johnf95111

I've been running test on my vacuum lines for the HVAC system. All lines, blue, orange, white, green & yellow hold vacuum. I checked the vacuum at the black supply line on the interior and get about 18psi at idle.

With the car off, I checked the black vacuum line leading to the interior and vacuum is held as I would expect based on the previous tests. But, when I start the car, the same test fails with the vacuum falling off quickly. With the car running I checked all the interior colored lines again. All are good.

I'm going to pull the vacum console next. Is there a common point of failure here?

Thanks,

Johh Fagerlund
'89GT (getting healthier by the day)

IcemanG17

18in at idle is not bad.......on Sunday I was reading 23in at the heater valve under the hood? Did you check the condition of the 4 way rubber "T" & check the blue-black check valve (they typically fail)?

So when the car is off all the pods hold...but as soon as the car starts there is a leak....this is really odd? I was thinking the black rubber vacuum supply manifold that the black line plugs into.....but if that leaked it would do it all the time, not just when the car is on? Its possible one of the solenoids on the strip is cracked internally and leaking......you could check it by turning each solenoid on when its hooked up to the mityvac.....and see if it sends vacuum like it should....but remember the default mode of the solenoids (when they fail) is to send vacuum all the time.....but my guess is one is broken and causing a leak......but again I would think it would leak all the time regardless of if its activated or not?? Very odd....it will take some troubling shooting to fix!

johnf95111

All hoses and rubber vacuum fittings were just replaced when I R&Rd the intake manifold.

I think I found the cluprit(s). The center comb flap actuator is now looking bad and the heater control valve has a smidge of a leak. Looks like I'll be replaceing both of those.

Why the mystery before???? Yo no say.

Thanks for the thoughts.

-j