Whistling/hissing sound when in Park or Reverse ONLY. 2003 4.4

[ArNarX5]

I bought my car from an Auction without seeing it in person. I know it's a bit risky and some might say how can you buy a car without seeing it?

For one, I picked it up for about 11K so I figured there would be some things that would need attention at that price. Since I had purchased a 14 day return guarantee on the car, I had a mechanic check it out once it arrived to make sure it wasn’t a money pit. Diagnosis came back saying the car did not look to be abused, but there were about $2,000 worth or regular maintenance and repairs, brining my total investment to 13K and some change. I am fine with this so long as once the repairs are completed, I’m good for at least a year.

I brought up the hissing sound to my mechanic and he did not seem to be too concerned with it, but he did say too much of that noise is not good. For reasons unknown, I did not ask him what the noise was from.

Does anyone know the sound I am talking about? It sounds like an air leak, hissing, squealing or a whistling sound at the same time. I think it's from the transmission, but I hear it from the front right of the car. I just don't know what is causing that noise and if it can be fixed easily or are we looking at a new tranny? If it’s a transmission going bad, the car has to go. The transmission is running at about 90-95% of what it feels like when new. Every now and then when it gets warm, I sense a very small kick when changing from 1st to 2nd, but I mean very small, but I know it's there.

I really love the car and hope it's a vacuum hose or something... Anyone??

[wullaby]

You know I have 2003 4.4i with 80K and i noticed some hissing noise, so I brought it in to a shop and they lifted it and we both looked, he says he doesn't see too many BMW's (The shop was Goodyear) but he said not to worry and keep driving it, but the noise came from above the transmission pan (the spot where you would drain and fill your trans fluid) the noise was like steam being released, not terribly loud but noticeable. There was a slight leak of tranny fluid and he tightened something and said that should help the leak. I wonder if I have low trans fluid that may cause it, he said not to worry and keep driving if it was him....I want to get a second opinion as well.

[ArNarX5]

Yup, sounds exactly like my issue. Steam being released was a very good way of describing it. It's not too terrible, but you notice it. I noticed today that it happens when I go from Drive to Park, Drive to Reverse, Reverse to Drive (basically in between gear changes).

Would love to know if others have experienced this as well. I'm getting concerned.

[TX_X5]

Any update on your hissing sound? My 02 4.4i has developed some sort of whining sound when in N or R, but not in D. I'm going to have someone look at it this week.

[ArNarX5]

Still no solid answer. Mine has been doing it for about 6,000 miles and I've taken it to two BMW "specialist" and they both think it's harmless. Does the same as you described and is quiet in D. If you get an answer to this, please let me know. Thx.

[m5james]

I'd double check the transmission filter. Some people do the tranny service and put in subpar filters which collapse under pressure and make that sound. You probably only here it in those gears because beyond that it's road noise taking over.

These cars are notorious for tranny issues, so I'd spend the few bucks it'd take to drop the pan and check and/or replace the filter with a brand new BMW unit.

[TX_X5]

Had it looked at by my regular indy shop and they do not seem concerned. I think I'm going to get a 2nd opinion. Interesting thing is that the noise only occurs when the transmission is warm. There is no whine when it's cold.

Good suggestion re: transmission filter. I'll look into that.

[m5james]

As long as a shop catches all the transmission fluid, checking the filter should be a fairly easy job with a lift. I've done it on both a lift and having the car about 1ft off the ground, shouldn't take more than an hour to check. Replacing the fluid opens a whole ball of wax that people will debate left and right, but replacing isn't part of the debate if that's in fact your problem.

[1stE53]

Originally Posted by m5james

As long as a shop catches all the transmission fluid, checking the filter should be a fairly easy job with a lift. I've done it on both a lift and having the car about 1ft off the ground, shouldn't take more than an hour to check. Replacing the fluid opens a whole ball of wax that people will debate left and right, but replacing isn't part of the debate if that's in fact your problem.

I have read hours on this but just wanted to ask you if you replaced your transmission fluid? If so, at what mileage?

[shooter]

I had that hissing noise you mention and it turned out to be my tranny fluid pump. It was clogged or something. I changed the filter and tried to flush the fluid by draining and adding over and over again until it got to the point where I was getting no where as the fluid was hardly changing color. I decided to just start the thing and run it through the gear while in the air with the tranny pan off. I had someone else do that while I was under it. Immediately after firing it up it you heard it unclog and all this thick nasty tranny fluid came pouring out. I assume from up in the TC. It looked like muddy chocolate milk. After that I filled it with fresh fluid and drained it again. Filled it one more time put the filter on, cleaned the magnets and put the pan back on. Amazingly it drove better than it ever had since I owned it after that. No whine or that hissing anymore. Unfortunately that was for like 3 weeks, until it just stopped working and needed to be rebuilt. See my thread "Horror from Underneath". I forgot who, but someone posted a video of the whine that you get before the tranny goes. I know the hiss you are talking about because I had it and its not to be confused with the whine in the video.