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.

[Darrell McCarley]

Jon, You said that you had your radiator routed. Do you know the best way to flush a radiator without removing it from the bus? What type of flush is best? My 8v92 is beginning to heat up in the western mountains during the summer on I-8 from Eloy, Az to San Diego. My temp gets to 205 and I then pull over to cool down. May be forced to remove the radiator but will wait for your advise. Thanks for the post on manifold gaskets. Replaced my gasket yesterday. Glad you told about anti-freeze when bolt and stud are both removed. I drained the radiator before starting. Replacing the manifold gasket was not as hard as I thought it would be. Thanks

[Jon Wehrenberg]

Darrell, The core of the radiator was blocked as yours is likely to be. The radiator was removed and recored. A big vehicle radiator shop can handle that pretty cheaply. It was too long ago for me to know the specifics, but it was much less than a new radiator. I have never back flushed or used any flushing materials.

The problem is silicone dropout. I changed coolant every two years and the conditioning filters every six months and used only anti freeze meeting the DD specs, but at 10 years of life the problem occurred.

I think Loc had a similar problem. It is common for an 8V92 to have this problem and it reinforces why coolant maintenance is critical.

BTW, hitting 205 would not have alarmed me, but if it did not stop there then I knew the time had come to address the problem.

[Loc]

Darrell,

If you are starting to have temperature issues, I would spend the money to have the radiator pulled and sent to a radiator shop to be rodded. I replaced the radiator on my 92 XL when I blew the engine because of a clogged radiator. I put a new radiator in from Prevost at that time. Two years later (approximately 45,000 miles) I had the radiator flushed and had it inspected. It showed about 15% blockage after two years and I was meticulous on my maintenance of the radiator. I pulled the radiator and had it rodded after two years. If I remember correctly, I spent about $900 to pull it and have it rodded. If you decide only to flush the radiator, remove the bottom hose and visually inspect the inside of the core as best you can. I would do it personally, as I had mine inspected at purchase and the mechanic did not note any issues with the radiator (I blew the engine 2 years later).

Loc

[Joe Cannarozzi]

I am not satisfied with the response to my circulating pump question. JPJ throws out this suggestion about a circulating pump that assists in cooling high engine temps and does not answer sufficiently. That's O/K cause it has urged me to bring up these questions that I have been meaning to get answered.

We have OTR A/C. I have noticed in the top of the OTR heater core/evaporator bay a circulating pump plumbed into the copper antifreeze lines.

It is my assumption that on a car the heater core loop is small enough that the water pump has enough volume to flow water through it sufficiently without the necessity of an additional pump.

I'm also assuming on the bus this is not the case, hence this pump. Or is it?

My Bus 450.jpg

My Bus 451.jpg

So, is this pump to circulate water through the main heater core, or to pump it forward to the smaller drivers heater core, or both? Is it 12 or 24 volt. If it fails will we still be able to draw heat off the system or not? Is it there for, as JPJ suggests, specifically to lower engine temps. when necessary?

Also for the older coach owners. Does anyone have this same dash switch as pictured below and what is its purpose? When would it be used? I have never had to use this switch.

My Bus 455.jpg