Hey Guys So my independant guy has been going over my exhaust system, and it turns out the bypass valve has been welded (didn't ask if it was open or closed, but I am assuming open)... He says it won't be possible to fix it, so it looks like I will be needing another valve... Does anyone have a spare (good working valve) that they would like to part with? Please PM me if available. Thanks!
Question - with the bypass valve welded open, would the car run lean or rich? I was told by the indep mechanic that the open valve has caused O2 sensors and thermocouples to go bad and the car is running LEAN - so not to drive till a new bypass is installed and the car tested again for any further faults... Is he right?
Neither, the engine runs closed loop (most of the time). What happens is that there are certain exhaust and intake resonances that get out of control below 3000 RPMs (+/-) and the car will run poorly (bucking and jerking) just over idle and into the lower 2s. If you don't putter around town, you might not notice it much. Maybe. {Speculation} If enough exhaust gas flow out of the expansion chamber into the y-pipe instead of going to the main cats, the main cats can drop below the temperature they "do their thing". If the engine has a problem (exhaust valve guides leaking oil) the cats can get clogged up due to the Cats having insufficient temperature; durring this time at insufficient temperatures, the O2 sensor and thermocouple might get loaded up with the same crap that is taking out the cats.{/Speculation}
I tried removing the Bypass, but it wouldn't come out... I removed the two long bolts holding the Y pipe and exhaust (tubi) together with the bypass in the middle... the bolts are out, but the valve won't even move a millimeter... So I've taken pictures with the bypass as it is installed... 1) you can see some welding on the side, I've taken a close up as well. Is this normal? Or is this welded in the open position? 2) The valve (phyisically pushing up and down) does not seem to be moving anything - I dont see any stem or anything move except the big valve face thing... Ideas to remove it? Ideas to fix it? Thanks!! Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
From what I can see, the valve can be 'unwelded'. Before this effort is started, you would want to find out why it was welded open. Maybe the vacuum actuator was no longer functional? Check the actuator and see if it holds vacuum. Use one of those hand vacuum pumps with a little gauge on it. If you do not have one and don't want to buy one, you can put a clean hose on it and use your mouth to pull vacuum. You just want to make sure the internal diaphram is not torn. The valve body has a raised lip that goes into the forward y-pipe and the muffler has the same feature, that fits into the back of the valve. That is why you cannot just take it out. Loosen the lower muffler clamps, just rearward of the cats. Then you can pull the muffler back and pull out the valve.
What would I be looking for by applying a vacuum to the valve? With the side welded, I will not be seeing any movement regardless of if the actuator is torn or not. Am I just looking to see if the valve holds a vacuum/isnt leaking to the outside?
You are correct, you will not see any movement. You just want to find out if the actuator holds vaccum. If it does not, it will be very obvious.
Ok Guys... I tried the vacuum test and the bypass appears to be working... on applying vacuum, it moved downwards (about a mm single its already open)... the vacuum held (pipe was stuck to my tounge... yum!!)... then on releasing the vacuum the valve tried to move upwards, moved about a mm and then stopped because of the weld... Still having trouble removing the bypass valve though... Which bolts on the exhasut do I need to undo to remove the bypass... I dont want to remove them all and have the exhaust fall off the back end... A? B? or C? Thanks! Image Unavailable, Please Login
Good to hear your actuator is functional! You should only have to remove 'B' and maybe just the forward bolt of 'A' while only loosening the rear 'A'. That should allow the muffler to move plenty rearward.
Use a dremel cut off wheel to cut the weld. Then work the edges down and smooth with a small round grinding attachment. You may just be able to carefully use a pry bar to open the gap enough to get the valve out.
That removal was a b**ch... since the valve was stuck open, moving the muffler with a prybar didn't help... I ended up removing one side from the cat to get enough space... but got it off!! Post surgery, this is what the bypass looks like... can anyone confirm if the 'gas filled orings/gaskets' are already attached or will I need to get them? I've labeled the sides 'inner' and 'outer' so incase one is missing, you guys can point out where... Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
They are both intact. They are usually as hard to get out as the bypass valve. Just be careful not to puncture or crease one and they are expensive little buggers for what they are. The good news is that it looks like the weld was easy enough to break and shouldn't really impact the long term use of the valve.
It's gonna rattle. Prob why it was welded while still functional. Lengthen the stem by two turns before re-install.
"by two turns" ?? Could you be a little more specific... Im not sure what/how you meant... Thanks!! And yes, it DID rattle last night... (I installed it and drove the car a little and could hear the rattle...) too bad I didn't read this thread before installing... Back to the garage tonight.....
Maybe a spring that has just enough tension to stop the rattle, yet not enough to stop the diaphragm from working.
Thanks everyone!! Now I have a working valve! But the vacuum isnt working... so I will be starting a new thread on that...
Before you go too far, you may want to give this a try. It worked on mine for quite a while but I eventually went with the Capristo valve. http://www.ferrarichat.com/forum/showthread.php?t=302716&highlight=355+bypass+valve+rattle
