brakes pulsating when applied
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More Turbo
Joined: Feb 2022
Posts: 657
Likes: 106
From: New Dominion, PE
brakes pulsating when applied
1987 ford f150 - 302 engine - 2WD
In the past 2 weeks, front brakes are pulsing crazily when applying brakes. I'm guessing the rotors are warping. I had things apart in the fall last year and
things looked fine. No scoring, ridges on the rotors and lots of pad life left. truck was in storage from Oct til spring.
When I have a small utility trailer attached with any weight and use the brakes it's definitely needing attention.
I have rotors and pads and slide pins for it along with the bearings and seal for the rotor/hub assembly. Question on the slide pins...
I'm assuming you take a wire wheel on a drill and clean the grooves and then put brake grease in these channels that the slide pins
ride in....correct? with this style caliper (ie: with these slide pins holding the caliper to the carrier bracket)...what provides the release
mechanism of the pads away from the rotors when you let off the brakes?
In the past 2 weeks, front brakes are pulsing crazily when applying brakes. I'm guessing the rotors are warping. I had things apart in the fall last year and
things looked fine. No scoring, ridges on the rotors and lots of pad life left. truck was in storage from Oct til spring.
When I have a small utility trailer attached with any weight and use the brakes it's definitely needing attention.
I have rotors and pads and slide pins for it along with the bearings and seal for the rotor/hub assembly. Question on the slide pins...
I'm assuming you take a wire wheel on a drill and clean the grooves and then put brake grease in these channels that the slide pins
ride in....correct? with this style caliper (ie: with these slide pins holding the caliper to the carrier bracket)...what provides the release
mechanism of the pads away from the rotors when you let off the brakes?
Laughing Gas
Joined: Jan 2023
Posts: 1,172
Likes: 114
When you let off the brakes, the square cut o ring in the brake caliper is what releases the brakes. When the fluid pushes the piston out, the square cut o ring deforms and when you release the brakes it will go back to its proper shape and in the process will pull the piston back in. This works for any car whether the calipers fixed, floating, sliding, etc.
Not sure about cleaning the caliper/bracket where the sliding pins go, I used a wire brush but I guess you’re supposed to use specific brushes depending on the material of the bracket. Also while you have your caliper off check the piston. If it has any chips or cracks in it the piston, the caliper should be replaced or the piston. When the phenolic pistons in these trucks get cracks, or chips they absorb water and then they swell and they won’t allow the o ring to properly release the brakes, or the fluid to properly apply the brakes.
Not sure about cleaning the caliper/bracket where the sliding pins go, I used a wire brush but I guess you’re supposed to use specific brushes depending on the material of the bracket. Also while you have your caliper off check the piston. If it has any chips or cracks in it the piston, the caliper should be replaced or the piston. When the phenolic pistons in these trucks get cracks, or chips they absorb water and then they swell and they won’t allow the o ring to properly release the brakes, or the fluid to properly apply the brakes.
Moderator
Joined: Aug 2002
Posts: 6,104
Likes: 384
From: Southern California
There are 2 things that will cause pulsation (disc0 brakes...1) Brake lining dust buildup on the rotors and 2) warped rotors. IMHO, take her out and at about 40 mph hit the brakes hard...in most cases it will remove the brake material buldup..... of course you can sand them as well with 80 grit and then clean them with CRC Brake Kleen or equivalent.
Hotshot
Joined: Jul 2020
Posts: 10,478
Likes: 2,636
From: Near Salt Lake City
Yes, your rotors are warped
Those caliper slide pins can be installed dry, but we used to lube them up with Ford disc brake lubricant (just some expensive high temp grease in a tube)
Those caliper slide pins can be installed dry, but we used to lube them up with Ford disc brake lubricant (just some expensive high temp grease in a tube)
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More Turbo
Joined: Feb 2022
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From: New Dominion, PE
I read on the forums that the vehicle speed sensor can malfunction causing the ABS to go ape. might this be happening here? if so, where is this wheel speed
sensor located on the 87 with the 302 and C6 tranny?
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Hotshot
Joined: Jul 2020
Posts: 10,478
Likes: 2,636
From: Near Salt Lake City
If the truck has ABS in 1987 it is RABS and the only speed sensor for it will be atop the rear differential
The one in the back of the trans is for the speeo and the cruise if equipped
So, you are working on ******* house in Maui?
Been there, folks and sister live there in Maui
Got a piece of bamboo for a project from his place
The one in the back of the trans is for the speeo and the cruise if equipped
So, you are working on ******* house in Maui?
Been there, folks and sister live there in Maui
Got a piece of bamboo for a project from his place
Thread Starter
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More Turbo
Joined: Feb 2022
Posts: 657
Likes: 106
From: New Dominion, PE
my truck (aka willie nelson)... 
so if I understand you correctly..the RABS sensor is for only controlling lockup of the rear brakes and not the front? the pulsation
feels to me like the front brakes. the "rear anti lock" light briefly illuminates at startup but goes away as soon as it fires up if that
matters.
I've been to maui to in the 90's. stayed at the grand wailea....a trip of a lifetime. but alas....things are different now.
so if I understand you correctly..the RABS sensor is for only controlling lockup of the rear brakes and not the front? the pulsation
feels to me like the front brakes. the "rear anti lock" light briefly illuminates at startup but goes away as soon as it fires up if that
matters.
I've been to maui to in the 90's. stayed at the grand wailea....a trip of a lifetime. but alas....things are different now.
Hotshot
Joined: Jul 2020
Posts: 10,478
Likes: 2,636
From: Near Salt Lake City
Right rear antilock only, and only the rear driveshaft or carrier, really (one brake can lock up)
The pulsation is most likely the front rotors being warped
The Grand Wailea is probably still the best one to stay at IMO - Big money though
We could never afford that, (staying there) we stay with the grups, and only eat at the grand wailea and mamas fish house when splurging
Went to the big island last time and stayed at the kings beach area Hilton OMG nice
The pulsation is most likely the front rotors being warped
The Grand Wailea is probably still the best one to stay at IMO - Big money though
We could never afford that, (staying there) we stay with the grups, and only eat at the grand wailea and mamas fish house when splurging
Went to the big island last time and stayed at the kings beach area Hilton OMG nice
Thread Starter
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More Turbo
Joined: Feb 2022
Posts: 657
Likes: 106
From: New Dominion, PE
Right rear antilock only, and only the rear driveshaft or carrier, really (one brake can lock up)
The pulsation is most likely the front rotors being warped
The Grand Wailea is probably still the best one to stay at IMO - Big money though
We could never afford that, (staying there) we stay with the grups, and only eat at the grand wailea and mamas fish house when splurging
Went to the big island last time and stayed at the kings beach area Hilton OMG nice
The pulsation is most likely the front rotors being warped
The Grand Wailea is probably still the best one to stay at IMO - Big money though
We could never afford that, (staying there) we stay with the grups, and only eat at the grand wailea and mamas fish house when splurging
Went to the big island last time and stayed at the kings beach area Hilton OMG nice
Laughing Gas
Joined: Oct 2014
Posts: 946
Likes: 186
From: Carnation, Wah
There are 2 3 things that will cause pulsation
they will overheat the rotors to where they warp (one of the 2 things)
and then you'll get the shudders. But only after you've been driving for a while.
And the hub will be warm.
Around here, I always find rust under the dust boots when I pull the brakes off mine,
and end up cleaning and resealing and (usually) replacing the phenolic pistons.
Raybestos (as of last year) still makes them in Canada, and they are inexpensive
and good quality.
A 'remanufactured' caliper may not cost much, but I have had zero luck with them,
often sticking or defective out of the box, and never lasting more than a year or 2.
t
More Turbo
Joined: Sep 2012
Posts: 739
Likes: 256
From: Zimmerman, MN
Two other things no one has mentioned yet....
If the master cylinder has been replaced, or looks "newish", check the depth of the pushrod coming out of the vacuum booster. Even 1/16" difference can cause the master to not release fully, causing the front brakes to drag, which will warp the rotors.
Also, what's the condition of the front hoses? If "unknown", and they look old, get them outta there.
Been there, done that (er, "them"), several times, on my trucks
If the master cylinder has been replaced, or looks "newish", check the depth of the pushrod coming out of the vacuum booster. Even 1/16" difference can cause the master to not release fully, causing the front brakes to drag, which will warp the rotors.
Also, what's the condition of the front hoses? If "unknown", and they look old, get them outta there.
Been there, done that (er, "them"), several times, on my trucks
Laughing Gas
Joined: Oct 2014
Posts: 946
Likes: 186
From: Carnation, Wah
Oh, yes- if the pushrod's too long, both front hubs will be warm.
But again, it should be a few miles before the vibes kick in.
And the hoses are inexpensive 'while you're in there' preventative maintenance.
t
But again, it should be a few miles before the vibes kick in.
And the hoses are inexpensive 'while you're in there' preventative maintenance.
t
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