Name that tune!

[sdb999]

01' 740i 85k miles, no issues whatsoever but it is new to me and it "sounds" different than my iL of the same vintage so perhaps I'm a wee paranoid. It's got an electric motor like sound that sings in perfect unison with engine rpms. Pitch beautifully follows the revs in park, neutral, or drive with no perceptible difference. Whether in motion or sitting still, and load has no impact either. I suspected the fan clutch, but removed the fan (leaving just the clutch intact) with no change. The attached video is with no fan installed. Maybe it's nothing, but sounds like a hydraulic pump to me so power steering maybe?

Thanks, S.

[gaspump]

Could it be coming from your stereo system? Like feedback etc.

[RXZero]

2nding, it does sound like an alternator whine, usually caused by a bad ground and presents it self as a noise that changes with engine rpms.

[sdb999]

Nope, radio and hvac both off and definitely coming from outside the car. Although could be alternator/idler/accessory bearing.....I really need to get a helper as it's not audible at at idle. I'm assuming the transmission has an internal hydraulic pump, but would it always spin at engine speed in neutral, drive and park? I ruled out transmission but maybe I was too hasty.

[sdb999]

Pushed 14 Liters of fresh atf through the transmission with little if any change in the noise. I'll finish the atf service when my filter arrives later this week, it was on the list anyway. But as I was sliding out after the final hot fill of the transmission I passed under the power steering pump. It was buzzing louder than I would have expected at idle and looked new-ish. I had checked ps fluid before but it's worth a revisit. Car is new to me so I'm not 100% on past maintenance and going through baseline. I will say this transmission shifts better than the iL, of course could be adaptations I suppose.

[Manny G.]

Pushed 14 Liters of fresh atf through the transmission with little if any change in the noise. I'll finish the atf service when my filter arrives later this week, it was on the list anyway. But as I was sliding out after the final hot fill of the transmission I passed under the power steering pump. It was buzzing louder than I would have expected at idle and looked new-ish. I had checked ps fluid before but it's worth a revisit. Car is new to me so I'm not 100% on past maintenance and going through baseline. I will say this transmission shifts better than the iL, of course could be adaptations I suppose.

I just went through a power steering overhaul.. my old one (single vane) sounded like it had marbles in it... I dont know if there are different sounds associated with the pump going bad, but have you checked the belt tensioners?

[sdb999]

Thanks Manny, yea belts and tensioners/idlers are on the target list. Ps fluid level is good, once the trans filter/fluid change is done I’ll get my wife behind the wheel and blip the throttle while I crawl around underneath to pinpoint the source. We’ll see.

[racer2086]

Another thing you can do is pull the belt and run it for a short time to see if the noise is gone. Sounds like a pulley or pump issue. Could be the oil pump in the transmission I guess, but more likely something up front.

[sdb999]

Oh, now that’s old school right there. I’d have already pulled the belt on any other car but figured that would throw all sorts of codes on a modern-ish bmw. That’s good to know if all else fails I can, at least for a few minutes, run it sans accessory drive. That would narrow the field pretty quick. Thanks, love this place.

[sdb999]

@racer2086 wins! It was on the accessory drive, ps pump to be exact, man that thing is screaming. I'll be ordering parts tonight for next weekend. Thanks for the shortcut, and sooooo relieved it wasn't the transmission. I have a parts car but I don't think I could have handled that by myself, maybe but not without much of a safety factor. Cheers all.

[sdb999]

Well, replaced the pump and something is still making a racket, same whine. It's a little better but I'm going back to square 2 and diagnose the source again.

[sdb999]

Ok, I bypassed the ps pump with a shorter belt and the whine went away so it's not the water pump or alternator. Two possibilities:

A. The rebuilt pump (Cardon) arrived defective in the same manner as the original pump.
B. The steering gearbox is causing the noise somehow by over loading the pump or causing cavitation, etc.

I'm going with A. I could not find a new pump immediately and went with a rebuild of dubious quality. Rare but not unheard of to bolt on a new part that is defective out of the box.

Is there any chance that scenario B could be at play? Pump inlet I believe is directly from reservoir so I don't see how it could get starved for fluid. Could steering box be restricted? Steering feels fantastic with nothing unusual.

If for any reason you need to bypass ps pump pics below show how with shorter belt and altered routing. Yes, tensioner is reversed, so gentle when you set tension.
Belt.jpgRoute1.jpgRoute2.jpg

[racer2086]

No more likely scenario A, I would say. I never have good luck with reman parts unless it is done by a mom and pop operation that cares.

Someone probably replaced their pump due to whine just like you and the company replaced seals and o-rings, but missed the main issue causing the whine.

[sdb999]

No joy. Brand new, not rebuilt, Luk pump and the squealing is still there. Maybe slightly different pitch but volume still drowns out the sound of the engine. I’m at a loss. It’s definitely the power steering system, and it emanates from the pump. What is causing the wailing pump is the question. Only three things that haven’t changed:
1. Steering box, but it’s not leaking and steering feel is consistent and stable at all angles and speeds
2. Steering fluid, still using synthetic atf.
3. Most of the lines and cooler integral to radiator. The two lines from the reservoir are new. I’ll confirm routing in the morning.

Once routing is confirmed I can easily change to non synthetic fluid first. Then, bypass cooler without too much trouble. But I really suspect something in the steering box. Need to research what goes on inside those things.

[racer2086]

I would make sure the new hoses you installed don't have a restriction or something. The synthetic fluid should be fine.

Is the fluid cavitated in the reservoir? Is the screen in the reservoir clogged with stuff?

Only other thing I wonder is if your tensioner is good or adding too much tension to the belt?

[sdb999]

The tensioners and idlers are new, Ina. But you’re right, I forgot to include the reservoir as a component that had not been ruled out yet. I’ll pull that first and investigate lines for obvious signs of blockage. As far as I could tell there was no cavitation, I’m assuming the fluid in the reservoir would be somewhat aerated? But if the reservoir outlet was clogged that would explain a starved pump and the noise. My son arrived this afternoon with a blown head gasket on his civic so I sent him home in the 7. When he comes back in a few days I’ll have a look. Racer2086 I greatly appreciate the extra eyes, embarrassed I missed the reservoir.

[racer2086]

The tensioners and idlers are new, Ina. But you’re right, I forgot to include the reservoir as a component that had not been ruled out yet. I’ll pull that first and investigate lines for obvious signs of blockage. As far as I could tell there was no cavitation, I’m assuming the fluid in the reservoir would be somewhat aerated? But if the reservoir outlet was clogged that would explain a starved pump and the noise. My son arrived this afternoon with a blown head gasket on his civic so I sent him home in the 7. When he comes back in a few days I’ll have a look. Racer2086 I greatly appreciate the extra eyes, embarrassed I missed the reservoir.

You would see the fluid aerated, yes. There's not much to the reservoir, except the screen filter screwed in there to catch large debris. I'm wondering the there's flash or debris in the hose from manufacturing causing a restriction. Not sure what else it could be

[mgrennek]

Have you had a stethoscope to the different pulleys to be 100% of the source. AutoZone has them cheap and they are a really useful tool.

[sdb999]

After two ps pumps, two fan clutches and many other attempts at isolating the whine it was the fan clutch. What caught me off guard was without the fan attached the clutch still whined. And it functioned perfectly, was just noisy. The second clutch, Behr I believe, was quiet as a mouse.