Cessna 120-140 Association

On my to-do list is replacing the engine mount bushings (C85-12 with conical bushings). Was wondering if there were any specific procedures or gotcha's involved with the process. Reason I would like to replace them is they are cracked around the exposed edges and I don't know when they were installed.
Thanks for any input and knowledge!
-Paul

I haven't been into those lately. Perhaps Randy Thompson would care to chime in?

It depends a lot on whether you have (or want) the steel spacers (0450195) Cessna (and no one else) used.

Easiest to hang the engine from a hoist and pull them all out at the same time. If you use the spacers, put some soapy water on them to help slip everything together. The holes in the engine casing were not engineered to accommodate the bolt, the spacer and the rubber mount.

Raising the tail so that the engine will slide straight out versus up and out due to the angle helps.
Chock main wheels also.

I used a short length of all thread to pull everything together enough to get the mount bolts in.

I didn't think to use the soapy lube as John suggested, that is a great idea.

Pretty much everything between engine and firewall will need to be disconnected to get it to move far enough to get the old out and the new in.
Pain but necessary.

Good luck.

Rick

8342 wrote: ↑Sun Jan 20, 2019 9:09 am Raising the tail so that the engine will slide straight out versus up and out due to the angle helps.

That's a great idea! (Why didn't I think of it?)

Pretty much everything between engine and firewall will need to be disconnected to get it to move far enough to get the old out and the new in.

I disagree here. All you need is about 3/4". I was able to do it without disconnecting much at all. Push all the controls full forward (throttle, carb heat and mixture, if you have it,) so that there is plenty of slack. There shouldn't be anything else inflexible between the engine and the airframe. Do one bolt at a time. If you don't install the spacers you may need some extra washers on the bolts to get the right torque without running out of threads.

Don't force anything, in case I'm wrong...

I have always liked the ones that fit the 3/8" bolts. Every one I have removed with the spacers, had two or three crushed spacers. I also found that the spacers were different lengths.
I use a hoist to get the engine away from the mount. Like John says it does not take much separation. Instead of leveling the airplane I tie a rope around the crankshaft to keep the engine in the same attitude it is on the mount. The tach drive cable is the only thing I remove.
Everybody has a method they think works best. My 2 cents..

In recent years it seems that I've had the small "surface cracks" form where the rubber is compressed. For the past several annuals, I've actually replaced the bushings...just skipping one annual when we experienced that just a very slight loosening of tension saw the cracks totally disappear with no other deterioration apparent. I've tried new bushings from the normal suppliers as well as NOS & it doesn't seem to make a difference. At last annual the IA said he's convinced that they're OK with no need to replace (I still plan to replace again soon 'cause I don't like cracks!). Neighbor/fellow 140'er Tom Reddeck and I have joked that mine seem to show cracking sooner than his, our only theory being that I'm maybe 600' closer to the coastal salt air (200+ miles away) than he is . FWIW, I've tried with and without the spacers and it makes no difference...in the cracking nor in the engine vibration (I do find that more washers are needed sans the spacers, as John mentioned). Mac

Thank you everybody for the tips!! I think they will make the process much easier when I am able to do it.