Need help diagnosing brake lock up

TJosh02

TJ Enthusiast
Supporting Member
Joined
Feb 6, 2019
Messages
243
Location
Toronto
So Saturday, I was the tail gunner on a fun trail for my club in slick greasy conditions. It was a 3 hour drive north to the trail we were doing. The night before I did an oil change, as I was a bit overdue. One thing I noticed was that I only got about 3.5-3.75 L of old oil out despite putting 5L in (I thought that was correct amount), and was a bit overfull. I mention this in case it matters, but plan to drain some out to make it right again.

Ran up there the 3 hrs no issues. Ran the trail no issues (~ 4hrs). Went to do an add on trail with 2 guys who wanted more like myself and kept blowing my fuel rail fuse in the box. There was lots of water on the trail, and I think it is a grounding out so wires, after I clipped the extraneous spliced wiring my dad has done to the passenger tail light for the trailer hookup I no longer use. (Again, just full details, even if it isn't relevant. I plan to do quite a bit of electrical "clean up" once and for all on some stuff, this happened once before last season so I knew where to look for this).

Got back, finished, aired up and when driving out the 10km of forest roads back to the highway, I noticed the power was terrible. It was bogged bad. Then one of my mates behind radioed he smelled something burning and saw smoke. We pulled over. I immediately went smelling and the front calipers were cooking. Up till now the brakes felt normal pressure wise. I turned it off and then the brake pedal was rock hard to push. Put it in neutral (5 spd manual) and the t-case in neutral and couldn't push it on flat ground (parking off as well, not that is is worth a damn anyway). Couldn't figure out why they were locked up, so I called CAA (like AAA but here in Canada).

While I was on the phone to CAA, I let my buddy who I trust investigate. He pulled the master cylinder from the brake booster and heard the pressure let off. They backed the brake booster push rod back some and put it back to use. It drove normally after. The brakes were not locked up, but the brake pedal a bit softer, meaning I had to push it in more. That makes sense since we experimented with the push rod adjustment, but it seemed more to due with letting out the pressure.

But why would this all the sudden be? Why was I getting too much pressure? It is like the vacuum was far too strong in the booster. The master cylinder seemed to function fine, but I have no frame of reference.
 
So Saturday, I was the tail gunner on a fun trail for my club in slick greasy conditions. It was a 3 hour drive north to the trail we were doing. The night before I did an oil change, as I was a bit overdue. One thing I noticed was that I only got about 3.5-3.75 L of old oil out despite putting 5L in (I thought that was correct amount), and was a bit overfull. I mention this in case it matters, but plan to drain some out to make it right again.

Ran up there the 3 hrs no issues. Ran the trail no issues (~ 4hrs). Went to do an add on trail with 2 guys who wanted more like myself and kept blowing my fuel rail fuse in the box. There was lots of water on the trail, and I think it is a grounding out so wires, after I clipped the extraneous spliced wiring my dad has done to the passenger tail light for the trailer hookup I no longer use. (Again, just full details, even if it isn't relevant. I plan to do quite a bit of electrical "clean up" once and for all on some stuff, this happened once before last season so I knew where to look for this).

Got back, finished, aired up and when driving out the 10km of forest roads back to the highway, I noticed the power was terrible. It was bogged bad. Then one of my mates behind radioed he smelled something burning and saw smoke. We pulled over. I immediately went smelling and the front calipers were cooking. Up till now the brakes felt normal pressure wise. I turned it off and then the brake pedal was rock hard to push. Put it in neutral (5 spd manual) and the t-case in neutral and couldn't push it on flat ground (parking off as well, not that is is worth a damn anyway). Couldn't figure out why they were locked up, so I called CAA (like AAA but here in Canada).

While I was on the phone to CAA, I let my buddy who I trust investigate. He pulled the master cylinder from the brake booster and heard the pressure let off. They backed the brake booster push rod back some and put it back to use. It drove normally after. The brakes were not locked up, but the brake pedal a bit softer, meaning I had to push it in more. That makes sense since we experimented with the push rod adjustment, but it seemed more to due with letting out the pressure.

But why would this all the sudden be? Why was I getting too much pressure? It is like the vacuum was far too strong in the booster. The master cylinder seemed to function fine, but I have no frame of reference.

Occam's Razor- something changed in the booster that caused it to move a slight amount and the booster push rod was adjusted too long to start with.
 
Occam's Razor- something changed in the booster that caused it to move a slight amount and the booster push rod was adjusted too long to start with.

I get it but I am not satisfied until I know the why. Don't mean you have to tell me but I'd like to discuss the possible causes