580/657/717 Exhaust Pipe Bolts

[wabash]

Referring to the three bolts and one stud/nut that holds the expansion pipe to the manifold. Here's the typical story. Bolts are fine never a problem for years then something happens requiring removal of the pipe and now after reassembly the bolts won't stay tight or they break. I've had both and currently have one I'm battling. Assembly followed proper service manual instructions and torquing. I've scrubbed the forums and browsed various kits and here are several options I've found.

1. OSD manifold repair kit. Four brass bushings to tighten up the holes in the pipe flange new bolts and nut with four thick washers. I'm assuming you don't use lock washers but still use blue loctite.

2. Replace the three 8mm bolts with 10mm. Stud stays the same? Not sure you could get a bigger nut in there. Also thick flat washers, no lock washers. Blue loctite.

3. Instead of blue loctite use high temp RTV on the threads

4. No loctite. Nevrseez on the threads and use nordlock washers instead of lock washers.

Last one I had trouble with I just used new bolts and stud and doused the threads in blue loctite. It has held good for about three years and has only half the rubber bushing in the pipe mount. This one was fine until I took it apart to fix a manifold to cylinder gasket. Now they won't stay tight. Has a good rubber bushing in it however I did find it loose once.


Suggestions/ experience?

 

[racerxxx]

Now for the big question......when you had that pipe off did you fix the bushings that mount that prior to the side of the exhaust manifold? Some are a single M8 screw as some are a dual are config. If you leave those out, or the bushings are worn, or the metal spacer in the bushings is gone or the washers our washer are missing, the weight of the pipe and the shaking of the pipe over wakes etc....Will snap those screws and studs. Use the recommended liquid fastener. I've seen this more than once. I always use blue loctite on all those screws for the pipe. It also helps that the holes and threads are uber clean and grease free to ensure the loctite works properly.

 

[mikidymac]

I totally agree with Racer. Never use RTV on bolt threads.
I use ThreeBond 1360 on every fastener on any ski or motorcycle.

It is a medium strength high temperature and in 25 years of using it I have never had a single bolt come loose.

 

[wabash]

Got two new bushing and spacer kits coming. Planning on addressing that. It seems like the bolt coming loose in the bushing is what starts the whole thing.

 

[racerxxx]

Yes, when the bushings are correct and the sleeve is installed you can torque the fastener correctly. Basically, the washers "bind" on the metal sleeve inside the bushings and allow the bolt to reach torque. Then the bushings take out the vibrations.

 

[wabash]

So fix the bushing and go back with 8mm bolts and blue loctite.

Mikidy I like that TB1360. Have you seen it to be better than blue loctite?

 

[wabash]

Anyone tried the new tape thread lock from Loctite? I used to get twist up sticks of blue and it was great but now I can't find it. Used the gel but it's messier than the liquid. The tape looks cool you can apply it to all the bolts in prep you don't have to do one at a time and easier to control where it goes.

 

[racerxxx]

I'm old school. Loctite 242. I've been using it for the last 20 some years at work, never lets me down. You saw where I posted the threads and tapped holes need to be spotless? The cleaner the area the better bond it makes.

 

[wabash]

Yep. Been using loctite/permeatex for 20+yrs. prob more permatex but don't see any difference. Clean is key however this last repair I had to do on the water while at the lake on vacation. Had basic tools and supplies. Holes were not as clean as they could've been. Also didn't get the bushing bolt as tight as needed on the first try. It backed out but was stiff due to the loctite. Didn't notice it till I put a wrench on it. I tightened it down and now the flange bolts are staying tight. Will take it all apart and do it up right when I get back home. Just looking for any suggestions that may be different than my own experience.