Corroded Engine Mount Frame

[Kevin McDole]

In a thread titled "Ceramic Coated Exhaust", SkyKing pondered: "I wonder how many others that have the P-models have had or are having surface erosion of the long upward tilting angle piece on the left side of their rear engine mount that sits next to the left-side exhaust and turbo?"

I took my digital camera out to my plane to check. Sure enough, the frame is showing surface corrosion. The picture is attached. My shop (who is new to this plane), said that is something they would routinely touch up at annual.

Are others finding this to be a chronic problem? Does it need a heat shield, or will high temp paint handle the job?

For those with sharp eyes, I placed a quarter (25 cent coin) between the vertical exhaust and frame at the far left in this picture. This was intended to show the approximate clearance. I’d estimate the clearance is about 2/3rds the height of a quarter.

[GMAs]

well ya it would be good to put a sheld over the motor mount frame... but, you have to make is so it won't interfer with the natural resonance of the motor mount... ya they do move and quite a lot let me add... so if you are going to put one on... I suggest that you not make it ridged... instead only attach it at two or three at the most places... and if you make them up.. you can use alu.. or SS... makes no difference except when the mechanic goes to work on it... then he will find SS has a sharp edge.. and cuts real well... better than safety wire... Alu on the other hand does a good job... and is lighter weight.. but, it will change color and no paint won't stick to it...

Some of the other heat shelds we have seen...

If you get the red fire sleaving from the hose shop... it has a red silicone outer layer and a big bunch of aspestos and other fabrics in it... then if you carefully slit it lengthwise... and put it around the mount tube... well it should go around the motor mounts where its real hot.. and keep them from getting hot... so long as the air is moving thru... after all red silicone will stand up to about 450 deg F... before it starts to change color... after that all bets are off... to hold it on... we have seen them use safety wire.. wrapped... no nlyon wire wraps are not good... they melt... and we have seen them use adle clamps as well as some that they made themsleves out of a strip of alu or ss... again alu is easyer to work with...

the fancy ones are the shield plates... ya they are bent on a press... and they make some real fancy heat getters... they will work in places where it get a lot hotter than 450... as the attached ends are away from the heat effected zone on the shield and thus have time for the heat to disapate some what into the passing air... but, they keep the tubing cool... and keep it from rusting because of it... again they use adle clamps the ones with the red silicone rubber and are made out of alu... commercial clamps... the clamp is tightened but, the sheld can pivot on the screw with its spacer to keep it away from the tube... about 1/8 to 1/4 inch is about all that is needed... If you want I can make up a small drawing and you can make your own... but, again you don't want to restrict the movement of the mount.. nor do you want to stiffen it.. as it will transfer the loading to some other part that will break....

As to cleaning the mounts... nothing like a good metal (red) scotch bright pad... or in the worst case some SS wire brushing... try and keep away from the power tools...which may remove metal... you want to keep the tubing clean and not allow it to rust.. or pit... as it will weaken it in that area... a good coat of barb-q or hot rod high temp paint is all that you need... some are self priming paints.. i.e no primer is needed... but, one word of caution here... about heat paints... you know them ones that are also refered to as powder paint... they take temp to cook them on... good.. but, they also require you to take the mount off.. and put it in a oven... not good... as it could warp it out of shape... and you will never get the thing back on... and if you did.. it would stand a good chance of cracking... but, with powder paint.. because they are so thick.. you would not see the crack... so we recomend that you stay away from them... a good high temp paint from the local hardware store is just as good... and also no epoxy paints... or water colors... as some paints now are made up with water in them... it will make the mount go the other way... and rust under the paint... so be careful what you buy... If you want to try it out... first.. climb under the car and spray it on the exhaust pipe behind the cat converter... drive around and see if it stays.. on the pipe and the underside of the car where you accidently goofed and got some on too... smile... testing on the plane is not what I would recomend.. smile.. the car is cheeper and it doesn't get as hot.. but, close... besides who is going to go looking under your car for paint marks...smile... ya I know some like larry would.. hmmmmm... gota talk to that boy...

And who is to say it has to be black... the paint comes in a lot of colors... ford engine blue... chevy red... dodge green... VW.. well lets stop at dodge... smile... yellow is nice ... and so is grey... but, as always ... it came black.. so it probably would be better to keep it that color...

As to the shelds... well here if you used alu.. you can alodine or send it out and have it anodized to a dark color...... or just buff it up... it will shine like chrome... with metal all..polish.. of course the SS stuff will have its own color and stay that way for life if its not cooked... we perfer the alodining as its a simple way... and keeps the parts from corroding in a moisture enviroment some what... and it kinda looks like a golden green finish... of course you could alway Hope this helps on the subject... of heat shelds and motor mounts... GMAs