87 911: Replacing dryer and expansion valve and lines. Anything else needs to be rep?

[bigchillcar]

hugh and others who may not have researched freeze12 and other potential substitute refrigerants, read a page from the epa regarding use and conditions for use of alternatives..this includes a table below of 'acceptable and 'non-acceptable'. fwiw, freeze12 is 80% r-134a & 20% r-142b (zero isobutane/propane blends) per the epa link below. also, freeze12 is advertised as non-flammable..visit www.freeze12.com for more info. duracool, another product mentioned often on this board, is listed as an 'unacceptable' replacement, just for an additional data point. although my 'research' of this info is purely online, a degree in chemistry does allow me to read and understand msds info.
ryan

http://www.epa.gov/docs/spdpublc/snap/refrigerants/macssubs.html

[msk1986911]

Is the receiver dryer under pressure when the A/C is not on? If I remove the current receiver dryer to replace it with a new unit, will I lose refrigerant?

I am taking my 86 coupe in for A/C service next week and would like to test fit the new receiver dryer before then so I can ensure that I have the correct part.

Many thanks as always.

Mike

[scottb]

Originally posted by msk1986911
Is the receiver dryer under pressure when the A/C is not on? If I remove the current receiver dryer to replace it with a new unit, will I lose refrigerant?

Yes. Once you crack one of the fittings, you'll allow refrigerant to escape and air and moisture into the system. The better, and more environmentally friendly, way to go is to have your local a/c shop recover the refrigerant. Then you can work on the system before having it recharged. Use care when exposing the new receiver/drier fittings to the environment -- there's a desicant in there, and if you allow it to be exposed too long to the elements, it will absorb moisture and not be as effective.

Good luck. Have fun. Be safe.

[wholberg]

I looked at the MSDS and Freeze-12 is 75-90% 134a, and 10-25% of some other CFC. Compared to hydrocarbon coolants, it should not be nearly as flammable. My only complaint with it is that it still has a CFC in there.

http://www.freeze12.com/pdf/6030.pdf

[Barrpete]

Originally posted by wholberg
I looked at the MSDS and Freeze-12 is 75-90% 134a, and 10-25% of some other CFC. Compared to hydrocarbon coolants, it should not be nearly as flammable. My only complaint with it is that it still has a CFC in there.

http://www.freeze12.com/pdf/6030.pdf

Actually, 142a is an HCFC (CH3CClF2) the same class as 134a - and it's not considered flammable.

[kepperly]

You guys with a large enough compressor can pick up a vacume
pump at harbor freight for about $15.00. Use it in conjunction with a set of a/c gauges and you are there.

Keith Epperly
87 slant nose turbo look carrera cabriolet

[1982911SCTarga]

I use the (Ken) venturi vacuum pump. Works for me.

Brian

[kepperly]

Another tip, go to your local a/c supply co. and ask for some "fin" clean. While you are there get a fin comb also. The front condensor fan is in the left front of the trunk. You can take it out and disassemble and relube the motor's bearing and reinstall.

Keith Epperly
87 slant nose turbo look carrera cabriolet

[Jim Sims]

"You guys with a large enough compressor can pick up a vacume
pump at harbor freight for about $15.00. Use it in conjunction with a set of a/c gauges and you are there."

Nope; these venturi pumps can't achieve a low enough pressure (enough vacuum) to get the water out. This is especially bad with the R-12 systems, for water and the R-12 refrigerant combine to make an acid that corrodes the systems from the inside.

[Barrpete]

Originally posted by Barrpete
Actually, 142a is an HCFC (CH3CClF2) the same class as 134a - and it's not considered flammable.

CORRECTION 142b IS considered flammable

[Motorhead-45]

I've already mentioned this several times on the board but if you live near an Autozone you can borrow a vacuum pump for FREE via their loaner tool program. They have a pretty decent electric pump and is yours for the asking and a $200.00 fully refundable deposit. Just make sure you buy fresh oil for the pump as you can bet what's in the loaner needs to be replaced.

[yogi]

I looked in the Pelican Parts catalog but couldn't find the front condensor fuse kit that scottb mentions. Can anyone direct me to it, or give me more information about it? thanks

[kepperly]

Jim Sims. BS I let mine run for 30 min. and achieved -30psi.
For the fifteen bucks thats a bargain, I have a 7.5 hp 220 volt 60 gal. upright compressor. I replaced the receiver dryer pulled a vacuum, recharged with r-12 and that was two years ago still running 38 degrees at outlet on a 90 degree humid day. Don't forget to take a valve stem tool and tighten the schrader valve most shops COUNT on seeing you once a year for a top off as a residual and leave the valve 1/2 to 3/4 loose to allow for a Small leak. And don't forget to run the a/c during the off months.

Keith Epperly
87 slant nose turbo look carrera cabriolet

[Jim Sims]

kepperly,

-30psi? Now that's BS or you're in a very deep hole in Kansas. Wait, the Kansas State School Board considers things magical there so maybe it's possible.

I assume you mean 30 inches of mercury of vacuum which of course is also impossible at the elevation of Kansas; atmospheric pressure isn't that high there. Vacuum in inches of mercury is read relative to local atmospheric pressure. You cannot use your Bourdon tube based harness gages to accurately read vacuum.

You have to get the pressure of the system below the boiling point of water at the system temperature for an extended amount of time to mobilize the water and pump it out the 40 feet of hose (in a 911 AC system) which has poor conductance for vacuum pumping.

Here are a few values at sea level:

vac (inches of mercury): 28.89 water boils at 80F

vac 29.18, 70F

vac 29.71, 40F

vac 20.86, 10F

This is at sea level, reduce the vacuum levels required for a given water boiling point by an inch of mercury for every 1000 ft of elevation above sea level.

Put the car in the sun, pump down to 40 microns (this requires a two-stage vacuum pump with dry (fresh) vacuum pump oil) and let the pump run for 3 hours.