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Tom

You are really discussing several issues. The issue of oil on the toad is not uncommon if the engine is leaking, or if you have crankcase vents (slobber tubes) dripping or even a modest fuel leak it is going to end up on the toad no matter what you do.

The area immediately behind the bus is a low pressure area as you travel down the highway so anything coming out of the engine or dripping from it immediately travels to that area and lands on your toad. When we had our first coach it took me a year and a half to find the source of a leak so small that at the end of the day the toad had a film on it, as did the inside of the engine doors. It drove me nuts until I found a loose fitting that took 1/16 turn of a wrench to make the problem go away.

From that point on the toad still got crud on it from the highway, such as dust and other airborne material, but at least nothing was coming from the coach.

A full width rear flap may have an impact on temperatures. I don’t have any way to prove it one way or another. I have never run with a rear flap because when I bought my first coach it was pointed out that our engines need a lot of air flow for cooling and a rear flap does not enhance air flow so I just never left them on my two coaches. Having said that, a lot of folks run with them so they may not pose a problem. My driveway is so steep a rear flap had the potential for being damaged so cooling was not my only reason to remove the flap.

Which leads into dings from rocks and stones. I towed a Jeep Grand Cherokee for over 200,000 miles. I found the tow bar puts the nose of the toad so close to the rear of the bus that any stones or sand kicked up in the course of driving cannot hit the front of the toad because the bumper of the bus is directly in the path of where the stones would have to be in order to do damage. So the rear flap from my perspective does look nice, but it may not offer any benefits that I can prove.

[Tom]

Tom,

Jon’s reference to the full rear mud flap and cooling have been researched over on Country Coach Owners site. After several CCO’s ran with and without the full flap the bottom line was, run without. Better cooling due to better air flow was found after removing the full flap. One guy said he only found one advantage for the flap and that was advertising for the manufacture.

Looking at the full flap one would think …thats’s really a great idea. With the creation of the low pressure area behind the bus just the reverse takes place.

[Paul]

My Marathon has the flap directly behind the tag wheels where it does not influence the engine cooling air but stops grit kicked up by the wheels.

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Thanks for all the replies. I do have the flaps between the drives and behind the tag. I have also made a oil catch out of PVC pipe for the slobber tubes. Hey Jon I know what you mean about chasing a leak. I had a leak on my Eagle that I could not find for several years and it turned out to be the cross over pipe on the rear of the engine. Just had to tighten a hose clamp!! Maybe I had better rethink if it will cause heating issues.

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I wouldn’t go so far as to say it will create heating issues, but I can say it will not improve cooling. If it caused heating issues Prevost would have instructed converters to do what Peter has mentioned, adding the flap behind the tag axle, but ahead of the engine.

Based on what Al said the original advice I was given and that prompted me to remove the flap appears to have been good advice. I am getting a newer coach and has a really good looking rear mud flap, and I found it will not get damaged by my driveway’s sharp angle so I am going to leave it on and record measurements over a period of time, and then I am going to remove it and see if I have the ability to document changes in cooling. It will take a long time but I will post the results because I would like to see the data.

I can say with conviction a mud flap will not prevent stone chips because I never had an issue with chips without the flap so there is no need for a flap for that purpose, and any toad is always going to get dust, and any fluids that drip or leak from the engine all over it.

[Tom]

Tom

Depending on where you place the mud flap, it will influence the temps.Some of that can be offset with things like vented engine doors, etc. Those kinds of adaptations all influence the engine run temps. We had an 89 40′ Newell with an 8V92 that never ran even slightly warm. I put this really nice mud flap on the back, right below the rear bumper to stop the slobber tube effuse from messing up my toad and guess what. The engine, all of sudden, started running warmer by 10-15 degrees. The slobber tube stuff was still there on the toad and my pretty mud flap got dirty with oil and grime. One day on a whim when I had nothing better to do, I removed the mud flap and my hotter engine cooled right down. The toad was still dirty with slobber tube stuff. Since you have the slobber tube catchment device in place, I would look elsewhere for the culprit. Look for a loose hose fitting, cracked hose, etc. unless of course your slobber tube catchment is cracked, hoses are loose, it’s full, etc.

Rob

91 LeMirage XL

Missouri

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Thanks Rob.

[John]

My experience has been the full width mud flap also has an effect on rear axle temps.

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With our latest coach I noticed a change that might make a rear mud flap an aid to engine cooling. Previous coaches had little or no air flow out the rear doors. The 87 had no ventilation through the rear doors and the 97 has a few rows of slots at the top of the rear doors so air flow through the radiator(s) in both cases is forced out the bottom of the engine compartment or out the RH side door.

On our 2006 however it appears anything that can contribute to creating the low pressure area behind the coach is likely to increase air flow through the radiator(s). Our rear engine compartment doors are almost completely louvered so a mud flap that almost closes off air flow along the area beneath the bumper may actually serve to enhance air flow from the higher pressure area in the engine compartment to the lower pressure area behind the doors.

I am only guessing at this, but with the large open area through the louvers on the doors it sure appears a full width mud flap will help. It does not do anything to keep the toad clean. Our Hummer had just as much dust and road crud on it as usual.

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As Marathon has no full rear mud flap there are some daming flaps under the bus. One behind tag and covers a larger area behind the tag tire. In the middle is a full flap in front of the engine running left and right. Then another mounted around the oil filters. This one about 3 ft long mounted with 3 bolts running north and south.

While idling with the rabbit engaged there is a large amount of air passing through the lovered engine doors. This probably is the same open door slots we both have. There is a high volumn of air moving while at idle and I can only guess it’s 10 fold while running down the interstate.

I have not experienced any high temp issues on our bus without the full rear mud flap. If both of our buses are the same air dam set up then what would be the advange for the full flap ?

Would there be any spinning effect of air around the rear of your bus resulting in more trash on your toad.? I still have trash but there seems to be less small pieces laying on top of the wipers.

Interesting topic as the Country Coach guys all said there engine temp ran lower without the full flap.

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We have a friend with a plastic coach with a full flap and on a gravel road the flap was bumping the road and spewing rocks all over the toad !! it pitted the paint all over their toad… we had one on out Navigator and didn’t notice that however on any road… but we try to avoid rocky roads too !!

[Greg]

I think as our speed increases the negative pressure area to the rear of the coach has a greater vacuum and thus tends to pull more air through the louvers on the door. As to how much stuff ends up on the toad I have no way of measuring because I don’t have a benchmark. I do know we have had just about everything that might be in the air, including all the rubber worn from tires that ends up on the road. The stuff on the toad is like the crud that ends up collected on the back of the coach. We all know rubber particles are part of what ends up on the toad because we get the burning rubber smell when we start the toad for the first time after towing.

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Intersting about the burning rubber smell! I never had that with my Eagle conversion but have had it since day one with the H3. I figured it had to do with something getting on the Jeep and last trip home I went immediately to the car wash and the smell stopped. Before it had taken 3 or 4 trips in the Jeep for the smell to burn off. I wonder what is different with this coach?

The engine door on the H3 is a panagraph door and has several rows of vents in the door.

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Do you have an oil leak? I had an 8v71 and it was a leaker and I had that problem of burning the oil off the engine after towing until I got a flap for the back. Greg

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No major leaks. I made a catch can for the slobber tubes and have a small leak at the power steering pump.