Replacing the A/C hoses in 911 80 SC
 

I don't see where any one has posted the question or answered it. I filled up my system last year with 134a and it ran great for about 2 weeks, then leaked out. I was told all I have to do is replace the A/C hoses with new updated barrier hose (Pelican sells them under ra-hoses-early and ra-hoses-late). At any rate, is this all I need to do is replace these 2 hoses? The next question is how hard and how much time? Do you have to the pull the engine to do this-I am not a wrench, but have a friend who works on BMW all the time-trying to figure out how difficult this job is.

Thanks
C

If you're going to continue using 134, then you will have to replace all the hoses, several of them running back to front and then back again. It's not a small job but many have done it at home. I have all original hoses and I'm still running R12. I have not topped it off in five years and it is still blowing relatively *cool*.

Why do I need to replace all the cables? Is there a difference between running 134a and R12? I thought there were only 2 cables running front to back? Again what kinda time?

Thanks

C

As I understand it, R134a inherently leaks faster than R12. It diffuses faster through the rubber of the hoses than R12 (smaller molecules?) and this is exacerbated by a higher running pressure than a similar R12 system. New gas = new (better) hoses.

If the R-134a leaked out in two weeks its not just due to non-barrier hose. You probably have a leak somewhere (compressor shaft seal, loose hose fitting, or a hole or crack in condenser or evaporator) plus old, damaged hose. R-134a will also diffuse (leak) through new barrier hose, just at a slower rate. A typical 911 AC system has 40 plus feet of hose for the refrigerant to diffuse through.

In an SC OEM factory AC system there are typically five sections of hose. There are two long runs fore/aft: the larger suction line from the evaporator in the smuggler's box to the compressor suction inlet and a smaller high pressure line between the decklid condenser and the front valence condenser. The engine does not need to be removed to replace the hose runs. It is mainly just a cramped, dirty job to replace the hoses with new hoses from a kit. The only skill/care is in tightening the flare connections; tighten only enough to effect a seal (after coating the sealing surfaces with "Nylog") and always back react the tightening torque with another wrench on the other side of the fitting.

What he said, r134 leaks faster.

There are several hoses in your system, 2 longs that run from front to back. A small one going from compressor to rear condenser and one or two more small hoses connecting the dryer.

This is a job I just finished. It will be easy with two people. One to pull and one to push the hoses where they go into the smuggles box and engine compartment. It can be done in a day if there are not snags. You do not need to drop the engine but the car needs to be a couple feet in the air if not on a lift.

Also, be careful with your connections as some of those components are old and fragile (grab some pb blaster to loosen things up). You will probably need a new drier (or procooler) as well as hoses. The more your system has been exposed to air the greater the chance you drier is shot.

Rennaire and Grifiths sell a hose kit (all needed hoses) for 350 or less. I used rennaire with no problems. I didn't price check pelican as I like to spread my cash around (but most of it is spent here).

BUT. . . before you do anything get some UV dye in the system and verify none of you components are leaking. note: you won't see the dye leak out of the hoses just the connections or components.

Good luck and don't worry there is lots of help here.

Jim, do you use the red or blue Nylog?

I use blue Nylog on both o-rings and flare fitting metal to metal sealing surfaces.

What about this reference:
"Flare Fittings:

Both faces of the flare as well as the threaded connectors are coated. Primary attention is given to the flare face. The majority of Nylog is pushed out of the flare boundary but not completely expelled. Helium leak testing of flares treated in this manner were tighter than flares coated with pipe dopes, resin adhesive, anaerobes, silicone, or a dry connection. Never use Teflon tape on a flare."

Have you used it on the flares themselves? Seem like you would run the risk of having some of this stuff in the system rather than just sealing it.

Metal to metal sealing surfaces are the flare surfaces; for sealing purposes (in my opinion) it is not useful on the threads of refrigerant hose fittings - these threads do not seal. Tapered pipe threads which are not typically found in moble AC systems would benefit from the compound. The blue Nylog compound is compatible with HCF's and tends to stay put so the small amount squeezed inward is not an issue.

That is exactly what I thought. If there were a leak it could come out of the fitting where the hose meets fitting and swivels as well as the threads. And I'm not sure if this stuff would help at the swivel.

Just on the flares sounds like the way to go.

So, thankfully I haven't opened up my procooler yet to button up the system. Nylog is on the way. Thanks for the tip Jim.

www.ackits.com if you need any parts or hoses.