Random thumping noise, '93 N/A

c1jensen · 11-10-2009, 03:15 PM

We (me and my shop) have been struggling to find a random rattling/thumping noise in the car. Let me start with what I've replaced in the last week...

BOTH half shafts and CV joints, rear tires, and all four wheel bearings. We did find the rear engine mount bolts loose, so those are now tight.

My shop has been very accommodating, and has taken a verbal vow to fix the noise at no further cost to me since I've spent a butt load of money there already, and the noise is still there. It sounds like it's coming from the right rear. HOWEVER, we all know how sounds can be thrown around a vehicle.

The next thing they want to do tomorrow, is to re-replace the front wheel bearings as they think the noise is coming from the front right one now.

It's a noise that only happens when rolling, but it's random, so it's hard to tell if it's rotational, or if it's a loose strut or something.

Any suggestions of what to look for today and tonight before I take it back in tomorrow?

datguydeni · 11-10-2009, 07:22 PM

what was the problem with mine when i heard a thumping noise was the brake heat shield hitting the inside of my rim's weight stickie. was quite annoying. so i would check for bent heat shields maybe. why would they replace the wheel bearing when it is already replaced?

c1jensen · 11-10-2009, 09:13 PM

Cool, I'll check heat shields when it's on the lift in the morning.

As far as the redoing the front wheel bearings, I'm not sure about this one yet. I am going to stand there and watch them install them <again> in the morning. I want to make sure they are actually doing it. Now that I'm not paying for it, they have to correct the noise, and they'll do it while I'm there.

I've driven it more this evening, it's definitely something rotational, and MUCH more noticeable during a left turn.

I think I have two separate issues here. The thumping noise is very random, and the more I think about it, the more it seems to be a shield or perhaps some loose bottom tray plastic. It doesn't sound like metal hitting metal, but thinking more like plastic rubbing or banging on something. It starts around 25mph, and doesn't change much above that. It's like the air flow under the car is causing the plastic to sway around and hit something. Hmmm...

The other issue is the grinding rotational noise. It's really sounding like the right front wheel bearing...we'll see...

datguydeni · 11-10-2009, 09:18 PM

most likely that rotational noise is the front bearing. i recently just replaced my whole steering knuckle with a new bearing. cause my old steering knuckle for some odd reason had the oem bearing loose.. when a new one was placed in.

hopefully things check out. don't forget to get an alignment

Sh0ty · 11-10-2009, 11:22 PM

I hear that the rear swaybar bushings could be the culprit. I have a similar problem as you (knocking noise, only happens over bumps at certain speeds though, seems like fuller compression of the suspension means higher chance of noise) and I replaced my struts, springs, bumpstops, rear swaybar bushings, and I'm currently working on replacing my other suspension bushings. Let me know if you ever figure it out.

c1jensen · 11-11-2009, 12:31 PM

Well, they're stumped. We put a stethoscope on the transmission and the rear wheel bearings...nothing.

I've driven it some more, and have done some speed testing on the noise this morning-

No noise below about 20mph straight ahead or in a constant left turn. I did three circles in a church parking lot, and there is zero noise, no thumping, no growl. I was turning quite hard, but not above 15-20mph.

Above 20mph, I get the random thumping noise constantly, and the rotational growling noise only in a left swerve or turn, so that has to be something on the right side of the car.

All wheel bearings are new (twice), so it can't be the bearings.

Could the growling in a turn be a transmission issue? CV interference when pressure is put on the transmission in a left turn?

That still doesn't explain the thumping tho...

datguydeni · 11-11-2009, 06:31 PM

mmmm tried going reverse? way back when i had this brake shield thing happen, it would occur more frequent when going in reverse, regular turns were just random.

Also when they put the bearing in the steering knuckle was it a tight fit? because according to my mechanic when he put the new bearing in, it was loose, which then i bought a new steering knuckle.

also have you lifted the car spun the wheel/tire and hear anything?

c1jensen · 11-11-2009, 09:31 PM

Yeah, reverse is not an issue. It's only a forward noise.

This evening, I went to the BMW shop where one of my good friends works. He gave me some time after hours to help me diagnose the noises. We drove it, and put it thru it's paces on some twisty roads...even did the swerve tests with the engine off, and the noises don't change. So we know it's not a transmission issue or the engine in any way. He is 100% POSITIVE that the growling is the rear wheel bearing. So, either they DIDN'T change it at my regular shop, or it's not in properly. We later put Chassis Ears on the car in three spots, and the noise is an absolute racket on the right rear. Definitely getting a new bearing in the right rear again tomorrow.

The random thumping noise is still a mystery though. Chassis Ears didn't help much tonight, but we ran out of time to keep looking, so I now have the Ears to borrow to the regular shop tomorrow. His only thought at this tonight with the time we had, is the ball joints. They do move a bit on the lift, so those may be the thumping, but it's hard to believe they would make this particular noise.

I've had it on a lift twice today, both times we spun the tires both manually, and with the car running and in gear. The thumping is not showing it's ugly head on the lift. There is a clicking noise that's barely noticeable when spinning the right rear manually, but with the Ears on, it's LOUD and CLEAR...that still points to the wheel bearing.

So now I'm going back to the other shop tomorrow armed with this info, and a set of Ears, and we go from there...

datguydeni · 11-12-2009, 01:06 AM

good luck to you man

c1jensen · 11-12-2009, 03:05 PM

Update for anyone still listening...it's FIXED! It was the LEFT rear wheel bearing making the growl, and both rear ball joints making the thumping noise.

As usual...something so simple stumped three expert mechanics...

datguydeni · 11-12-2009, 05:41 PM

glad to know everything is working out. now go get it aligned lol
take care

tadamany · 11-12-2009, 09:00 PM

I've been following this and glad you found the problem.

masagsxr · 11-12-2009, 09:22 PM

I was going to say check the ball joints but I guess i was too late heheee... Glad you found the problem.... I'm surprise the shops didn't bother doing some inspection/testing first before replacing parts. That could have been time and labor they could have saved. Its cool that they stand by their work tho.

11-10-2009, 03:15 PM	#1 (permalink)
c1jensen No Skills Join Date: Oct 2009 Location: Bloomington/Normal, IL Posts: 35 Thanks: 2 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Random thumping noise, '93 N/A We (me and my shop) have been struggling to find a random rattling/thumping noise in the car. Let me start with what I've replaced in the last week... BOTH half shafts and CV joints, rear tires, and all four wheel bearings. We did find the rear engine mount bolts loose, so those are now tight. My shop has been very accommodating, and has taken a verbal vow to fix the noise at no further cost to me since I've spent a butt load of money there already, and the noise is still there. It sounds like it's coming from the right rear. HOWEVER, we all know how sounds can be thrown around a vehicle. The next thing they want to do tomorrow, is to re-replace the front wheel bearings as they think the noise is coming from the front right one now. It's a noise that only happens when rolling, but it's random, so it's hard to tell if it's rotational, or if it's a loose strut or something. Any suggestions of what to look for today and tonight before I take it back in tomorrow?

11-11-2009, 06:31 PM	#7 (permalink)
datguydeni Turquoise not Teal Join Date: Jul 2007 Location: San Diego CA Posts: 1,492 Thanks: 3 Thanked 25 Times in 22 Posts My Google Map iTrader Rating: (0/0% )	mmmm tried going reverse? way back when i had this brake shield thing happen, it would occur more frequent when going in reverse, regular turns were just random. Also when they put the bearing in the steering knuckle was it a tight fit? because according to my mechanic when he put the new bearing in, it was loose, which then i bought a new steering knuckle. also have you lifted the car spun the wheel/tire and hear anything? Last edited by datguydeni; 11-11-2009 at 06:38 PM..

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11-10-2009, 07:22 PM	#2 (permalink)
datguydeni Turquoise not Teal Join Date: Jul 2007 Location: San Diego CA Posts: 1,492 Thanks: 3 Thanked 25 Times in 22 Posts My Google Map iTrader Rating: (0/0% )	what was the problem with mine when i heard a thumping noise was the brake heat shield hitting the inside of my rim's weight stickie. was quite annoying. so i would check for bent heat shields maybe. why would they replace the wheel bearing when it is already replaced?

11-10-2009, 09:13 PM	#3 (permalink)
c1jensen No Skills Join Date: Oct 2009 Location: Bloomington/Normal, IL Posts: 35 Thanks: 2 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Cool, I'll check heat shields when it's on the lift in the morning. As far as the redoing the front wheel bearings, I'm not sure about this one yet. I am going to stand there and watch them install them <again> in the morning. I want to make sure they are actually doing it. Now that I'm not paying for it, they have to correct the noise, and they'll do it while I'm there. I've driven it more this evening, it's definitely something rotational, and MUCH more noticeable during a left turn. I think I have two separate issues here. The thumping noise is very random, and the more I think about it, the more it seems to be a shield or perhaps some loose bottom tray plastic. It doesn't sound like metal hitting metal, but thinking more like plastic rubbing or banging on something. It starts around 25mph, and doesn't change much above that. It's like the air flow under the car is causing the plastic to sway around and hit something. Hmmm... The other issue is the grinding rotational noise. It's really sounding like the right front wheel bearing...we'll see...

11-10-2009, 09:18 PM	#4 (permalink)
datguydeni Turquoise not Teal Join Date: Jul 2007 Location: San Diego CA Posts: 1,492 Thanks: 3 Thanked 25 Times in 22 Posts My Google Map iTrader Rating: (0/0% )	most likely that rotational noise is the front bearing. i recently just replaced my whole steering knuckle with a new bearing. cause my old steering knuckle for some odd reason had the oem bearing loose.. when a new one was placed in. hopefully things check out. don't forget to get an alignment

11-10-2009, 11:22 PM	#5 (permalink)
Sh0ty Armchair Racer Join Date: Aug 2008 Location: Novi, MI Posts: 1,273 Thanks: 22 Thanked 57 Times in 54 Posts My Google Map iTrader Rating: (3/100% )	I hear that the rear swaybar bushings could be the culprit. I have a similar problem as you (knocking noise, only happens over bumps at certain speeds though, seems like fuller compression of the suspension means higher chance of noise) and I replaced my struts, springs, bumpstops, rear swaybar bushings, and I'm currently working on replacing my other suspension bushings. Let me know if you ever figure it out.

11-11-2009, 12:31 PM	#6 (permalink)
c1jensen No Skills Join Date: Oct 2009 Location: Bloomington/Normal, IL Posts: 35 Thanks: 2 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Well, they're stumped. We put a stethoscope on the transmission and the rear wheel bearings...nothing. I've driven it some more, and have done some speed testing on the noise this morning- No noise below about 20mph straight ahead or in a constant left turn. I did three circles in a church parking lot, and there is zero noise, no thumping, no growl. I was turning quite hard, but not above 15-20mph. Above 20mph, I get the random thumping noise constantly, and the rotational growling noise only in a left swerve or turn, so that has to be something on the right side of the car. All wheel bearings are new (twice), so it can't be the bearings. Could the growling in a turn be a transmission issue? CV interference when pressure is put on the transmission in a left turn? That still doesn't explain the thumping tho...

11-11-2009, 09:31 PM	#8 (permalink)
c1jensen No Skills Join Date: Oct 2009 Location: Bloomington/Normal, IL Posts: 35 Thanks: 2 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Yeah, reverse is not an issue. It's only a forward noise. This evening, I went to the BMW shop where one of my good friends works. He gave me some time after hours to help me diagnose the noises. We drove it, and put it thru it's paces on some twisty roads...even did the swerve tests with the engine off, and the noises don't change. So we know it's not a transmission issue or the engine in any way. He is 100% POSITIVE that the growling is the rear wheel bearing. So, either they DIDN'T change it at my regular shop, or it's not in properly. We later put Chassis Ears on the car in three spots, and the noise is an absolute racket on the right rear. Definitely getting a new bearing in the right rear again tomorrow. The random thumping noise is still a mystery though. Chassis Ears didn't help much tonight, but we ran out of time to keep looking, so I now have the Ears to borrow to the regular shop tomorrow. His only thought at this tonight with the time we had, is the ball joints. They do move a bit on the lift, so those may be the thumping, but it's hard to believe they would make this particular noise. I've had it on a lift twice today, both times we spun the tires both manually, and with the car running and in gear. The thumping is not showing it's ugly head on the lift. There is a clicking noise that's barely noticeable when spinning the right rear manually, but with the Ears on, it's LOUD and CLEAR...that still points to the wheel bearing. So now I'm going back to the other shop tomorrow armed with this info, and a set of Ears, and we go from there...

11-12-2009, 01:06 AM	#9 (permalink)
datguydeni Turquoise not Teal Join Date: Jul 2007 Location: San Diego CA Posts: 1,492 Thanks: 3 Thanked 25 Times in 22 Posts My Google Map iTrader Rating: (0/0% )	good luck to you man

11-12-2009, 03:05 PM	#10 (permalink)
c1jensen No Skills Join Date: Oct 2009 Location: Bloomington/Normal, IL Posts: 35 Thanks: 2 Thanked 0 Times in 0 Posts iTrader Rating: (0/0% )	Update for anyone still listening...it's FIXED! It was the LEFT rear wheel bearing making the growl, and both rear ball joints making the thumping noise. As usual...something so simple stumped three expert mechanics...

11-12-2009, 05:41 PM	#11 (permalink)
datguydeni Turquoise not Teal Join Date: Jul 2007 Location: San Diego CA Posts: 1,492 Thanks: 3 Thanked 25 Times in 22 Posts My Google Map iTrader Rating: (0/0% )	glad to know everything is working out. now go get it aligned lol take care

11-12-2009, 09:00 PM	#12 (permalink)
tadamany MR2 Withdrawl Join Date: Oct 2009 Location: Wisconsin Posts: 290 Thanks: 5 Thanked 5 Times in 5 Posts iTrader Rating: (3/100% )	I've been following this and glad you found the problem.

11-12-2009, 09:22 PM	#13 (permalink)
masagsxr Cage Fighter Join Date: Sep 2008 Location: Norwalk, CA Posts: 3,534 Thanks: 1 Thanked 81 Times in 81 Posts iTrader Rating: (1/100% )	I was going to say check the ball joints but I guess i was too late heheee... Glad you found the problem.... I'm surprise the shops didn't bother doing some inspection/testing first before replacing parts. That could have been time and labor they could have saved. Its cool that they stand by their work tho.