1968 wiper vacuum readings info and questions

[George W.]

Morning all and Happy 4th

Problem:
Wiper door does not open or close with vacuum system (slight "help" on actuator rod does initiate both opening and closing.)
Wiper motor works properly if door open, low/high/park.

Vacuum readings obtained:

19" from rear intake port at 750 rpm idle, (shop temp 80 degrees, 1,700' elevation, 427/390 running a rec. port 3x2 setup on oval port heads, lowered compression pistons installed 25 years ago---150#'s each cylinder, unknown cam grind--hydraulic.)

11" coming to relay mounted on inner fender.

4"/5" coming to either side of wiper door actuator.

Headlights operate a bit slow, (have not checked readings to them)

What I have done so far:

Pulled lower left dash and confirmed proper routing of all hoses and "reverse" checked each hose for leaks--none found.
Lubricated the wiper door hinge pivots
Changed out relay on inner fender ( got worse readings to the door actuator ---I have more of these relays, how do I bench test these?
Tested limit switch on cowl---good
tested override switch under dash--good
Manuel vacuum ports under dash operate headlight doors, but not wiper door.



Questions:

1) How much vacuum should be getting to either side of the wiper door actuator for proper function?

2) Why do I have 19" manifold vacuum, yet only 11" from the storage tank getting to the relay?

3) Any suggestions?

Thank you,
George
You can text or call 210-748-4693 if you'd like

[Bob D.]

Re: 1968 wiper vacuum readings info and questions

George

To bench test your relays I usually follow these steps. Remove the filter on the bottom so you can see the bottom of the plunger. Apply vacuum to the small port on the top and see if the plunger moves and that the diaphragm will hold vacuum. After you have done that cover the top plastic port and you have to apply vacuum to the top metal port and the center plastic port. The upper plastic port should hold vacuum. The last of the is to apply vacuum to the center plastic port while covering the bottom plastic port. It should hold vacuum. If any of the ports do not hold vacuum, your relay will not work properly.

Good Luck.

Bob

[George W.]

Re: 1968 wiper vacuum readings info and questions

Thank you
back at it tomorrow

[Bob D.]

Re: 1968 wiper vacuum readings info and questions

George

If you have more questions let me know and I will send you a PM.

Bob

[Curt S.]

Re: 1968 wiper vacuum readings info and questions

I had a similar situation on my 69 427/435. It turned out to be a leak in the underneath seam of the vacuum tank. I took the tank to a gas tank renu shop. He found it repaired the tank and the system has worked flawlessly since . When you said you had a significant vacuum loss at the tank ,I thought this might help. If your car has power brakes, the removal of the tank is a character builder. Hope this helps. Curt

[George W.]

Re: 1968 wiper vacuum readings info and questions

Thanks Curt,
the supply tank is holding perfectly
g

[George W.]

Re: 1968 wiper vacuum readings info and questions

Success
Tested the 15 odd relays I had in a box and found only one that 'passed" the test procedure (thank you Bob)
Can these relays be rebuilt?
New vacuum readings:
19 from intake manifold
11 from storage tank
9 to each side of wiper door actuator
All systems go
Thanks all
G

[Bob D.]

Re: 1968 wiper vacuum readings info and questions

George

Yes the relays can be rebuilt. Send me a PM and I can give you the details.

Bob