How much oil in AC system?

[default]

1996 Sunfire 2.2 Liter

Driving down highway, flipped the ac on, heard a pop and saw something in the rear view, looked back to see a giant cloud of smoke from what I think (haven't looked closely yet)was the high pressure hose failing and blowing out all the 134a and a lot of oil on the exhaust manifold. I immediately shut the AC off, it was on maybe 30 seconds, I doubt it ran that long, the pressure switch probably killed it sooner.

This thing lost a lot of, if not all of the oil, at least 4-6 ounces. There is oil all over the front of the engine bay. Sticker under the hood says to use gm 12345923 oil, I assume this is just a high viscosity PAG oil. But does not give the amount. Is it going to hurt anything to put in a little more rather than a little less when I replace the line and recharge?

 

[Rock_Hudstone]

Originally Posted By: default
Is it going to hurt anything to put in a little more rather than a little less when I replace the line and recharge?

Too much oil will slug the compressor and reduce a/c performance. Insufficient oil can cause premature compressor failure. Its important to have the correct amount of refrigerant oil or very close to it.

On the other hand, if its just a beater car you want to sqeeze another season out of, go ahead and guess, but err on the low side as its much easier to add oil than remove. You also should replace the reciever/drier now that the system has been exposed to the atmosphere for a lenght of time.
I'd also investigate why the hose ruptured, don't hear about that happening often.

 

[Dakota1820]

i seem to remember it being 6oz dont quote me though

 

[default]

Originally Posted By: Rock_Hudstone
Originally Posted By: default
Is it going to hurt anything to put in a little more rather than a little less when I replace the line and recharge?

Too much oil will slug the compressor and reduce a/c performance. Insufficient oil can cause premature compressor failure. Its important to have the correct amount of refrigerant oil or very close to it.

On the other hand, if its just a beater car you want to sqeeze another season out of, go ahead and guess, but err on the low side as its much easier to add oil than remove. You also should replace the reciever/drier now that the system has been exposed to the atmosphere for a lenght of time.
I'd also investigate why the hose ruptured, don't hear about that happening often.


It is just a beater I want to have working AC when I dump it in the spring, and for the remainder of the summer till I get the Yugo on the road. I plan on replacing the expansion valve to be safe and hopefully regain some performance(before the explosion, it liked giving up around 90*). Does the drier really need replacement on a beater? I have access to a vacuum pump, would pulling vacuum on it for a while be good enough? It's only another $15 on top of a $65 hose assembly, whatever an expansion valve goes for, 2 cans of 134a, and the oil. But that's $15 more out my summer job paycheck.

How would I know I'm low on oil? Will the compressor complain?

 

[mechanicx]

Six ounce of PAG 150 is a good estimation. It won't be overfilled on oil at that amount as long as you don't also overcharge with refrigerant. Old R12 system get converted to R134a and 8 oz of PAG oil is added and the R12 mineral oil is left in the system.

The accumulator (drier) should be replaced but if you pull a vaccuum it will probably work out OK without replacement. There is no expansion valve, but an orifice tube. These usually don't need to be replaced. Hopefully your compressor isn't damaged and there's not wear debris to contaminate the system. I'm guessing not from what you said happened.

I would wonder why the hose failed though. Maybe the system was overcharged or something else.

You are going to replace this car with a Yugo?

 

[default]

Charge on the system is/was guessed. It had a very slow leak somewhere, took about half a can every spring to bring the pressures and vent temps up to normal levels. The leak could have been a defect in the high hose for all I know, the thing is wrapped in wire loom and a heat shield where I think it failed.

The Yugo is a sort of trolling device, and a property devaluation machine. It's also as simple as a car from 1988 gets(effectively being a car from 1969), I enjoy working on simple cars.

 

[mechtech2]

Adding oil to an AC system is tough to gauge.
We have no clue what was lost.
Too much is horrible, as is too little.
Find out what the system holds [lube wise], and guesstimate by adding 1/2 of that back. Maybe 2/3 if you really dumped the system.

 

[mechanicx]

I double checked and GM service info says a large leak loses 3 oz of oil. I think 3-4 oz will suffice. If you replace the accumulator you should add another 2-3 oz.

 

[mechtech2]

Originally Posted By: mechanicx
I double checked and GM service info says a large leak loses 3 oz of oil. I think 3-4 oz will suffice. If you replace the accumulator you should add another 2-3 oz.


Your homework netted you a great solution - it is your best bet.

 

[wtd]

My AC capacity book for your vehicle says it holds 9 ounces of oil. It will be a PAG oil. I usually use PAG 150 for r134a systems.

I would probably add the amount that has been suggested since you wouldn't have lost the entire amount since the condensor, accumulator, evaporator, and compressor will hold the most of the oil. Since you shut the AC off right when it happened, I doubt the compressor pumped out all of it's oil.

Of course the only way to get the exact amount back in is to flush the condensor(if it is flushable), evaporator and lines, replace the accumulator and drain the compressor and then add the 9 ounces back in. Good luck.

Wayne

 

[default]

UPDATE

Cut the heat wrap off the high hose to see what happened, hose is fine. Further investigation by slowly introducing 134a into it and looking for oil mist found that the compressor relief valve blew out. Explains all the smoke, it points right at the downpipe. What could have caused this? The AC worked fine the day before. Does this change how much oil I'm going to need?

Should I just throw a blowoff valve at it or what?

 

[default]

Pulled the orifice tube to check for bits of compressor and accumulator. It was not very dirty, a little gunk around the oring and a few little metal flakes on the screen. I would guess this is normal wear and tear for a high mileage system?

bad cell phone picture:

 

[wtd]

That is normal for a higher mileage vehicle. Just replace the valve and add some oil and recharge and see what happens.

 

[yonyon]

For what it's worth I'd go ahead and replace the whatever it's got as a fan relay as well. Worst case, the money you waste replacing a perfectly good relay isn't much.

 

[Chris142]

The reliefe valve does not normally blow off unless the radiator fan(s) are not working.

 

[JHZR2]

Since the system has been opened, substantial work must be done anyway. Id get solvent, do a flush, possibly replace the condenser or at least try to flush it, definitely put in a new receiver dryer, add the OE amount of oil in the dryer and compressor, seal up with new O-rings anywhere I could, and then fill with Nitrogen and R22 or an equivalent refrigerant suitable for sniffing. Overpressurize it and leak check, when youre OK with that, pull it to 500 micron of vacuum for 30-90 minutes (longer is better) and then fill with the right mass of 134 per the OEM setup.

Good to go.

 

[JHZR2]

Originally Posted By: wtd
That is normal for a higher mileage vehicle. Just replace the valve and add some oil and recharge and see what happens.


What??!? No way. You trying to kill the AC system once and for all?

 

[default]

This happened when I turned the AC on for the first time all day, at 75 mph. Car has a working air dam. Definitely not the fan relay.

Originally Posted By: JHZR2
Since the system has been opened, substantial work must be done anyway. Id get solvent, do a flush, possibly replace the condenser or at least try to flush it, definitely put in a new receiver dryer, add the OE amount of oil in the dryer and compressor, seal up with new O-rings anywhere I could, and then fill with Nitrogen and R22 or an equivalent refrigerant suitable for sniffing. Overpressurize it and leak check, when youre OK with that, pull it to 500 micron of vacuum for 30-90 minutes (longer is better) and then fill with the right mass of 134 per the OEM setup.

Good to go.


I have about $800 into this car, including the purchase price and one crash that required a tow truck. I'm going to replace the orifice tube, any orings I touch, and the blown blowoff valve. Dump 3-4 oz of pag 150 in it, pull a vacuum for an hour with an old robinair pump, dump 2 12oz cans of 134a in it (1.5 lb system) and go.

 

[JHZR2]

You're not even going to replace the dryer after opening the system???!?

You have to be joking. There is cheap, and then there are bad decisions.

 

[TFB1]

Originally Posted By: JHZR2
You're not even going to replace the dryer after opening the system???!?

You have to be joking. There is cheap, and then there are bad decisions.


It's a beater that only needs to last the season, I'd do same as OP mentioned, evacuate it for a hour, dump in the oil & charge, monitor pressures, done...