96 850T CBV Diaphragm Replacement?

Post by **RussB** » 24 Jul 2014, 08:54

I need to replace the CBV diaphragm in my car. It flutters and struggles to hold boost. I have the Mitsubishi part here. My question is, can it be replaced with the turbo on the car? Looks like a tight fit in there...

Post by **jblackburn** » 24 Jul 2014, 09:05

It can, but it's a PITA.

I removed the heater hose, which dumped out a bunch of coolant, but made it much easier to access.

https://www.matthewsvolvosite.com/forums ... =1&t=38338

http://www.ipdusa.com/files/product/507 ... %20WEB.PDF

Post by **erikv11** » 24 Jul 2014, 12:01

Definitely, I have done a few this way. I lay on top of the engine and it is kind of hassle, but mostly the small-spaces-big-fingers--dropped-bolts kind of frustration, not from anything that is physically difficult. You will want 1/4 drive sockets and a swivel.

Never messed with the heater hoses to do it, just come in from the top. Remove the heat shield and probably the coupler.

Post by **RussB** » 24 Jul 2014, 15:03

Thanks folks!

I just did the swap. I removed the heat shield along with the turbo inlet and outlet piping. I cleaned up the area with brake cleaner and an old toothbrush. The "tool-to have" was a 10mm ratcheting swivel box end wrench. It was tight fit for sure!

Note the new diaphragm came with an O ring...you can see it sitting on the old unit. There was not an O ring in there, so I did not install it. Looked like there was no room (groove) for it

here's the 18 year old diaphragm...

Vlvspd · Post by **Vlvspd** » 28 Jul 2014, 08:41

What are the symptoms of a torn diaphragm? Mine may be due for replacement

Post by **rspi** » 28 Jul 2014, 10:23

Weak or over boosting. If you put a vacuum pump on it (loaner tool) it should build and hold vacuum. Same for the waste gate.

Post by **erikv11** » 28 Jul 2014, 11:48

Usually no symptoms at low boost, then when it gets above a certain level the boost leaks out. This shows up either as weak boost or as jerking due to the boost leaking out then rebuilding in succession. If the tear is big then the boost is weak (leaks out) throughout the range and the car has overall weak boost.

I don't think there is any way a torn CBV diaphragm can lead to overboosting, but maybe I am wrong there.

Post by **RussB** » 28 Jul 2014, 15:45

Vlvspd wrote:What are the symptoms of a torn diaphragm? Mine may be due for replacement

I was running a cone filter and a manual boost control (MBC) along with a boost gauge. I could see the boost fade when getting on it, and when I'd let up fast on the the throttle, I could hear the diaphragm flutter.

Now I can hear the turbo spool up faster, boost holds steady and the car has more power

Vlvspd · Post by **Vlvspd** » 29 Jul 2014, 04:05

It's time to replace mine then. It boosts up to 14 then fades down to 6 within about 4 seconds. I had been trying to find a leak in the piping or intercooler. Isn't it possibly to do a CBV delete and just add a recirculating BOV?