Thumps and Thuds

[Mark]

Hello Usergroup, You all have been a great resource. I have another one
for you that has me baffled. Something with the brakes/suspension/steering
mech. My 1999 Forester gives a slight shimmy with feedback through the
steering wheel when braking. I've been told that the rotors need to be
turned (I've got new pads tho). 104K miles on it now. This makes sense but
there are a couple of other things wierd.
1- When braking you can hear a slight "Thud" sound when you
first depress the brake and it has been more than a couple of minutes since
you last braked. Doesn't do it when sitting around -just when driving.
Sound is not pronounced but seems to be from the front. My auto mech said
he couldn't hear it a few weeks ago- so he couldn't offer anything as
source- but it is more distinct now.
2- Also a few weeks ago this one showed up. When you are
driving very slow, like turning into a 90degree parking space and you give
the wheel a hard turn to make the turn you can hear a rapid "Thumping" noise
from the steering and feedback into the steering wheel. It's pretty
noticeable, maybe thumping at about 3 or 4 thumps per sec. Happens when
turning either direction and your turning hard (doesn't have to be up
against the limit tho).
The next one is probably not Steering/brake related.
3- Another thing is with the car at idle or on shifting from 1 to
2 , sometimes 2 to 3 you hear a high frequency rattling
noise-intermittently- it's not always rattling. My mech said it was the Cat
converter and replaced it. Problem seemed to go away then showed up again a
few weeks later. He "tightened" up the heat shields and it went away for a
couple of months. One more "tighten" but it ain't gone now. Now I'm Not so
sure it was the Cat or the loose shields.


Looking for any suggestions so I don't get burned (like on a Cat
Converter). Thanks, Mark

 

[Carl 1 Lucky Texan]

Hello Usergroup, You all have been a great resource. I have another one
for you that has me baffled. Something with the brakes/suspension/steering
mech. My 1999 Forester gives a slight shimmy with feedback through the
steering wheel when braking. I've been told that the rotors need to be
turned (I've got new pads tho). 104K miles on it now. This makes sense but
there are a couple of other things wierd.
1- When braking you can hear a slight "Thud" sound when you
first depress the brake and it has been more than a couple of minutes since
you last braked. Doesn't do it when sitting around -just when driving.
Sound is not pronounced but seems to be from the front. My auto mech said
he couldn't hear it a few weeks ago- so he couldn't offer anything as
source- but it is more distinct now.
2- Also a few weeks ago this one showed up. When you are
driving very slow, like turning into a 90degree parking space and you give
the wheel a hard turn to make the turn you can hear a rapid "Thumping" noise
from the steering and feedback into the steering wheel. It's pretty
noticeable, maybe thumping at about 3 or 4 thumps per sec. Happens when
turning either direction and your turning hard (doesn't have to be up
against the limit tho).
The next one is probably not Steering/brake related.
3- Another thing is with the car at idle or on shifting from 1 to
2 , sometimes 2 to 3 you hear a high frequency rattling
noise-intermittently- it's not always rattling. My mech said it was the Cat
converter and replaced it. Problem seemed to go away then showed up again a
few weeks later. He "tightened" up the heat shields and it went away for a
couple of months. One more "tighten" but it ain't gone now. Now I'm Not so
sure it was the Cat or the loose shields.


Looking for any suggestions so I don't get burned (like on a Cat
Converter). Thanks, Mark

This one;

2- Also a few weeks ago this one showed up. When you are

driving very slow, like turning into a 90degree parking space and you give
the wheel a hard turn to make the turn you can hear a rapid "Thumping" noise
from the steering and feedback into the steering wheel. It's pretty
noticeable, maybe thumping at about 3 or 4 thumps per sec. Happens when
turning either direction and your turning hard (doesn't have to be up
against the limit tho).

may very well be a bad duty solenoid C or viscous coupling. If you have
an auto, try putting the FWD fuse in place nad do tight turns in a
parking lot. If the problem goes away - possible tranny troubles.

The first may be just rotors, but it may be worth trying rotation the
tires to see if it get better - seems that there are a lot of tires
nowadays that have 'issues' before the tread wears down. But there are
reports of brake pads shifting around and clicking. maybe if a
reverse/forward duplicates the problem at least your mech. could hear it.

let us know what you find out OK?

Carl


And I've read that other folks have reported heat shield rattles on
Impreza chassis quite a bit. I'd bet that's not unusual.

 

[news.radiant.net]

warped rotor is a definite possibility for the brake shimmy.
The mileage is not high, but the thud you describe could come from a worn
bushing(s) in the suspension. Either for a strut or a control arm.
It could also be a strut.
Try the reverse-brake/forward-brake sequence to see if you can reproduce it.
Have you ever replaced the half-shafts? The mileage is high enough that
this could be an issue, more likely than a worn bushing somewhere.

Hello Usergroup, You all have been a great resource. I have another one
for you that has me baffled. Something with the brakes/suspension/steering
mech. My 1999 Forester gives a slight shimmy with feedback through the
steering wheel when braking. I've been told that the rotors need to be
turned (I've got new pads tho). 104K miles on it now. This makes sense but
there are a couple of other things wierd.
1- When braking you can hear a slight "Thud" sound when you
first depress the brake and it has been more than a couple of minutes since
you last braked. Doesn't do it when sitting around -just when driving.
Sound is not pronounced but seems to be from the front. My auto mech said
he couldn't hear it a few weeks ago- so he couldn't offer anything as
source- but it is more distinct now.
2- Also a few weeks ago this one showed up. When you are
driving very slow, like turning into a 90degree parking space and you give
the wheel a hard turn to make the turn you can hear a rapid "Thumping" noise
from the steering and feedback into the steering wheel. It's pretty
noticeable, maybe thumping at about 3 or 4 thumps per sec. Happens when
turning either direction and your turning hard (doesn't have to be up
against the limit tho).
The next one is probably not Steering/brake related.
3- Another thing is with the car at idle or on shifting from 1 to
2 , sometimes 2 to 3 you hear a high frequency rattling
noise-intermittently- it's not always rattling. My mech said it was the Cat
converter and replaced it. Problem seemed to go away then showed up again a
few weeks later. He "tightened" up the heat shields and it went away for a
couple of months. One more "tighten" but it ain't gone now. Now I'm Not so
sure it was the Cat or the loose shields.


Looking for any suggestions so I don't get burned (like on a Cat
Converter). Thanks, Mark

 

[Sparky Polastri]

1. I dont know.

2. Check your tire pressure before doing anything. Could just be it needs
air. (Get a dial/needle one, not one of those stupid sticks.)

 

[k. ote]

warped rotor is a definite possibility for the brake shimmy.

I thought warped rotors were a myth and that modern brakes can potentially
leave a deposit on the rotor which causes future braking shudders, if you
stop hard and let the pad cool while gripping the rotor?

 

[Kurt C. Hack]

The theory I heard was a little different. Had to do with stopping hard
and leaving the brakes applied, not allowing the rotor to cool evenly
and causing warpage. I would think the deposits left on the rotor would
easily be scraped off the next time the brakes were applied, but I am
certainly no expert.

-Kurt

 

[CompUser]

The theory I heard was a little different. Had to do with stopping hard
and leaving the brakes applied, not allowing the rotor to cool evenly
and causing warpage. I would think the deposits left on the rotor would
easily be scraped off the next time the brakes were applied, but I am
certainly no expert.

No, it's pad deposits..."cementite"..and they're
harder than the rotor iron, so they don't wear
down, while the rest of the rotor does, getting
progressively worse.

 

[Kurt C. Hack]

Interesting... well as interesting as warped rotors can be. Thanks
for the info.

-Kurt

 

[CompUser]

Interesting... well as interesting as warped rotors can be. Thanks
for the info.

I think stoptech (?) has a good essay on
this...possibly over on tirerack.com too...