On my way home tonight I heard a knocking sound everytime I hit a bump in the road. I dismissed it for something loose in the back as the sound was kind of faint. As the drive went on the knock started getting louder and I started hearing it when I applied the brake as well. Within a couple of miles everytime I hit a bump the knock was so loud it felt like something was going to fall off, and I could also not only hear it while applying the brake pedal but could feel it in the pedal as well. By the time I got home when I applied the brake I would get two loud knocks coming from the right rear, and the car would come to a stop without any subsequent knocks solong as I kept my foot on the brake pedal. Releasing and reapplying resulted in two more knocks. I intend to jack it up and invesigate in the morning but I was hoping someone might have some insight as to what to look for. Thanks, it is a 2003 325iT.
jeremy0000
Check your rear shock mounts. They can fail, and cause some noise. Hopefully, they don't look like this:
Untitled by MJLavelle, on Flickr
Another possibility, which would be much worse, would be rear subframe damage. You can find plenty of info on here as to what you need to check.
B
It could also be a brake issue. Some things to look for would be any calipers that are loose, meaning the mounting bolts are not locked down, or a broken or missing caliper pin, which would be rare, but possible. You may have a caliper that is sticking, and not moving freely on the guide pins. One sure sign of this would be excessive heat on the sticking caliper after a short drive. Take the car out for a few mins, press the brakes a few times, and when you get back home, check and see if one side seems much hotter than the other. It could also be a parking brake issue, where the pads are rubbing all the time, because they need adjusted, or have rusted, and are rubbing all the time. That would also be pretty rare.
Other issues could be a suspension issue, where something has come loose, like a sway bar. Another remote possibility would be a bad bushing, possibly your RTAB's, or the rear differential bushing.
The rear shock mount or a rear subframe issue is a more likely explanation, if the noise is as loud as you say it is. I hope I am wrong, but if it has to be anything, I hope it is the rear shock mount, since that is a fairly easy and cheap repair. But the list of possibilities is fairly long, so you have plenty of things to check.
Untitled by MJLavelle, on Flickr
Another possibility, which would be much worse, would be rear subframe damage. You can find plenty of info on here as to what you need to check.
B
It could also be a brake issue. Some things to look for would be any calipers that are loose, meaning the mounting bolts are not locked down, or a broken or missing caliper pin, which would be rare, but possible. You may have a caliper that is sticking, and not moving freely on the guide pins. One sure sign of this would be excessive heat on the sticking caliper after a short drive. Take the car out for a few mins, press the brakes a few times, and when you get back home, check and see if one side seems much hotter than the other. It could also be a parking brake issue, where the pads are rubbing all the time, because they need adjusted, or have rusted, and are rubbing all the time. That would also be pretty rare.
Other issues could be a suspension issue, where something has come loose, like a sway bar. Another remote possibility would be a bad bushing, possibly your RTAB's, or the rear differential bushing.
The rear shock mount or a rear subframe issue is a more likely explanation, if the noise is as loud as you say it is. I hope I am wrong, but if it has to be anything, I hope it is the rear shock mount, since that is a fairly easy and cheap repair. But the list of possibilities is fairly long, so you have plenty of things to check.
Shock mounts, suspension mounts, differential mounts, exhaust system banging around.
Maybe you should put the car on jack stands and crawl under it to look around. There are lots of things that can make noise when going over a bump.
The first thing to do is look to see if the spare tire is secured in the trunk, and that there are no cans rolling around in the spare tire well.
Your question is sorta like, "Good morning you guys, what should I do first today?" Have you gone to the bathroom yet? Had breakfast? Where do we start?
Maybe you should put the car on jack stands and crawl under it to look around. There are lots of things that can make noise when going over a bump.
The first thing to do is look to see if the spare tire is secured in the trunk, and that there are no cans rolling around in the spare tire well.
Your question is sorta like, "Good morning you guys, what should I do first today?" Have you gone to the bathroom yet? Had breakfast? Where do we start?
Check any thing that might be loose in the trunk.
Factory jack, spare tire, wheel chock.
I once mistook the loose factory jacks for the busted RSMs and ordered them with reinforcement plates and all the hardware. I used them when I mounted my coils anyway. It might not be in your case.
But never hurts to check the RSMs. Remove the rotors and check the parking brake as well. May thats loose and hitting something within the hub.
Factory jack, spare tire, wheel chock.
I once mistook the loose factory jacks for the busted RSMs and ordered them with reinforcement plates and all the hardware. I used them when I mounted my coils anyway. It might not be in your case.
But never hurts to check the RSMs. Remove the rotors and check the parking brake as well. May thats loose and hitting something within the hub.
Yah do both sides. With suspension and brakes always do in pairs.
Check out the DIY's on rsms and rear shock installation. RTAB might be too much of a DIY if you are just starting to work on the car and don't have correct tools.
You might want to add z3 reinforcement plates is you are doing rsms.
I'd say check all the components of the suspension and change what you think is important and feasible.
If I had money I'd change every component but if I had money I'd buy a new car as well.
It's important to prioritize what you feel is important and what should and can be done while you change the bump stops.
In my case I changed the shocks, springs, rsms, washers, nuts and bolts. My shocks were leaking and I wanted to lower the car a little so I went with coil overs. My inside side of the tires were wearing out quickly so I did the RTAB with limiters as well. And since my rsms were old, I changed to new rsms and hardware.
I spent almost 6 hours as because of the Rtabs. If it were just shocks, it can be done in an hour both sides.
Check out the DIY's on rsms and rear shock installation. RTAB might be too much of a DIY if you are just starting to work on the car and don't have correct tools.
You might want to add z3 reinforcement plates is you are doing rsms.
I'd say check all the components of the suspension and change what you think is important and feasible.
If I had money I'd change every component but if I had money I'd buy a new car as well.
It's important to prioritize what you feel is important and what should and can be done while you change the bump stops.
In my case I changed the shocks, springs, rsms, washers, nuts and bolts. My shocks were leaking and I wanted to lower the car a little so I went with coil overs. My inside side of the tires were wearing out quickly so I did the RTAB with limiters as well. And since my rsms were old, I changed to new rsms and hardware.
I spent almost 6 hours as because of the Rtabs. If it were just shocks, it can be done in an hour both sides.
Yes, if the insides of your rear tires wear out a lot compared to outsides it's most likely the Rtabs. This was the condition of my rear tire and shock. Sure enough my rsms were shot too. I did everything at once.
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And no the washers don't some out as a set. I can check if I have the part numbers for them.
And no the washers don't some out as a set. I can check if I have the part numbers for them.
Your RSM and RTABs are probably not causing you as much trouble as your old shocks. You can see if the RSM is bad by removing the trunk liner; nothing in your picture suggests it is bad. However, since your bump stop is old enough to be literally cut in half, your shocks are probably completely toast as well. I'd start by replacing those.
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