Brake pedal went soft - random event

[viven44]

I have been thinking about getting ready for long distance driving on Big Blue 2WD.

I recalled this one random event yesterday. This was right around the time when I lost and found cylinders middle of April. https://forum.garysgaragemahal.com/Curious-case-of-lost-and-found-cylinders-tp151540.html

It was a nice 80F day. When I got back from a 80 mile roundtrip to pick up some old Ford radios, the brake pedal went to the floor randomly.. I may have been brake checking some... to see how tight the pedal was possibly. Anyway after pumping the pedal a few times the pedal became hard and since then I've refrained from brake checking... and I have been just fine.. 1000 miles and 4 months later... with many days of driving at 95F+ days.

I was curious if this still warranted a brake master cylinder change....

Also I have an old school trailer brake controller which is tapped into the hydraulic system... I don't know if it is electrically hooked up to anything, not sure how it works.

How does the brake bleed process work with something like that ?

Can I eliminate that thing and will that affect using a UHAUL trailer ? There is a 7 pin harness in the back and I don't know what the trailer brake controller does in addition.. I had understood the UHAUL trailers had their own trailer brakes.

[thelastkeg]

My experience with every U-haul trailer I've used is that they all have the little 4-wire hookups for lights and surge brakes built into the hitches.

If it was me, I'd replace the master cylinder.  Or at a minimum make sure you're comfortable with the condition of your parking brake in case you lose hydraulics.  My 68 Chevelle had the same issue last year with brake pedal going to the floor randomly.  Pumping it once or twice would firm it back up.  I replaced some very old pitted wheel cylinders (4 wheel drum brakes on this car), the probably original front rubber hoses (which I cut open and they were swollen shut), and the brakes no longer pulled hard to one side, but the pedal still went to the floor at times.  I replaced the master cylinder and now the brakes are working like a new 4 wheel drum brake system should work.  

Edit - I've never fooled with a trailer brake controller that is tied into the hydraulics.  I'd be tempted to remove it and go to an electric controller, only because that's what I've had on so many trucks.  

[85lebaront2]

I have an old Kelsey-Hayes hydraulically operated trailer brake controller on Darth.

When I bought Darth, he had one of the electronic controllers, this old beast works much smoother and predictably than the electronic ones.

[viven44]

Bill, Thanks!

Can you educate me on the differences in operation between electronic vs hydraulic brake controllers ? How do these things work and what is their function ?

Can't a stop light signal provide the electrical input necessary to perform a trailer braking function ?

[viven44]

Yes I agree I probably should replace it before my trip so I'm not paranoid the whole way... the strange part is how in the next 1000 miles there have been no issues. Even in stop and go traffic. The master cylinder looks somewhat new and per the previous owner a brake job was done maybe 3 years ago by his son....

[thelastkeg]

I missed the part about 1,000 miles later and it hasn’t happened again. I actually probably wouldn’t worry about it then.  Could’ve just been some air in the line.  

[viven44]

Yes! It has also given me appreciation since then to not just jam the brakes just for the heck of it.

If I drove all my vehicles like my father-in-law they would last FOREVER. He is so gentle with them. He is just going through his first set of 4 wheel drum brake hardware (all of it from master cylinder, rubber lines) on his 69 Chevy Pickup that he bought after getting back from Vietnam. I told him to hang onto the factory originals!! He is just replacing them out of abundant caution, they still worked fine. Garaged truck so that probably is a factor.