I have a '67 with factory air. The A/C works fine but I have noticed that over time an oily film gathers on the underside of the hood above the compressor. I'll clean this film off and it will reappear after a few hundred miles of running the car.

It appears that the A/C compressor is losing a bit of oil, but so far not much. So my questions are:

1. What is this oil? Is the compressor designed to lose a certain amount?
2. How do refill the oil?
3. How much oil is contained in the compressor?
4. Should I worry about the amount being lost? As I said, it isn't much, but over time will the loss of oil damage the compressor?
5. Is the oil being lost whenever the engine is running (i.e. rotating the compressor pulley), or does oil only get lost when the A/C compressor is engaged?
6. Is there supposed to be a guard or shield in place to keep the oil from being sprayed on the underside of the hood? Where should this guard or shield be installed?
7. Lastly, what do I need to do to fix the leak? Is a full rebuild of the compressor required?

Thanks for sharing your expertise with me.

 

I won't answer all your questions, but I will tell you that there is a shield that bolts to the compressor mount to protect the hood. If that oil leaches into your fiberglass, the paint will come off the other side and you'll end up having to replace the hood, or cut a chunk of fiberglass out and replace it to keep paint from bubbling off.

http://www.ecklerscorvette.com/corve...1963-1976.html

 

That is your biggest issue/concern. The others are minor in comparison.

Now for your other questions:

1. There is 11 oz of mineral oil contained within the C2 Corvette AC system. It provides lubrication to the compressor and other AC parts. The AC system should not lose any measurable amount of oil. R12 is also lost along with the oil.

2. You can buy cans of the special AC 525 SUS mineral oil that are under R12 pressure and add them SLOWLY into the compressor suction. You could also buy a special AC tool to do this. Or you could depressure the system, add the oil, and then refill the system with R12 again. The question becomes how much do you add?? You do not want to overfill (or underfill).

3. The compressor holds about 4-6 oz of special mineral oil. The rest of the system holds about 5 oz of oil. Total system oil charge is 11 oz.

4. Yes you should be concerned about the oil loss. It will damage the hood fiberglass and could also damage the compressor (if too much oil is lost).

5. Typically the most oil is lost when the compressor is running, but it could also be lost if the compressor is off..........if the compressor seal is bad enough. However, in this case, you would also quickly lose the R12 refrigerant charge.

6. The factory did not provide a compressor seal shield, but you can buy one from a few Corvette parts suppliers. Ecklers is one. The current shields were designed by a member of our C2 forum. I helped him initially in this work. There are pics of the development in the archives. The guys screen name is Nitromainia. His actual name is Kevin. You can find the pics if you search under his screen name in the C2 Forum.

7. The compressor seal needs to be replaced. You can do this yourself with the right tools and knowledge, however we have recently determined that the current ACDELCO replacement seal is basically junk. Dom Tallarita is a member of this forum and has the skill and correct/alternate parts sources to replace the seal and rebuild the compressor. He is the best in the country for this work. You can try it yourself, contact Dom, or buy a new A6 compressor from ALMA Products in Michigan. The new compressor will look like the old one, but will be metric and have a modern double lip seal on a chromed compressor shaft.

Larry

 

Search under "compressor shield". Part # 33-282080-1. About $40. Corvette and Camaro part is the same.

Larry

 

I would check to see if someone along the way changed your system to 134A from the factory R-12 system. They use different oils and cannot be mixed. Jerry

 

Get the shield and remember to clean the spray below the shield around the heater hoses. My 66 is leaking also and last year I added a can of sealer / 134A sealer that slowed down the leak. To get the pulley shaft seal fixed, your going to need to find a way to remove the freon to service the pulley. A set of specialty tools be needed. For me I live in area where AC is nice to have but not needed. I normally don't use my AC because accelerating from stop is a pain when the RPM's are lowered to about 500-600.

As mentioned above, Dom Tallarita is the expert to rebuild your A6. I spoke to him once and he is one great guy and knows his stuff.

 

Thanks everyone for the good tips. I've cleaned the film of oil from the underside of the hood. Luckily it hadn't damaged the paint, so maybe I was lucky there.

How can I tell if my system has been converted from R-12 to R-134A? I can't see any decals or other info (other than the stock Frigidaire decal on the compressor.

Is it feasible to add the correct oil to the system without having to recharge the refrigerant?

 

Does anyone know if they make a shield for a compressor that is mounted on the driver side? All I see is for the passenger side.

 

I think I answered it in Post #3. But maybe not in enough detail for you.

First you need to determine if R12 or something else. If the AC suction and discharge fittings are still the R12 Schraeder type, chances are it is still R12. A very good AC shop can analyze the refrigerant and tell the differences. You can also check the pressure versus temperature in the system and perhaps tell the difference.............but you need to keep the temperature CONSTANT in an insulated garage or storage building for about a day or two to let the temperature stabilize so you can get an accurate pressure vs temperature reading.

If R12, you can buy cans of refrigerant and oil mix and SLOWLY (very slowly ) add them to the system. I guess you could do this either running or off, but the add procedure would be different. Let me know if you go this way. Then you can crack open the drain connection on the A6 compressor with the compressor off and see if oil comes out. Oil will only come out if the compressor is overfilled.............if no oil comes out (only refrigerant gas) then the oil level is either low or okay. Dom brought this fact out a few years ago. You could call him for additional details and ask more questions if needed. He has the most knowledge about the compressor internals and what steps are needed to be done. It may even be in the archives under his name, since he explained it all to us awhile back. http://www.ebay.com/itm/INTERDYNAMIC...RXafAl&vxp=mtr This is the oil in a can............price is way too high, I bought all mine for about $2/each many years ago. I guess "supply and demand"

The other way is to completely discharge the system and measure the oil in the compressor. Then add back the correct amount. The Chevrolet Service manual Section 1A has the procedure for this.

Larry

 

The shield is specific for the A6 compressor. As far as I know, the AC compressor was only mounted on the right side (pass side) in the C2 Corvettes.........and AC was not available from the factory for C1s.

Other compressors have different shields............I know the R-4 compressor had a special one. Not certain about Sanden, Pro6Ten, Denso, etc.

You can also make one with a bit of time and skill. That is how the current A6 shield came to be. After the prototype was build a commercial sheet metal shop took over the job of making the others.

Larry

 

Larry,
You are the expert on the system and I would like to get your opinion on the oil that is compatible with R-12 & R-134? I know it is always best to keep all oils the same but some shops are using the oil that works in both.

Dom

 

Dom:

Yes, Ester Oil is compatible with both R12 and R134a refrigerants, and is the choice for folks converting from R12 to R134a. It will mix and should not create any issues in either R12 or R134a systems. I believe that Ester 150 viscosity is the best one to get for our old A6 compressors, but Ester 100 viscosity (thinner oil) will also work just fine. The 150 should provide a bit more protection for the system in the hotter climates where AC is normally used/desired. However a friend in Connecticut (Northeast part of the country) used 100 viscosity last year and it was just fine.

Here is a good writeup on the various oils, etc. But then again you already know this. http://www.e38.org/pparish/oil.htm

I believe a person can buy mineral oil, ester oil, and PAG oil all pressurized under their compatible refrigerants in small cans, just like the picture I posted earlier for R12. But you have to search a bit.

I just don't like adding ester oil to a system that might have another oil already in it..............without first trying to remove the previous oil.......even if they are supposed to be compatible.

Larry

EDIT: Another table about oil types and viscosities for everyones reference. Although this shows Ester 100 for the A6 compressor, other companies/rebuilders etc show Ester 150. http://www.e38.org/pparish/oil-tabl.htm

 

I should have been more specific. Not for a Corvette but for a 79 Camaro Z28. To me the compressor looked the same but mounted on the drivers side. I've looked on line and Camaro parts vendors but only see them for 67/68 Camaros.


Thanks,
Rich

 

I owned a 1978 Z28 years ago (special factory order), so I am very familiar with the car.

Being that the hood is metal/steel the mineral oil will not harm it or the exterior paint. Now if you switch to R134a and PAG oil..............well

I never had a shield for the A6 compressor on that car and never needed one. But as stated earlier, you could "reverse engineer" one by using the one that is available for right-hand mount, and then make it up in your shop. Best I can do for you. Back then the compressor shield was a product that wasn't needed...........so it wasn't made.

Larry

 

The A/C unit does have R134a and the oil really does come right off with Sprayway glass cleaner and a cloth and doesn't hurt anything.

Thanks,

Rich

 

That is GOOD...............it also could be that Ester (typical retrofit) oil and not PAG oil that is in the R134a system.

Larry

 

Larry,
Thanks for the info. I printed it to keep in the shop. Always more to learn.

Dom