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68 Impala, R4 compressor- oil and 134 charge

Cautrell05 on Wed August 18, 2010 1:52 AM User is offline

Year: 1968
Make: Chevy
Model: Impala
Engine Size: 350
Refrigerant Type: 134
Ambient Temp: 90
Pressure Low: ---
Pressure High: ---
Country of Origin: United States

Title pretty much says it all. The 68 is just about to charge and Have a few questions on the oil and freon charge. The GM service manual I have says 3 pounds 12 ounces and 11 ounces of oil. That was with the big a6 compressor. It currently has acc brackets and the R4 from a 91 impala(new of course). The condenser and dryer are new. all rubber lines replaced, the metal lines and evaporator flushed out. In the manual it lists system oil charge as 6 ounces for the compressor, add 3 ounces if replacing the evaporator, and 1 ounce for the condenser or dryer. Just wondering how much to put in. Thanks


iceman2555 on Wed August 18, 2010 5:47 PM User is offlineView users profile

The total lube listed in the post reflects a charge of 10 oz.....this may well be within specs. Most GM systems (automotive) require 8 oz of lube. GM states that the system will perform with an extra amount of lube equal to one full charge. I would never suggest for anyone to over charge a system to this amount. Although for all you that retro fit.....this was the standard GM procedure. The systems were not to be flushed...and a complete recharge of PAG was to be introduced into the system. Heck, if the vehicle had less than 40k they did not suggest to replace the accumulator or drier.
My suggestion would be to introduce 8-9 oz to the system. Go for the full 10 if you like....esp since many new/clean parts are being installed. It is not necessary to add lube to this part and that part...a little here...a little there...simply add app 3-4 oz to the suction side of the compressor....the big hole in the center......the remainder can be introduced thru the inlet side of the accumulator...if equipped...if a rec/drier/filter is being used...add 1 oz to the drier.....the remainder could be added to the evaporator prior to closing the system.
The key is getting the system fully charged....this is the protection for the must have a constant supply of lubricant being resupplied. This is another function of the refrigerant in the system.....the A6 did not require this tue migration since it has a lube sump. Failure to properly charge the system will result in compressor doubt about it.
Suggest to start recharge rate at least 85%....prefer 90%. Remember to add app 4 oz to the recharge rate to accommodate the amount to pre-charge your manifold assembly.
These 'ole' Impala's had some weird fan shrouds....if my memory works as it that the fan clutch is operational and all other engine cooling system components are working as they should. Insure that as much air flow as possible is thru the condenser/radiator.
Good luck !!!

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