BMW E38 AC whine/Noise when AC is on due to lack of oil

[@robbongiovanni807]

Thank You, Thank You, Thank You!!! 3 shops (2 BMW dealers and 1 foreign car shop) told me that I needed a NEW COMPRESSOR. Today I had the AC system flushed and new oil added as you recommended. The whining sound is GONE!!! Your video saved me somewhere around $1,000.00. THE BEST!!!

[@BMWorks_NL]

Rob BonGiovanni glad it fixed your problem, it can come back after a few months

[@teravolt6113]

@@BMWorks_NL The noise can normally come back after a few months even if you don't have a leak and i'll explain you why. The compressor has a mechanical control valve that regulates the compressor displacement by looking at suction pressure so that the evaporator won't get too cold. The groaning noise is the compressor working at lowest displacement. When it's at a greater displacement the compressor is silent. In the colder months the evaporator gets colder much faster and the control valve apparently makes the compressor destroke earlier than in the summer because it sees lower head pressures. However, in a correctly charged system and with a healthy control valve, what should happen is that the noise only comes back after some time that you've turned ac on, i.e. the compressor should immediately pick maximum displacement especially if the weather is mild (>13°C) or warm; if you begin hearing the noise only right after the air from the vents has got very cold then everything is ok, the compressor is reducing displacement to avoid frost as it's expected to do when the thermal expansion valve begins closing down. If the noise starts as soon as you turn AC on and the weather isn't cold then you either have a refrigerant level problem (probably caused by a leak) or a control valve problem (might also be a thermal expansion valve problem because one that doesn't work right also makes the control valve not work correctly). Too low refrigerant causes the suction pressure to go down too fast and that's what keeps the compressor from entering full stroke when refrigerant is low. Also listen for any loud hissing from the vents or the evaporator box, the loud hissing means low refrigerant charge especially if you get it as soon as the compressor engages. Liquid flowing noises alternated with quiet hisses mean correct charge instead.

[@teravolt6113]

FYI i researched that further and it's the noise of a variable displacement compressor stuck on lowest displacement. The noise is normal as long as something isn't forcing the compressor to stay in lowest displacement. The problem is not that small amount of oil (10 grams is usually the amount of oil removed from the lines when the refrigerant is evacuated) but what can make the compressor stay on lowest displacement (either too low refrigerant, which can also imply a leak, or a faulty compressor control valve)... low oil gives rattling noises from the compressor, not groaning ones... groaning, like in the video, is the reed valves inside the compressor opening and closing very rapidly due to the pistons traveling a very short stroke. The noise travels to the evaporator through the suction line and that's why you hear it inside the car. You probably had very low ac refrigerant in the video and the control valve kept the compressor always destroked, seeing very low suction pressures and thinking that the evaporator was frozen up, that's why the regas fixed everything up.

[@MetroRatRace]

Are you saying one should add more coolant/ anti-freeze when you say refrigerant?

[@teravolt6113]

@@MetroRatRace AC refrigerant. If a car requires R-134A refrigerant it's R-134A refrigerant. But remember, forget about the stuff in a can. It does more harm than good. Let a licensed professional work on the system with the aid of a recovery station. That's the way you correctly charge systems equipped with variable displacement compressors.

[@MetroRatRace]

TeraVolt thanks! I’ve had my car for almost twenty years (2001) and have never added refrigerant believe it or not. It’s very low mileage (98K). A year ago my engine oil was empty from a leak and it caused a rattling noise as you mentioned when oil is low. If I understand correctly the level of oil doesn’t really have much bearing on this noise issue; the reason is low refrigerant.

[@teravolt6113]

@@MetroRatRace You're right. It's not the oil. It's low refrigerant making the compressor stay in lowest displacement. And in lowest displacement, any variable compressor not equipped with suction shutoff valves or internal bypasses makes the evaporator resonate with the reed valve sound (the groan you hear). My car makes this noise too, but only when the evaporator has reached its coldest temperature and the compressor is therefore unloaded to keep it from freezing up.

[@teravolt6113]

@@MetroRatRace Unfortunately you leak some refrigerant over time even if you don't have any leaks. There are o-rings, and there's a compressor shaft seal. And these can leak even more if you don't turn AC on a few minutes every month, even in the coldest months. You should have the system checked for leaks, evacuated, vacuumed and regassed every 3 years. The refrigerant is what brings the oil to the compressor so with less refrigerant the compressor wears more rapidly.

[@fabini14]

tanks men, my ac does the same noise, and not make cold air, now i know its because not have oil and gas in the system.

[@job1bf]

My 2001 740 was doing the same thing. dealer did a purge and refill - solved the problem. Fluids were only slightly low - was still blowing cold air. So be aware - it only needs to be just a bit low for this to occur. Thanks E!

[@mossnation7245]

job1bf you are correct mine was slightly low and doing this. Got one of the kits that had oil in the can also and fixed the problem got it to 50 or what not.

[@aleather]

Hi Edwin, would you be willing to make a video showing the fix for this step by step? Thanks a lot.

[@aleks0001]

I had the same issue on a 2006 E90 325i. Turned out my schrader valves were slowly leaking. Had them changed, re-filled the system and no more noise.

[@BMWorks_NL]

Have the system emptied, add compressor oil and the charge to the correct weight

[@charliefunboy5210]

I really appreciate your channel. Quick question: My 2001 740 does this. I had it "topped" off two years ago and the noise stopped. Back now. I understand your explanation, but is it absolutely necessary to have the system pulled empty, etc. Or can I simply top it off again (thinking of using a DIY AC solution that has the oil mixed with the refrigerant) I only drive the car a few times a month and I'm trying to keep the cost down. (214K miles and still a beauty) Thank for your help

[@benm6899]

I have same issue. So you flushed the aircon system. Then topped up Oil and re gassed ?

[@emmanuelkwabenaasante4707]

I'm facing this issue now with my bmw e53. Do you think it's the compressor?

[@黃宣諭-b7p]

10 grams of oil !!! weight or volume ?

[@tambo0121]

I had compressor and belt replaced and now when I turn air on I get this noise, the gentleman who fixed it said it has to be something else but only makes noise when air is on, plus passenger side not getting cold. Single female life issues 🙄 what kind of oil are you speaking of ?

[@gtarules1]

You mean the whirring noise, right? I hear some squealing the background, even after you turn the A/C off.

[@mark-xk6yf]

Hi! im experiencing the same with e90. so you need to add 10ml oil extra on top of the amount that is pulled from the system along with the refridgerant ? becasue when pulling system empty you are also removing some oil from the circuit.

[@Ehteez]

Thanks so much.

[@Ehteez]

My E38 2001 has the same problem.What should be the fix.Thanks.

[@BMWorks_NL]

Nee echt OLIE! Vaak vergeten ze dit en na een aantal jaren krijg je deze symthomen, systeem laten vacumeren en 10 gram olie laten toevoegen, juiste hoeveelheid gas (700 gram) en daarna heerlijk koel en stil

[@BMWorks_NL]

We hebben een heel mooi forum of wel e38forum punt nl kan heel goed een kachel klep zijn die je hoort

[@jamesyun7541]

I am driving a 2012 F02 730Li. Few weeks ago, have the same issue. A new compressor change will cost $1000 oem n labour. Saw this youtube. Went to a shop. Cost me $70 to flush oil and gas. They use a machine to do it. Dirty oil came back 50ml. They put in 100ml new oil. Now no noise. I will monitor for another week.

[@nugzarshin1877]

what is the right oil for my 2001 bmw 740i sport thank you

[@BMWorks_NL]

Any shop can tell you the correct oil needed. 10 grams is enough

[@teravolt6113]

Oil is PAG 46 but that really matters only when you're filling up a new compressor with the full charge of oil. When it's only a matter of ten grams (such as when the usual regas is done) most shops tend to use POE oils or PAG 100 oil.

[@estranged85]

I have EXACTLY this sound.

[@BMWorks_NL]

Then you know what to do ;)

[@bhvm333]

cant hear anything even in full vol.

[@teravolt6113]

It's a low groaning noise, the one a power steering pump makes when low on oil...

[@fahdyehia628]

Thank you very much