Muffler bolts keep coming loose

Esox07 · #1 03-30-2020, 01:05 PM

Starting up my mower for the first time this year, it sounded awful loud. Sure enough, I took over the cover to look and find that one of the exhaust bolts holding the muffler to the exhaust manifold is missing and one is about 1/4 of the way out. This happened year or two ago as well. At the time, I bought a new bolt and gasket and torqued them both down to specs. Now this year, same thing. I don't want to have to replace bolts and gaskets every year or two. So, what is the best fix. I thought loctite, but I do want to be able to remove them later on if necessary and then you have the heat issue as well. I read that some people use the High Heat Red RTV silicone. What would you guys suggest?
Bruce

cooperino · #2 03-30-2020, 01:50 PM

Quote:

Originally Posted by Esox07

Starting up my mower for the first time this year, it sounded awful loud. Sure enough, I took over the cover to look and find that one of the exhaust bolts holding the muffler to the exhaust manifold is missing and one is about 1/4 of the way out. This happened year or two ago as well. At the time, I bought a new bolt and gasket and torqued them both down to specs. Now this year, same thing. I don't want to have to replace bolts and gaskets every year or two. So, what is the best fix. I thought loctite, but I do want to be able to remove them later on if necessary and then you have the heat issue as well. I read that some people use the High Heat Red RTV silicone. What would you guys suggest?
Bruce

Did you use lock washers?

ironman · #3 03-30-2020, 04:42 PM

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CADplans · #4 03-30-2020, 04:45 PM

The bolts come loose because of corrosion of the threads that the bolts screw into,,
With the threads oversize, the bolts loosen easily,

I like coop's idea of lock washers,, I might add flat washers also.

You are trying to stop the vibration,,

Well, there is one other answer,,

You could replace the block, is that cheaper than new bolts?

RLause · #5 03-30-2020, 05:03 PM

I like the safety wires

Mike McKown · #6 03-30-2020, 05:24 PM

Replace the bolts with studs and run them in as far as they will go and I don't mean with your fingers.. Cut to length and then use nuts with lock washers.

ironman · #7 03-30-2020, 05:55 PM

Quote:

Originally Posted by Mike McKown

Replace the bolts with studs and run them in as far as they will go and I don't mean with your fingers.. Cut to length and then use nuts with lock washers.

Good idea if there is room to maneuver the muffler in and get it on the studs.

cooperino · #8 03-31-2020, 08:57 AM

Quote:

Originally Posted by ironman

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I like these also....

ol'George · #9 03-31-2020, 09:49 AM

I would suggest to re torque the bolts after it is run a while.
Also suggest look to see if there is an additional support for the muffler, and that it is attached and tight.
From the look of it,I would think support is needed besides just 2 bolts on the pipe flange.
Also forget the silly cone, it will turn to smoke in 60 seconds.
I'm not a fan of loctite in exhaust situations and aluminum situations, but it might work.
I like the idea of bend over retaining clips.
Spring lock washers in my experience on exhaust manifolds, loose their spring at those temps.
If it were me, I'd replace the gasket/bolts torque to spec, run it a while, like a regular mowing or two, and retorque, that should work.

ironman · #10 03-31-2020, 09:52 AM

Quote:

Originally Posted by ol'George

I would suggest to re torque the bolts after it is run a while.
Also suggest look to see if there is an additional support for the muffler, and that it is attached and tight.
From the look of it,I would think support is needed besides just 2 bolts on the pipe flange

Other support comes from 1/4" bolts (#6 in the drawing above).
They go into the cylinder head and perhaps his could be broken off.