1978 530i A/C Oil charge

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dsw99a
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1978 530i A/C Oil charge

Post by dsw99a » Sun Aug 18, 2019 5:12 pm

Not sure how to refill compressor with oil. it says in the manual to remove oil inspection bolt and add oil in crankcase till overflows out of said oil inspection orifice. However it does not point which place to introduce the oil? there are two valves corresponding to the two hoses into the compressor and one plug(?) on the rear of the compressor. Which place do you replenish the oil. it states further, to have a/c not running. Please help! Im working on this as i enter this message. A quick response is appreciated. thanks.

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528i-1981
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Re: 1978 530i A/C Oil charge

Post by 528i-1981 » Mon Aug 19, 2019 4:51 am

Use a fluid transfer cylinder or a syringe with tubing and use the inspection hole. When it dribbles out of the hole, you're done. Keep some rags handy, this can get messy especially if your car isn't on a lift.

The total system volume of oil is what's important. The compressor is lubricated by oil entrained in the refrigerant. So, you can also add oil to the drier (which you must replace after opening your circuit) and also the hoses, and when the system is running it will distribute the oil. Just be careful not to add too much and create a lock in the compressor. Lastly, you can have oil injected when your system is recharged. If you didn't evacuate and then flush the system, there's really no way to know how much is still in there with any precision, so you'll have to make some educated guesses. There are ways to guesstimate how much oil should reside in each component of the circuit after full distribution throughout.

Of course, be sure to use the right oil - mineral oil with R12 and PAG or ester oil with R134a. Mike's FAQ on AC repair covers this.

Good luck!
(oo=00=oo) Eric
1981 528i Manual

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dsw99a
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Re: 1978 530i A/C Oil charge

Post by dsw99a » Mon Aug 19, 2019 2:44 pm

thanks.

In the manual and on my compressor the hole is located on the bottom of my compressor. there is hex piece that comes out the back. Is that the correct place to inject the oil? ( and then watch to see the oil come from that hole?) I have mostly got the recharge done, so the system is closed. can i use one of the ports on the compressor itself? Im guessing to intoduce it to the low pressure port? Its blowing cool air i will have to add one more can.

I used the air duster that has been rumored to work. Just want to protect the compressor. glorious cool air!!

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528i-1981
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Re: 1978 530i A/C Oil charge

Post by 528i-1981 » Mon Aug 19, 2019 7:10 pm

I have the Bosch 0 140 903 506 axial compressor. The BMW service manual specifically says that the compressor plug should not be removed with refrigerant in the circuit, and that the circuit must be emptied before opening. I took our Bavarian brethren at their word and slavishly complied, so I honestly don’t know what will happen if you open the plug. I’ll leave that to FFers that are smarter than me. I suspect the risk of refrigerant escape is non-zero, and if the pressure in the crankcase is high, you might take a nasty spray of oil and freon.
(oo=00=oo) Eric
1981 528i Manual

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dsw99a
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Re: 1978 530i A/C Oil charge

Post by dsw99a » Tue Aug 20, 2019 2:32 am

So, i read everything from adding refrigerant at the drier, which really seems problematic. I seen guys just suck it up right from the can to the low side? I didnt think ,however + about the system being loaded with refrigerant,and pulling the veritable plug, good call on that. It just stated that the system not be ON when injecting oil?

I have to say, i had cool air. I dont think i got 2 complete cans of refrigerant in. But the compressor was dead silent. Didnt even hear it cycle up or down? Ive heard they were quiet, but this, so far is a bit shocking! Knock on wood!!

Im trying not to, but i may just bite the bullet and buy the injector tool. It just seems the same can be done with manifold gauge? On the fence.

anybody have any more decisive/certain options for tackling this query?

thx.d

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528i-1981
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Re: 1978 530i A/C Oil charge

Post by 528i-1981 » Tue Aug 20, 2019 5:20 am

There are inexpensive injectors (basically cylinders with a short hose and a stopcock) you can attach to the service line through the manifold gauge set. You use these using the low side service port, similar to introducing refrigerant. Sounds like things are well under control.
(oo=00=oo) Eric
1981 528i Manual

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Lock
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Re: 1978 530i A/C Oil charge

Post by Lock » Wed Aug 21, 2019 2:06 am

I second using the injectors on the low side line. One thing I always do though is run a (fused) wire from the positive terminal of the battery, around the fan and over to the compressor to control it manually. If it keeps cycling on and off it will take a long time, and may not build up enough suction on the low side to draw in the gas/oil.
Personally I use the cans because they are already pressurized and make injecting faster and easier, but you need to be very careful about how much you're putting in and keep an eye on the glass gauge plus use manifold pressure gauges. Personally I always used the low side, not the dryer.
It's also recommended to get new Schrader valves if they're original because after 40 years they're unlikely to hold pressure and you don't want your new gas to leak out. You can just screw them on top of the existing ones.
1979 528i 5-speed conversion G260/6

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