I am new to truck ownership and won't be doing my own work like you guys. However, I'm really excited about my truck and want to be an educated owner.

I have a 1987 F250 6.9l with about 133k that my dad gave me last week. It's has two owners (my dad and one other). It's an oldie but has been well maintained. The prev owner have us a big file of all the maint records, extra parts, etc..... My dad had the truck for the last 10 years or so using it to haul a 2 horse trailer for short trips and around the farm.

Brake issue: I used the truck to haul a 2horse trailer ( less than 7,000lbs) and after going down a long steep drive the brakes went to the floor and we had no stopping power. We dropped the trailer and the brakes came back with light pumping. I drove it to the mechanic with zero problems.

Mechanic checked it out and couldn't recreate the problem. The abs light is stuck on but he said that happens in the older trucks. He replaced the MC, drove it for a week himself and gave it back.

I got it back last week and put about 100miles on it. I made several trips with the empty trailer (my horse ads 1,200 lbs) then picked my horse up. Went down the same driveway and thought my brakes felt a little soft but if I lightly pumped they were back to normal. Two miles later down a windy curvy road my pedal went to floor (trailer brakes still engaged like they should). I had nothing. Pumped brakes they came back. Pulled over for about 15 mins then finished my trip with zero problems.

Should I point my mechanic in a particular direction? I don't want to give the truck over to him and spend a bunch of money just to have the same issue again.

Are there any things I could look for myself to help diagnose? My dad is pretty handy and would help.

Should I be worried mechanic didn't figure it out the first time and be thinking about changing mechanics?

Is this a common problem? Does it mean my old truck is shot? I'm hoping it isn't one of those things that's just too expensive to fix. The engine works great and hauls my little trailer around town like nothing.

Sorry for the novel!

 

For now pay attention to if you are riding the peddle, we had a pasture truck that if you rode the breaks they would go away, but if you just stomped then fully released the breaks they worked all day, We never fixed it because it wasn't on the road and we knew how to drive it.
There is a abs module that causes most the break problems on the 87-92 trucks. it is behind the drivers front tire on the inside of the frame.

 

Thanks. I normally don't ride my brakes but this particular driveway is wicked. There's no way to avoid using riding brakes. I even adjusted my trailer brakes up for that hill.

 

We try riding your breaks on flat ground to see if they go away, then you can recreate it for your mechanic. My money is on that abs module, I'm guessing that your truck is an auto as well, you can downshift to help with hills

 

Edit: Oops. Misread that the MC already got replaced.

 

I agree that it sounds like the abs module. I had the same problem in my 93 and 90 abs module fixed it right up. kind of pricey but way better than no brakes.

 

the kelsey hayes rear wheel anitlock brake unit is very sensitive to debris in the system and will easily malfunction.
most people just bypass it and eliminate it from the brake system.
here is a very good writeup on what it is, and how it works: http://www.aa1car.com/library/abs_kelseyhayes_rwal.htm