Intake manifold won't stay connected

[Lzybmbjj30]

I bought new screws and nuts for the manifold and tightened them down but when I go to mow after a few minutes I look under the hood and they've fallen off and the muffler comes loose. Why does this keep happening and how can I prevent it?

 

[redmaher]

Intake or exhaust manifold?

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[redmaher]

Locktite

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[L.C. Gray]

If they're exhaust manifold bolts as well, I'd be afraid of using a chemical based lock due to the heat.

See what Stage 8 has that might fit. They're about the ultimate in fastener locking. Outside of that, drill the bolt heads and get out the safety wire pliers...

I had a truck that no matter what the factory did in design or dealer did in warranty repair, the oil cooler lines would not stay tight and dump the entire oil supply at most inconvenient times. After taking it back in several times with them doing nothing but tightening the lines up, I drilled the tube nuts and safety wired the fittings against each other. Never had an issue again.

 

[D2Cat]

Be sure you're using metric hardware.

 

[CountryBumkin]

Also, be sure to use a lock washer under the head of the bolt, or nut (if it uses a stud).