| Author | Message | ||
| Mark Renner (Boomer)
Registered Member Username: Boomer Post Number: 128 Registered: 11-2006 Posted From: 206.58.200.38  Rating: N/A |
I have a question about the full length mud flap (apron) used behind the drive axle on GMC coach and transits. I understand GM installed it to evacuate the hot engine bay area via creating a low pressure area in the engine compartment when under way, promoting an out draft under the rear bumper. Does anyone have any real world experience as to whether this piece actually works? Anyone added the apron or removed one and noticed a difference? I don't believe any other manufacturers used this. Perhaps something to do with V drives? Opinions? Facts? | ||
| Gus Causbie (Gusc)
Registered Member Username: Gusc Post Number: 789 Registered: 11-2005 Posted From: 208.54.200.34 Rating: N/A |
Mark, This has been thoroughly hashed out within the past year or two. Try a search. | ||
| Mark Renner (Boomer)
Registered Member Username: Boomer Post Number: 129 Registered: 11-2006 Posted From: 206.58.200.38 Rating: N/A |
I did. I remember it being discussed but could not find the subject. | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 143 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
Mark, I have a 4106 and have in the past had some heating issues after installing an automatic trans. That said I resolved those issues by greatly venting the engine bay out the rear upper section above the tailgate. So I would agree with GMC that the engine bay heat is a large factor in overall heating issues.>>>Dan | ||
| Frank Allen (Frank66)
Registered Member Username: Frank66 Post Number: 97 Registered: 10-2005 Posted From: 64.12.117.73 Rating: N/A |
dan , would like to know exactly what you did, seems everyone who put the automatic in a GM has this trouble, wish i had left mine alone, most of the time GM knew exactly waht they were doing when they built these things, then we come along and change it all Frank Allen | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 144 Registered: 1-2005 Posted From: 208.66.38.60 Rating: N/A |
Frank, I installed two large polished stainless steel marine louver asembles across the rear above the tail gate hinge line and two more in the right hand trans cover door. It has been the most evective thing I've done to control engine heat build up.>>>Dan | ||
| Bob Baldwin (Bob4106)
Registered Member Username: Bob4106 Post Number: 162 Registered: 10-2004 Posted From: 24.74.180.20  Rating: N/A |
Dan Do you have any pictures you could shair with us? | ||
| Luvrbus (Luvrbus)
Registered Member Username: Luvrbus Post Number: 606 Registered: 8-2006 Posted From: 74.33.35.55 Rating: N/A |
Mark, I think that works only on the GM buses I tried that on my Eagle and tempatures rose on the transmission and engine by 10 degrees on each.I tried to give it to somebody not long ago good luck | ||
| Austin Scott Davis (Zimtok)
Registered Member Username: Zimtok Post Number: 301 Registered: 9-2006 Posted From: 216.37.73.226 Rating: N/A |
My 4104 does not have the full length mudflap and it seems to be OK temperature wise. It also does not have the belly pans under the engine. I'm sure that both the pans and mudflap were removed to make maintenance easier, but I've often wondered what effect there removal had on the bus. . | ||
| Jim & Linda Callaghan (Jimc)
Registered Member Username: Jimc Post Number: 60 Registered: 2-2004 Posted From: 66.175.206.159 Rating: N/A |
I have a 4106 with a 730 trans, and in almost 5 years I have never seen the temp gauge rise over 185 degrees. I think it is the total combination of equipment (in proper working order) that keeps it from getting hot. Jim | ||
| Frank Allen (Frank66)
Registered Member Username: Frank66 Post Number: 98 Registered: 10-2005 Posted From: 64.12.117.73 Rating: N/A |
Jim, what kind of transmission oil cooler do you have?? Frank Allen | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 145 Registered: 1-2005 Posted From: 208.66.38.115 Rating: N/A |
Jim, you run that puppy in the western states much and I certify you WILL see temps much higher than that.>>>Dan | ||
| Dan West (Utahclaimjumper)
Registered Member Username: Utahclaimjumper Post Number: 146 Registered: 1-2005 Posted From: 208.66.38.115 Rating: N/A |
Bob, I'll round up my camera and try to post my vents.>>>Dan | ||
| Mel La Plante (Mel_4104)
Registered Member Username: Mel_4104 Post Number: 103 Registered: 7-2006 Posted From: 64.180.195.100 Rating: N/A |
on the under engine covers i have ran with them on and with them off and never seen any change in temp. either running the flats or the hills in BC. however i have seen piles of them behind bus shops and when asked the meck. all say the same thing that they were placed on there to help keep the engine compartment clean and they may have when all the flaps were on in the right places and the proper length. the old timers when asked say, they took them off as all they did was collect mud and oil and every time you lower them down you got a face full of crap. remember the time they came out was before cheap presure washers and in those years before you had to use a steam cleaner to get the grim and oil off and us old fellows know how fast a steam cleaner cam cause you trouble. at this time i do not run with the covers on but i do have the flaps and hose the engine down when it starts to get grimmy. | ||
| Mark Renner (Boomer)
Registered Member Username: Boomer Post Number: 130 Registered: 11-2006 Posted From: 206.58.200.38 Rating: N/A |
I think the belly pans were just an option for cold country operators. I know MCI offered it. It seems like that would defeat the purpose of the full length mud flap, holding heat in the engine bay instead of letting it out. Clifford, it sounds like your experiment with the flap didn't work out. Maybe it worked for GM in slow speed transit ops only where the air flow from the fan was blocked from migrating forward by the flap, forcing all the air from the fan shroud to the rear only. Have you tried the old trick of blocking open the tailgate a few inches when needed? | ||
| john w. roan (Chessie4905)
Registered Member Username: Chessie4905 Post Number: 1264 Registered: 10-2003 Posted From: 71.58.110.9 Rating: N/A |
The flap should stop turbulence behind the rear wheels, but in front of engine. The louvers will let the heat out. The ones people install at the bottom of rear bumper keep most of the grime off the rear of coach, but it is all over front side of bumper flap and everything on bottom area of engine. | ||
| FloridaCliff (Floridacracker)
Registered Member Username: Floridacracker Post Number: 390 Registered: 7-2004 Posted From: 97.101.146.143 Rating: N/A |
Mark, I reinstalled the flaps on my 4905 just before a 2000 mile trip last summer. I used conveyor belt. I found that the my engine temps were much more consistant in all terrain and that there was less DD droppings on the rear of the coach. Cliff | ||
| Jim & Linda Callaghan (Jimc)
Registered Member Username: Jimc Post Number: 61 Registered: 2-2004 Posted From: 66.175.206.159 Rating: N/A |
Frank, Sorry it took so long, here is a picture of the trans cooler I have. It has the engine coolant running to it along with the trans fluid lines. I have no idea who makes (made) it as there is no name tag on it. Maybe someone else will recognize it. All I can tell you is that it seems to work. Dan, you are probably right, I have yet to be climbing the big hills in high temps. The hardest climb I had so far was coming into Tucson Arizona in about 70 to 80 degree weather. Jim  | ||
| Ricky D. West (Gg04)
Registered Member Username: Gg04 Post Number: 15 Registered: 11-2006 Posted From: 32.176.45.236 Rating: N/A |
When we repowered and changed hp to 350 we had to fight over heating..now have flap (conveyor belting) air dam same belting and 1 3/4" airdam in front of rad opening...190 thermostats and flexolites 28 inch pusher fan in a custom shroud . And finally it stays at around 190 constantly..mountains or flats...gg04 |