A new twist on the bypass valve fix

I think mine may have just started to rattle, I will try the re-tension way first, then will move to this if that doesn't last.

Thanks for taking the time to post this, it's great to have this sort of information available .

 

Mine doesn't rattle at all....Oh, yea, cause I don't have the valve on my car....lol

Nice fix Monte!!!

 

Looks like it will work fine Monte ........... when I 'used to have' a by-pass valve ..... I did something similar (slightly open) to 'kill the buzz' ......... I passed emissions no problem ........

+1 ........... 'no by-pass' is the way to go ........... I have actually noticed the overall vibrations of the engine have gone down a bit on my car ........ also the shifter 'used' to buzz hard on my car at certain RPMs .......... that shifter buzz has been reduced about 90% since I installed my new exhaust ...........

 

Thanks monteman. i used your method to stop a by pass rattle. It worked a treat, good advice.

 

Have you tried increasing the "pre-load" tension? All you have to do is loosen the nut near the ball joint. Then remove the three screws holding the diaphram, and then lift it up, and unscrew the diaphram two turns, maybe three, then reinstall on the base, and retighten the locking nut near the ball joint. This extra tension can often times eliminate the rattle, which is usually due to the valve not fully closing, from low tension.

Your fix works, because you are taking out the "slop". The only concern is how much exhaust is getting past. On an OBDII car, there is a thermoprobe just past the valve, and that is telling the Motronic whether the valve is open or closed based on temperature. If it is hot when it should not be (should be closed) it could throw a "check engine" light.

You should have no problem passing an emission test. Most tests are done by connecting to the OBDII test port. As long as your CE light is off, then you will pass.

 

Thats where it belongs.

 

Monte,
Sorry, did not read thoroughly your introduction to the problem, only your solution!
My bad...

Dave

 

BTW, I STILL had a mild exhaust rattle around 3k rpm that was intermittent after fixing the really bad rattle at idle by increasing tension on the valve. I decided to try the new Capristo valve a couple years ago and it works great, but did not totally eliminate my annoying and intermittent rattle. I finally got it diagnosed this summer at Ferrari of Seattle as a loose baffle inside my muffler! Fortunately they made me a great deal on a low mileage one they had in their basement.

So along with the valve, the muffler AND the heat shields on the Y pipe can also cause metallic rattle sounds. (I previously had the heatshields tacked down on my Y pipe)

 

Yes that solution has always been the first port of call for the 355s rattling bypass valve problem for years. However that method works only in ideal world conditions.
With the rattling bypass valve in hand, and due to the ball joint and the 3 nuts holding the vacuum/diaphragm having never been loosened or removed since the car was brand new. There was some corrosion bonding them in place, regardless of soaking them in penetrating oil they were buggers to remove. So to avoid the studs sheering i used Monteman's method which worked a treat and now the butterfly valve operating rod is now under slight tension. Now the valve has zero rattles and the engine bay sounds great again.
Just for information, holding an unmodded bypass valve up, one can clearly see that the butterfly valve does not completely block of the tube 100%, there are gaps around the edges. So when after i had modded the bypass valve, there was hardly very little difference in the gap along the edges of the butterfly valve. So any emission issues would not be a problem.