If you have a Detroit Diesel 6V92TA and you look at the top of your engine you'll see a vent cap with a metal vent pipe going down toward the ground from the center of each valve cover. The vent pipe from the driver's side valve cover goes toward the rear of the coach and then down toward the ground. Look carefully at the hoses the vent pipe is rubbing against. Climb on top of your engine with a flashlight and stick your head back there and you'll see a little metal shielded high pressure fuel line that's probably rubbing on the vent pipe. Mine had almost worn through when I discovered it. You'll probably have a major engine fire when this happens. Also notice the vent pipe is probably rubbing on the rubber coolant hose that comes out of the thermostat, and another small hose also. You may be able to keep all these hoses away from the vent pipe with wire ties. I cut a piece of rubber hose and slipped it over the vent pipe. I check all these hoses every day before I start my engine. I can check the fuel line without climbing on top of the engine if I reach back there and feel down the vent pipe. The vent pipe on the passenger side of the engine goes toward the front of the coach and doesn't touch anything. I wish the driver's side vent pipe went toward the front of the coach also. If it continues to cause problems I may replace the pipe with rubber hose and reroute it. Go check that fuel line right now before you forget. You'll have a terrible fire if it rubs through. Check it every day before you start your engine from now on. I spotted this when I had the radiator out of my coach. My friend is a good mechanic and so am I but neither of us could figure out how to change the fuel line if it had rubbed all the way through. Even with the radiator out you can see the fuel line, but you can't replace it. I think you might have to remove the supercharger from the top of the engine to replace the fuel line. That would be a question to ask Detroit Diesel. Okay, so you know about this dangerous situation and how to easily check for it... While you're there check to see if you have a fiberglass fan (you probably do) and replace it with a nylon fan now before it explodes without warning and destroys your radiator... Yes, that's exactly what happened to me, but hey, at least I discovered the high pressure fuel leak before it happened... and told you about it... call me if you need help finding this stuff.
Scott
(615) 482-7650
WOW....you got my attention!! Anyone else know about this issue or had a problem? I will check mine this week and report back.
I have a Detroit 6V92 Turbo in a 1993 40' GV U300...is this the same engine you are describing? Please advise, thanks!
Yes, any Detroit Diesel 6V92TA with the vent pipe going toward the rear of the coach will probably have hoses rubbing on the pipe, including the high pressure fuel line. It's an easy fix if you find it before it rubs all the way through. Stick your hand back there and feel down the vent pipe and you'll find the fuel line... or crawl on top of your engine with a flashlight and you can see down there.
Scott:
I read your post with interest, I have a 1991 GV U300 40ft with a 6V92TA. You mentioned pulling the radiator, how did you do that - do you have to take apart the rear fiberglass panels to get it out, or does it drop out the bottom. I may need to re-core mine at some point, it had some small leaks and I put in Bars-Leak for now, which stopped the leaks.
Peter
I had a 6v92 coach burn down way back when. We never knew why. Thanks
Bob,
What kind of coach was it? My parents had a Vogue with a 6V92 and it caught fire. It was electrical though. They had a fire suppression system so the coach was saved.
Scott, thanks for the heads-up. We looked at a coach with that engine on Friday. I'll add that to what we look at as we continue our searches.
I just checked my 93, U300 with the 6V92. I don't have a vent pipe coming out of the valve cover on the drivers side and can see nothing related to what you described. On the passenger side the vent pipe coming out of the valve cover does connect to a braided line but I believe it is a hydraulic line and shows no wear so I think we are in the clear. The 93's and later have a side radiator and the back of the engine is perfectly visible and easy to reach.
Is it a given that diesel fuel will ignite if it spill on the engine?
If I understand RRadio, the vent pipe exits the valve cover in the rearward direction. There is a short rubber hose piece that connects the valve cover output pipe to the extension pipe that travels to the end of the engine (next to the fuel and radiator hose) before it bends straight down towards the ground. I took a few pictures. The picture with labels is looking directly towards the rear of the coach. Coaches with side radiators ('92 or later) might be configured differently.
One thing I see that keeps the fuel line away from the vent pipe is a hose clamp that is bolted down with one of the thermostat housing bolts. Maybe this was left off on RRadio's coach during some previous service?
I have never had any issues with cable or hose chaffing in this area in 12 years I've had my coach. I have the same model and year coach as RRadio. It would be good to know what other owners find.
Detroit Diesel 2 cycle engines are probably the least likely of all the diesels in motorhomes to catch fire. Unlike the 4 strokes, there are NO high pressure lines anywhere on the engine. Low pressure fuel is delivered from the fuel pump to the cylinder heads where it goes through internal passages to the combination high pressure pump/fuel injector at each cylinder. Everything is under the valve covers and hidden from view (and harm).
With 4 cycles, the fuel goes from the injection pump on the mechanical engines through exposed steel lines at high pressure (about 3000 psi) to the injectors. With the 4 cycle common rail, electronic engines, fuel is supplied to the injectors at around 30,000 psi in the latest engines.
With a 6V-92TA, the pressure at the secondary filter (up high, driver's side of the engine) is about 20 psi at idle to 50-65 psi at 2100 rpm so this is called the low pressure side. From the secondary filter, fuel goes up to the ECU (electronic computer) where it flows through it to cool it and then to the engine. It makes a 90 degree turn downward as it leaves the ECU. At this location, it is about 4 inches from the main body of the turbocharger. All of the external, low pressure lines are wrapped so if the line were to deteriorate, it would be unable to spray and would likely run down and find it's way to the ground. It is doubtful it would come in contact with a heat source that could ignite it. The self-ignition temperature of diesel is at least 420 degrees so it's not the easiest to light off.
The 6V-92TA is more likely to catch fire from old insulation hanging down from above. PM here is clearing away old pieces of the foam and perhaps fitting a reflective blanket to the underside of the bed compartment roof.
Will all diesels, hose lines don't last forever and when checking the oil level, it never hurts to glance at the fuel lines, belts (especially the hyd pump belt) and make sure the air cleaner tell-tale is green. If ever replacing a engine fuel line, make sure it has the protective wrap on it and not just an exposed rubber hose.
Our U300 has nothing like the vent described in one of the above posts. Sometimes, installations are modified and new pipes, brackets, etc. could be in a position to chaff the hose so good to check your installation.
Pierce
Peter, I did recore my radiator. It was quite a job. It takes a full day to remove the radiator and you need two guys to do it. It takes another full day to reinstall the radiator and it takes two guys also. The radiator comes out through the rear door. There's a specific procedure you have to follow or else you'll never get it out. If there's interest in this I can write up the procedure and post it in here. It's pretty long and emotional for me and I don't want to relive that unless I have to! (laugh)
David, be sure to have the seller replace the fiberglass fan with a nylon fan before you buy any coach. I think almost all of them have fiberglass fans waiting to explode without warning and destroy the radiator.
Kent, the vent pipe doesn't connect to the braided fuel line, it runs perpendicular to it and they rub against each other. If you don't have a big vent cap in the center of each valve cover you don't have this vent pipe.
John, you got a good photo of the vent cap and vent pipe. The vent cap on mine is black and says "Detroit Diesel 92 Power" on it. I suspect there's a way to turn that driver's side cap 180 degrees so the vent pipe goes forward, away from the hoses. I'll be in Nacogdoches in a few days and I'll ask about that.
Pierce, it probably isn't high pressure diesel inside that fuel line, at least not compared to four stroke diesels, but it is pressurized and it's probably hot, and that's what concerned me. Any source of ignition, like a spark from the alternator brushes, would cause a major engine fire. I may be paranoid now, perhaps rightfully so after what's happened to me lately, but I'm checking that fuel line every day right before I start the engine, no exceptions. I don't think Detroit Diesels are dangerous. To be perfectly honest, it's the only diesel I'd even consider owning. I know a lot about them from working with them over the years and I bought my coach specifically because it has a two stroke Detroit. If I had known about the fiberglass fan issue I wouldn't have bought the coach unless the seller replaced it with a nylon fan. Sorry, just being honest here. I'm glad I didn't sell my coach when I was depressed and no diesel mechanics would work on it. It was a boost to my self confidence to struggle through the radiator replacement myself. I'm now even more impressed with the Detroit Diesel after working on it and noticing things about it. Sorry to be such an alarmist but a potential fuel leak seems like a major fire danger that people should be aware of.
Again, all you really have to do is reach back there and slide your hand down the vent pipe each day before you start the engine. Feel the fuel line and make sure it's not rubbing on that pipe. Mine was, possibly for 20+ years, and it was almost rubbed through which would have caused a fuel leak and probably a major engine fire. Call me if you need help finding this stuff, and look at the photos John posted because yours will probably look similar.
Scott
(615) 482-7650
RRadio,
Diesel has a MUCH lower vapor and volitile content than gasoline. Translated, this means no spark from an alternator (or anything else) will cause it to explode around the engine. With the right air/fuel ratio and very high temperature, it would be possible to create an explosive mix in the fuel tank but not likely with our coaches. You can put a match out in diesel. Try (don't) that with gasoline. OSHA only classifies diesel as a "moderate safety hazard."
Pierce
If the fuel line he is talking about is the supply line, there is only a vacuum, no pressure, so call off the panic until it runs out of fuel in a minute or so, then cry for help.
Dave M
Scott:
Thanks for the reply, I have written down your phone number. Did you by chance document any of the teardown with pictures or videos? Also, where did you find the replacement fan?
An update on my radiator leak, I was rooting around with a flashlight the other day and I discovered both hose joints on the top of the radiator were leaking (engine side). Last summer I think this was seeping through to the other side, and made the appearance of a leak in the radiator core near the top. I loosed and repositioned the hose clamps and snugged them up, and this seems to have stopped the leaking. Probably while in storage the cold (Minnesota) winter loosened the seal and made the leaks re-appear again.
Peter
And the USDOT classification for diesel is "Combustible", while gasoline is classified as "Flammable".
Peter,
I will write up the procedure and post it on here if you want me to. You definitely need to replace the fiberglass fan with a nylon fan at the same time.
The rest of you need to consider how an oil burner works. The big oil burners work by vaporizing the oil with heat and then igniting it with an electric spark. The small oil burners work by ionizing the oil by pumping it through a tiny nozzle, then igniting it with an electric spark. All of these conditions exist in this particular situation. The diesel, which is fuel oil with additives in it, would be hot for sure, and would be forced out through a tiny hole in the hose, just a few feet away from the air cooled alternator with sparking brushes inside it. This will cause a major engine fire. In my 20+ years as a journeyman heating systems specialist I've seen a bunch of boilers burning fuel oil explode when the flame first went out, then the oil vapors got to a spark several feet away and ignited... I'm gonna reach back there and check that fuel line every day before I start my engine no matter what you guys say. Anyone with common sense who had seen the things I've seen over the years would do the same.