Test A4LD Vac Modulator

[stfree]

Hello all,

I'm trying to determine what to expect in applying a vacuum to a suspect vacuum modulator on a A4LD '90 Ranger. Should I be able to pump a specific number of inches of vac and expect it to hold? What I see now is that I can rapidly pump down to about 10" of vac but it bleeds off within 3-4 seconds. I'm connected directly to the device straight off the pump with a known good hose.

Thanks

 

[BrooklynBay]

It probably has a ruptured diaphragm if it can't maintain vacuum.

 

[markhenry63]

Would this failure to hold vacuum create a problem shifting from 1-2?

 

[BrooklynBay]

Yes. In addition to this, the engine will collect transmission fluid, and the transmission will be low on fluid.

 

[markhenry63]

So I evidently don't have this particular problem as the fluid levels are fine and I don't detect any fluid at the vacuum tree hose end and engine oil has normal color/level. So...I will check vacuum at the hose end at the vacuum tree and see if it holds vacuum there...If I did have a vacuum leak sufficient to cause shifting problems, wouldn't I also have problems with engine vacuum and rough running engine?
Thanks all!

 

[BrooklynBay]

Check the hose ends for cracks. Sometimes they split, and then you have a leak. The metal tubing should be fine.