I was driving on the freeway (75-85 mph) when all of a sudden, the transmission shut down. Luckily, I was able to get over to the shoulder. I put it in neutral and coasted to a call box. Tried turning it off/on. It started and drove rough (later found out that's "limp mode.") Turns out it was a faulty bypass valve, and not uncommon.

 

Thread moved and title changed to make it more descriptive

 

yep... I did.. had to change bypass, new software and some other darn thing...

 

Yes. It has happened to lots of us. My personal opinion is that there are a LOT more CooperSs that have bad bypass valves and the drivers don't drive them hard enough to notice. It's not like the car will idle or run bad so if someone doesn't accelerate to the redline they will never know. I asked my service advisor if they routinely check the valves and he said not unless there is a complaint. I suggested lots of people will notice this after their warranty runs out even though the valve went bad within the 50,000 mile warranty. He just smiled. I did not.

Rich Wolfson

 

Thanks Dave. Still learning...

 

Had a bypass valve go bad on mine, car wasnt making any power and wouldnt get out of its own way .

It all happened under warranty so dealer fixed it.

 

This happened to my Mini as well. The bypass valve stays open so the boost pressure is released. It drives like a standard Cooper but with a dragging supercharger taking 30 more hp away. My car would shut down over 4k rpm with more than 1/2 throttle. The power loss is noticable right from the start. My gas milage improved though. The dealer replaced the bypass valve under warranty. The valve isn't so expensive, but the labor to get to it is. From what I read this is a common problem.

 

I got a new BP Valve from Detroit Tuned. $125.00 and made all the difference in the world

 

I'm interested, how difficult was it to change out your bypass valve? I'm just guessing that you did it yourself.

 

It's not difficult to DIY. No special tools needed as well. Just a couple of spanners and follow instructions given by Detroit tuned and you'd be a happy camper!

 

It wasn't too bad. A friend & I did it in about 1hr. Don't even try to re-use the oem hose clamps. I even have the same small channel locks Randy uses and still a bi-ch.

 

Cool, ordered one from Detroit today! Thanks!

 

Hi,

I've got a car that has a really rough idle and only seems to start now in limp mode - could the bypass value on my mcs gone bad - how can i check if this happened?

Thank you

TopgearNut

 

so for Idle, it would be open anyway, so a bad BPV shouldn't affect idle. It will affect operation when it's supposed to close. When you put your foot down.

If you have a rought idle, it's probably somethings else....

Matt