Bus Engine Shutdown

[Jon Wehrenberg]

One of our group experienced an engine shutdown while driving, and it has gotten me to thinking.

The first reaction is that our coaches will not shut down without warning, but the time to react is very limited. If you get an indicator light to advise you the coach will shut down, you have literaly seconds to respond. You can over ride the shut down feature by pressing the override switch (it has a red colored square) which will provide you with a few more seconds to get off the road and to a safe place.

But beyond getting off the highway and in a safe spot now what do you do?

There are only three malfunctions that will make you shut down.

43...LOW COOLANT LEVEL
44...OIL OR COOLANT HIGH TEMPERATURE
45...LOW OIL PRESSURE.

There are many other codes, but none of the others will shut you down.

It has been my experience and this opinion has been reinforced by anecdotal evidence that usually the sensor has failed in some way. If you get the engine warning light, scan the gauges to verify you do not have high temps or low oil pressure and when safe verify the coolant level is above the sensor.

If you are OK then the sensor needs to be replaced. I am now going to order and keep on hand in the bus one of each sensor relating to these three codes. It will save a service call or more importantly having the coach sit somewhere overnight while waiting for service or parts.

Of the three, the most common sensor failure I have heard about is coolant level, followed by the oil pressure sensor.

[tdelorme]

Jon, any chance you have the part numbers for the sensors? Have you checked prices at different sources or just going to call Prevost parts. Also, the location of each sensor would be good to know.

[Jon Wehrenberg]

Ted,

I am going to visit my local DD dealer and get part numbers and specific information about exchanging sensors.

I will write an article because this is not just a simple swap. If you remove the coolant sensor for example you are getting a hot anti-freeze bath. I want the professionals to give me tips along with part numbers for the different engines and costs.

[jack14r]

Jon,Can you ask if the part numbers for the series 60-V are the same as the others?Jack

[phorner]

Jon,

Don't know if this applies here, but I once had a sensor failure on an Aqua Hot unit and the factory talked me through a simple by-pass of the sensor, which got me through until a replacement sensor could be available. This was also a low coolant level sensor, which had failed.

So, is there a way to by-pass any of these critical sensors, once you have positively determined that the sensor is at fault and that the critical condition does not actually exist, until a replacement can be obtained?

If this is possible, it might come in handy some day... or does the potential for a by-pass to be ignored for too long pose a greater risk?

[Jon Wehrenberg]

If my local DD guys will tolerate me I intend to dig all the poop up on sensors. I think that the vintage of DDEC influences some of the sensors so I will try to get the variables documented.

I got partway into this a while back and for some reason did not go further, but as I recall about $300 to $400 is the cost for spare sensors. If there is a way to bypass a sensor I will find that out because there is no sense buying a spare if temporary repairs can be made.

[Orren Zook]

Jon,

you can save the cost of a spare low coolant sensor - just keep a paper clip handy to jump the terminals and some electrical tape to hold the clip in place until you can get to a service / parts provider.

[bluevost]

Jon,

You may remember I had an oil pressure sensor changed in Knoxville shorly after POG III. It cost about $90.00 at that time and one hour of labor. The guys at Covington took good care of me.

Ken

[Jon Wehrenberg]

There is a theory that the low coolant level sensor can be bypassed. That in fact may be the case, but before anybody accepts that as the gospel I will check further.

Some DDEC models measure resistance and just jumping across two wires may not provide the correct value.

So for now lets see if we can verify some of this.

[Kevin Erion]

I just received the following for my 01 XLII, I now feel confidant that I will never need them.

TPS part # 531402, $166.10
Oil sending unit part # 561095, $29.43
Coolant level sending unit part # 562396, $27.71

But if I do, I just hope I remember the hiding spot I stash them in!

[dalej]

I know what you mean Kev, the harder I try to organize my STUFF! the harder it is to find it.

[0533]

You guys must have a trailer full of spares where ever you go. I try and keep up with all of this and am finding that I have filled up just about every square inch with spares that I read about on POG.

[Jon Wehrenberg]

The article has been written, it gives part numbers and costs, and has links to show codes and locations of sensors.

I will give it a final review and then I think Jim will post when it goes on line.

Yes you can use a paper clip or anything to jump across the two lines on the coolant sensor, but no other sensors can be jumped because they measure resistance values.

[Jon Wehrenberg]

The sensor article has been posted by Jim Skiff on the POG Articles page.

If you print out the two links and keep them in your coach along with the spare sensors you or your mechanic will have all you need to get you along the way again.

[merle&louise]

I just received the following for my 01 XLII, I now feel confidant that I will never need them.

TPS part # 531402, $166.10
Oil sending unit part # 561095, $29.43
Coolant level sending unit part # 562396, $27.71

But if I do, I just hope I remember the hiding spot I stash them in!

Kevin,

Are these Prevost part numbers or DD part numbers?

[Kevin Erion]

Tuga, these are prevost part # and they look a little different from Jon's pictures. My bus is in storage so I can't verify these parts until I compare to the OE ones.

[Jon Wehrenberg]

The photos shown were DD original equipment parts, and they have the DD part numbers stamped on them. The prices are full retail from the local DD dealer.

With DDEC and other computer controlled engines out there I am certain these sensors are likely available as generic parts at much lower prices.

I think if you are also going to carry the SRS and the TRS sensors, then you might as well include the throttle position sensor, turbo boost sensor and a coolant level sensor because they all have the ability to stop you from running.

[merle&louise]

Jon,

Thanks for the article on sensors: I just printed it out along with the diagram of their location on the engine. I am going to order all of them to keep as spares. Thanks for taking the time to post this important info. I really appreciate it.:D

[truk4u]

Great article Jon. I'm not quite clear if the 8V's have the same sensors, even after reading the DD info on the site. Could you clarify that please?

[BrianE]

Sorry for the late reply but I've been behind the wheel for the last few days.

There is one more very real malfunction that will shut you down and there may be others that are related to this such as a broken wire in these circuits.

If any of the four identical engine ignition relays fail (two in the front electrical panel under the driver and two in the engine electrical panel) your engine will shut down immediately with no warning whatsoever. This shutdown will be recognized due to the fact that there will be a total electrical failure in which all engine functions will be totally dead. This malfunction was discussed in an earlier thread. There are 2 that power the 12volt engine circuits and 2 that power the 24v circuits. Since these relays mount a little differently than other plug in relays it would be advisable to carry at least one in your spares kit. They are 24volt 70amp relays, Prevost PN 561991.

[Jon Wehrenberg]

Tom et al,

The sensors cover DDEC coaches with the exception of EGR coaches. I have not found a diagram of sensor locations on 8V92 coaches, but if I do I will add that to the article.

Adding to Brian's previous post, there are three circuit breakers which handle DDEC functions in the rear electrical box. The numbers may vary, but on my coach they are 19,20 and 21. If those breakers trip the engine will not run either. Assuming the CB is not bad, however, merely resttting the tripped breaker gets you running again.

To all the new owners..............we are not trying to scare you and these sensor, relay or circuit breaker failures are not common, but they do happen. Nobody here needs to be an expert on this stuff, but only needs to be aware there are some component failures that can shut your engine down. There is no preventive maintenance that I know of, nor is there any way to predict if or when a part will fail. In every case however the diagnosis of what failed is fairly simple and a call to the Prevost or Detroit 24 hour help lines will often allow you to pinpoint the problem.

If you use your coach in the pursuit of business you may wish to study this topic a little and carry some spares.

[Jeff Bayley]

In order to prevent posting a new thread I just did a search for "coolant" and found this existing thead.

My sensors (ordered complete set at Jon's article suggestion) finally arrived today and installed what I belive was the faulty one but will road test tommorow. Now, while we were waiting, my wife keep saying, "What about the water........it could be low water.........we should add water". So I added a gallon of water to the overflow tank. It was half way at the site glass as the time of adding it. The conversation about "the water" continued. No amount of explaining would close the hole about how the ebb and flow of the water when hot and cold and that that overlow tank didn't need to be topped off. Finally, I couldn't take it anymore so to end the "We need more water there" conversation, I let her watch me dump yet another gallon of water in. This brought the level all the way to top and overflowed. I figured a half gallon or gallon would blow out through the overflow hose and I got to end the insanity. BUT, the cap went on and off sort of hard and I just got done reading Jon's coolant change article and it got me to thinking that if the cap fails to open and allow the water to purge, something else may give way and blow a gasket in the system. So I think I should siphon a gallon out tommorow before shoving off. I think the first gallon was ok to add to get it above the site glass but not the 2nd.

Can someone confirm if I'm correct to leave some empty space in that tank ?

[JIM CHALOUPKA]

I'll confirm that!

JIM

[Jeff Bayley]

I thought about it and don't think the cap needs to purge after all and in fact does not ever purge. I was thinking about the spring loaded cap and got myself mixed up but that spring is just helping keep the cap on tight, not opening and closing to allow the overflow to purge I'm pretty sure. I think when the overflow get's full, the water simply finds it way out through the top hose. Jeez, now if that's the case the system woudn't be sealed up and create preassure. Ok, back to needing clarification whether to let some water out and give the overflow some breathing room.

[Jon Wehrenberg]

The header tank, or surge tank has two caps on my bus. The lower cap is for filling and the upper one is not accessible for filling.

Both caps have a spring designed to hold about 14 PSI system pressure. If the system did not have pressure the coolant would boil prematurely. The pressure raises the boiling point which is a good thing because our coolant can get as hot as 205 to 210 degrees during normal ooperations.

Once the pressure exceeds the system pressure limits as determined by the cap, the bottom seal on the radiator cap lifts and excess water is purged out through the hose.

When you filled and overflowed the tank, there was still a small amount of air above the liquid level. I suspect however that when your 22 or 24 gallons of coolant is heated, it will expand and push the excess out the vent line on the lower filler neck.

[Jeff Bayley]

Thanks Jon. I almost understand the whole thing but don't quite get how the system builds up preasue when the vent line is below the fill cap. Yet I know it does because you get the "Wooosh" of air coming out when you remove the cap in two stages. I guess I just need to look at it again and I think it's a good idea to siphon a little out and leave the overflow tank half full instead of all the way full.

Also, I'm about to order more spare parts (I want to be like you.......prepared). I'm going to do the flush on the coach coolant per your article and I also noticed a posting somehwere in the last day of browsing for a relay.

Prevost Part 561991 is $11.19 (this relay is suppsed to be slightly different than the others and the writer says a good idea to keep an bus). Ok, the post was by BrianE and is on page 2 of this thread.

The Detroit coolant filter is a "Nalcool" filter part number 550630 and is $22.43 and Prevost Parts has it. While I'm at it, does Jon or anyone else recommend any other spare parts to order so I can get it all in on one order ? Already have belts of course but nothing else besides all of the sensors I just got.

[Jon Wehrenberg]

If you are ordering spare parts make sure they will work in your coach. Prevost has used several generations of relays for example. I don't know what relay you refer to, but my current coach does not use the same relays as my previous coach.

[Darrell McCarley]

Jeff...........Just to add to Jon's comment. You should have a fill cap on the front side and a 14 lb cap on top to release antifreeze to a plastic overflow or a small hose to the ground when your pressure gets above 14lbs. I fill my tank all the way to the top and let the pressure take care of the amount of antifreeze needed in the tank. The 14lb pressure cap on top will release pressure before you blow a gasket or hose.......Just some added thoughts.......Darrell

[merle&louise]

If you are ordering spare parts make sure they will work in your coach. Prevost has used several generations of relays for example. I don't know what relay you refer to, but my current coach does not use the same relays as my previous coach.

Today the DD parts guy asked me what my serial # was in order to get the correct sensors for my production year engine. I gave him the part numbers Jon posted and he will double check them against the ones for my engine.

UPDATE: All of the part numbers matched up with my serial #. Thanks Jon!

[Denny]

When I was at Williams Detroit Diesel ordering the above mentioned parts, the service mgr. also said that there is a sensor on the Allison Transmission that will stop the bus. I apologize that I don't have the part name or number because I told him I would take it. His recommending this was good enough for me since he knew that I was trying to be prepared in the event of certain failures. I will try and get a part number and better description if any interest is shown.

[Jon Wehrenberg]

Denny,

I may be wrong, but there are a number of transmission sensors that may cripple the bus. I know for sure of one because we were stuck because of it.

The temperature sensor will not allow you to shift if it thinks the temperature of the transmission is below a certain value. We had gotten a "do not shift" warning while driving. When I found a place to pull over the transmission would not downshift, was literally locked in gear and stalled the engine.

The sensor was displaying a -20 temperature when it was hooked to a reader. If you cannot shift into gear or out of gear you effectively are shut down. I believe there is a sensor that detects RPM. If it thinks the RPM of the engine is above idle it will not allow you to shift into gear.

There may be others.

[Jeff Bayley]

I got 5 or 6 spare sensors finally late Wednesday and installed the "Engine Oil Overheat" which was suspect based on the flashing error codes and comparing against the legend. Code 44. Appears to have fixed it if the 35 miles trip to get home was test enough. My engine got up to 195 but mostley was about 180-190 at 60mph. No check engine light so presume the sensor change was the fix as advised here by Jon and others. Shoudn't Jon have a lodge hat or something to wear that says "POG King Poo Bah" or something like that ?

Regarding the transmission going into gear at high idle, I'm certain my bus was requiring me to switch into low idle before it would engage BUT when I had the RPM tuned and adjusted at detroit, it no longer required this. I belive this is becuase my high idle is around 9,000 RPM and my low idle is around 6-7k RPM. It WILL go into gear on high idle but I suspect that is either becuase my high idle is not high enough (to mandate I put into low idle) or maybe Detroit's software has an adjustment to determine at what RPM it makes you idle down just as they do for many other engine adjustments (like how you want your coach to react when one of sensors it triggered) and mine is set in such a way that it goes into gear. It DOES idle down simultanous with going into gear to for just a split second before engaging. While we're on this topic, what do others like to have their high and low settings on ? Also, I need to buy a DDEC reader if anyone comes across one.