8V92 Temperature?

[Loc]

The Prevost owner's manual that I had for my 92 XL (91 chassis) had a limit of 1,200 degrees for the pyro's. The manual indicated that normal operating temperature (coolant) for the 8V92 is 180 to 195 degrees. It also stated that the engine is not considered to be overheating until it hits 215 degrees. However, I would have freaked out if the temperature got above 200 degrees given my prior experience with catastrophic engine failure. In the old XL, we could run all day long in the Texas summers with the bus air on and stay just below 195. If we were climbing hills, the bus seemed to stay at or below 195 degrees if I kept the pyros between 900 and 1,000 degrees and turned the bus air off. This required downshifting to keep the rpm's up around 1,800 and didn't make us the faster one to the top of the hill, but we got there.

[BrianE]

Great discussion! LOC, thanks for the input, we've had the same sad experience. That sinking feeling of seeing a huge cloud of steam in the mirror followed by a sudden forced landing made me very sensitive about seeing coolant temp in excess of 200f. Thanks for the manual references also. Sometimes we have to gang up on Jon just a little to keep him honest.
JON, I certainly agree that ambient conditions are the main ingredient to engine performance. There are lots of 6% grades in the Sierras and Rockies and we try to climb them in the cool. All in all, I'm feeling the money we've sunk in the '94 has been well spent and will continue with a program of upgrades/preventative mtc. She currently sits with wheels off and shocks, hoses and brake chambers laying on the floor for replacement. One doesn't understand the full significance of polishing the slack adjusters until having to clean them up after 14 years of normal use. Sevierville or bust!

[dalej]

We're proud of you Brian! Keep us posted also some photos.

[Jon Wehrenberg]

I followed the "balls to the wall" method of operating. Since DDEC decides when the temperatures are dangerous, and the internal sensors are likely more accurate than the gauge with numbers and hash marks almost too small to read accurately my only concern is that the temperature needle did not keep moving to the right.

A 6% grade of several miles in 95 degree temps was a thermal challenge, but except for when the radiator was starting to plug, the temperature gauge stopped climbing at some point and as long as it was below the 215 point by some clear margin I was good to go.

The Series 60 runs much hotter as has been discussed, and the same hill will see the coach fan cycle between the low and high settings and the temperature gauge will not stabilize at some high temperature, but will go up or down to match the temperature set points in the computer for the fan clutch which has two speeds.

I think our gauges as small as they are lack the accuracy of digital readouts that have been calibrated, but they are good enough to know if we are approaching trouble with temps or pressures. I only look to insure the gauges are sitting in a "normal" position, normal varying with temperature and other factors, and if they are moving in the wrong direction and not stable.

[Loc]

Jon,

I followed the same operating procedure until I trashed the engine. I figured as well that the DDEC II would properly regulate everything. I had checked the DDEC set up to ensure that all of the temperature and low oil pressure shutdowns were turned "on". When we blew the engine it did not protect itself. I assume that the temperature sensor was encrusted like the radiator and did not properly function. After the unfortunate engine trashing incident, I used a little less of the long pedal on the right and watched the temperatures like a hawk (coolant, pyro and transmission temp). The transmission temp had a significant impact on the degree (pun intended) to which the coolant temp would increase quickly. Gearing down and keeping the rpm's up had a visible impact on the tranny temp. I also had the radiator flushed every 2 years or 50k miles whichever came first.

It is a little different with the Series 60. I am still trying to get used to the normal operating range of the temperature guage. The first couple of times climbing a hill I freaked out because the temp would climb and then drop and then climb again which was not what I was used to with the 8V92. I figure in a couple of years, I will be comfortable with S60.

[Petervs]

Hi LOC

My series 60 coach came with a nice mod from the first owner. He installed two additional idiot lights with dim LEDs in them ( so you can just see them on in the daytime, but not to bright at night. Each one indicates the on or off status of the cooling fan, low and high mode. They are wired to points in the electrical bay under the drivers side window.

So for me it is very easy to see how the engine cooling is behaving. Both lights off, means no fan on at all, when the engine is first started and still warming up. Then the LOW FAN light comes on and stays on for all normal driving. When you climb a hill, the LOW fan stays on, the coolant temp gradually rises from it's thermostat setting of 195 degrees, and when it gets to 200, the HIGH FAN light comes on in addition to the LOW FAN, and you can see the coolant temp begin to drop. On the longest hill on the hottest day I have never seen more than 210 degrees.

He also added a switch that allows me to manually turn on the high fan prior to a big hill, but I have never seen the need to do that.

[Jon Wehrenberg]

Loc,

I never relied solely on the DDEC shutdowns to protect me. I am always looking at my gauges, and the defining moment for me to recore the radiator was a temperature that kept creeping up while climbing a hill.

The coolant sensor in the tank is only intended to function if the coolant drops, not in response to rising temps. That is another sensor.

[Loc]

Jon,

My bad, I meant the high coolant temperature sensor not the low coolant sensor in the surge tank. I didn't rely on the DDEC to protect the bus, but I did make a note that it did not.

[Jon Wehrenberg]

In response to Peter's post, he has a nice set up as he described.

In our buses, unlike trucks we do not have natural flow past the radiator so a fan is critical. In the early coaches there were instances of temperatures getting too high due to the clutch settings. It is my understanding that they are now set at 204 and 208 for the low and high speeds of the fan.

I don't have the lights Peter describes, but I can watch my clutch cycle between the two speeds on the temperature gauge during normal driving. This has been stated previously but for those new to the forum, if you ever have problems with overheating due to a failed clutch there are two metric bolts in the end of the fan drive shaft that can be removed and inserted in two tabs that are on the fan hub to secure the fan to the rotating inner shaft. That in essence locks the fan in the "on" position all the time.

[Kevin Erion]

The fan also turns on low when you turn the Prevost dash air on, does not mater what temp the motor is. Today I spent some time changing my clutch for the fan, along with playing with the Webasco, but we will talk about that later. Not so easy but doable for me, I estimate about 4 hours including cleaning. My old clutch was starting to make a noise like a bearing was going out. I like doing the work at my shop, not on the side of the road. On my old bus I also installed a switch to turn the fan on, towing 17000lbs, you better make sure to turn it on before the hill when its warm outside!