Leaking brake fluid from MC

[oakback]

I replaced my MC in 2024 (but not the accumulator, I swapped it to the new MC). It's leaking badly now from the line that goes from the accumulator. My personal rule is do something myself, and if it fails, take it to a shop. So that's what I did. The shop says the MC and accumulator should never have been separated or the line can leak because of the high pressure. I'm not sure why Toyota was able to sell me the MC without the accumulator, but I guess that's on me and I'm sure some folks are gonna remind me of that anyway, lol.

Does this sound right? Is there anything I can try before replacing it all? I can't afford a new MC/accumulator, they're currently going for $2,200+.

 

[frawstme]

I don't have personal experience with this exact system but if there's a hose that a manufacturer can install without leaking, then anyone can install that hose without leaking with the right tools. It seems a waste to replace a brand new mc. Is this a flare fitting? how is the hose secured currently?

 

[Mchodl]

That sounds incorrect. What part number did you use to replace the master previously and what issues were causing you to do that? Have you tried tightening the line that is leaking?

 

[GTV]

I replaced my booster at 165k and I’m still running the original master now at 230k.

 

[oakback]

That sounds incorrect. What part number did you use to replace the master previously and what issues were causing you to do that? Have you tried tightening the line that is leaking?

I don't remember the part number. It was doing the screeching sound when the pump ran, there are a bunch of posts documenting this problem. Other posts mentioned leaking seals within the master cylinder, seals that can't be replaced by rebuilding the MC alone (which I tried first, and failed to fix it). I've tried tightening the line, no change. The brake shop also tried, and said they couldn't tighten it any further without risking damage.

The MC assembly is not old, but the hard lines are original. I'm thinking maybe the hard line has a hole or crack in it. It's the red line that connects the accumulator pump to the master cylinder.

Does anyone know this part number? I've been searching partsouq and other sites and can't seem to find it.

 

[oakback]

I don't have personal experience with this exact system but if there's a hose that a manufacturer can install without leaking, then anyone can install that hose without leaking with the right tools. It seems a waste to replace a brand new mc. Is this a flare fitting? how is the hose secured currently?

It's a typical flare nut hard line, the one with the red covering.

 

[Dirt J]

44551C in the diagram? If so, it's 44551-60010 for my year model. Check Partssouq for yours to double check.

Partsouq is showing no availability for that part # but looks available elsewhere per Google.

 

[2001LC]

We can replace just master or booster pump/motor or booster/pump accumulator or just accumulator. But as a rule at this age, we just replace the whole booster ASSY w/master.

If the red high pressure line, is the leak. It would be at flare nut. So, first make sure that is the leak.
If it is: Booster motor would run continuously and eventually burn out. Brake lights and alarms would warn of pressure loss, long before motor burn out.

One can pin point leak:
IG Key off. Pump brake pedal 40 times, to depressurize accumulator. Clean area of all brake fluid. Then turn IG key ON, running booster pump pressurizing accumulator and red HP line. Watch for brake fluid leak, to pin point leak.

If leak at a flare nut. Try removing pipe and find cause:

• Either it was not torque to ~11ft-lbf.
• Debris in flare end of pipe.
• Flare end of pipe damaged
• Flare nut cross threaded.

If leak on pump side and due to cross threading flare nut. Replace pipe and pump. Best would be new booster side ASSY (accumulator, pump and motor)
If leak on master side, due to cross threading of flare. Then replace master and pipe.

 

[oakback]

Tightening the flare nuts did not stop the leak, but replacing the red line did. I can't see any obvious damage on the old line, but I assume with high enough pressures it can leak through a very small imperfection.

Here is the old leaky (MC) side of the red line. I'm not sure if the visible corrosion was there when I removed it, or formed while being exposed to air and humidity after removal.

I'm very glad this fixed it, I really did not want to replace the MC again.

 

[Terra Dactyl]

I replaced my MC in 2024 (but not the accumulator, I swapped it to the new MC). It's leaking badly now from the line that goes from the accumulator. My personal rule is do something myself, and if it fails, take it to a shop. So that's what I did. The shop says the MC and accumulator should never have been separated or the line can leak because of the high pressure. I'm not sure why Toyota was able to sell me the MC without the accumulator, but I guess that's on me and I'm sure some folks are gonna remind me of that anyway, lol.

Does this sound right? Is there anything I can try before replacing it all? I can't afford a new MC/accumulator, they're currently going for $2,200+.

Bell Toyota Phoenix quoted $2000.00 that’s my local supplier. They accept Costco agreement which can lower your parts / service costs by I think up to 15%.