Vortech mondo Blow off Valve break down.

[SniveTroll]

a blow off valve - Its purpose is to prevent compressor surge, and reduce wear on the turbocharger and engine. Blowoff valves relieve the damaging effects of compressor "surge loading" by allowing the compressed air to vent to the atmosphere, making a distinct hissing sound, or recirculated into the intake upstream of the compressor inlet.

-reference wikipedia

operation:

a BOV should open in 14.7 atmospheric pressure of 5hg of vacuum at manifold pressure. under Wide open throttle the valve plunger closes and creates a boosted environment depending on power added application(turbo or supercharged). when throttle plate is closed the valve opens and dumps the excess air.

most common break down illustration is:

here is the example of diaphram

adjustment screw plate & tensioned spring.

valve plunger with o-ring seal

adjustment screw

some valves have filters to help the valve with reliability. it prevent materials from damaging the diaphram.

Most common issues with these valves are boost creep, sticking open and fluttering.

a. boost creep: in cases theres a rubber o-ring in the circumference of the plunger. they break or come out during open and closing.

b. fluttering: the diaphram has tears or holes. the valve can not "accordion/bellow" as needed to open or close. \

c. sticking open: the plunger becomes disconnected from plunger valve stem or valve guide is galled.

mine in particular was stuck open.

i cleaned valve stem with brake cleaner and 220 grit sandpaper. i then mixed 2 part jb weld.