[Rick & Denise]

I haven’t had internet the last few weeks but I have been reading on my phone and keeping up with everything. I have an update on my cooling situation.

It was so cool the day I left Florence, Montana that I did not bother to lock the fan clutch manually or electronically. I made it over the passes and through all of the mountains without any problem at all. I did keep the RPMs up near 2000 as recommended.

Once I was in the flatland and getting close to Wichita the daytime temps outside were way up but I drove in the early morning and again, no problems.

I left Wichita and drove overnight to St. Louis. The next day it was near 90 so I decided to take the 85 tab off of the relay and check the fan clutch. It would not turn at all with the key on but not started so that was a good sign according to Prevost on another thread.

My temps stayed between 180ish and 195 with the outside temp of 90 and pulling the 15,000lbs. Of course there were no hills to climb going across Illinois and Indiana.

For the 120 mile drive today from Indiana to Ohio I took the doctored relay out and put in a new one. My temps were 195-200ish. (My guage is numbered at 170, 195 & 220) That has been the normal for me since I bought the bus in 2008 although the outside temps were about 70-75 today.

What do you think? Do I have a problem that needs to be checked out further? Or were the slightly warmer temps on my way west in the mountains a result of the altitude, the heavy load and the high ambient temps?

DKO

[Don]

From memory on my previous coach, Series 60.

Normal operating range based on educated guesses at what the gauge was telling me was I ran normal 200 to 205. That seemed reasonable because the 1st speed on the fan clutch is supposed to engage at 204.

On long steep hills in high ambient temps I would see the temp hit around 208 to 210. I would never see it exceed that amount and when it got to that point, even if still pulling the hill it would drop. Not surprising because the 2nd fan speed is supposed to kick in at 208. If it were to have kept climbing then I would have a problem, but because it got to that point and then dropped it indicated I have ample cooling capacity and the fan clutch was working.

When running with a locked fan the coach would cycle between 190 and 195. That indicated the engine thermostat was functioning. There were no hills or ambient temps I ran in with the fan locked that raised the temps above 195.

For reference the coach weighed 46,600 and was towing a 6700 pound H2 Hummer for a gross weight of 53,300 pounds.

The only time I would be concerned something needed attention would be if temperatures did not stabilize or drop regardless of how steep the hill or how hot the outside temps. If the temps are climbing on the gauge something is wrong. It could be as simple as not enough RPM or something indicating a problem.

[Greg]

DKO

I grew up on a farm in western OK and often traveled to the area you mention hauling heavy farm equipment, like 20-30-40K combines, tractors, etc. Almost all our hauling equipment was Cat powered. Cat powered equipment almost always has to be run on upgrades in low gear to keep engine RPMs high (1800-2000) while speed goes out the window. I owned, as my first experience with a detriot equipped coach, a 38 foot Newell with an 8V. The manual said basically “put your foot in the throttle all the way and keep it there until you reached the peak of the grade”. That worked well for the 38 foot but my present coach, a 91 XL 40 with an 8V will overheat in a heartbeat if I do that. My coach only has 86K original miles on it and I think I need to recore my radiator, but I cannot drive it like I did the Newell. I have to drive it like it has a Cat. That by the way is as you start up the grade back off the throttle to keep the temp below 205, when you cannot keep it there by lowering the throttle by failing to keep some speed, downshift the trans by one gear while moving the throttle to the majic window of 1800-2000 RPMs. When your temps raise above the 205 mark again, repeat the downshift. Watch your temps and when you can keep the temp at a max of 205 with your current throttle and gear selection, you are at the right gear, right RPM, right throttle and right speed. I can tell you hauling what you are, you are going to be crawling at the crest of the grade. You think this is bad but it isn’t, it starts you down the other side at a slow speed giving you reaction time for the inevitable speed freq that whizes past you out of control and honking at you because you are so slow. BTW, the newer Cat stuff is not as bad as the old but still has the same recommendations from the manufactuer. HTH

Rob

91 XL 40

Missouri

[Archived]

I have a 91 xl 40 8v92 and had a GMC with a 8v72 before that. I drive both with the rpm between 1800-2000 and watch the tail pipe for black smoke if I see a lot of it I back off on the throttle and downshift. I think the black smoke means the engine is lagging and creating heat. I could be wrong but it has worked for me.

[Tom]

I hope everyone realizes different engines have different characteristics. For Rob if he is experiencing those temps he has a problem. It could be his radiator needs recoring due to blockage or because the fins are disintegrating. An 8V92 as installed in our coaches is unlikely to exceed 195 even in high ambient temps unless it is pulling an extensive load. Jim and Chris often travel the mountains and maybe they can post their 8V92 numbers.

As to DKOs numbers his Series 60 is supposed to run at numbers that would be considered high for an 8V92. The engine thermostats are set at 195 (I think) and the fan doesn’t engage until the temps hit 204 and the second speed of the fan doesn’t come into play until 208 degrees, both being programmed into DDEC.

The only time I would be concerned with a Series 60 is if the temps continue to climb past 208-210 degrees. If they max out there or drop once reaching that point everything is working as intended. The gauges are so small and the markings are not at good reference points so it is near impossible to determine exact coolant temps so the trend as viewed on the gauge might be the only accurate means of determining if everything is OK

[AL]

I had a new radiator in my 1989 XL40 and had to drive as Rob describes to keep from overheating. Admittedly, I was in ambient temps of 100-115, hills, and towing 12000#.