I just rebuilt a system on a much smaller car. Freind had a refrigeration vacuum pump I was going to borrow so I didn't have any worries there. But for the heck of it I connected up my small hand operated MityVac to the system. To my surprise it pulled about 27+ inches. I was reading this from 2 gages---my manifold set and the mityvac gage. Also thought it would take forever, but in 5 minutes it was there. I would not use it to recharge refrigerant though. Maybe as a vacuum leak check. Only way I would recharge behind the Mityvac is to break the vacuum with dry nitrogen several or more times. Then I would have to be desperate. It takes the best vacuum you can pull to get the moisture out of the system and at lesser vacuum you'll leave non-condensable air or N2 in the system which might affect performance. But if you have no choice you may be stuck with the hand pump route.

They do make a hand pump that will get to 29+ for refrig use----$300. MityVacs weren't meant for that. On a sad note I ruined the wiper on the MityVac piston the my third time, I tried it. It would only get to 24-25 inches so i opened it up.....partial tear. Shoulda stopped when I was ahead. Gotta get me a new one!!!
BTW I cut open the drier I replaced. I have a better vision of how they might plug now. Also, did "autopsy" on the compressor. Even more interesting. Have great pics of internal of both. Will post if anyone is interested.

 

Pic's oh boy lets see....



Dick

 

I second that. I've been wondering what the inside of a dryer looks like. The compressor would be cool too especially if it's a scroll type.

 

Will try to post pics tonite. Gotta get them on a website so I can load them on forum. Compressor is/was a rotary vane. Aerostar has another style I think. But still surprising to look at. Will place in a separate thread.

 

You guys are great!! Thanks for all the info. I am very busy next week but will get this job done the week after. That means I probablly will have more questions. Pictures would be very nice to see too.

 

I just went through this, and hope the following will help.

I replaced the O-rings at all the fittings that showed leakage. The sad thing is that they were the seals that Ford replaced shortly after I got the van, and that I replaced again a few years ago because they just never held up. The interesting thing is that some of the O-rings I bought a long time ago actually look thicker than others of the same size, made by the same company. So maybe they will hold their seal better. The bad newss is that I can't seem to find any more of them in my local auto parts stores (Pep, Kragen, AutoZone). So I may have to order them from online sources.

In my first attempts to draw vacuum, the system would lose it pretty quickly. I got the impression that there were lots of gasses trapped in the system. However, after a short drive through the hot afternoon, the system actually built up pressure. So I tried drawing the vacuum again, and this time, it held. I held the vacuum (30" Hg) in the system for about 1 hr, and then left it closed for about 8 hours. Amazingly, it held. So before you try to pull vacuum, run the engine to get everything nice and hot.