Learning curve on the Detroit Diesel?

[Tully]

Will be getting the 90 Prevo Country Coach 4/15/08. My previous American Dream had a 8.3 cummins. Very easy to start, run and did idle very well.

How is the Detroit Diesel Silver engines from that vintage? Anything I need to pay close attention to? I though I had heard not to idle too long and somelthing about rev up the rps when going up hills?

What procedure do I use to start and run this coach?

Can someone give me a fast and easy to understand lesson on this type engine as far as what I need to really watch out for.

How much life do you get out of these engines before they have to be rebuilt?
And, approximate cost to rebuild these "in chassis" rebuild?

Thanks so much,

Tully
1990 Prevost Country Coach

[Orren Zook]

How much life do you get out of these engines before they have to be rebuilt?
And, approximate cost to rebuild these "in chassis" rebuild?

In over the road trucks they run about 400,000 before a major - but like everything else it depends on how you (and the previous owners) take care of the equipment - I doubt you'll see that kind of service in you bus. Depending on how much you replace it could run $22-26k. It might be a little cheaper to just stick a DD reman engine in from a labor standpoint. Lead time for the 8v92 complete was six to eight weeks in January 2008.

[BrianE]

Tully,

Welcome to the nut house. There is a ton of info here about the 8V92. First I would suggest you click on the search tab at the top of the page and type in 8V92. The results should keep you busy for a couple of hours.

The pertinant info regarding engine operation can be found in the DD operators manual. Don't leave home without one. The basics are:

1. Avoid extended idle time.
2. Use high idle when idling. It keeps the engine cooler, reduces belt slap and other stuff.
3. When pulling hard,(climbing) keep the engine between 1700/1900 rpms to take advantage of max torque and keep the engine from lugging. It hates to be lugged down.
4. Watch coolant temp closely when climbing. Slow down and shift down to maintain rpms. You will probably have to do this manually. If temp goes above 200f, turn dash heat full on and open the windows, it is guaranteed to reduce engine temp by 10f initially.
5. For best fuel mileage, run below 65mph.

Variations of the DD two stroke engine ran reliably for years in trucks, busses, industrial and marine applications. An engine that has not had a serious overheat "event" should run well over 300k miles before overhaul. My engine did have such an event at about 90k miles. The cost of the inframe OH was $16000 in '05.

They sound very cool also.

[Loc]

Tully,

Welcome aboard. That is a nice/clean looking coach. It has the updated headlights / taillights and looks to have significant solar power capabilities.

We had a 92 Angola conversion that we purchased in 2002 with 156k miles on it. If the coach has had good/regular maintenance it should be good for many miles. Unfortunately, ours had not been as well cared for. We blew the engine at 208k miles. I had the bus checked by two mechanics prior to purchase and neither noted any issues with the cooling system (we flushed it just after purchase). The cause of the failure was a significantly blocked radiator. The 8v92 is a good engine, but it does not like to get too hot. For what it is worth, either get a good mechanic or do it yourself, and visually inspect the radiator. Pull the bottom hose off and look inside. It is not difficult, but requires capacity to hold a lot of cooling system fluid (about 25 gallons if I remember correctly - Jon will know the exact number and I may be off). If it looks suspect pull the radiator and replace it or have it rodded or have a new core or re-cored. The engine rebuild ran just under $16k. In addition, we put a new radiator in from Prevost at $2k.

Ditto what Brian said. The engine is really robust and you shouldn't worry. If it is cold (lower than 45 degrees) cut on the block heater for a couple of hours before you plan to start the coach - it will make it easier to start and there will be less smoke. Other than that keep the oil changed (our coach liked to have the oil no more than halfway between full and add otherwise it seemed to find a way out), expect to have a few oil drops on the floor when you park. I changed ours every 10k miles which equated to about every 5 to 6 months. Use straight 40 weight oil that is approved for the DD 8v92 (Rotella, Delo 100 - not 400, or Detroit Diesel - old Mobil Delvac). The oil specifications are on the Information Sharing section which is accessible from the home page of the POG website - its about 5th from the bottom. Keep an eye on major leaks, but you will likely have some minor leaks which are not the end of the world and can be fixed, but it takes a fair amount of work to keep up with it.

My technique for driving the bus was to watch the water temp (normal between 180 and 190 degrees unless really cold - not overheating until over 210 degrees) and gear down going up hills to keep the rpms up and keep the pyrometers generally at less than 950 degrees unless a short acceleration. The owners manual says to keep the pyros below 1200 degrees at all times - which is easy if you pay attention and don't hold the accelerator to the floor.

Good Luck,

Loc

[tdelorme]

Tully, I too just came out of a Cummins 8.3 into an 8V92T. You will miss the acceleration of the Cummins. The Detroit is slow off the line and it takes a few trips to get used to it. Other than that, I love this old engine. Mine does not leak and hopefully I can keep it that way. I did have a turbo tube failure and if you have original tubes you need to be up to speed on what to expect when one fails and how to do the replacement. If I had known then what I know now, I would have purchased both of the turbo tubes and had them with me when I lost one. I'd still be on the side of the road if not for Jon. With his help we were back underway in four hours instead of four days.
I think you can expect to have a few issues with any 8V92. These are not new engines and hoses, belts, gaskets are all going to need replacement at some time. My engine will use a gallon of oil every 2000 miles. She starts immediately and purs like a lion drunk on diesel. 5.6 MPG at 65 MPH pulling a Jeep. I might back down a bit and see if there is any improvement on the way up to Sevierville. Now go get that bus and come to Tenn.

[Jon Wehrenberg]

That coach will have DDEC II which will provide some protection. DDEC will literally shut the coach down or reduce HP if you start overheating or have low oil pressure.

Having said that however, as driver and the person responsible for maintenance the best thing you can do is use the coach frequently, as Brian says don't let it idle for extended periods, and keep the oil and fuel clean. Frequent oil changes (around 5000) miles should be the norm.

The engine and cooling system as Loc points out requires good maintenance. The coolant needs to be changed every two years and the chemistry of the coolant needs to be monitored. If you have them change the coolant conditioning filters every six months, and if not chek and adjust the chemistry by using the products specifically designed for that purpose. I was fanatical about that and at around 10 years my radiator needed to be recored.

I was not as conservative as Brian. When I went up a hill it was foot to the floor and max RPMs. It didn't seem to hurt it.

What is critical however is monitoring the engine temp gauge, and if I was pulling a steep long incline, I would see my engine coolant temps hit 200 or maybe 205. I wasn't as concerned about the number as much as seeing it reach a particular level and then stabilize. That told me the cooling system was working. FWIW, DDEC will gradually reduce HP on the engine if the coolant temp reaches around 210 or 215. If DDEC has to do that you are not doing your job as a driver, and you have ignored needed maintenance on the cooling system.

I would avoid cold starts by pre-heating, and I would allow the engine to come up to temperature a little by running it on high idle before I ran it hard at highway speeds. The 8V92 has a bad rap about dripping or leaking oil, but that is not the case. If it is dripping or leaking something is wrong and it needs to be fixed. The engine can be a very dry and clean one.

There is not a sweeter sounding engine than an 8V92.

[Tully]

Now that is what I am talking about. Great info that I can really use.

I cannot wait to take delivery on this coach.

The owners are heart broken and call it their baby and love of their life. With his age and recent stroke/s it simply was not safe anymore to drive this big bus.

Gonna feel and look like a rock star driving this thing down the road.

Tully

[Orren Zook]

Jon mentions issues with the radiator - make sure that you use a low silicate HD truck anti freeze not any automotive brands, the temperature drop in the antifreeze as it flows through the radiator will cause the silicon content of automotive antifreeze to separate from the liquid and settle in the radiator core also excessive idling at low RPM will cause oil dripping in the 8v.

[Tully]

Will do. Sounds like the most important thing to do is get anti-frez/ radiator looked at.

I know when I spoke to the owner he said he uses strips to test some ph or level to make certain things were where they should be.

Tully

[Orren Zook]

Will do. Sounds like the most important thing to do is get anti-frez/ radiator looked at.

I know when I spoke to the owner he said he uses strips to test some ph or level to make certain things were where they should be.

You can use/buy your water filters with a pre-charge built in to maintain the levels or add a liquid concentrate. The test kit should give you the SCAs, freeze point, nitrite and molybdate. There is also a coolant cleaner available that will dissolve scale, and corrosion while removing the silicate gel. Depending on the condition of the radiator this would be an inexpensive solution.