the flyin' scotsman

Just rxd my new/rebuilt Porsche a/c compressor (thx Roger) and I need to transfer the hose inlets from old to new.

My questions are:

should I use the O rings that came with the new pump for the hose inlets (they're black and I thought I'd read that R134a Orings are green)?

my system was converted to R134a; do I need to change the oil in the new compressor and if so what do I use and how much?

Here's a pic.

cfc928gt

When I rebuilt my compressor the kit I used, which was for both R12 and R134a, came with the black ones also so you should be good. As far as compressor oil, they usually come with fresh oil but you need to check with Roger on that and find out what type was put in. Was there a tag that said what type oil it was filled with? IIRC the system holds about 8 oz but you should check the manual, it's in there and it will tell how much to allow for if you change the dryer and how much should be in the lines and condensor, etc.

WallyP

O-rings that are suitable for use with R-134a may be blue, green or black. Conversion kits and aftermarket rings are usually blue or green, with the color being coding to reassure the end user.


You need to be certain what oil is in the compressor - mineral, POE, or PAG. If it is anything other than POE, it must be changed.

PAG is the factory fill for vehicles using R-134a from the factory. PAG is NOT suitable for any system that has ever run R-12.

Mineral oil is the factory fill for vehicles using R-12 from the factory. Mineral oil is NOT suitable for use with R-134a.

POE is the only suitable oil for a system that has been converted from R-12 to R-134a.

ZEUS+

As Wally said the correct oil must be used. Ester oil works well, pag is best with modern vehicles. Use green seals if available, black seals pose no problem. Most likely compressor has mineral oil and should be drained and flushed. You can use ester oil to flush, if flushing agent is not available. Add 5oz of ester to compressor after flush. WSM 87-14 and 87-103.

the flyin' scotsman

Much thx Wally and Zeus.

Is there a proceedure to flush and fill?............compressor is on the bench. POE oil is available where?

JHowell37

If it were mine, I'd probably put on new green o-rings that you know for certain will be compatible. If you don't know what kind of oil is in it, then dump it and go with ester. Since you're putting on a new/rebuilt compressor I'd take the extra time to see just how much of a retrofit had been done previously. In other words, I'd replace every o-ring, flush the evaporator and put in a new expansion valve and drier.

One suggestion I have is to not put the oil in until the compressor is installed with the hoses attached to it and tightened. You can just pour the oil into the compressor through the hose. It's easier that way, and you'll be less likely to make a mess.

JHowell37

POE is ester oil which is readily available at most parts stores. The advantage is that it's compatible with the other types of oil.

You can't flush the compressor. Flushing the condenser in unlikely to yield any results so don't bother. About the only thing you can flush is the evaporator and it's not hard. Remove and discard the expansion valve. The flushing solution should have a hose attached to the can. Press the hose tight against the evaporator and place a catch rag over the outlet on the evaporator. Spray the flushing solution through. Then blow some compressed air through it to push out any remaining solution. Reassemble with new o-rings and expansion valve.

Most flushing solutions are water based and it's not imperative to get things completely dry inside before reassembling. If you leave the car on the vacuum pump for a few hours, whatever is left of the flushing solution will boil out.

ROG100

Compressor is a Porsche factory rebuild.
Factory paperwork does not define R12 or R134a.

I will confirm with Porsche tomorrow morning.

Wally,
No info on your site either - do you know the answer please?
Roger

JHowell37

How much does a rebuilt compressor from Porsche cost?

ROG100

Supplied by 928sRus $465. Core charge $200.

ROG100

Wally,
Sorry I read your earlier post.
This compressor would be R12 so we need to change out the oil.
I learn something new every day 8>)
Roger

dprantl

Fortunately, it's very easy to get the oil out of the 6E171. In fact, it has a handy drain plug for it directly at the bottom.

Dan
'91 928GT S/C 475hp/460lb.ft

the flyin' scotsman

So we conclude the oil has to be changed and POE is the correct oil per Wallys direction.

The WSM gives varied quantities from 350 to 280cc and also describes where the oil resides after the system has been run. I'm assuming that if I measure the oil thats in there now when drained that'll give me the quantity of POE required..........correct?

WallyP

Yes.

To recap the oil usage:
R-12 system using R-12 - Mineral oil
R-12 system converted to R-134a - POE (ester)
R-134a system using R-134a - PAG

In the past, I have found that flushing the condenser can help. The high temps can cause the oil to cook in the condenser. In one case (Jaguar), I pumped mineral spirits thru the evaporator for four hours, and improved the flow greatly.

SteveG

When I installed re-built compressor the techician told me 8-9 ozs of oil. Put 3 oz oil in compressor (before installation), 2+ in dryer, 3 in bottom of condensor, change all the seals you can get to. I did not touch the fuel cooler. It has been great for 3 years. It was r12 to r12.