Bellhousing plug

bottomacher · May 25, 2011, 04:33:38 PM

I just noticed that I have a hole in the bottom of my bellhousing on my mc9 (740 automatic.) It appears to take a 3/4" pipe plug, which is not there. Is there any reason that I can't put in a plug? It might help keep the rear of the bus cleaner. Thanks

lostagain · May 25, 2011, 06:49:14 PM

You can put in a plug. Just remove it once in a while to drain any oil that has leaked past the rear seal.

JC

NJT5047 · May 25, 2011, 08:46:52 PM

I wouldn't plug that hole...the bell housing may rapidly fill with oil and eventually come out thru the starter housing and unused motor mount holes in the bell housing once it reaches the level of the ring gear (not very much oil). That'll make a huge mess in your engine room.

It isn't intended to be plugged on OTR vehicles. Maybe in marine applications.
If oil is dripping from the hole, you've got a rear main seal failing, or (this is bad) a leaking bell housing bolt. Some of the bell housing bolts are sealed. They can leak if loose.
Likely a rear main seal if more than 150 K on the engine...or a bad seal install.
With any oil leak, steam off the engine and be clear on where the oil is coming from. Stopping every seep is probably a pipe dream. However, the road draft tubes and airbox drains will spot up a bus rather quickly. So will a leaking rear main or any other leak of consequence. Steam that puppy off and then drive it a short distance and have a look. A rear main seal leak won't typically "blow out," but it'll get progressively worse to the point that you'll get tired of adding oil and seeing a "trail" behind the coach. Whatever, don't let it run out of oil.
If you find yourself replacing a rear main, be sure that you get the correct rotation seal, the correct seal for the sleeve, and a new sleeve, and pay attention to the new Teflon install instructions. Teflon seals lips are usually assembled dry. For sure, follow the instructions with the seal.

JR

bottomacher · May 26, 2011, 05:21:48 AM

Thanks to both of you for the reply. I have installed reservoirs for the slobber tubes, but I haven't driven the bus on the road since then. I can't actually say I have a drip from the hole; it's just damp all around the bottom of the bellhousing. I noticed it when I was trying to find potential drips. I just painted the bus white, and I'm trying to keep the rear clean. Would a small reservoir like the slobber tube ones do any good? Apparently the only way I can find out how much it leaks, if at all, is to drive it (and keep washing the bus.)

JackConrad · May 26, 2011, 05:30:14 AM

When we started noticing fluid leaking from that hole, I thought is was the rear seal failing. I made a small catch can, ran a couple hundred miles and drained the catch can. That is when I discovered my transmission front seal was leaking. I monitored the catch can until we returned home and replaced the transmission front seal. Had I plugged the hole, I would not had discoved the problem until the fluid was leaking out at a higher level. Not sure what that fluid would have done to my starter? Plus the flywheel spinning in the fluid would surely use more horsepower/fuel. After confriming no leaks, we removed the catch can. Jack

bottomacher · May 26, 2011, 05:49:37 AM

Thanks, Jack. Did you put a vent in the catch can?

luvrbus · May 26, 2011, 06:24:04 AM

I have to tell you guys this story about the plug I have a friend that has a MCI 7 his plug was leaking so he removed it called me and said he drained 4 gals of oil from the bellhousing.
He called back in 2 days and told me his bus would not move now, long story short he had a wet torque converter and he had drain the transmission fluid and I LMAO

good luck