8V92 Temperature?

[ajhaig]

Since we had our exhaust manifold gasket replaced I've noticed that our motor (8V92) is running about 4-5 degrees warmer then it had before. The temp will peak at about 196 after a long up hill climb. Could this increase be related to the new gasket?

Also, we now have much more power and a cleaner engine compartment!

AJ

[Jerry Winchester]

AJ,

Our old 92 would do the same thing when pulling hard. The more efficient exhaust feeding the turbo should produce rated HP and that will also cause more heat. I had this same issue with a leaking manifold tube that runs from the manifold to the turbo turbine inlet.

I don't know how accurate the gauge is on our new coach, but in the "Gauge Mode", the digital readout says the water temp is always around 200, so go figure.

[Joe Cannarozzi]

AJ the 8V is a pretty cool running engine from what I have learned.

In the flat ours almost gets to 180 but not quite.

196 at the top of a hard grade is probably close to normal.

The newer diesels run a hotter thermostat, 195 t0 205, compared to the old standard 180. The only reason I can figure is for better emissions. Don't care for it, less room for error when a problem does occur. I switched my Cat, that is a 1992, from an original 195 to a 180 about 10 years ago and I believe it has added years to that engine.

On a side note our 8V's have 2 thermostats one for each side and the temp gauge is only monitoring one of them. Fortunately they are designed to fail open not closed.

[Jon Wehrenberg]

AJ,

Joe is on the money with his comments. You are doing exactly the right thing noticing subtle changes in your gauges. Often an imminent problem first appears as a slight change from what is normal in the gauges.

All 8V92 engines and their cooling systems are prone to cooling issues if the correct coolant (antifreeze) is not used or maintained. It is not uncommon for the radiator tubes to become blocked due to lack of maintenance so temperature is a good indicator.

The turbo boost gauge, and the pyrometers also tell a story. If you had a bad gasket you may not have been able to reach full boost and maybe the pyros were different. The 8V92 also has had a history of failed manifold gaskets or cracked manifolds.

The transmission temperature gauge is another good indicator of conditions. That five speed transmission is very robust, and the temps should track the engine temps. But overfilling it even by a little could cause higher trannie temps.

You could end up the 8V92 guru because you are running your coach and putting on the miles, and learning all the way.

[BrianE]

AJ,

Since we had an in-frame overhaul about 8k miles ago, our numbers may be useful comparisons. We do a lot of mountain driving in the west and our climbing coolant temps are identical to yours. We run a little less than 180 on a cool day flat terrain which may say something about the guage accuracy. Since the overhaul we are getting a full 24" of boost on the hills and can maintain high boost for long grades as long as we keep the pyros below 1000F. When starting what we think will be an extended grade, I don't hesitate to open the windows, turn on the dash heater and circ. pump and slow/shift to help maintain coolant temp. Using this method we easily keep the coolant temp below 200 and it's seldom that we can't take an extended grade in 3rd or 4th gear. My next project is to install a straight-through stainless muffler and while I don't expect much in the way of mileage, I am hoping that it will help to maintain pyro temps on the grades. By the way, the more I learn about the old 92 the better I like it.

[Jon Wehrenberg]

Brian,

I don't think EGT (pyros) matter. At full throttle and 2100 RPM I could hit 1100. I think they are useful for comparative purposes, and possibly to detect overly rich or plugged injectors, but unlike in our planes I don't think we have a limit. If there is a limit I have never seen it written or discussed anywhere.

And yes an 8V92 is sweet. If only they got better mileage.

[ajhaig]

Thanks everyone... we had a nice ride to Buckhorn Lake Resort in Kerrville, TX today.

Don't mess with Texas!

[BrianE]

Jon,

Agreed. I haven't seen limits either. It has been my experience however that high pyros will see coolant temps following soon after. It's a trend instrument like the rate of climb.

[Jon Wehrenberg]

Brian,

When the pyros are high, as in full throttle heavy load conditions such as hill climbing, my experience has been that the temps will rise, but then stabilize.

We have a hill north of us on I 75 that is steep and several miles long. We run it often and in hot and cool months. On both of my coaches I would go to full power and take whatever speed the coach gave me holding my foot to the floor for the duration. I would see 55 to 60 in either coach with the speed neither dropping or climbing. As I recall on the 8V92 my pyros would stabilize almost equal at 1100, the boost gauge would be pegged, and varying a little depending on OAT my coolant would be 195 to 205 where it would stabilize. I used to worry about temps on a 95 degree day, but when I consider that the engine is producing less HP due to the less dense air I realize that Mother Nature has a way to automatically compensate for high OATs.

If I turned off the AC all gauge indications would be the same, but I would pick up a little speed (maybe). I think the outside air temp had more of an impact on performance and gauge readings than anything else, including my techniques.

The transmission differences between the two coaches appear to me to be the biggest factor in how I climbed the hills, with the 5 speed being the better in my opinion because it would not upshift with full throttle until I hit 2100 or so. The 6 speed will do the same, but I have to select either performance mode or manually select a lower gear. The six speed and the rear end gearing on the current coach are OK, but are not optimal for steep hill climbing. I think depending on how an 8V92 with the 5 speed is geared the coach may reach an equilibrium or hunt up and down the gears unless manually shifted.

The only time I saw engine temps exceed the above is when the radiator was gradually plugging, and within a year from when I first noticed the temps climbing I had to have it recored.

[JIM CHALOUPKA]

Jon, is that your current bus that you had recored, or was it the previous one?

It would be interesting to know if your trans. updating has an effect on your gage readings and performance on the hill you speak about above?