80 Series Diesel in Costa Rica - nice ride but having a strange prolonged issue with the brakes (1 Viewer)

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Joined
Apr 26, 2025
Threads
1
Messages
4
Location
Costa Rica
I have attached some photos of my 80 series - Turbo Diesel - and a bit of the journey I've been on. My mechanic and I found the listing for this car on Facebook marketplace. It had been in an accident and the front transaxle was severely bent, and the axle shafts broken. We retrieved the car and sourced a new transaxle casing, and it is now back on the road. It is lifted about 4 inches, and was initially on 37" tires, which I found impractical for the combination of dirt road and limited pavement driving we do down here. I put 35" tires on it shortly after purchasing and I am much happier with the handling and ride. My journey into town involves daily river crossings, and car has been just great at dealing with the water, which is currently just running board height. It has the pull out awning, ARB bumpers, and a solar panel on the roof. Will add a shower tube shortly for the beach.

My big challenge right now is the braking system. When I got the car, the brake fluid was incredibly dirty. The pedal was soft, and under constant pressure while running, it would descend to the floor. At times, in reverse, there would be no brake force at all. If I stood on the brake pedal in D, the pedal would slowly descend to the firewall, and the car would start moving. Replaced the master cyclinder, and had the same problem. Removed the booster, and found it filled with fluid. Replaced the booster (which it turned out had failed) and the pedal continues to have the same behavior. When pressed with force for a long duration (1 minute or so) it will slowly descend to the firewall. Fluid level does not change at all in the car. The only think I can think of is that there is a leak in the soft lines feeding the booster and I am slowly losing vacuum assist? Does that make any sense to anyone? No fluid is leaving the system - that's for sure. To be totally transparent, the vehicle currently has a Hilux master cylinder and booster installed (while I wait for the correct parts to arrive) - but the use of those parts doesn't explain the softness of the pedal. 4 wheel disk brakes. no ABS. Something else is going on.... any ideas?

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Nice looking truck. What is the build year? It does sound like you have air in the brake lines. If the soft lines are original it'd be good to replace them in any case.
 
Air in the lines sounds likely. An expanding soft line less so. They tend to balloon out pretty quick, but as stated above, if they are origainal it would be best to replace them.
The only other thing would be the fluid is pushing back past the seals in the new master cylinder. The fuid has to be "going somewhere" for the pedal to slowly settle with load on it. So either the brakes need to bled of air because the fluid is compressing air bubbles, or you need a new master cylinder, which is on order as you stated.

If you had a vacuum leak to the booster, the pedal would be easy to move at first, then the load would stack up hard; like stand-on-the-pedal-with-both-feet-to-stop hard.
 
Nice looking truck. What is the build year? It does sound like you have air in the brake lines. If the soft lines are original it'd be good to replace them in any case.
Thank you. Unclear on the year of the build. I picked it up after the accident and damage - I think based on some photo history it wasn't that long ago - maybe 2022 or 2023. I am going to check all the soft lines over and replace anything aged. I am also going to start a full bleed again, starting with a bench bleed of the master, and see if I can detect anything odd with it when it is on the bench.
 
Air in the lines sounds likely. An expanding soft line less so. They tend to balloon out pretty quick, but as stated above, if they are origainal it would be best to replace them.
The only other thing would be the fluid is pushing back past the seals in the new master cylinder. The fuid has to be "going somewhere" for the pedal to slowly settle with load on it. So either the brakes need to bled of air because the fluid is compressing air bubbles, or you need a new master cylinder, which is on order as you stated.

If you had a vacuum leak to the booster, the pedal would be easy to move at first, then the load would stack up hard; like stand-on-the-pedal-with-both-feet-to-stop hard.
Thanks for the diagnosis of how the booster vacuum issue would manifest. I appreciate it.
 

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