AC Questions: jetjock cleared for landing on Runway 24

[Davismj711]

I have done a diligent job of searching each thread for information on this topic. I have learned enough to be dangerous. I am near the end of my 9 year erbuild on a 1987 7Mgte.

My original rebuild was done in 1995. Once completed I took it to have the AC recharged and the tech told me the condenser had a leak. He vaced out all of the charge and that is the way it stayed for the two years before this build started in 1998.

Currently compressor lines are off, I will be installing a new condenser ( another nightmare in ordering there ) drier, and new R134a seals.

My questions are as follows.

A flush of the compressor was suggested in a post, what is the best way to do this with unit off the car?

I plan to vac the system myself once it is installed, does this look like a reasonable pump to use ?
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=005&sspagename=STRK%3AMEWA%3AIT&viewitem=&item=150121780952&rd=1

Or if I plan on charging the system myself is this an acceptable Manifold and vac setup?




Or should I simply asemble and vac it and let the charging to the pros ??

jetjock I know you like the R12, I do also, however I have nearly as much R134a in cans as you do R12. Economics require I use it if I can.

Many thanks to all responders

 

[Nick M]

I am not sure about flushing a compressor. There are valves inside that are kind of delicate. When you flush a system, it is usually because the compresssor is bad.

A flush kit usually comes with every thing but compressed air. You take the lines off and blow the cleaner through. Then with clean air. New reciever to go with new parts. At least dump out the old oil from the compressor.

Robinair is pretty much the industry standard for A/C service machines. That doesn't make them the best, but they work good. You should vacuum it for an hour, and make sure it holds.

 

[figgie]

Davis

that robinair pump will work but won't pull enough of a vacuum for R-134. You need the bigger guys starting at the 4cfm front and if you can afford the 6 cfm or 10 cfm that would be a lot better

Also if you don't like wasting time you can get a thermistor based vacuum gauge that way you know when the system has pulled all the moisture out.

barring that, I would not use the pump you posted as it is just not powerful enough to pull a good vacuum.

 

[jetjock]

What figgie said. Venturi pumps are a weak compromise at best. Get a real rotary vane (preferably a 2 stage) that can get down to at least 27 in hg. Depending on how long the system was left open it's gonna need it.

Compressor flush is a cake walk. Drain the old mineral oil out, fill with PAG or Ester, and slowly rotate the shaft. Not the clutch mind you, the compressor shaft. Do that twice. Hold the compressor vertically and slowly rotate the shaft each time you drain. Frankly the compressor isn't the problem so much as the system itself should also be flushed. Anyway, charge the compressor with the right amount of oil, change to HNBR O rings, install new receiver/dryer, evac, leak check, charge, and performance test.

Btw there is a 24 I land on often. At least I think it's 24....my eyes are usually closed. I know when to flare from the screams in back

 

[Davismj711]

Thank you both for the speedy reply.

Figgie my concern with the equipment purchase is as you said, not strong enough. Since I hope to only do this 2 or 3 more times (who really knows ), I am trying to balance money invested, to return on investment. Age old dilemma when you never take a car to a shop, which I never have. I will check prices on the 4 or 6 cfm units.


Nick, it was jetjock that mentioned the compressor flush, only reason I am looking into it. I have rebuilt 1000's of transmissions, but have only done a few AC systems. So I only know enough to be dangerous, and from reading the other threads my previous AC repair or rebuilds were nearly all wrong.

Many thanks again ^^

 

[jetjock]

The mantra in MVAC is "do it right, do it once". How long the system lasts is directly proportional to the effort put in. Done right it will work without problem for many, many years.

 

[Davismj711]

jetjock you posted as I was replying to Nick and Figgie
. Runway 24 was the strip I used when I got my Private, ( Ebensburg Pa ) I was the 7th of 9 children required to do so by our Dad. He was an instructor, before he passed away many years ago he had logged over 24,000 hrs ^^ Instrument and multi engine. he flew up to a few months before he passed.

Any good inexpensive sources on said vac ???

Thanks again ^^

 

[Davismj711]

On a side note::

How long would it take a good AC tech to properly vac the system ? Is this a realistic request from a shop ??

Found this unit on eBay for $140 shipped, FJC 2.5 CFM 2 Stage R12 / R134 A/C Vacuum Pump 6908. This do the trick ?

 

[jetjock]

That should do it. Cheap too. I guess pumps have come down these days. Mine cost a lot more than that.

Lots of people do their own work and then use a shop to evac and charge. Should take an hour or so.

Your Dad had a lot of time alright, a record to be proud of.

 

[Nick M]

Putting in the cleaner and rotating it slow sounds good. A flush usually has compressed air, that is what I wanted you to avoid.

 

[Pantaloon007]

Putting in the cleaner and rotating it slow sounds good. A flush usually has compressed air, that is what I wanted you to avoid.

Dont forget to blow out any remaining gas w/ nitrogen before you put the lines back on the comp, if you have access to it. You dont have to do it, but it does help clean out anything in the lines prior to getting moisture out w/ the vac. The charge is 1.65lbs(~26oz) max for R-12. You want to go w/ 90% of that with the 134 if you are using the stock-size condenser. I dont know if Toyota sells a larger condenser to compensate or if it is identical to the original stock one. R-134 needs a larger condenser to get a proper subcool. The easiest(not best) way to counter that is using a bit less.

My vac cost way more than that too. The longer you do a vac the better, but after an hour or so you get diminishing returns. With a 2.5cfm, it will obviously need to go a little longer.

 

[figgie]

the problem is not the vac but how many microns it pulls to. Most can go to 40. The 6 cfm go down to 20!

The issue is a pressure gauge will never tell you that. You need a thermistor based vacuum gauge to tell you if you achieved that in 5 minutes or let it go for one hour.

 

[3p141592654]

JJ no doubt uses a Turbomolecular vacuum pump :biglaugh:. The STP-iX455 is nice!

Seriously, a Robinair 15300 is good enough, and not very expensive. 15600 would be even better for a little more cash.

 

[jetjock]

^ Lol. Yeah, that 10E-3 stuff is for whimps

 

[3p141592654]

Yup, wrap the AC system in heater jackets and pump down to 1E-7.

 

[Nick M]

You guys are funny!

 

[jetjock]

A little high vacuum humor Nick. Very little

3p actually makes a good point. It's why experienced AC techs try to evac a system when the engine bay is hot.

 

[Nick M]

A little high vacuum humor Nick. Very little

3p actually makes a good point. It's why experienced AC techs try to evac a system when the engine bay is hot.

I never thought about it. But I will say this. They never come in for service when it is cold.