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Rear rock guard/ mud flap
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Tom,
Any chance you might show a picture of the slobber tube catch cans?
Chuck – thinking it might be a good idea- thanks -
Tom
I second Chuck’s request. I have a pic of the unit available from Detriot but they want $250 for theirs and I am pretty sure I can build one cheaper than that. I would love to see a home made version if you have a pic you could post.
Rob
91 LeMirage XL
Missouri
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I have a 98/99 CC 40 footer and just returned from a trip to Houston – Dallas and back home to Monroe Louisiana and the coach did seem to run a few degrees cooler without my full length flap on the back. The thermostat did not seem to cycle as much (the temps did not rise and fall as much as before).
And on mine, the burning rubber smell is really horendous.
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If I were to guess I would surmise that we would be unable to measure the impact a mud flap has on our coaches without doing a very detailed study of temperatures under extreme conditions.
Under normal use, normal being less than continuous maximum horsepower, average ambient conditions and repeatability of those conditions with and without the mud flap the temperatures we see are likely those that reflect what our coaches are set up to maintain. We all have the engine thermostat which is going to maintain temperatures within a range based on its set points. For discussion consder the thermostat to open at 195 and close at 190. That means with the fan locked the coach is going to run in that range unless it is being run at high horsepower and high ambient conditions. But our coaches are not designed to run at 190 or 195. They have a low speed fan setting of 204 and a high speed fan setting of 208. That means the fan doesn’t even engage until it reaches those settings. The temperatures may not be right, but let’s use those for an example.
So under most conditions which include some hill climbing and high ambient temps it is likely we will see our coaches indicate temps cycling around 204 degrees and below with temps hitting 208 under heavier load. I am sure there is ample margin built into the cooling system such that except when in worst case conditions such as a hill climb in triple digit outside temps we will not really see a significant difference with or without our flaps. What we are likely to see is less time spent above the low fan speed set temp, but my guess is if your coach is cycling between the high and low set points for fan speed you might have an issue other than a mud flap.
The engine manufacturer certifies the engine installation because it is providing a warranty. That is why each horsepower increase Prevost makes is not as simple as just reprogramming the engine. The engine manufacturer want to be certain the heat caused by the increased horsepower can be dissipated. There is ample margin built into the cooling system so while a mud flap is likley to have an impact it is probably not as much as we might imagine.
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Hey Jon, while we are on the subject of horsepower, my engine id plate says a 12.7 LTR engine. I was told this was a 500 HP engine. Would a 12.7 be 500 ?
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I don’t see why not.
If you go here and put in the data for your coach look under the technical information, section 9 and it should give you confirmation of that. http://prevostparts.volvo.com/technicalpublications/en/manuel.asp
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I will try to get a picture of the catch can tonight after I get off work, but it basically is a 3″ PVC pipe about 18 ” long. The 3″ is overkill and I will probably make the permanent one smaller. One end has a cap on it and the other has a clean out plug. I glued in side of the pipe that would be the top 2 hose bibs to fit the slobber tubes the same width as the tubes hanging down. Also on the top I placed a breather to keep from building pressure. The breather is what is on the top of a hydraulic unit. That’s it, just hang it under the engine connect the tubes and drain as often as needed for you engine.
I had one made for my Eagle out of a steel pipe and had the ends welded on it and then had a drain plug put in the bottom. I will probably do this for the Prevost when I discover how much it is putting in the can. It sure makes the wife happier about the oil on the concrete drive!!!!!
I have heard of guys hanging 1/2 gallon milk jugs underneath each pipe as well. they are just a little harder to drain. -
Dumb question probably, but, what and where are the slobber tubes? I too have a oil leak/spray problem.
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I believe you have two tubes about an inch in diameter on each side of the engine that are to vent the crankcase. If you have a lot of “blowby” through the rings it puts pressure in the crankcase and oil vapors are exhausted from these tubes. Often the amount of oil coming from the tubes is thought to be a lot more than it really is.
Some have hung a can such as a coffee can from these tubes to catch what might drip from them. Having fought the battle with a 2 stroke engine to identify sources of oil I can say if you are serious about identifying sources and curing the problem step one has to be to clean the engine until you can wipe it with a white glove, anywhere, and not detect any dirt. Then after running it on a short trip start looking closely at it to see if there is any evidence of oil leakage, fuel leakage, or wetness on the ends of the “slobber” tubes. Only after the engine is clean can you do a good analysis of the source and take steps to correct it.
In my case it took me 1 1/2 years to finally locate a fuel fitting that needed about 1/16 turn to forever stop a leak that was leaving a light film on my inside of the doors and my toad after a trip. Until I figured out the fuel leakage which was so slight it never showed a wet spot on my less than clean engine I suspected the slobber tubes. From that point on I was fanatical about keeping my engines clean and painted.
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A 2 stroke Detroit has an air box. It’s the area that surrounds the
intake ports of the cylinder liners. This area is where the pressurized
air from the supercharger and turbo (if it has one) is waiting for
piston to clear the intake ports and allow the fresh air to enter the
cylinder and help force burnt fuel out the exhaust valves. The
pistons in a 2 stroke have a set of rings (3) on the top, 2 of them
provide sealing against the cylinder walls for compression and the other
one kinda acts as sponge to hold oil for piston to cylinder
lubrication. The unusual thing about 2 stroke pistons is that they have 2
rings on the bottom of the piston, These rings keep the oil thrown from the crankshaft from getting into the airbox and the pressure
from supercharger / turbo from getting into the crankcase which would
result in blow by out the valve cover vents, Since neither set of rings
are 100% efficient at doing their jobs some oil enters the airbox. The
airbox drains (slobber tubes) allow a place for the residual oil to
exit. Detroit came up with check valves at some point for the airbox drains. These valves are pressure sensitive and shut off the drains once the internal
airbox pressure is over 6 PSI. This happens just above idle and helps
reduce leaks while traveling. The airbox drain tubes are about 3/8 inch ID
and the crankcase vent tubes for the valve covers are about 1 inch. As the
engine wears and the piston rings become less efficient at their job
more oil enters the airbox and more blow by exits from the valve cover vents.
If the engine has no obvious leaks tiny oil splatters on the towed
vehicle usually come from the airbox drains. If you build a catch tank
for your drains it must also have a vent. This is a somewhat simplified version of the process and there maybe a better way to
explain it, that’s my best shot.
Ken -
Wow……..you guys really explained it better than I could have imagined. Thank you!
Now I will spray the entire engine with degreaser, rinse it off and start checking for the leak source.
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After I posted that reply I thought about a statement that a friend would make after some long winded explaination from someone like me. “I just asked what time it was, I didn’t need to know how to build the clock” Hope I didn’t expain too much.
Ken
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I do want to know how to build a clock…………..anybody can read the time!
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As to the HP rating I have a 14Liter and is 515HP, I believe the 12.7 is infact 500HP Gary
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