# Exhaust Manifold Bolts Coming Loose



## salarmi (Jul 10, 2006)

Have leaf vac 20 hp kohler recently had some work done on it and now I noitice when the engine heats up the exhaust manifold bolts loosen up, I asked the repair shop and they said they replaced the bolts. Anyone what is causing this and the fix?


Thanks


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## 30yearTech (Sep 14, 2006)

Make sure they are properly torqued and it should not be a problem.


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## paulr44 (Oct 14, 2008)

30yearTech said:


> Make sure they are properly torqued and it should not be a problem.


If I might add, we had the same (recurring) problem with older Magnums on Giant Vacs, 18 & 20 HP (1980s). We ended up using stainless steel Allen bolts. These had short, about 3" manifolds pointing upward, into a 5" or so pipe with the old pepperpot mufflers.
Paulr


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## salarmi (Jul 10, 2006)

Thanks!!! will try your suggestions !!


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## salarmi (Jul 10, 2006)

Anyone know how I would find out what the bolts should be torqued to?


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## paulr44 (Oct 14, 2008)

What model engine is it? CH20S, or M20S?


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## salarmi (Jul 10, 2006)

I think it is a CH20S is there a difference in torque between the two of the motors (M20S)
and tighten with motor hot?


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## paulr44 (Oct 14, 2008)

Per Kohler's repair manual:
Muffler Retaining Nuts Torque .................................. 24.4 N·m (216 in. lb.)
Torque the nuts cold. Knowing these engine well, I strongly cleaning the flanges on both sides well, using new gaskets and nuts, and replacing and studs showing wear or partially stipped threads. Kohler doesn't use locknuts, and we haven't had a problem with them loosening. If you want to procure locknuts, you'll need "crown" or "compression" type nuts. Nyloks would just melt. You can run it, and re-check the torque when cold, but as I indicated we haven't had a problem. We have numerous of these engines on Billygoat vacuums that we service for various customers.
Paul


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## paulr44 (Oct 14, 2008)

P.S. the studs & nuts are 8mm, NOT 5/16


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## paulr44 (Oct 14, 2008)

Wait, if you have bolts you may have an M20. An M20 has opposed cylinders -spark plugs point almost straight up, while a CH20 is a V-twin with spark plugs pointing pretty much straight out sideways. If a magnet hangs on the blower housing, it's an M20. A CH has a fiberglas resin housing. That will make a difference on bolt torque, as an M20 has a cast-iron block that the manifolds bolt to, and a CH20 has aluminum heads that the exhaust pipe bolts to. I gave you info. for the CH.


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## salarmi (Jul 10, 2006)

Hi Paul
do you have the bolt size / nut size and torque M20?


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## paulr44 (Oct 14, 2008)

Okay, I was tired - the M20 has cast-iron cylinders that the exhaust bolts to, the block is aluminum. Per Kohler's manual, TP-2204-B, it's 120 inch lbs. Seems kind of light considering the CH, with exhaust studs in aluminum calls for more. Been 20 years since we had the problem I described in prev. post. I don't remember if those are 5/16" or 3/8", but if you get a grade 8 bolt you can go here for general torque specs: http://dodgeram.org/tech/specs/bolts/SAE_bolts.html
Kohler publishes general specs in their repair manual, but you can't view that online at their site unless you're a dealer and logged in, but you can look up parts at www.kohlerplus.com - just click "enter as guest."
Can't hurt to throw some red loc-tite on 'em either.


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