone?  Running that cold gives me one heck of a margin before she gets hot enough to make vapor, boil or otherwise hurt herself.

What do you guys think?  Would the performance or mileage improve if I get her to run hotter? Would it be worth it?

Looking forward to your learned replies, thanks.

Casper

[Ncbob]

There's two thoughts I have in connection with your line of thinking....and please don't misunderstand..I'm in no way trying to be rude or a KIA.

The Engineers who built these old Detroits performed exhaustive tests on them before releasing them. Without question they want to be run at or about 180 Degrees.  They run more efficiently and run longer.   Running any engine too cold builds up sludge in the crankcase, around the overhead, etc.  If you've ever had to disassemble one of those sludged up engines my guess is that you'd love to wring the neck of the person who allowed it to get in that condition.

On a word, run 'em hot...like you hate 'em and you'll love 'em.

FWIW

Bob

[bernie]

my 4104 runs about 180 and on a hill the temp goes up a liile.my fuel milage is only about 8.5 when towing the car. good luck
           Bernie

[gus]

Casper,

I've had my 4104 not quite a year and I had the same experience as you. It runs around 150 in moderate to hot weather and will increase maybe to 180 on a hard climb.

In cold weather it runs even cooler than 150 and in really hot desert weather it may climb to 170  on level ground.

I just recently discovered that the radiator shutters work, I thought they were locked up but the air was shut off to them because of a bad air leak. I fixed the leak and am leaving on a trip tomorrow to see if they open up when up to proper temp?

I don't see how you ever get 11.4 mpg unless you are driving around 50-55 mph or going downhill all the time?? My average for over 10,000 miles is 7-9 at 60-65 mph and that is about what I have been reading on this board that others get.

Hill climbing and oil leaks are about the same for me also. I just find the right gear on a hill, pull out the throttle and sit back and enjoy the view!

[DrivingMissLazy]

Maybe I am kinda dumb, but if a vehicle has a 180 degree rated thermostat then the engine will come up to that temperature and stay there unless operating in very cold weather. I know my 4104 did as well as the Eagle.

The thermostat is a very inexpensive device and should be replaced, or at least tested in a pan of hot water with a thermometer to determine exactly when it opens.
Richard

[Casper4104]

Thanks for the replies,  I think I will take the Tstat out (assuming it's there) and test it this weekend.

About the MPG - my dad taught me to drive in a little old R-model Mack pulling the legal at the time 76,000lb gvw with a little 237 Maxidyne and a 5 speed.  Patience is a virtue that I acquired at an early age.  I run her about 60-62 on the flat, a little more on the downs and try hard to never lug and never EVER make soot.  Keeping my butt in the seat, I did the Marietta Oh to Poquoson VA run (480 miles each way) in 10 hours, in the car I do it in 8, maybe 8-1/2 with a lunch&gas stop.  I did this round trip plus a little running around the hometown on 88 gallons, which comes to 11.36 mpg.  I do baby the old gal, and she rewards me.

Shutters?  These things are supposed to have shutters?  Mine are long gone, no doubt removed by an earlier owner.

I have my pan, my meat thermometer and a piece of coathanger wire - we'll get to the bottom of this.

Thanks again,

Casper

[pvcces]

Casper, I'll bet you've got the high compression engine. It does make a difference on light loads. And then, IIRC, there are something like three different axle ratios for those old girls.

In any case, it sounds like you've got a good combination.

Reports that diesel efficiency rises with temperature are all over the place. As long as you don't overheat yours, you should be fine with good thermostats of 180 degrees. You might want to call Luke and see if he has anything useful to add.

When they were building our airport in Ketchikan, the contractor ran his Detroits as hot(190) as he could. The given reason was for durability. I do think it keeps the oil cleaner.

For what it's worth.

Tom Caffrey
Suncatcher
Ketchikan, Alaska