I hope I'm just being paranoid.....

[Yankee802]

Took the coach for it's maintenance run this weeked and have some questions.

For the most part, my coach has been running around 180 - 185 degrees for both coolant and oil, this run she was at 195/200 respectively. When I stopped to fill up (always top off on the way home), she cooled down to 180 for both. The temps when back up on the way home. I checked the to see that the radiator fins were open, they were. Now it was pretty hot out, but I believe the ambient temprature shouldn't be that much of a factor, from what I've read here, and I've run it on hot days before. And I did nothing unusual, like hill climbing or anything, all flat roads.

Now I don't know if this is a factor or issue, but when I check my oil when the engine is cold, it's considerably over the full mark, but when the engine has been running, the oil level is right on full. I'm hoping that it's not over full, Prevost Jacksonville did the service in April.

Also on my run, untill I got to the truck stop, one of my air guages (bottom) was fluctuating close to 75psi, and this had me worried. I opened the valve (forgot the name for it) to bleed moisture from the aux tank ( I have no idea where the one for the main air tank is, or is that what the air dryer or scrubber is for?) and I got a LOT of water, well, more than I have gotten before when bleeding it. On the return trip, the guage seemed to go back to normal hovering around 100psi.

And I have a request, if anyone has the ability, guages and R12, my galley A/C needs a recharge. I think I have a leak because I had it filled last summer, so I need to try to find it and repair it. Being we are on a budget, and I don't know who to call around here for it, I would appreciate any help with this at the rally. :)

Anyway, I hope I'm just being paranoid and these are fairly normal things...

[truk4u]

Yank,

195/200 is pretty much at the high end of the heat scale for an 8v92. I'm sure you checked coolant and also made sure the fan and belt assembly were in good order. Also, compare the dash gauge to the manual gauge in the engine compartment.

If your overfull on oil cold and the oil color is normal, Prevost probably overfilled. If the color of the oil is not normal and looks milky or some other color, that is a problem and could relate to temperature problem above. Let's hope it looks normal.

The primary and secondary brake tanks should be close to 120 psi when the dryer pops off. You said it went back to normal at 100 psi, do you have a separate gauge for the aux pressure or are you referring to the brake tank gauge with 2 needles? The aux should also go to 120 psi when the dryer pops. If you only getting to 100 psi, you could have a governor or compressor problem.

[Jon Wehrenberg]

Yank,

Keep an eye on the temps. Something has changed. My initial reaction to an 8V92 running hot is always due to a radiator issue because even with good coolant maintenance they seem to plug radiators. But if this is a sudden change in the temps the next suspicion is thermostat or radiator shutter thermostat if equipped.

One thing a lot of folks do not realize is the 8V92 has 2 thermostats but the guages and DDEC only monitor temps on one side if my memory is correct. (Any 8v92 experts out there need to correct this if my memory has failed) This is a case where an infra-red temperature meter would help with the diagnosis to see if one side of the block is at a different temp than the other side after a good heat up. Your temps are not in the danger zone, but need to be monitored carefully. What is unknown is if they will climb out of control if pulling a long steep hill so this change should not be ignored.

Monitor your oil level also. The issue may have been a simple overfill, or it may be something more sinister. 8V92 engines have a potential for a failed fuel line in the head to leak fuel into the crankcase. If the oil level increases it could be that. Also, make certain you are not seeing the oil a milky color after running. The oil level could also be up because coolant is getting into it via cylinder liner seals or a cracked head or bad head gasket among other things.

Don't you love it when you hear all this negative stuff? The good news is if something is wrong, catching it early saves serious dollars.

[travelite]

Yank,

We had a fellow on the Wanderlodge forum who recently had the same issue with his 8V92. Turns out on the WL when the dash A/C is turned on, the fan overrides to full speed. For as long as he could remember his bus ran at 180 to 185, then suddenly he went to a cooler climate and the temps increased to 195 to 200. Turns out in the cooler climate he turned his dash A/C off. I know you said that it was hot out, but is there a chance that you were running w/o your dash A/C on? (or doesn't Prevost dash air work this way)?

Another thing I'd like to run by you guys is the use of Weir Thermostats in 8V92's. The 8V92 WL folks have issues with coolant temperature oscillations, or thermal cycling. I suggested that the reason the S60 can operate continuously at any temp within the stats operating range is because of the use of a Weir stat. Do any of you 8V owners have experience with running a Weir in your engines?

[Orren Zook]

You could also buy an oil analysis kit and take a sample to see if there is fuel or water in the oil, turn around time is usually less than a week for the results. These sample kit's usually cost around $18. I had different two instances on my 8v92, one where an an o-ring failed on a liner allowing coolant into the oil and on the other occasion the flare fitting used on older Detroit applications cracked allowing fuel into the crank case. Both times it was the dip stick showed over full.

[Yankee802]

I have noticed this level ever since the maintenance, the oil looks perfectly fine on the dip stick. I'm pretty sure the level hasn't changed from April. On (I believe) a similar note, when floored from a stop, she never smoked before April, now she does. Just the 'normal' puff that almost all diesels give off, but mine never was noticeable from the rear view, but is now, so I'm thinking it's too much oil. Any way to drain that amount or should I worry about it?

I have my infra temp gauge handy, where should I point it and what should I be expecting for temps? I didn't check coolant levels, and as I sit here thinking about it, I'm not sure if I know where to look, I don't remember seeing anywhere to check. I guess someone should tell me. :) I was running with the A/C on, and it wasn't all that cold either, but that's not my main concern. I think I'm hoping it to be a thermostat, sounds like the cheapest problem.

My air gauges on the dash have pretty much always hung between 100-120, being pretty close together. but mostly around 100. When I checked the aux, it showed like 150 on that gauge.

I'm really looking forward to all you guys going over my coach at the rally! I just want to make sure we get there (and back) without issues. :) She has been pretty much a trouble free and fine coach, and I'd like to keep it that way.

[Jon Wehrenberg]

Yank,

Given your correct concern it might pay to get a DD dealer to give it a once over. It is unlikely the air pressure issues relate to the engine concerns, but you have enough legitimate questions that an 8V92 expert can address them easily. I believe there is one near Gulfport just off of and visible from I-10. Williams?????

Forgot to add that if the air pressures are running low and cycling up and down, do a DOT check and you may find the emergency brake chamber has a failed or failing diaphragm. With air pressure up, turn off the engine. Chock the wheels. Release the emergency brake. The air gauges should drop slightly, and then hold steady. If they drop and then continue to drop, no matter how slow expect a leak in the emergency brake diaphragm unless the pressure drops even with the emergency brake on.

[Yankee802]

Ok, will do, but after she has sat awhile, should I expect the air pressure to eventually drop or not? When I start her up each month, the air pressure has to build up, and I had assumed it was normal for the pressure to drop over time, I guess the question is, how much time, at what rate. Could my gauges just not be that accurate?

[truk4u]

The Prevost 8v fan is one single speed and does not cycle with the dash A/C, at least my Liberty was that way.

[Jon Wehrenberg]

If the coach is operating as designed the brake system air pressure should not drop over time. When the bus is parked no air pressure goes to any brake components so if it leaks down over time there is a problem. Too many potential leak sources to cover here, but a coach should sit for months without losing brake system air.

Your aix system is a different story if the coach uses air for various purposes, but if the coach is perfect (none are) that should also hold if not used.

For purposes of a brake check, once an emergency brake is released (engine off, wheels chocked) the pressure should hold after the initial drop. If it does not hold you need to replace the leaky brake chamber.

I do have a concern about your air system maintenance and it is not related to the air pressure issues you are discussing. When you resolve the loss of pressure, your compressor will not cycle as often. Each time it has cycled you are pressurizing atmospheric air and all the humidity it holds. If your dryer has not been serviced and your air tanks not bled of moisture you add a small amount of water every time the compressor cycles. Get past the current issue, but consider replacing your air dryer element and bleeding the tanks. This is especially critical if you run your aux air compressor because it has limited drying capacity (or should) and water in the aux system can mess up a lot of expensive Norgren valves.

[mike kerley]

Yankee,

Our CC had an issue with main and aux gauges dropping from 125 LBS to 60 or less in a weeks time. I found the plastic tubing connecting the guages had worn through just before entering the guages themselves. Ended up putting new brass fittings on the guages (from NAPA) and new lines from well below the guages and the leak stopped. I can hold at 120 LBS now for weeks on end (well, we never set for more than 5-7 days) but it does not leak. Aux air is a different story. Our 12V pump runs about twice a day for a short while each time.

[Yankee802]

Thanks guys for all the advice. The only tank I know where/how to bleed is the aux, where is/are the other bleed points?

When I had the coach serviced at Prevost in April, I asked about the air dryer, they said it was find and didn't need to be replaced yet.

[Jon Wehrenberg]

Yank,

You can see a small tank in your steer compartment, but the others are located beneath the coach over the steer and drive axles. You need to access them from below. Whenever your coach is lubed the tech should include draining the air tanks as part of his tasks.

[Yankee802]

Well, it appeared the guys at Prevost Jacksonville were pretty thorough and I'm sure the tech did as you described. This was of course back in May, so I don't know how often they need to be bled. I've opened up the drain on the aux, no more water/moisture.

I did some more diagnosing and discovered some odd things. Of my air gauges in the dash, the top one appears to be for the brakes, and was at 100# at last check, and the bottom gauge was on 0. The air is out of the suspension, she is on the 'ground'. The aux has 90#, and maintained by the aux compressor.

So from this I believe that my dash gauges are for brakes and suspension only, is this normal? I guess this would explain why my leveling system isn't working like everyone eles's, thankfully everywhere we have parked the coach as been level, and she only gets lower and not unlevel.

I was reading one of the recent threads about coolant, and thought I'd just add my additional thought/discovery about that here, I have a tank in my bedroom closet with antifreeze in it, and I know it is for the webasto, so I'm wondering if my webasto is a seperate system from the engine? When the webasto is on, the bedroom tank can be heard cycleing, and gets hot, but not when the engine is on. (unless the webasto is on too, and I don't do that, no need) I guess you guys can tell me at the rally. :)

[Jon Wehrenberg]

Yank,

If you only have 2 air gauges on the dash they are for your two brake systems. A third gauge would be for the aux system, and it is rare when there is an aux system pressure gauge on the dash.

We will cover this in a seminar at the rally, but there is a misconception about the relationship between aux pressure and the leveling system. On coaches of your vintage when you have leveled the bus your air bags will have XXX PSI in them. As long as you maintain aux pressure in excess of approximately 30 to 40 PSI that air bag pressure should remain unchanged regardless of whether the aux pressure is 40 PSI or 100 PSI. That is assuming your suspension system, and specifically the air bags and the 5 port Norgren valves are leak free. Because of your vintage and the way the system was designed, once your aux pressure drops below 30 to 40 PSI your tag axle air bags will dump air causing the rear to settle.

For those with newer vintage coaches (I'm not sure of the model year but it is somewhere around 1994, 1995) once the coach is leveled and the key is off, no matter what the auxiliary air system pressure is the pressure in the air bags is "locked" in the air bags.

Your suspension is not like the majority of those out there but not because it is defective, but because it is how it was designed and built for your vintage coach.

I have no specific knowledge of your conversion but I would guess your theory about the Webasto coolant tank is correct.