# Squealing Power Steering



## Keitharm (Sep 5, 2004)

I've been reading this board for some time, and found some really wonderful info. Now I've got an issue I don't understand.

1997 540iA. Eibach springs, Bilstein sports, M5 rear sway. 95,000 miles. Oh, and I changed the radiator and related parts based on recommendations from this board and others.

Here's the deal. When it's cold, and only when it's cold, my power steering squeals like crazy, but only when I turn the wheel. No issues in a straight line, and never if the temperature is over 40 F. Fluid is at normal levels.

What's that about?


----------



## Garik (Feb 15, 2005)

problem sounds like not enough steering fluid....


----------



## Nick325xiT 5spd (Dec 24, 2001)

Exactly.


----------



## wschubert (Jan 31, 2005)

Since you claim the PS fluid is at normal levels, but hear squealing at low temperatures, then maybe:

1. You are mis-reading the PS fluid level, and it is too low (as others have pointed out). In this case, have you checked your owner's manual for the correct level checking procedure?

2. The PS pump belt is slipping when the fluid is cold and most viscous, then stops slipping as the fluid warms up. I've heard my PS pump belt squeal from slippage when the idle was low and I was turning the wheel at a full stop. Your PS belt might be slipping due to a worn belt or weak tensioner; alternatively, your PS fluid might be the wrong type and too viscous.

Walter


----------



## Keitharm (Sep 5, 2004)

I've checked the level both hot and cold, and the belt is new. ATF in the power steering reservoir.

Any way to check if the tensioner is bad?


----------



## wschubert (Jan 31, 2005)

Ok, have to ask: are you checking the level with the engine on, or off?

ATF is the right fluid; how new is it?

I don't have tensioner specs, but there are two of them, one for each belt. If you compare the amount of force necessary to move the tensioners, you might be able to detect if they are significantly different.

Walter


----------



## Keitharm (Sep 5, 2004)

Ok Walter, I appreciate your replies. But just so you know I'm not a complete idiot, I've been working on cars all my life, and I'm pretty sure I know how to check fluid levels. And this is my second BMW. (first one was a 98 528).

But since you asked, there is no change in the level in the P/S reservoir with the engine on or off. When hot, either on or off, the fluid level is at the upper tick mark.

I'm the second owner, so I have no idea how old the fluid is. But it's ATF, and it's still red. Prolly should change it just to be sure.

So why would a bad tensioner cause belt squealing only when it's cold outside? That's the part I don't get. I don't just get a bad squeal. The steering wheel indexes, rather than turning smoothly. Kinda like the second hand of a watch. Tick tick squeal tick.


----------



## wschubert (Jan 31, 2005)

Didn't mean to offend you; since you didn't offer any details that you read the manual or had checked using the procedure in the manual I just wanted to make sure the problem wasn't low fluid. Now that you've explained your experience with auto mechanics I'm very sure the fluid level is not the problem here. Surely you've heard what a slipping belt sounds like; does your squealing sound anything like a belt slipping? I would use the word squeal to describe a belt slip, but use the word moan for the air-entrained sound of low fluid.

You mention the steering kicks back when it squeals, which leads me even more to think it might be a slipping belt, because each time the belt slips, the PS momentarily loses boost and makes the steering harder to turn. This used to happen to me on a previous car with the old style v-belt, and was cured by tightening it up. Of course, with a serpentine belt automatic tensioner, the spring does all the belt tightening. 

My theory was that the cold weather resulted in cold fluid that was more viscous and harder to pump, and thus the higher load on the PS pump could cause a marginally loose belt to slip and squeal. When the fluid warmed up, it was less viscous, and the PS pump load was lowered enough that the belt would stop slipping. Does it always squeal when colder than 40, or only when colder than 40 AND the steering wheel is being turned at a full stop (maximizing the PS load)? An experiment to try to prove/disprove this theory would be to maximize the load on a slightly warmed system (when you wouldn't expect squealing) by turning the wheel at a full stop to see if you can force the squeal; the opposite experiment would be to try to minimize the load on a cold system by turning the wheel slowly while the car is rolling to see if the squeal wouldn't happen. If you can get the opposite (squeal while warm, no squeal while cold) of what you expect to happen under those temperatures, it would tend to support the theory.

Alternatively, if the fluid is abnormally viscous, then the tensioner might be fine. Does old worn-out fluid get more viscous? Does dirty fluid get more viscous? Or maybe it's the wrong type of ATF? Perhaps changing the PS fluid would be the easiest thing to try.

Good luck, and let me know what you find out. I'm very intrigued by this!


----------



## Keitharm (Sep 5, 2004)

Below 40F, start the car, back out of parking spot with lots of racket from the steering. Even when turning the wheel slowly. You're right about the squealing vs groaning. It doesn't really sound like belt slippage, but it's hard to say.

Drive my kids to school, about 7 miles. No weird noises in a straight line, or even on curvy roads, but when I take the 90 degree turn into the school, more racket. Pull out of the school parking lot, more racket. Drive 15 miles to work, and by that time all is good. No more silliness.

Never happens when it's warm outside. Very weird. I'm changing the P/S fluid tomorrow, and then I'll wait for a cold day. Stay tuned.


----------

