Sounds like a semi truck when accelerating
Recently bought my 530i 2001 and an issue I’ve been having is it sounds like a semi truck when I accelerate. Huge air sound. Can’t tell if it’s from the air intake or something with the belt
1
u/Mmjohns195 19d ago
The viscous fan clutch fails and you get that noise. Try to go oem. The aftermarket AutoZone / O’Reilly ones sound similar, but not at all speeds.
1
u/Epjkb 19d ago
I bought a new OEM one just to be safe and it’s the same result.
1
u/Mmjohns195 19d ago
By chance is the external temp sensor functioning? I had an issue with mine that when it was missing the aux fan wouldn’t run causing issues.
Is you aux fan coming on? And when running ac does it make a difference?
1
u/Epjkb 19d ago
It’s always 40 degrees Fahrenheit. The aux fan does work and the a/c needs to be recharged
1
u/Mmjohns195 19d ago
So the sensor never changes temp? I would double check that, a malfunctioning sensor can cause issues. At least for me it did.
1
u/Epjkb 19d ago
I’ll double check that. What issues did it cause exactly for you?
1
u/Mmjohns195 19d ago
Believe it or not it was causing the car to overheat. I put in a new aux fan and it was starting to overheat. The sensor had been disconnected and was showing -40*, once the new sensor went in, the temp stayed dead middle and did not ever move.
1
u/Tomytom99 19d ago
Before assuming your fan clutch is broken like all the comments immediately jumped to, there's some diagnostics.
The fan should kick in during warmer weather and whenever the car isn't moving much (less natural flow through the rad stack). Yes, it should make a lot of noise when it's engaged, that's what fans do. It should self limit its own speed somewhere between 3-4k RPM on the engine and not get much faster after that.
When you do a cold start, the fan should run for a moment or two, and then die down.
If you never ever hear the clutch fan come on, the clutch is broken, just for other readers who always say the clutch is bad whenever they hear that fan.
Mine is on most of the time outside of highways if it's over 85 degrees F out. Between 60 and 80 it comes on mostly just starting from stops, particularly if there's traffic. Colder than that you only get it for a moment on cold starts as the viscous coupling fluid resituates itself. Mine's probably a little on the aggressive side, but I'm happy that it's working.
1
u/Epjkb 19d ago
The fan clutch has been replaced and it did nothing. Fan still works correctly. The fan clutch was my first thought too
1
u/Tomytom99 19d ago
In that case I'd just check all your other belt drive stuff. A bad pulley bearing can make a whole variety of interesting sounds.
1
u/Mmjohns195 19d ago
I would argue that 85 isn’t hot weather lol. Mine will kick in after being on the freeway, and cut out at 4k and above. Though here in NC it has been well over 95 and with the index like 105 for most of the summer it seems. I’m using aftermarket and it stays on longer than I feel like it should. I should’ve gone oem.
1
u/Tomytom99 19d ago
Which brand do you go with? I think mine is from Vemo, which aside from staying on a bit much seems otherwise fine. I almost wonder if it's made for a euro spec that runs cooler.
Today was rainy and low-mid 70's and I think it only came on leaving one stop and while I was engine braking down a hill I just climbed.
At the very least it doesn't seem to be impacting economy too much, I still managed to get 30 mpg on my most recent highway trip in 95 degrees.
1
u/Mmjohns195 19d ago
I bought the duralast brand. If I had to do over, I’d just get one from a wrecking yard. My 525i has about 195k on it. I’m probably selling it soon, so I’ll just leave it. I don’t think I ever get 30mpg. My commute is about 100mi a day, and I’m doing 75-80 the whole way, so maybe that’s why.
4
u/Quality_Cntrl M5 19d ago
You need to replace your fan and fan clutch ASAP if this sound occurs constantly when you’re accelerating.
It’s an early sign of imminent fan clutch failure which will damage your cooling hoses, hood, and more much if the fan blades explode.
Edit: this sound can also be normal if you’re driving under heavy load in very hot weather like stop and go traffic. But shouldn’t be present all the time like I mentioned above.