8V92 running water temp

[BillhymerMD]

Just wanted further input regarding the running temp on my 8V92. Had it out this weekend for a short trip here in Florida and while driving in city traffic observed that the engine temp runs between 210 and 215 and approaches 220. A recent service has been performed at Prevost. The radiator was flushed and filled to the appropriate level. The coach is now at Coach Worx for a few updates and am going to discuss with Rick and the guys either a coring out of the radiator or whatever needs to be done. Just wanted to know if anyone has encountered their detroit diesel running at these temps and what remedied it. Thanks, Mike

[Coloradobus]

Michael, Our 1992 Silver 8V-92 hovers around 185 degrees pulling Vail Pass, a 7% grade on I-70 east bound, towing 5700 lbs of Lexus 470 with coach in 2nd gear with pyros screaming at 1000 -1050 degrees., maybe touching 1100 if I am not totally fixated on the guage, On the flat, it water temperature sits at 175, and tranny temp with Transynd sits at 180 degrees. City traffic encounters tranny temp climbs to 200.
Even pullling the "Baker Grade" east on I-15 east of Baker Ca, the raidiator temps rarely peak any higher than 185-90.
Another ex is east I-15 pulling the grade up the hill to Oak Hill/Hisperia California, pyros at 1100 tranny in 3rd gear, radiator temp 185 degrees
We have never hit the temps you are experiencing. Our coach weighs in at 41,680 pounds.

[BillhymerMD]

Is there not an engine overheat light and if so what temp does it come on to indicate that you are approaching a dangerous temp?

[Jerry Winchester]

Michael,

We saw ours run in the 210 range pulling hard with pretty high ambient temperature. The DDEC engine computer will reduce the available engine HP when the temp gets to a dangerous level. You may then see the Check Engine light come on. When we had high temp, we shut the OTR AC off and also pulled over for a few minutes at high idle. That usually cured it. I also made sure we were locked in gear when pulling a grade rather than watch the transmission swap from converter to lock-up which is a sure fire heat builder.

Short of a catastrophic failure, the DDEC computer should keep you from having a car-b-cue.

Jerry

[Charles Spera]

We usually pull a 12000# stacker and run OTR until the Divine Miss Barbie claims to be freezing. I drive race cars and the temperature and pyro gauges are a constant vigil. We run right around 185-190 (indicated) and on a rare occasion have seen what looks like 200. Just because I like to be safe, we will be pulling the radiator and sending it to the radiator shop for a check and recore if needed. New thermostats will probably be fitted as well.

[Jon Wehrenberg]

Michael,

I think the 8V92 engine for some reason requires strict adherance to the coolant maintenance schedule, and even with that it tends to plug radiator cores. That is my personal experience only.

You should run in the 180 to 190 temperature range and when pulling long steep hills the temps should stabilize at 195. You don't say if you have radiator shutters, but my comments assume if you do they are functioning as intended. If there is a question turning two valves locks them open so they are not part of the problem.

Unlikely, but just verify the fan is not slipping. The engine has two thermostats and they both have to function as intended. Ironically the gauge only registers on one side. It might be worth checking them to verify they function. If all else checks out you are looking at recoring or replacing the radiator. Don't delay this because the temps you mentioned are excessive and you are very close to having the DDEC start to shut you down. You can turn a 8V92 into an expensive paper weight very quickly with over temp conditions.

[LA-HODAG]

Michael, the early 90s Country Coaches are notorious for instrument inconsistency and I suspect yours is no different. On mine, the dash temp gauge always reads at least 10 degrees hotter than the mechanical gauge back in the engine compartment. My dash gauge shows about where yours is when pulling hills or running the desert while towing my Jeep. When I switch on my headlights or running lights, the dash temp guage jumps up even higher, by about 10%. Others on the board have similar experinces when the dash is illuminated but nobody has been able to figure out how to fix. I just take the dash gauge readings with the appropriate grain of salt. The one time I got a check engine light for high water temp I was pulling a long grade in 110 degree heat near Needles. The dash temp gauge read nearly 240. I have replaced my radiator since that time and have had no more check engine warnings. It is best to be vigilant, as you are, but as long as your cooling system is well maintained, you should be fine. Check the temp gauge in the engine compartment against the dash gauge.

[joelselman]

I agree with Jon; you are marginally too hot. I would run those temps with high ambient temps on grades with a 44000# coach and 12000# trailer. I did have the radiator replaced and coolant converted to red during my term of ownership. Someone touched on transynd; synthetic trans fluid. That change will reduce trans operating temps and, I believe, the trans oil is cooled by the radiator system; hence the benefit. I also had the series 60 radiator fan fitted (more blades) without a clutch to keep airflow up.

[Coloradobus]

JoelSelman, Your last sentense above, did you fashion a Series 60 fan blade to the 8V92? Is that correst? Cool!!!

[BillhymerMD]

Bryan...that is very interesting to hear. I have often wondered how accurate that gauge is and I should have already checked it against the mechanical gauge. Should know more soon after the Coach Worx evaluation.

[gmcbuffalo]

Would the dash guage problems be generalized to 91 Prevost not just country coaches?

[Jon Wehrenberg]

I would take what the gauge shows as the gospel and I think it is wishful thinking that the temperature problems are related to the gauge. I say that for two reasons. First, if the coach temps have been more normal and have started to creep upward it is a probability that you have been watching the gradual plugging of the radiator core.

The second reason I would rule out the gauge is because the fastest way to ruin an engine is excessive heat. I treat an over temp situation as an emergency situation that requires immediate attention because of that risk.

A well maintained 8V92 cooling system will run 30 to 40 degrees cooler than what was posted and that temperature spread has virtually eliminated the margin of safety. Those 180 to 185 degree normal temps are for the average coach pulling a toad in almost any outside temperature, with 195 being the highest seen pulling steep grades with no modifications from the original factory design.

[truk4u]

My Liberty ran 180 - 185 and I never saw anything over 195. 210 - 215 is trouble time coming. For an 8V, heat is the enemy and I would confirm the temps with a heat gun.

[Loc]

Having blown an 8V92 due to excessive heat here are my thoughts. The engine temp guage generally ranged from 175 to 190 depending on the ambient temperature and how hard I was driving. If I ever saw anything over 195 degrees I started getting nervous. When climbing grades in the summer that meant slowing down and keeping the rpms up without getting the pyros above 1,000 and shutting down the OTR air to reduce the load on the engine. Don't trust the DDEC to shut down the engine before there is a catastrophic failure. When we pulled the radiator it had significant blockage. In addition the sensor was crusted with a calcified substance and the engine failed prior to shut down or warning light actuation.

I would take the bus to a reputable shop and have them thoroughly inspect the radiator. I would seriously consider have it recored or replaced as a safety precaution. It isn't cheap to do, but it is a lot cheaper than a rebuild.

[Jon Wehrenberg]

There are three conditions which will cause DDEC to shut an engine down. Oil pressure, coolant level and coolant temp. It is not a coincidence that two of the three relate to the coolant system.

While it is theoretically possible DDEC will shut your engine down before the temps damage it, if you as a driver are relying on that happening you are likely skating on thin ice. To see those temps in Florida where the highest hill is a landfill that coach is in serious need of attention because when real hills are encountered the temps will be out of sight.

A radiator flush is unlikely to open up a radiator core that has been blocked over many miles of silicone drop out. At least you are in good hands at Coach Worx. They will make the correct diagnosis and suggest the best course of action.

[BillhymerMD]

Appreciate all the input.

[joelselman]

Coloradobus: The series 60 fan blade was installed by Prevost Mira Loma at the time they did my radiator replacement. If I'm not mistaken, there is a service modification bulletin, but it's been a long time. Everything was bolt-in though...no "fabricating".

[LA-HODAG]

I hope my experience with the dash/mechanical gauge differental is helpful. You should also check whether the dash temp gauge jumps when you switch on the headlights. You won't notice it when the engine is cold, but I see it happen when the engine is at operating temp. Prevost Mira Loma told me they have seen dash gauge grounding issues in many Country Coach conversions and at least one other Pogger with a sister bus has observed the same 10% headlight jump as I have noted. Let us know how it works out.

[rahangman]

My experience last summer (2009)- Left Home for Denver with "possible" heat problems due to seeing Drivers gauge into the 200 degree while topping a pretty substantial grade in Missouri. Monitoring, watched same happen through the Ozarks, once into Kansas stayed pretty good although a little higher than normal...Left Denver-went to Chicago then home worked around it, temps going up to about 210 or so. Got home, saw a POG note about a radiator followed up, went to get it. Found out it was wrong radiator, but had the original re cored. Wound up with all problems solved. Company doing the recorring thought it was probably the worst radiator they had seen in many a year. Visual Inspection of radiator had told me it was approaching necessary replacement, and so glad I did. Subsequent trips have proved that the radiator was my problem. We now stay right about 180-185 with small increase to 195 on long sharp grades. I had monitored temps by stopping, shut down engine run to rear of coach and saw about 5-10 deg difference on direct reading gauge in engine compartment which I figured ruled out the front gauge (also replaced temp sensor). Used my IR gun and found several different readings across the face of radiator. Hmmm not much left to do, so we did the recore. All is fine, I am happy.

[Yankee802]

My temps seem to stay pretty much at 195, needle straight up. Only a few times when going to and from POG IX did it go right of 195, I'm guessing 200, but no more. I'm doing my major replacement/overhaul this year instead of next, due to expected price increases. After reading this, I'm concerned about getting my radiator flushed/looked at by Prevost in Jacksonville, would I be better going to Coach Workx?

[Jon Wehrenberg]

You need to define what you are talking about. Are you overhauling the engine? If that is what you are doing Prevost is not going to do that. Only a Detroit Diesel shop or someone equally qualified will do the overhaul. I question why you are doing an overhaul. What specifically requires you to do that.

But no matter what your decision regarding an overhaul, one thing that is critical is the cooling system and if you are experiencing 195 degree temps as normal it is probable your radiator is becoming plugged. Before you ever consider rebuilding an engine it is critical you fix the cooling system so that new engine isn't damaged by high temps. Prevost can replace your radiator or have the existing one recored. I suspect Coach Worx can do that also. I would ask for quotes.

[AmeriStar]

The 2 cycle Detroits were the workhorse of the bus industries for over 40 years for one simple reason, they were tough and would run even beyond needing an O H. With that said, the main enemy of the 2 cycles is HEAT. The 92 series was designed to operate at 180 -185. On occasion an increase to 190 - 195 might be warrented due to engine load, ambient temputure or altitude, but sustained operation at the increased temps will shorten the life of the engine dramatically. Remember the design of the 92 series evolved when most of the country had a 55 mph speed limit.

Usually a lack of cooling capacity is the culprit for increased temps. Cooling system's are the most overlooked mechanical systems on buses. CHANGE your antifreeze every 2 years. I know that 15 or 20 years ago the engine builders actually put tags on the filling necks that said 'permanant glycol antifreeze', this led to the radiators becoming plugged and many engine failures. Buses do not have the front radiator set up of most vehicles that force air thru, air flow in buses is disrupted because of their inlet location and highly rely on the fan system to 'pull' air thru.

I still love the sound of the 2 cycles, and there are still quite a few on the road, because they are a great engine. Service your cooling systems, fluid, belts & radiators and the 92will give you many trouble free miles.

[Yankee802]

My fault guys, I'm sorry. I miss-used the word overhaul, it's more than my annual maintenance, because in addition to the normal annual stuff, I'm replacing a ton of stuff, tires, batteries, bags, shocks, fuel lines, and having the radiator flushed and looked at. So other than regular maintenance, the engine isn't being touched. If it's found that my radiator requires it, I'll replace it.

[Jon Wehrenberg]

If you are experiencing the temperatures you posted you need to get a look at the core to see if the radiator is getting plugged. Usually flushing the radiator will not cure the problem.

Maybe it is my imagination but the 2 cycle engines appear to need good cooling system maintenance and at a minimum it requires strict adherance to the coolant change schedules called for. I am not aware of the Series 60 engines having problems with build up in the radiator core.

[BillhymerMD]

Driving to Cape Canaveral for shuttle lift off and dash temp reads 205 - 210; stop bus and walk to rear to look at gauge in engine compartment and it reads 175. Which temp should I believe???...likely the engine compartment gauge I guess. However, I'll have the radiator recored anyway I suppose.

[Jon Wehrenberg]

Michael,

The damage high temps can do to your engine is substantial so in this case it is better to err on the side of conservatism. At the very least break the tie and get an IR temperature gun which you can point at the engine block to see which of the two readings is the more accurate. You can always use the gun at rest areas to check tire and hub temps.

One of the problems with trying to get readings after a run is that as soon as you lift off the accelerator pedal to coast into a rest area you are removing the heat of combustion and the engine can cool down pretty quickly masking a problem. Driving on the flat in Florida your temps should be at their lowest point unless you are running flat out into a headwind. If you hit the hills and mountains you would likely see an engine shutdown or the creation of a boat anchor if it does not shut down fast enough.

Recoring or replacing your radiator is not cheap, but compared to an engine it is chump change. Once you verify which gauge is the more accurate by aiming the IR gun at the location of the temperature sensors you will know enough good information to ignore what may be a guage problem, or to proceed further to verify the core is getting plugged.

[BillhymerMD]

Bryan mentioned that he has noticed the same temperature difference between the mechanical gauge and dash gauge. Has anyone else observed this and if so what was done about it?

[rahangman]

The past summer I agonized over temperature differential between drivers "indicator" and the direct reading gauge in the engine copartment. Using an IR gun as Jon suggested pretty much determined the inevitable. And yes, he is right, I found that by the time I would pull over to check rear gauge it would be several degrees lower with just a moment at no load. Do the radiator, it is not cheap, but it sure makes the difference. PM me if you like for some ideas. I used a local tour bus company as it is a bit of a job for anyone not outfitted to do this big(ger) job.

[Jon Wehrenberg]

Michael,

Let's assume Bryan is correct. If he is you have a gauge issue. But what if you do not have a gauge issue?

If your gauge is reasonably accurate, and by that I mean within 10 degrees, you still have a serious problem which is going to cost you a whole lot more than an IR gun, and 5 to 10 times the cost of a recored radiator if you continue to be in denial. You need to see temps in the 180 to 185 degree range and you are so far above that range with running on flat roads something is wrong.

Don't trust your DDEC to save your engine. It might, but if your temps are really as high as your gauge shows it is now the only and last chance you have to save your engine. Do we have your attention?

When you tell a patient they have a terminal disease don't they go through a period of denial? Does that period of denial change the outcome?

[BillhymerMD]

Actually Jon there are 5 stages of grief and denial is the first of the five stages. They occur in this order: Denial, Anger, Bargaining, Depression and Acceptance. I have moved beyond denial and anger and am now in the bargaining stage. I am looking forward to depression but it should only be a short hop and skip to acceptance. However, perhaps Im already at acceptance as Coach Worx is set to take my radiator out for recoreing in a couple of weeks. Thanks, Mike

[Jon Wehrenberg]

Mike, you are in good hands and they will make it right. I hope you recognize I am pulling your chain because I went through the same thing you are now facing but I at least did not do any harm to my engine. Loc on the other hand paid the price.