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Subframe? Or something else?

2K views 24 replies 5 participants last post by  P_T 
#1 ·
Alright. So just a little background on the car. 2000 328ci. 100,000 miles. 5 speed. Subframe "fixed" in the last year. No suspension upgrades. Coolant system overhaul etc. etc.

I love my car, especially after my previous 328i's automatic transmission grenaded itself right before I had planned to sell it.

Anyways. Both my problems are coming from the rear of the car. As mentioned, it had the subframe "fixed" by a reputable collision shop in town about a year ago. I don't have the typical symtoms of a busted subframe IE. beer can crunching noise coming from the rear under acceleration. But...

1) Squeaking noise coming from the rear when I take corners at a slow speed. The noise is very similar to a creaking bed. No issues if I'm driving straight, or even taking a moderate corner. The sound is more pronounced when I take 90degree corners at really low speed. I assume lateral movement is the culprit. Any thoughts?

2) When I drive over large potholes or manhole covers the rear suspension makes a loud banging noise from the rear, almost like my trunk is falling out of the car. It is progressively getting louder.

3) Another symptom, which I noticed only last night. I was accelerating quickly ( around 4800 RPM) up a steep hill doing about 65 k/h when I started to feel a lateral shifting in the rear, followed by a violent sideways shuttering of the rear as I pushed the RPM over 5300 RPM. Now my rear tires are completely shot, like we're talking 20% tread left maybe?

My first thought was that the body shop did a ****e job repairing my subframe and its broken again. Or, rear trailing arm bushings/ shock mounts?

Any help with this would be greatly appreciated. I'm very thankful to the users on this forum, as they helped me through many issues with my previous E46.

Thank you.

Connor
 
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#2 ·
I'd check your rear shock mounts first and foremost, they might have broken causing the poping sounds. In addition, it would allow lateral movement. I am sure your RTABS need replacing too though. Tough call. Did they do the full removal and replace of the subframe like my car or did they do the "magic foam" fix?
 
#6 ·
Smolck, thank you.

From my inspection this afternoon it looks like magic foam. I lifted the truck floor and the battery cover and there seems to be a foam/glue looking substance between the top of the spare trunk locker and where the battery cables are.

My assumption is that the magic foam falls short of a full subframe replacement. How is it that they would do this and not the entire job?

Not looking good...
 

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#8 ·
Well its definitely that injection foam. And they tried to paint over it. According to my records, the car spent close to 6 weeks in their shop, So I dont see how a simple lowering of the axle and foam injections can take that long. help!
 
#9 ·
BMW had two fixes for cracked subframes. In my case where the mount completely ripped out of the floor pan, they had to replace the entire floor pan. In cases of "cracks" and not total tears, they used the "magic foam" to reinforce the subframe. Not desireable because it doesn't change the design of the floor pan whereas my car got the entire section from the newer cars.

BUT, you have two things going for you. 1. All BMW subframe repairs should have come with a 2 year warranty. 2. It still might be the RSM's or the RTAB's. Check the RSM's.
 
#11 ·
Smolck,

One slight problem, and I am not sure if it pertains to this type of warranty, but the subframe repair was done by the previous owner as a condition of my purchase. So technically the repair wasn't done under my name. I know this is a problem for other warranties..

Would I have any other obvious symptoms? The car handles great, the rear is surprisingly tight. Ive had two friends with subframe problems on their E46's, and both experienced serious cracking and crunching noises from the rear under acceleration in a straight line. Not the case with my car.
 
#20 ·
Alright, Problem solved! Paid 130$ with labour to replace both RSMs today..and wow...the difference is major! The ride quality is 100% better..IE. it actually feels like I have a rear suspension now.

So to any E46 owners with the same problems, rear banging over potholes and squeaking from the rear under low lateral load, fix those rear shock mounts! I've been considering an Audi S5 for a long time now..but I am reminded now as to why I fell in love with the E46.

Here are some pictures of the destroyed RSM;s. Some pretty nasty wear.
 

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#23 ·
Yeah pretty cold here in British Columbia. And I dont have the time/tools to do such a job. My indy shop treat me well..saved my skin with my last 328i.

After a spirited drive tonight, I'm shocked at the improvement of the ride quality. I had a terrible door rattle which is now gone, and no rubber ducky sound from the trunk! The first picture shows how badly the inner pin had sheared off.. No rubber left!

Smolck, yes a major relief to learn that it wasn't the subframe. However, the 'magic' foam job is still sketchy, I think.

Next job. Oil pan gasket. Mechanic had a look around and said thats the only problem area right now.. Says maybe 5+ hours..drop the front subframe? motor?
 
#24 ·
Next job. Oil pan gasket. Mechanic had a look around and said thats the only problem area right now.. Says maybe 5+ hours..drop the front subframe? motor?
I did it in 4 hours, in my driveway, and no help. Just drop the subframe, it isn't hard at all.
 
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