I recently replaced most of my turbo hoses and the small "delay valve" ( the red and gray valve sitting atop the valve cover on the B230FT). The car runs great. Boost is where it should be, no hesitation or stumbling, ... steady idle.
Decent gas mileage...just over 20.

One annoying turbo problem remains. I'm getting a high-pitched whine from the "check valve" (aka CBV valve I believe). This is the large valve sitting between the AMM and the radiator with several vacuum hoses flowing to and fro. The valve has an adjusting nut and bolt on top, right in the center of the device. If you tighten the bolt, the high-pitched whine increases in pitch. If you loosen the bolt, the whine gets lower in pitch. I suspect there is a diaghram inside that device and I suspect that diaghram is leaking, which is causing the whine.

Do you guys know what that valve does? If the whine indicates a leak, should and can it be repaired or replaced? Is there a "rebuild kit" available? I believe Bosch makes a replacement part that performs the same function, but uses a different design. I've heard the Volvo replacement part is very pricey.

Thoughts and tips would be appreciated.

PS, thanks to Steve and others who recently informed me how to replace my FPR.
New one was $15... FCP Groton. Works great.

I believe that is the exhaust recirculation valve. My 90 turbo had a leak, found by using a vac gauge. I took mine apart and it wasn't the diaphragm but a pin hole leak where the plastic mold cut off was. I was able to seal it with some super glue. It's been 5 years.

This is from the FAQ's in the turbo section.

Replacement Diaphragms for CBV. Various turbo rebuilders carry the diaphragm repair kits for reasonable prices. Check Rick Banas at D&W Diesel (r.banas@dwdiesel.com) for Mitsu diaphragms and some Garretts.
--
"Be blessed in your quest'' 89 764 (110K), '94 940T (180K) , '92 745T (totaled 2-10-05 RIP)

How does one get to this diaphgram.
I had this part in my hand few times,
and can't see how diaphgram can possibly
come out. It's a sealed unit.
Also, there are no plastic parts to it
that can be glued.
It's all metal.

Not sure. I got that info from the 700/900 FAQ's. It does mention a way to check that part though.

Quote:
To test the unit use a rubber hose connected to the CBV and suck on the end of the hose. When you have sucked as much air out of the CBV as you can, stick the tip of your tongue in the end of the hose. Wait a minute and see it it holds the vacuum. If it doesn' hold vacuum, it has a bad diaphram and needs replacement.
--
"Be blessed in your quest'' 89 764 (110K), '94 940T (180K) , '92 745T (totaled 2-10-05 RIP)