Is your L300 Leaking Brake Fluid? **READ**

Folks,

I'm going to start by being honest. I'm a mechanic. And sometimes, I know it's broken but I know what's involved with fixing the problem so I put it off as long as possible until it leaves me stranded. Long story short, I can be an idiot.

Such a situation happened in September of 2017 during my evacuation from Hurricane Irma. We had the Deli packed to the gills with whatever we could fit. Two chihuahuas, a bunch of dry food, blankets, a 7 month old, and two stressed out parents. I knew that the master cylinder had been leaking for a few months but had neglected to do anything about it. About 20 miles in, the brake fluid light came on and the pedal went softish. GREEEAAAAT. With the interstate starting to jam and the hurricane at our heels, I stopped at an advance auto and just filled the reservoir up. It actually lasted the entire trip north and back, only to come on when we got home. But it really leads you to wonder where in the hell all that brake fluid was going?! I was really hoping that the master cylinder wasn't pumping fluid into the brake booster, which would surely murder the diaphragm inside and kill the power brakes. After the hurricane was over and things settled, I decided to order the parts needed to fix the master cylinder. See below for the teardown.



Is your Booster bracket wet? You better get ordering parts.


The dash panel must come out to remove the booster/master/pedal assembly



Brake Booster and Pedal assembly with master cylinder removed. Note how the brake fluid leak ate the paint off the booster body.



Beginning to rebuild the Master Cylinder with an OEM Rebuild Kit.


You must source MB004276 Brake Reservoir Cap gasket/o ring x2.



Using mechanics wire, secure the caps like so. Try not to apply too much pressure, as it just needs a touch of pressure to keep fluid from escaping from under the cap. If it ever leaks or weeps in the future you can simply tighten the mechanics wire!

K

I'm seeing what I believe is brake fluid leaking on the floor mat (and pooling up over time). I'm not sure where it's leaking from, but like you, I'm reluctant to tackle this job. I think it may be the master cylinder - It drips from the booster and runs down the pedal where it finally drips to the floor. Where did you get the rebuild kit? Where any special tools required to do this?

I ordered the rebuild kit from my local mitsubishi dealership. The only tools you will need beyond some hand tools are a set of snap ring pliers for the master cylinder.

Howdy. I'm about to tackle this exact same thing. Is the rebuild kit specific to an american import model? Just wanna be sure I get the correct kit for my '89 Delica. Much thanks for any info!

OK, think i got the info. I grabbed the part # off the box in one of your pics and according to the Mitsu site I order from it fits my year. Master Cylinder Repair Kit - Mitsubishi (MB928395)

Yesterday I replaced the gaskets as well as installed new caps and clamps. The old caps came right off super easy, whereas the new caps actually required me to tap them on, sort of like a slip fit vs a press fit. If anyone plans to redo the gaskets I would recommend replacing the caps as well. Totally worth buying everything for like $12. Seriously, a huge difference in fitment for me. Unfortunately I am still leaking so I will be rebuilding the internals soon enough.

Gaskets - MB004276 --$1.29 ea
Plastic Covers - MB004274 --$2.34 ea
Clamps - MB044679 --$2.52 ea

I purchased a master cylinder from a US spec van.
Works fine just needed to rotate thep lastic hose connectors.
Also you just have to remove the gauge cluster to get access to it. Not the whole dash

Where does one procure a new assembly rather than rebuilding the master?

You can do an ebay search. Autozone and orielly's seem to have them, and I think I called napa at one point and they did not.

https://www.autozone.com/brakes-and...t-new-master-cylinder-brake-system/672345_0_0
https://www.autozone.com/brakes-and...ed-master-cylinder-brake-system/482935_0_3508

https://www.oreillyauto.com/shop/b/...d/1989/mitsubishi/van?q=brake+master+cylinder

Where does it leak from? is this unit something that needs to be replaced, or just an old O ring? Currently I have this problem, I purchased the Autozone link posted by Neww. When I opened the box however, my new unit does not come with an O-ring on the end that connects to the van (I Haven't opened up the van yet, just want to check before I dismantle the dash this weekend)

Chanchi

there is no oring that connects to the van. It is a metal on metal interface, master cylinder to brake booster.

The part that leaks are white caps on top. They have gaskets underneath that go bad. Additionally, as was the case with mine, the piston mechanism had a leak so fluid was pouring into my brake booster. I had all the leaks. In fact I think I won!

Something is still leaking on mine. There was soo much dot fluid in my brake booster, that was definitely an issue and I wonder how much more is still captured and pouring out. It had sat for six years and I take it that it was leaking before the guy parked it. I wouldn't doubt that reservoir was filled several times and not all of it went onto the floor.

This seems to be to easy to fix, am I missing something? Other than the pain of removing the dash, I got the master cylinder off, cleaned out the black gunk that had built up on the brake booster, and replaced with the new one from AutoZone. Everything fits perfectly for once! Other than bleeding the brake fluid, do I need to do anything else? Bleed the clutch?

Chanchi

You either picked the best or the worst vehicle to learn the basics on!! Best bc you'll have plenty of opportunity to dial things and worst because you have plenty of opportunity to dial things in.

Somewhere in the technical thread you will find a link to all the manuals. I would read through the brakes and follow the bleed procedure. Most likely you will have some air bubbles in the system from swapping the master cylinder over. I also recommend doing a full system flush if it hasn’t been done. You will know right away when the fluid comes out. If it’s clear you’re good, if its grey or discolored then keep doing the bleed until it’s coming out clear. Just buy some clear hose from the hardware store, only a few cents per foot, get a milk jug, feed the tube in and then down the handle, this way it doesn't try to pull out and give'r.

It'd also, be smart to hit the bleeder valves with a touch of penetrating fluid before hand if it's rusty under there. careful not to over do it and get things over your rotors and into the drum.

Make sure you have a torque wrench and flair nut crows foot and flair nut wrench. This is for the nut on the hard brake line that attaches to the mater cylinder but also not a bad idea for the brake bleed screws. See below.

Follow the torque!! Especially for the master cylinder flair nut. Too tight and you can strip or deform the hard line. Before I do any job I find all the torque and write them out separately on a piece of paper. this way I am not looking through the book when under the van. Do all the conversions ahead of time if necessary as well. Foot Lb and Newton Meter are kind of close but not really.

While you are in the dash you may think about a clutch bleed if it's not accessible otherwise. Use your judgement on that. Probably more to flush it than to bleed air out of the line. Also, with the dash i off I highly recommend pulling all of the vents out and washing them and whatever is behind the dash. 25 years of dirt, dust and mold. Give your lungs a brake. I had mold all up in mine. t'was nasty!

Nenw- great response, thank you!

I figured 6 years with an 87 4wd Toyota van would have prepared me for the Delica, I can't believe the tight spaces on this rig are worse than my old yota haha.

I was able to replace the MBC, and get everything clean and reinstalled. Funny, there had been a noise coming out of the vent with the defroster setting- check out this old Japanese receipt I found when cleaning the vents!


Anyway, I bled 3 of brake lines, they actually came out pretty clean, so the last owner must have serviced the brakes just before I bought it. I'm still hearing air release from the MBC when I push the brakes, and the brakes are quite soft still. When it was too late to work last night, I read over the manual and saw that the 4th bleeder valve is not on the wheel, but actually near the center of the van.

Also, I followed torque specs on the flair nuts, but didn't see any torque specs for the MBC attachment bolts.

I'm going to try to bleed brakes one more time this evening, then read the manual again. Hopefully that takes care of the soft brakes and wheezy noise I'm hearing from behind the steering wheel. If not, I might have to adjust the brake booster distance (where the MBC attached)? I might look at flushing the clutch fluid today too if there's time...

Chanchi

Old MBC (left) vs new from AutoZone. That gunk built up on the old was probably causing my leak. I could have cleaned and reused it, but I figured the new one would be a better option in the long term, especially for the seals on the top where brake fluid comes in.

Love that receipt, so they ordered a Dolphin, lol!

That reciept is classic!!

I found a canadian quarter. Not nearly as exciting!

I just translated it, its a coupon to go play with dolphins. Only 1900 yen for an adult, 900yen for a 'dwarf' haha. What a deal!
Chanchi

Just about to do this, got the parts ordered. Is it necessary to remover the Brake Booster and Pedal assembly or can you remove the master cylinder from it in place?
Is it a case of "easier to remove the whole thing than work on it in place"?

I didn't replace the brake booster and pedal assembly, and my brakes seem to be working fine. It seemed like less work than having to remove the entire brake booster... the brake fluid ate through the paint on my (and I'm guessing yours might be the same). I'm hoping it won't corrode over time, and wished I have maybe taken more care to remove the whole assembly and repaint. maybe It won't be a problem? it's definitely a PITA job, I hope you have dainty fingers

Chanci