B230FT losing/lost vacuum Edit:Fixed

[herbiedriver]

Rebuilt B230FT, new pistons, rings, bearings, head machined, etc. About 4000 miles on the rebuild, running 10 psi (TDO4 13C).

Since the rebuild the car had 18-19inHg vacuum at idle and go to 21-22 on deceleration, on an aftermarket vacuum and boost gauge. Last week the car dropped to 14inHg thought it was because of the AC being used. Yesterday the car started idling at 10inHg and hits 12 on deceleration, the needle is steady, no oscillation. The dash turbo gauge shows the same.

Did a smoke test to check for vacuum leaks, found one minor leak at the IAC, fixed that and checked again, no leaks found. Car seems to run fine, a bit of hesitation on throttle that wasn't there before.

EDIT Fixed in case someone else runs into this. It was the vacuum check valve for the interior heat flaps. Would leak under vacuum, hold under boost.... phew.

 

[hessam69]

Where is the vacuum check valve located?

 

[herbiedriver]

Mine was on the firewall, almost center and has a premolded elbow attaching it to the vacuum line from the manifold.

 

[Khrrck]

On American N/A 240 it's in a vacuum line that runs from intake manifold, then through the firewall on the passenger side of the car. I'm not sure if it is different for RHD cars but I don't believe any other vacuum lines go through the firewall unless you have a boost gauge, so it should be easy to find.