1998 F150 front disc rear drum.
rear brakes will skid on light brake pressure.
new front and rear brakes.

 

wow... thanks for all the details...

first guess would be a bad proportioning valve

 

Right rear locking up in the mornings? In the rain? Then OK when they heat up and dry out? Normal, until I rebuilt with new wheel cylinders, shoes, and drums.

This can also be caused by a leaking axle seal. Gets on the shoes, and they will stick with lettle pressure applied.

 

Got RABS?

 

what more information do you need?
all four wheel brakes new about 3000 miles on them, no axle seal leaking.
rear tire skid before the abs works.

 

Are the rear shoes on the correct sides? If you have them reversed, they will grab.

 

have you changed anything lately? any specific conditions, or all the time?
You say "rear brakes will skid"... I assume you mean the rear brakes lock up and the rear wheels skid on the pavement?

Do you have rear abs? You say "light pressure"... does the ABS kick in eventually and stop the skid? Or does heavy pressure somehow cause the skid to stop?

whenever you have questions, post insane amounts of details. The things you might think are pointless could be key facts.

I still think its the proportioning valve. This valve should limit the pressure to the back wheels. If it has failed, you will be pushing the same pressure to both front and rear and since there is not much weight in the rear (I'm assuming... is your bed empty?) the rear wheels lock up.

 

This is the same situation I'm experiencing as well. After sitting in the driveway overnight, my back brakes lock up and you can tell the fronts are not working AT ALL...at least for that first aplication of brakes down at my first corner stop. What seems to help correct this is backing out of my driveway at a higher than normal back-up speed and applying the brakes somewhat agressively to stop. The fronts then kick in. Again, this only seems to happen after the vehicle sits overnight. Something isn't right here.

 

sorry, but no... not quite the same situation.
The front brakes do not have a proportioning valve, only the rears. The proportioning valve is used to reduce the pressure going to the rear brakes since the back of the truck is (usually) lighter and therefore cannot brake with as much force as the front.

The front brakes are plumbed direct to the wheels, so even if you have a bad proportioning valve on the secondary circuit, you will still have front brakes.

It sounds like you might have a half-system failure in your master cylinder. My first thought is that the seal on the primary circuit might be bad... hence the reduced braking. Do you notice a longer pedal travel than normal?
A possible explanation for it only happening in the morning - perhaps the seal bypass is due to cold temperatures from sitting over night. But if you really hammer the brakes, you can get the seal to close.

I'd suggest having a competent brake shop check it out... its really hard for me to make any definite suggestions over the web.

 

It appears as though your front brakes aren't working. What is really going on is the right rear brake locks up, and that screws up the anti-lock system. It's even worse when in 4WD. Makes the whole truck shake.

In my truck, it did this for many years, especially in high humidity and rain. Until I used the brakes in forward, it would do it. Then all was fine, until the next morning. Since completely rebuilding my rear brakes, I have not noticed this.

 

I had the same problem. Ford knows about the problem. There is a Technical Service Bulletin about this problem for 97/98 F150's. TSB 01192. I use to be able to view the TSB's but now I guess you have to pay to view now. From what I remember, it was about high humidity when setting over night. I think Ford had a different brake shoe for this problem. They also recommend replacing the hardware the holds the shoes on. I have done either but I will be changing my brakes soon. I still have the orig. hardware now (10/11 years old). I going to replace it this time. As far as the shoes, I'm not sure if I'm going to use Ford or not. You would thing that there would be plenty of good quality manufactures. Norm

 

I can view the TSB again. Maybe it will help. Maybe not. I think the hardware replacment was a suggestion on a different fourm. Norm



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01-19-2 BRAKES - REAR DRUM - GRABBING DURING FIRST FEW BRAKE APPLICATIONS WHILE BRAKES ARE COLD

Publication Date: SEPTEMBER 18, 2001

FORD: 1997-2000 F-150



This article is being republished in its entirety to update the Model Year coverage.

ISSUE:
A grabbing condition from the rear brakes during the first few brake applications after extended humidity exposure may occur on some vehicles. This may be caused by a rear brake lining that is sensitive to humidity exposure.

ACTION:
Replace rear brake linings with revised Rear Shoe Brake Kit (F85Z-2200-AA). Refer to the appropriate model year F-150 Workshop Manual, Section 206-02 for service details.


PART NUMBER PART NAME
F85Z-2200-AA Rear Shoe Brake Kit


OTHER APPLICABLE ARTICLES:
NONE

SUPERSEDES:
99-10-7

WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage

OPERATION DESCRIPTION TIME
011902A Replace Rear Brake Shoes 1.2 Hrs.

DEALER CODING
BASIC PART NO. CONDITION CODE
2200 49

OASIS CODES:
301000, 702200


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Copyright © 2001 Ford Motor Company