I have a question. I'm replacing my exhaust manifold (header). The repair manual say to replace the self-locking nut. Is that really necessary? What's the difference between self lock nut and regular one? I have a 1994 civic ex coupe.

 

Are you talking about the 9 nuts that attach the header flange to the front of the head? If so, I don't think replacing them is necessary. I've never replaced the nuts and they still work fine after the couple times i've taken the header off.
A regular nut is not a good idea. A self lock nut is a special nut designed in such a way that it is harder to come loose than a regular nut. Make sure if you replace the nuts that you use the special Honda ones. Standard lock nuts will not work because they have a plastic "locking" material that cannot withstand the heat. The Honda ones are all metal and have a specially designed "locking" design. Also, after you put those nuts on and torque them down, keep your eye on them for the next couple hundred miles and re-torque them as necessary. The heat from engine use will cause them to come loose but after a few times of torquing them down they should stay.

 

A self locking nut prevents it from coming loose, it's also called a flared nut. because of the hot and cold expansion in the metal they would just come loose.

Another thing you could do, what I did with my midway bolts on my header if you can't find any flared nuts with that size and pitch. Was I bought some stainless steel reg nuts, than used lock washers. Been holding up fine.

 

they wear over time from rust and putting on and off. If they aren't worn don't worry about it.

 

Quote:

Originally Posted by trustdestruction

Are you talking about the 9 nuts that attach the header flange to the front of the head? If so, I don't think replacing them is necessary. I've never replaced the nuts and they still work fine after the couple times i've taken the header off.
A regular nut is not a good idea. A self lock nut is a special nut designed in such a way that it is harder to come loose than a regular nut. Make sure if you replace the nuts that you use the special Honda ones. Standard lock nuts will not work because they have a plastic "locking" material that cannot withstand the heat. The Honda ones are all metal and have a specially designed "locking" design. Also, after you put those nuts on and torque them down, keep your eye on them for the next couple hundred miles and re-torque them as necessary. The heat from engine use will cause them to come loose but after a few times of torquing them down they should stay.

yes I am referring to the 9 nut attach to the header flange. The manual point to one self locking nut only. Not sure if it was just that nut on the end is self locking or all 9 nut are self locking. Is this self locking nut a one time use? If you take it off can you reuse it again provide that its still in good condition. Will it still lock when you reuse it?
Sorry I just don't want to do the job twice and spend money on unnecessary parts. They cost $3.95 a nut at Honda!! Stupid manual is not clear.

 

if they're still in good condition they are probably reusable. all nine are self locking.