355 I’m about done with this car…Capristo Bypass Exhaust Valve Issue (Videos)

I cannot catch a break with this car. I’m on the verge of selling it, but I really don’t want to…

Just got it back from getting a new clutch and now there’s an issue with the Capristo bypass valve. This was just installed less than 500 miles ago when I had my engine out service completed. Car sounds odd and the rattle/culprit seems to be coming from the Capristo unit. Any and all insights would be appreciated. Videos below

 

Sent videos to a mechanic buddy who said "seems like it's either a vacuum issue or an internal diaphragm issue"

 

That would have been removed during the clutch install so most likely connections need to be checked. Capristo warns on their website that if it doesn't get full vacuum it can rattle.

 

I wouldn’t be selling the car based on this. I know it can be trying at times but it looks like a simple fix. You have probably been working through a history of deferred maintenance issues and our fixes and repairs due to the age of the vehicle. Don’t stop now.

Keep persisting it will pay off.

 

I appreciate the words but the frustration is not from this small issue. It has been an 18+ month sequence of events. Some of which is just bad luck and some of which is attributed to owning a 30 year old exotic. It's my childhood dream car, I don't want to sell it. And if I did, I would lose my ass on it for how much money I've put into it since I bought it in March of '24. I literally have not had 2 consecutive months to enjoy it without an issue popping up. We will see if I can finally enjoy the ownership experience after this gets resolved. I've replaced/upgraded/fixed/serviced almost everything you can on this car since I bought it. Hoping for smooth sailing after this.

 

I just drove mine 1500 mostly trouble free miles on a rally and it was probably the greatest car related experience of my life. I did not take it easy at all whatsoever.

Remember, it is a 30 year old race car for the road, but persist and you'll be rewarded with one of the all time great driving experiences available to us.

 

Yes I wasn’t talking about just this issue. I have owned a couple F355’s spanning a decade I’m well aware of how testing they can be. But the result when they are sorted is well worth it. Keep going.

 

Check the small metal tube where that vacuum line attaches. Mine failed years ago.

Check the other side of that little metal tube where the vacuum line attaches to the vacuum tank.

That tube cracks.....

Check the vacuum tank connections. The tank connectors crack. Mine failed years ago.

I bought a new tank and ran a vacuum line right to the bypass valve skipping the little metal tube.

It's the tiny little tube poking up between the numbers #34 & #37

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Sorry to hear your woes, i skirtted around this issue to some degree and just bought a 328 which is my dream car so i completely understand how painful the experience might be for you in constantly dealing with issues and thinking of letting it go, both of which sound pocket and heart breaking. I have also just had a Capristo valved exhuast fitted to my 328, these answers are very useful and i am sure the support here will help you find a solution to any difficulties. I can't imagine there is much left to go wrong after 18 months of repairs, talk to forum members here to possibly find someone else, fully qualified for a second opinion on where your car sits, at least it may give you a better idea of how much still needs attention and the cost involved. My 2cents.

 

4 weeks after buying the car I had a private track rental and took the 355 out there. I fell in love with the car. It was fantastic on circuit and such a gem to drive. No issues and drove beautifully. Drove it for another month or 2 after that and pure bliss. Following that was a 10 month engine out service fiasco, then issue after issue after issue.

I know how good the car is when it's good, and I'm trying to channel those memories, but they are fading. Hopefully I am close to getting back there!

 

Thanks very much for the words and the info above. I will look into that