questions regarding conversion to r134a- what o-rings need to be replaced, other ???s

[clydesdale]

I currently have the compressor out of the car. I can't find the friggin leak, yet it leaks out quickly. I am going to convert to r134a. I know I need a new receiver drier and need to pull a vacuum. But, what if any o-rings need to be replaced?

[Kershaw]

what year is the car?

iirc, late models have r134a compatible o-rings, while early models do not.

the o-rings you'd replace are all in the engine bay.

[clydesdale]

I have an 87 and it has a rebuilt compressor that has o-rings that were fine for r134a or r12. But, it has been in play for the last 2 years and had r12 in it, until it all leaked out.

[burndup]

Just slap 'er back together with some new O-rings and charge the system with propane. System will blow unimaginably cold air, and it'll likely never leak again as the propane molecule is much larger than the freon molecule.

Just be real careful not to get in an accident! ;)

[dude8383]

Just slap 'er back together with some new O-rings and charge the system with propane. System will blow unimaginably cold air, and it'll likely never leak again as the propane molecule is much larger than the freon molecule.

Just be real careful not to get in an accident! ;)

WHAT? Is this true?? I can't even begin to imagine how dangerous that could be.

[burndup]

Not so much. Google "DuraCool," then google "r-290 refrigerant."

[91 318is]

don't you have to change the drier too? I need to convert mine over to R134.

[browntown]

Not so much. Google "DuraCool," then google "r-290 refrigerant."

Hey wait a minute. That's my avatar.

[dude8383]

Not so much. Google "DuraCool," then google "r-290 refrigerant."

http://www.engineeringtoolbox.com/refrigerants-properties-d_145.html

Highly flammable...risky.

[Jean]

what year is the car?

iirc, late models have r134a compatible o-rings, while early models do not.

the o-rings you'd replace are all in the engine bay.

There are actually a couple connections under the dash as well... evaporator to expansion valve to lines going through the firewall.

[DJB]

No e30 came originally with o-rings or hoses designed for R134a.

Early years often used compressors with Viton seals. Later years tended to use compressors with a cheaper seal material (nitril / n-buna / neoprene). Viton is a better seal material in most respects, but it break down when exposed to R134a. The cheaper materials don't break down just from the chemical exposure, but their age, the increased pressure from R134a and the poor lubrication from PAG/PAO might do them in.

The reason you see the suggestion to change the o-rings isn't because they usually fail. It's because they cost $0.10 each, a small assortment covers most cars, and they are fairly easy to change. The compressor seals are much more expensive and unique to each compressor type, but in our case they very likely need to be replaced. Hoses can cost over $150 each and vary by model year and compressor brand, so you don't usually see a recommendation to change them, but they will often be the source of slow leaks.


Here are my notes on o-ring counts and locations.



O-ring info
The A/C system is built with SAE sized hoses and connections.
BMW lists o-rings by I.D. in mm, vs standard sizes or dimension
Thus a #6 o-ring, which is 3/8" or 9.525mm, is listed by BMW as 7.64mm

O-ring count and locations
7.64mm 4 (liquid hoses at condenser, drier x2, firewall, expansion)
11.1mm 4+1 (hot vapor hose, expansion valve liquid out, press. switch)
14mm 3+1 (EV adjustment vapor hose at expansion valve, firewall)
17mm 1+1 (Bosch compressor inlet and manifold)


Expansion valve and evaporator, 17/19/22/24mm wrenches
One 7.64mm #6
Two 11.1 mm #8 x 1/16" I.D.: 11.1mm O.D: 14.3mm T: 1.6mm
Two 14 mm #10 x 1/16"
(Fifth o-ring is for the superheat adjustment plug)
ETK lists 11.1 and 14mm (602/603) for evap side of exp valve
Compressor
64-50-1-468-464 11.1mm for outlet (see high pressure hose)
Either
64-50-1-468-466, 17mm (19x17mm) (3/4", #12) for Bosch inlet
or
64-50-1-468-465, 14mm (#10) for Denso inlet
Condenser
64-50-1-468-464 11.1mm for inlet (high pressure hose)
64-50-1-468-463 7.64 for outlet (hose to drier), 17/19mm wrenches
Drier
64 50 8 390 601 Two 3/8" (#6) o-ring for tube fittings
64 50 8 390 602 One 1/2" (#8) o-ring for pressure switch
Note: For two pressure switch drier only. Switch with wire leads
is pipe threads, pronged switch is o-ring sealed. New style drier
uses a combined pressure switch with a Schrader valve connection.
Firewall
Liquid connection 17/19mm wrenches
64-50-1-468-463, 7.64mm (3/8", #6)
Vapor 24/27mm wrenches
64-50-1-468-465, 14mm (#10)

O-ring count: 5X #6, 5X #8, 3X #10, 1X #12
64-50-1-468-463, 7.64mm (3/8", #6) new part number for '601
2@ drier, 1@ tube connection, 1@ E.V., 1@ condenser outlet
64-50-1-468-464, 11.1mm (1/2", #8) new part number for '602
1@ drier switch, 2@ E.V., 1@ compressor, 1@ condenser inlet
64-50-1-468-465, 14mm (#10)
2@ E.V., 1@ tube connection, 1@ compressor suction (late compressor)
64-50-1-468-466, 17mm (#12)
1@ E.V., 1@ compressor suction (early compressor), 1@ Bosch manifold

Hoses:
High pressure hose (64-53-8-391-052), compressor to condenser:
Two 64-50-1-468-464 11.1mm
Behr $62.75, German $69.81
64-53-9-067-572 High pressure liquid hose, condenser to drier
64-53-8-391-041 Part number for later cars (improved?)
Uses two 7.64mm (3/8", #6) o-rings
$93.20/$74.56 Behr@rockauto 17.70
Liquid hose, drier to expansion valve:
64-53-1-380-094 metal tube, and 64-53-8-391-047 interior tube
64 50 8 390 601 Two 7.64mm (3/8", #6) o-rings
Metal tube to 9/87 only
Vapor hose, evaporator to compressor
64-53-8-391-048 interior vapor hose
64-53-1-377-821 exterior vapor hose assembly R12
#10 hose, with a #12 connection i.e. a #10-#12 reducing fitting
64-53-8-391-051 exterior vapor hose assembly R134a (really 5/8"?)
64-53-1-380-542 heat exchanger
R12 $109/$86.14
R134 $151/$141.91

[Jean]

DJB - what is this?

64-53-1-380-542 heat exchanger
R12 $109/$86.14
R134 $151/$141.91

[DJB]

DJB - what is this?

64-53-1-380-542 heat exchanger
R12 $109/$86.14
R134 $151/$141.91

That's the ultra-spiffy fuel cooling system -- the cannister that is around the vapor return line on a few lucky cars.

[mark_i]

Hi All

This is a great article, thanks to DJB for the most comprehensive description of o-rings required.
Here in Oz, we are still in summer, +100'F days, so I need the a/c working.

Question is: Does an older R12 compressor require any internal mods to work with R134A?

Thanks in advance. Mark

[Kershaw]

That's the ultra-spiffy fuel cooling system -- the cannister that is around the vapor return line on a few lucky cars.

my eta has this.