73 M400 Brake Master Cylinder

[TheAccountant1969]

I have been searching for a cheaper alternative to buying the very pricey brake master cylinder for my Dodge Titan from Alretta.


We found a master cylinder that matches the picture on Daves website: http://dave78chieftain.com/MCBendixDual/Figure03.JPG


Car Quest has it listed under a 73 M300 though. Which according to Dave's website should look like this: http://dave78chieftain.com/MCBendixDual/Figure01.JPG


Does anyone have any experience with this? We disassembled the master cylinder and found that several of the cup seals were torn and the o-ring had some nicks in it. We are currently awaiting the arrival of a 73 M300 rebuild kit that we are hoping we can at least steal the seals off of and put on the old setup.


I'll have to wait and see when I get the new master cylinder in my hands to compare it to the old one, same with the rebuild kit. Just wanted to see if anyone has any experience dealing with finding parts for this chassis and if they've ever found any parts listed under the wrong chassis that are in fact the correct parts for their chassis. It seems like there is a lot of confusion industry wide as what parts go to what chassis and its almost impossible to find an 73 M400 even listed anywhere with available parts. Hm?

[TheAccountant1969]

This is the master cylinder we found:


http://www.dormanproducts.com/itemdetail.aspx?ProductID=14824&SEName=m39012


From what I can see right off the bat, its for a system with both drum and disc brakes given the different reservoir sizes which is promising.

[legomybago]

I found this source to be my savior when I rebuilt my hydrovacs on my FMC. They had misc parts and pieces I needed.
http://www.yellowpages.com/atlanta-ga/mip/brake-specialty-co-inc-6870150?lid=6870150

[TheAccountant1969]

Thanks! I'll give them a shot.


We struck out all over town (Sacramento, CA) trying to find a place that even stocked cup seals for brake master cylinders.

[Rickf1985]

Here is an interesting tidbit for you to ponder. Here, at least in the state of NJ, it is illegal for me to rebuild a master cylinder for anyone BECAUSE I am a certified Master mechanic. It is considered too risky of a job and should be a replacement part only. ( But it is ok to put one in that some Chinese kid rebuilt in a hut!)
Now here is the kicker, It is perfectly legal for the owner of the car, (you) to rebuild your own master cylinder.  So basically they are saying that it is not legal for a trained mechanic with the correct tools to do it because it is a risky job but the homeowner without training or proper tools is allowed to do it because it is their car. Got to love this place.

[DaveVA78Chieftain]

39013 is for a 73-75 M400 (RM350) Chassis with Dual Hydrovac Boosters (1 1/4" cups)
NAPA (M or P 4959)
Amazon
Rock Auto
Cardone 13-1576
EBAY 39013
EBAY 13-1576

Master Cylinder Kit for 39013
NAPA UP 792

39012 is for a 76 M400 and later chassis with Hydroboost (1 1/4" cups)
NAPA (M2134)

M300 used NAPA 36461 (1 1/8" cups)

Dave

[TheAccountant1969]

Dave,


I've said it before, but, you're a savior.


I reserved a 39012 (M2134) at the local Napa. Can I just drop the whole unit in my coach? I'm assuming so.


Thanks again!

[TheAccountant1969]

Here is an interesting tidbit for you to ponder. Here, at least in the state of NJ, it is illegal for me to rebuild a master cylinder for anyone BECAUSE I am a certified Master mechanic. It is considered too risky of a job and should be a replacement part only. ( But it is ok to put one in that some Chinese kid rebuilt in a hut!)
Now here is the kicker, It is perfectly legal for the owner of the car, (you) to rebuild your own master cylinder.  So basically they are saying that it is not legal for a trained mechanic with the correct tools to do it because it is a risky job but the homeowner without training or proper tools is allowed to do it because it is their car. Got to love this place.

Ha! Well we're doing all the work on this one ourselves so we havent even inquired at any shops, not sure what the laws here in the PRC (People's Republic of California). While none of us are mechanics by trade, we've all spent the majority of our lives as gear heads building muscle cars and drag cars. Our Vintage RV has proven to be a different beast so far but nothing we cant manage as long as we can find parts. Everyone here has been helpful and I appreciate all the input. 

[DaveVA78Chieftain]

I'm a little confused.  Why are you ordering a 39012 for a 73?  That's for a hydroboost rig (powered by power steering pump) like this.
 

For 73, you should have 2 vacuum boosters mounted to the frame rail like this which uses the 39013

[TheAccountant1969]

If I'm being perfectly honest, because it was cheaper. My thought process being, whatever is happening after the master cylinder hydro vac or hydro boost, shouldn't effect the the operation of the master cylinder itself. Will the brakes not function properly with the 39013?

[Rickf1985]

Different part numbers so I will bet you are going to find that while the cups are the same size there may be differences in the springs and other seals in the kit. It is best to get the kit for exactly what you have. These are your brakes, you do NOT want to shortcut on this item!!!!

[DaveVA78Chieftain]

The Master cylinder for a later module Hydroboost system is mounted after the hydroboost unit so it generates the full hydraulic force of the system.

The Master cylinder for the earlier Hydro-Vac system is located before the booster units therefore it is not subjected to the amount of pressure a hydroboost system master cylinder is.  This system (yours) has additional master cylinders mounted to each Hydro-Vac unit that generate the full hydraulic pressure of the system.

Because of these differences, the construction and internal parts for each master cylinder are different.

If you are determined to use a kit rather than a complete master cylinder, then I would first see if NAPA has the UP 792 kit available.
Dave

[TheAccountant1969]

After thinking about it I ordered the correct part yesterday.  D:oH!

Thanks for your help gents, I'll update after the install.