Brake master cylinders

[ES_97Sport]

If you guys can, can you check your brake master cylinders and see if there's a bore diameter stamped somewhere on the aluminum? I'm trying to get an idea of what seems to come on what.

The sizes may be stamped underneath so you may have to use your smartphone or a mirror. Looks like its stamped under the end next to the battery.







The first seems to be common on the Sport. The second apparently comes on some Sports but I don't know which ones. The third may only be on the TT GT3000 VR4s. In theory, they're all interchangeable, but I want to make sure.

Post what the size is and what make, model, year, etc. Especially if its a 'Wide' or 'Narrow' Sport.

I found out today that apparently there are two different disk sizes on the Sports. Since I run Exploder/GM brakes, I've never really paid any attention.

Edward

[jkdv8]

Yea I'll take a look if I remember when looking for leaks. Might be a day or so.

[dirk]

For rotors, I know I used the larger ones for my 2001 XLS.

[ES_97Sport]

1997 Montero Sport 3.0L LS 4WD Wide - 15/16"

2003 Montero Sport 3.5L Limited AWD - 1"

1999 Montero Sport 2WD/4WD - 15/16" - according to the FSMs

1999 Montero Sport 3.5L Limited 4WD - 15/16"


(Bore size is cast into the body on the bottom end next to the battery.)

<edit>
"Bore size is cast into the body on the bottom end next to the battery."

This isn't always true. Some after-market brake master cylinders do not have the size cast into the piston casting.

Nabco appears to be the manufacture for the OEM BMCs and their name is cast into the underside of the piston casting in 1/2" tall letters. All Nabco BMCs - Montero, Sport, 3000GT, etc. - that I've seen have both their name as well as the size cast in next to each other.

Note: The Nabco castings are A LOT better quality than the after-market castings I've seen. I have two Nabco BMCs - one OEM and one after-market - and have compared them side by side. The quality is identical. Again, obviously much higher quality than the China knock-offs.
<edit>

And this is why I hate getting non-OEM parts. ARG! I stopped by Napa this morning hoping they'd have one in stock I could take measurements off of. They list the bore diameter for the '97-'99 Sport as 13/16". I have yet to see any Montero or Montero Sport from the low '90s though '04 with anything smaller than 15/16". In fact, I've never seen 13/16" referenced for any Mitsubishi SUV. :rolleyes: I presume this is yet another error in their parts catalogs for our vehicles. Sigh.


Edward

[ES_97Sport]

Mitsubishi tool for adjusting the brake booster push-rod to the brake master cylinder. Not required but its a lot easier to use than the block and ruler technique.







Edward

[ES_97Sport]

I confirmed that most, if not all, of the '90s Montero, 3000GT, Plymouth Laser brake master cylinders are interchangeable with the Montero Sport BMCs with some modification.

The reservoirs are different between the 3000GT and the Montero/Montero Sport, but can be swapped. In some cases use of the 3000GT off-set reservoir might be useful for clearance reasons.

The 3000GT used a 15/16", a 1" and a 1 1/16" BMC. The Montero used a 15/16" and 1". And the Sport used 15/16" and 1".

So, if you're really desperate, these would be something to look for in the salvage yards.

Note, that the push-rod (shown below) will need to be correctly adjusted as the different BMCs above have different piston depths. YOU MUST DO THIS and it MUST be done correctly! You will need a small socket wrench and an angle nose needle nose pliers according to the FSMs, in addition to the tool above or a 6" ruler, block and maybe feeler gauges.



Edward

[pinstryper]

And what will this do? Increase braking? Or options if original fraters?

[ES_97Sport]

Nov 18, 2015 1:20:31 GMT -5 pinstryper said:

And what will this do? Increase braking? Or options if original fraters?

This is just reference material. Stuff is getting harder to get so its nice to know that in an emergency it might be possible to get a part from a different vehicle. There's not a lot of cross-reference to other vehicles out there as most everyone knows by now.

Under no circumstances would you want to start swapping brake parts without knowing what the effect will be. Installing a larger or smaller bore brake master cylinder on an original working system IS NOT AN UPGRADE. Fluid volume and pressure, swept area, rotor diameter, booster ratio, pedal linkage ratio, etc. are carefully calculated and parts are matched to a system. Which is why its call a 'brake system'.

There are at least 7 pieces on a non-ABS and at least 8 on ABS brake systems - brake pedal linkage (leverage), brake booster, calipers, rotors (rotor diameter & swept area), brake master cylinder, proportioning valve, and ABS system and maybe a load-adjusting proportioning valve on some vehicles. There's a lot of math that goes into making this all work.

For example, changing the size of the brake master cylinder (BMC) will have two different effects. A smaller diameter piston creates more pressure but moves less volume of fluid. A larger diameter piston produces less pressure but moves more volume. If you used a large diameter BMC piston on small volume calipers or visa versa, it will totally screw up your braking. Changing the BMC piston diameter may also mess with the proportioning valve which can cause the back brakes to lock before the fronts in a panic stop - ALWAYS A VERY BAD THING.

This is an interesting read ...

4x4 Wire - Brake Upgrades

Edward

[pinstryper]

You come up with the best reads, keep em coming Sir...

[ES_97Sport]

This comes up and I thought it was an appropriate place to put it.

One Man Bleeder review

I've tried #1. Complete waste of time. Never worked worth a damn on anything I've ever tried it on.

The dealership techs use a huge professional vacuum bleeding system. Which - if properly used - works extremely well. Its also extremely expensive piece of equipment. It still does not negate 'bench' bleeding the BMC when a new one is installed.

The article did not mention 'gravity' bleeding. That technique is hit-and-miss in my experience. In the article the writer mentions getting bubbles attached to rough internal surfaces to come loose. Gravity bleeding will not accomplish this so the risk of having air left in he system is pretty high. However, this is adequate for bleeding the system well enough to get the vehicle to a shop for further work or further bleeding with a mechanical system.

Edward

[redraif]

I guess its a one inch...

2001 3.0L 4wd automatic XLS, 4.9 gears,


front and rear disk,





Exterior: two-tone white and charcoal, chrome trim, wide body, non-heated mirrors, no fogs, 16x7 with matching spare...



Interior: grey cloth, non-power seats, power locks, mirrors and windows, non infinity stereo, no cd changer, keyless entry

[dirk]

I finally got a chance to look at the one installed in my vehicle. It is a 15/16 bore BMC. I did notice that the area where it is stamped on it is not flat with the square around it but molded onto the round body on opposite side of the BMC from the 1 inch BMC I got from a 2002 limited. Makes me think it is aftermarket. And since my brakes are dual piston with larger diameter discs, someone replaced it with the wrong one. That explains why I always found my brakes to be mushy even after replacing almost everything including fluid. It was better but not great like it should be.

So now that my fuel filter is changed, BMC and steering stabilizer is next on to do lists lol going to need to order one of those BMC tools if the dealership doesn't have one.

[ES_97Sport]

Dec 15, 2015 19:45:53 GMT -5 dirk said:

I finally got a chance to look at the one installed in my vehicle. It is a 15/16 bore BMC. I did notice that the area where it is stamped on it is not flat with the square around it but molded onto the round body on opposite side of the BMC from the 1 inch BMC I got from a 2002 limited. Makes me think it is aftermarket. And since my brakes are dual piston with larger diameter discs, someone replaced it with the wrong one. That explains why I always found my brakes to be mushy even after replacing almost everything including fluid. It was better but not great like it should be.

So now that my fuel filter is changed, BMC and steering stabilizer is next on to do lists lol going to need to order one of those BMC tools if the dealership doesn't have one.

If it doesn't say Nabco on the bottom it's probably not OEM. That doesn't mean it was installed by a dealership. Raybestos and ACDelco both get some of their BMCs from Nabco.

Edward

[ES_97Sport]

I looked this up in the FSMs last night 'cause it needed it to plug into Bill's brake spreadsheet calculator. (dl link is on his page)

Pirate4x4 - The BillaVista Tech Garage Brake Bible

The brake booster boosting ratio for the US Gen 1 Montero Sport is 7:1. 2/4WD, 2.4L, 3.0L, 3.5L, ES, LS, XLS and Limited, 'wide' or 'narrow'. So, all models.

This is different from overseas models. I found several FSM references for the Pajero, Pajero Sport, etc. that listed 5:1, 6:1, 6.5:1, varying depending on engine displacement and 'wide' and 'narrow'.

Gen 1 Montero Sport (all) pedal ratio appears to be almost exactly 4:1.

I would strongly recommend reading Bill's Brake Bible. Even if you skip over a lot of the math, there's a lot of interesting information in there that explains how brakes work. If you work on your own vehicles it'll definitely help in troubleshooting brake issues.

Edward

[ES_97Sport]

For those who are interested, here are the Raybestos P/N for both the Gen 1 and Gen 2 Sport brake master cylinders. Gen 1 is 15/16" and Gen 2 is either 15/16" or 1". I included the P/N for the 3000GT just for reference.

These are the same OEM master cylinders that Mitsubishi installs on their vehicles and sells over the counter. If you need a BMC, this is a cheaper way to get the OEM part than buying it directly from Mitsu. In my experience, they're about 40% cheaper than OEM and about 30% more expensive than cheap rebuilt no-name parts.

1 1/16" - Raybestos MC39983
1"      - Raybestos MC390654
15/16"  - Raybestos MC390156

!!NOTE!!

All three of these are interchangeable and the 1" and 15/16" parts are virtually identical. ALWAYS check the bottom of the casting for the bore size before installing. Nabco BMCs will have the size cast into the aluminum casting at the opposite end from the mount.


See the example above where at the left end of the casting, a numeral '1' is cast into the housing.

Edward