I have an R53 with tune by Jan, cam, larger injectors, exhaust etc. that makes a terrible racket when the A/C is turned on while idling in Drive or Reverse. Can't hear it while driving, or in Park/Neutral.

He replaced the A/C compressor, re-charged the A/C, and both motor mounts but it really didn't fix the noise at all.

I replaced the power steering pump's electric cooling fan, but that didn't help either.

It might be the front electric fan that comes on when the A/C is on, but to me it sounds like a knock, or a lifter or something internal to the engine. I've described the problem as, it sounds like the engine is going to explode.

Anyone have any ideas? Thx!

 

It is unlikely that engine starts to knock when AC is on and doesn't knock when AC is off.
It is easy to see if it is a radiator fan by just disconnecting it.
You kinda rulled out the most of the potential issues - AC compressor, steering fan....
The fact that it is NOT happening on Park / Neutral makes me think it might be tranny or torque converter related. Try to use stethoscope to localize the sound (and maybe record a video to post here).

 

You might be onto something. I had a transmission error code on the car before. I'll see if it's returned.

Where's the plug to disconnect the radiator fan? Thanks!!!

 

Next to the AC filler ports left (US drivers) side forward, just behind the radiator assembly frame

 

is your AC working? Mine's doing it but it likely is the AC comp itself as it only happens when clutch engages. I'm thinking bearing

 

Yes, AC was and is still working great after replacing the compressor (which didn't get rid of the noise).

I still need to try disconnecting the radiator fan wire.

I did replace the power steering electric fan, but that didn't help at all either.

The noise is worst when stopped, in gear, with AC on.

 

Has the original crankshaft pulley / harmonic balancer / damper been replaced? These sometimes make all kinds of funny noises (or none at all) before failing. If it only happens with the AC on, might make sense because of the added load on the belt and damper.

https://www.realoem.com/bmw/enUS/sho...89#11237525135

https://www.outmotoring.com/MINI-Coo...2007-2008.html

 

Yes, when Jan originally replaced the A/C compressor, he did the motor mounts and the damper. It's a PWR fluid gel type high end damper. None of this helped the horrendous noise it makes.

Did some more experimenting today.

The noise is loudest when the car is in gear, stopped, AC on. It's mostly affected by AC on.

I finally unplugged the main cooling fan today. I don't think it's that fan/bearings etc.

However, with that fan unplugged, the AC compressor wouldn't run very long (probaly because temp was too high without fan?) and the noise would pretty much go away with compressor cycled off.

I'd be shocked if I had a bad compressor and replaced with a bad compressor with the exact same problem!

*** One more interesting thing...... AC On, car in gear and stopped. If I rev the engine 1-2K RPM, the noise seems to go away.

The engine does shift fore and aft a lot in and out of gear, but motor mounts are basically new. I thought maybe engine was shifting and rattling on something, but it doesn't seem to be.

Need Help!

 

At this point a video would be helpful, to get a sense of location, frequency, pitch, intensity etc. in or out of gear, at RPM etc Also try to probe with a stethoscope where possible as suggested above. Thinking it has to be somewhere along the accessory belt route, to include the compressor, alternator, crank pulley, tensioner and idler pulleys, supercharger. Could also remove the belt, and check each component for end/axial play by hand for any sense of unusual resistance, vibration, or grinding.

By chance did he replace the AC compressor itself but not the compressor clutch; unlikely of course but if it's the case the latter should remain fairly high on the suspect list.

 

That's a good call about the AC compressor clutch.

But, I looked back at some invoices.

In March, 2021 I supplied a compressor clutch off of eBay that he installed. Didn't help.

Then, in August of 2021, a new "Compressor w/Clutch" was installed on the car. Didn't help again.

I've tried to video the noise before without much luck. I could try again.

It sounds like it's coming from the passenger side where the accessories are, but it's so much racket, it seems like it's emanating from everywhere in the engine compartment. It's mostly an embarrassing noise that can be heard 20 feet from the car.

 

take the belt off and start the engine, is the noise still there? If so, then it's inside the engine. If not, then it's one of the pulleys or the accessories that is driven by the belt that is making the noise

I went through 5 AC compressors right out of the box one time on my Dad's Cadillac until I got one that was quiet...just because a part is new, doesn't mean it's good

Bryan

 

That's a good idea. I wonder what would actually happen with the belt off when the AC is turned on?? I think Jan's tune raises the RPM of the engine by 100 when the AC is on. Other than that, I don't know if anything else is different.

 

The compressor will not turn with the belt off. This diagnostic test is to determine if the noise is inside the engine, or on the outside of the block and head.

Bryan

 

This is a great idea! How difficult is it to get the belt off? I haven't removed it before.

 

It's not easy unless you have the correct belt removal tool to release the tensioner. Even with the tool, it's not fun.

You can buy one most anywhere for around $25. Comes with the tensioner lock pin as well

The tool is different between the R50 and the R53... make sure you get the right one

Bryan

​​

 

https://www.outmotoring.com/mini_coo...2007-2008.html

https://www.pelicanparts.com/More_In...L-026518SCH01A

>Removal tool
Bunch of Chinesium ones at Bezos Mart for less but considering the precarious nature of their intended use would opt for known quality from reliable vendors. I carry the thing in the car as part of a minimum essential road kit, also not a bad punk-be-good stick for certain unexpected contingencies...

Take your time with it; quasi-manageable alone, optimally a two man operation to use it.One guy on the tool, the other guy inserting the pin with a long set of needle nose pliers. Mod Mini demonstrates it solo at about the 4:00 point:

 

...Good advise.
I imagine you may have read one of my earlier post a while back,, with respect to the belt tentioner tool and the precarious encounter I had late evening at a darkened quck-mart/gas station.- "the tensioner also makes a handy weapon/deterrent in a pinch".
I'm glad you brought up it's many other uses besides being just a essential belt removal tool.

 

Which it doesn't even do very well. They could have just designed it better. Best of all design the tensioner not to need one. I've pulled belts with a 3/8 or 1/2 inch ratchet or breaker bar where the manufacturer conveniently put a square hole in the tensioner frame for just that purpose (for once, thank you Ford engineers). No special tool, no finding a helper, no winding up on your *** because you weren't braced right / didn't have the two 3x3mm pegs firmly planted in their tiny little holes working in crappy garage light on a greasy floor. And certainly no taking it to the stealership out of frustration / desperation. But something tells me BMW knew that already...

 

Update - in progress - Car it at shop and I hope Jan can narrow it down.

Pulley tensioner was vibrating too much (sort of in sync with the terrible noise) when A/C was on. Checking all bearings etc.

Thinking A/C clutch again, but that would be the 3rd one.

Somewhat of a mystery.

 

Solved. Turned out to be just the tensioner pulley assembly going bad.

 

Was the idler pulley checked while serpentine belt was removed ; pretty common issue on a majority of cars ….