normally, to prevent, rolling, pinching, tearing, twisting etc. and to promote proper seating in the "0-ring land", one lubricates with the same fluid as the system where the o-ring is being used. I often just use a very thin coating of silicone grease like dielectric ignition grease. In an ac system, one would normally try to use just a drop of compressor oil, or a bit of the escaped "oil/dye" on the end of a finger. if in doubt dry is OK, but I rarely ever put anything together dry. It allows the o-ring to seat better and allows the two mating surfaces to assemble cleaner. Moreover, when pressure is applied, on a microscopic level, a bit of lube allows the o-ring to "flow" into tiny cracks.

Compressor oil if ya got it. Never used anything else on AC systems.
Someone else speak...

 

uh-oh...sorry Dr Bob...didn't see you were already...in the house!

 

Its called Nylog.

Reminds me, I should buy another bottle of it. Need to sort AC in a couple of 928's this summer.

 

Had the evacuated on Friday in preparation for flush on Monday. Removed the drier/receiver and wanted to document a couple of things. Here is the expansion block/valve under the cowl. In the picture you will see that the plate on the engine side is not flush with the mating surface. That cannot be good. I'll see if I can do better on the reassembly later.

 

Just a tip, always be careful of trying to line the AC lines/block up with the firewall for aesthetics and then bending / cracking the hard lines just on the other side of the firewall. If the block is flush with the mounting / sealing surface, it may be just fine, if the seal is leak free of course. don't even ask me how I know. an evaporator is a terrible thing to waste!

 

If you loosen the fuel cooler strap the expansion valves come out a bit easier. Ask me how I know.

The rear expansion valve was original to the car and still had the black R12 o-rings. And the lower 3mm rear air block plate screw was finger tight.

Tomorrow it is off to the shop for flush before replacing all the o-rings.

 

Is this list complete?

According to the Nichol's website I need:
==============================
part number; size(mm); # front; # rear
==============================
999 707 284 40; 6.6 x 1.5; 0; 2
999 707 247 40; 7.5 x 2; 4; 3
999 707 261 40; 9.0 x 1.8; 2; 0
999 707 250 40; 10.6 x 2; 3; 1
999 707 251 40; 14.0 x 2; 3; 4
999 707 252 40; 17.0 x 2; 2; 0

Front A/C:
==========
1. expansion valve (under plastic tray next to intensive washer reservoir): 2 x #251, 1 x #250, 1 x #247.
2. return line from expansion valve, middle of firewall: 1 x #252.
3. compressor fittings: 1 x #251, 1 x #250.
4. other side of return line to compressor at low side fill valve: 1 x #252.
5. heading into condenser: 1 x #250.
6. bottom of condenser heading up to receiver/drier: 1 x #247.
7. pressure and temperature switches just before receiver/drier: 2 x #261.
8. at receiver/drier: 2 x #247.

Rear A/C:
============
1. expansion valve: 2 x #251, 1 x #250, 1 x #247.
2. solenoid valve under passenger seat: 2 x #284.
3. 2 pipes under car from solenoid valve to front connections: 2 x #251. 2 x #247.

My o-ring count I got from Jeanie is greater than that so I think the list above missed a few. I would guess the fuel cooler uses a couple.

Is there an exhaustive list for our cars with rear air?

 

Which viscosity ester oil do we use? Autozone stocks three different versions.

 

All the o-rings have been replaced, vacuumed down and is holding vacuum @ 20#s rock steady.

Tomorrow it is off to get the A/C charged.

There was a missing o-ring on the compressor, lots of black r12 o-rings left behind when it was converted, the rear expansion block has been leaking in the past as evidenced by the black crud in side the expansion block and the on the copper tubes leading into it. Cleaned them with wet/dry sand paper until they were nice and shiny.

Could not have done this without the gauges, vacuum pump and counselling Dave Davies provided.

 

Well, they checked the vacuum and it is perfect - they recharged the system, but seems like they did not listen to me about pressures and weight. I tested the pressures and like I expected they were a bit off. At 2k RPM 130 / 30. Way off. I'll revisit them tomorrow. My heater valve is not getting any vacuum, I'll wire it shut before I take the car back.

 

Tied off the heater valve and I get 58 degrees at the front center vent.

 

Had a chance to use the A/C at the Frenzy. The a/c cooled the cabin quickly and only needed to be on the first fan setting to maintain the cool - even without the rear a/c.

 

I am getting to this thread a bit late, but if you find the freon leaks still there are a couple other items to refresh.

You can get a compressor rebuild kit pretty cheap from a farm supply store and replace the shaft seal and other o-rings. Also, you can replace the compressor to/from hoses.

 

Something must have happened betw. post 41 and 42, 'cuz 58° isn't cooling much.

I take it you tied off the valve, took it back and had them take some out? Add Freon?

I'm just curious.

 

A/C compressor and high side line from compressor were leaking - replaced both today. Hope to evacuate and recharge tomorrow.