Why do my brakes pulse again?

  • Thread starter Thread starter Ted S.
  • Start date Start date
T

Ted S.

I have a 1997 Jeep Cherokee Laredo 4x4 with 36,000 miles on it. I do mostly
"around home" driving (not really city or highway driving).

My question is why my brakes 'pulse' once again. When braking, it feels
like there are high and low spots on the discs. I had them ground once
which fixed the problem but it's back yet again. I'm very easy on the
brakes. Someone said they may warp when hot and hitting a puddle but that
doesn't sound reasonable.

Any ideas as to why this keeps happening would be great. Thanks.
 
Ted said:
I have a 1997 Jeep Cherokee Laredo 4x4 with 36,000 miles on it. I do mostly
"around home" driving (not really city or highway driving).

My question is why my brakes 'pulse' once again. When braking, it feels
like there are high and low spots on the discs. I had them ground once
which fixed the problem but it's back yet again. I'm very easy on the
brakes. Someone said they may warp when hot and hitting a puddle but that
doesn't sound reasonable.

Any ideas as to why this keeps happening would be great. Thanks.
Click to expand...

Several things can cause rotor warping or nonuniform thickness:

1. Overheating from severe use (long hills, towing, etc.)
2. Marginally designed rotors (most vehicles today unfortunately)
3. Overtorqued lug nuts
4. Rust from lack of use
5. Probably several more that I'm not aware of!

I think overtorqued lug nuts are one of the most preventable causes, at
least next to avoiding severe use. Rotors are more likely to warp a
second time after being turned. There is now less metal to absorb heat
and less metal to resist the stresses induced by the heat. I think on
most new cars and many trucks, it is a waste of time to turn the rotors.
Better to just replace them, and the cost delta isn't all that great
anyway.

Matt
 
Ted said:
I have a 1997 Jeep Cherokee Laredo 4x4 with 36,000 miles on it. I do mostly
"around home" driving (not really city or highway driving).

My question is why my brakes 'pulse' once again. When braking, it feels
like there are high and low spots on the discs. I had them ground once
which fixed the problem but it's back yet again. I'm very easy on the
brakes. Someone said they may warp when hot and hitting a puddle but that
doesn't sound reasonable.

Any ideas as to why this keeps happening would be great. Thanks.
Click to expand...

Prior to any of the events, had anyone rotated or removed and
replaced any tires? This can cause the rotors to warp. Once
that happens, just replace them with an aftermarket set of
your choice. Turning them takes away metal which make them
more susceptible to warping in the future.
 
Matthew S. Whiting said:
Several things can cause rotor warping or nonuniform thickness:

1. Overheating from severe use (long hills, towing, etc.)
2. Marginally designed rotors (most vehicles today unfortunately)
3. Overtorqued lug nuts
4. Rust from lack of use
5. Probably several more that I'm not aware of!

I think overtorqued lug nuts are one of the most preventable causes, at
least next to avoiding severe use. Rotors are more likely to warp a
second time after being turned. There is now less metal to absorb heat
and less metal to resist the stresses induced by the heat. I think on
most new cars and many trucks, it is a waste of time to turn the rotors.
Better to just replace them, and the cost delta isn't all that great
anyway.

Matt
Click to expand...

Yep, #3 is the one I'd bet on. Usually by over zealous use of the air
wrench by the place that rotates your tires.

PC
 
What does rotating tires have to do with warping rotors?

I think it's over tightened lugs.
 
Ted S. said:
I have a 1997 Jeep Cherokee Laredo 4x4 with 36,000 miles on it. I do mostly
"around home" driving (not really city or highway driving).

My question is why my brakes 'pulse' once again. When braking, it feels
like there are high and low spots on the discs. I had them ground once
which fixed the problem but it's back yet again. I'm very easy on the
brakes. Someone said they may warp when hot and hitting a puddle but that
doesn't sound reasonable.
Click to expand...

Having warped disk rotors ground, or "turned" is a good short-term fix. The
problem is, however, that the more they are turned, the thinner they become.
The thinner they become, the more susceptible they become to warpage. So it
is a vicious circle kind of thing.

You probably need to have the rotors replaced. But if they wore out at only
36K miles, something ain't right. Maybe they can be replaced under
warranty.

-Cyberbilly
 
there are some good points that everyone has made so far. but the best
point that I can make is...
"on Car" machining of the rotors is the most effective and longer term
fix for this condition, for this vehicle.
Furthermore, check with you local Jeep dealership, because there were
certain models with this condition that they had recalled, which was
replacment rotors,caliper kits. Could be worth checking into. all they
need is the last 9 digits of your VIN, current mileage and last name.
If you cant find the information. Contact me and I will check for you.
 
The simple answer is Chrysler rotors are JUNK. My '96 Stratus rotors were
doing the same thing at 15,000 miles. Chrysler replaced them, but said that
the warranty on "wear parts" was only 12,000 miles. I had the same problem
with them at around 25,000 miles. I replaced those with the cheap NAPA ones
in the green box and they were on the car until I traded it in at 186,000
miles. They were $16 each.

I bought a new Sebring convertible about three months ago. I have 9,000
miles on the car and the brakes are pulsating already. It has 4 wheel
disks, so I'm bringing it in next week to see what they are going to do
about it.
 
the xj rotors are a composit metal and warp real easy once they have be
resurfaced
the rotors don't take well to heat up after that so i would recommend new ones
 
ya right!!!!! like the wj rotor fiasco when the wj came out and jeep made
all the dealers buy on the car brake lathes and held bac warranty monies
intill all complied and the fact that brake system was a PISS POOR DESIGN
from the beginning and the real cure was new calipers/pads and rotors and
now the wj bakes are covered 3/36. nice try! but you are as wrong as 2 boys
fucking
 
We service thousands a cars of many different brands in our fleet
service business.. We have discovered a common problem
among the many different brands that have recurring FRONT rotor
problems. The REAR brakes are very often the problem, not the
front! When the rears are out of adjustment or not functioning
properly for some reason, that causes the front brakes to do most
of the work and overheat. Since we began adjusting rear brakes
at every service interval, front rotor problems have been reduced
dramatically. The problem is MOST prevalent on vehicles that are
driven MODERATELY. Rear brakes that are out of adjustment WILL
assist the front on HARD braking but often not help on light
braking. Check the rear brakes WBMA. DO NOT
use the left foot to brake, that too will overheat the rotors
as well!


mike hunt
Click to expand...


"Do not use the left foot to brake" sounds like something
Dave Barry would write! Is there an explanation there or
is that indeed humor? - RM
 
We service thousands a cars of many different brands in our fleet
service business.. We have discovered a common problem
among the many different brands that have recurring FRONT rotor
problems. The REAR brakes are very often the problem, not the
front! When the rears are out of adjustment or not functioning
properly for some reason, that causes the front brakes to do most
of the work and overheat. Since we began adjusting rear brakes
at every service interval, front rotor problems have been reduced
dramatically. The problem is MOST prevalent on vehicles that are
driven MODERATELY. Rear brakes that are out of adjustment WILL
assist the front on HARD braking but often not help on light
braking. Check the rear brakes WBMA. DO NOT
use the left foot to brake, that too will overheat the rotors
as well!


mike hunt
 
We service thousands a cars of many different brands in our fleet
service business.. We have discovered a common problem
among the many different brands that have recurring FRONT rotor
problems. The REAR brakes are very often the problem, not the
front! When the rears are out of adjustment or not functioning
properly for some reason, that causes the front brakes to do most
of the work and overheat. Since we began adjusting rear brakes
at every service interval, front rotor problems have been reduced
dramatically. The problem is MOST prevalent on vehicles that are
driven MODERATELY. Rear brakes that are out of adjustment WILL
assist the front on HARD braking but often not help on light
braking. Check the rear brakes WBMA. DO NOT
use the left foot to brake, that too will overheat the rotors
as well!
Click to expand...

I didn't know that the brakes could tell left feet from right feet! :-)


Matt
 
RickMerrill said:
"Do not use the left foot to brake" sounds like something
Dave Barry would write! Is there an explanation there or
is that indeed humor? - RM
Click to expand...

Yes, your left foot should be pushing the clutch! The only problem
braking with your left foot is that some people rest their left foot on
the brake thus continuously dragging the brakes slightly. If you don't
do that, there is nothing wrong with left foot braking for an automatic
transmission car. Then again, if all cars were stick shift as they
should be, then this wouldn't be a problem! :-)


Matt
 
Many have already suggested improperly torqued lug nuts. My previous
98 Z28, a model which was infamous for warped rotors, developed the
dreaded pulsing brake pedal/warped rotor syndrome. But one time after
having the tires rotated it completely went away. And tire rotation
prior to that was done by a meticulous high performance shop who
always said they torque properly by hand, so I can only assume even
they made a mistake.
 
About driving school: you should go back yourself, because the new
classes DO teach using BOTH feet in an emergency - if only to avoid
the "unexpected acceleration" should your right foot hit the
accelerator pedal by accident. - RM
 
Matthew said:
Uh, Rick, I never said that left foot braking was wrong. Read again my
post ... or learn to make proper attributions.

Matt
Click to expand...


You said it was hard on the brakes, originally. Then you refused to
say why that might be so. Then you got on your high horse about
classes. Could it be that you're taking yourself too seriously?
Hmmm? - RM
 
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