Idler arm for power steering pump question
 

Hello All,

Am a little tight on time and unable to get under the vehicle to verify so was hoping someone could throw a quick answer if someone knows.

Which serpentine belt drives the power steering pump and in turns also drives the idler arm? Is it the: waterpump/alternator or the A/C compressor?

Reason I ask this specific question is because on cold start and sometimes warm too, the belt slips and especially when cold, when I turn the steering wheel, the belt screech. Belts were replaced a couple years back and only a few thousand miles on them now.

My hunch is the idler arm is not doing its job of maintaining tension and allowing the belt to slip especially under steering load.

Thanks in advance!

Chris

Idler arm for power steering pump question
 

Check your level. Wife's e53 would squeal like a pig when cold if the ps fluid was just a little low.

Everything but the AC is driven from the same belt. Unless your tensioner is shot it's very unlikely to slip in the pulley, I've always attributed the sound to something internal but it does sound like a slipping belt.

When you release tension, does the tensioner really snug the belt? It should be very tight.

Also confirm the routing path is correct I have a feeling it might be possible to have more than one solution of how it's wound.

I replaced the belts back in 2018 (summer) when I did a major top overhaul.
Belts installed the way they came out (had diagram drawings of how they were routed).

The tension is tight while the engine is off. Screeching happens only on the first start (when motor is cold). All subsequent starts, it's perfectly fine and quiet.

The idler tensioners are all original and there's about 155K on the clock.

Thanks Andrew for the info. I'm guessing then that the waterpump/alternator belt tensioner is the one to get.

Cheers,
Chris

Could be your idler pulley or tensioner pulley. I had to replace mine at about your mileage. The bearings in them were shot and would make noise when cold. Betting its that and not the belt or the power steering pump. Power steering pump makes a low vibration noise when at idle when they go bad. Could also be low fluid level.

Replace the tensioner and idle pulleys. Replacing them both is easy once the belt, shroud, fan, and clutch are off. Release the belt tension. Free spin all the pulleys by hand. You'll fid the bad one easily.

Thanks guys. Yes, the offending tensioner will be replaced.

Did I miss if you checked the PS level?

No Andrew, you didn't. Sorry, I failed to mention that I did check the fluid level and it's topped off.

Regards,
Chris

Mine leaked for years before I bought mine. I had to add fluid shortly after buying it. Plus, I know something was leaking after finding stains on my driveway. I took off the stock one time use BMW clamps. They are stamped BMW. The clamps were replaced with worm gear. The worm gear clamps stopped the leaks for now. Eventually, I'll replace the hoses and reservoir.