old87yota

Hello, I hope everyone is doing well today.

Truck: 1987 Toyota 2wd truck

Today I have been in the process of replacing my brake master cylinder because brake fluid started leaking out of the back. I bought a brand new master cylinder from Napa (might be a new Cardone MC???) and tried to bench bleed it using the instructions provided. The instructions said to remove the shipping plugs form the ports and fill the reservoir with brake fluid. Then wait until the brake fluid drips form both ports (gravity bleeding?). Then you connect plastic fittings into the ports and attach vinyl tubes and run them into the reservoir (submerged in fluid). Then it says to slowly push the piston in 3/4 to 1 inch and release slowly to purge the air.

Now to my problem: the front port will not move any fluid regardless if I push the piston in or out. I can see about an inch of fluid in the bleeding tube that will not move. The rear port pushed out some air bubbles and then a good amount of brake fluid like I expected.

Any suggestions as to what could be going on??

Thanks in advance.

old87yota

Bump!

wyoming9

iTrader: (1)

Take it back it is not working !!

Another milestone to Chinese quality!!!

AKHeathen

while it's submerged, put a plug in the rear port and bleed the front section. if that doesn't work, it's bad.

Terrys87

iTrader: (1)

Its bad. Not the first time this is happened and not the last. If you dont need the truck right away, try to find an Aisin on online. It will be about the same price and better quality.

old87yota

I took the master cylinder back to Napa and exchanged it earlier this morning.....

Terry's87, you said it!

The replacement did the same thing! I followed the provided instructions word for word.

I went with OEM with my brake pads, rotors, brake shoes, and wheel cylinders.

I guess I will order an Aisin one if I cannot figure out what is going on.

How have you bench bled your master cylinders?

Odin

They need to start boasting like Mc Donald's.


I think

OVER ONE BILLION FAILED

on the boxes might hurt sales a little though.

wyoming9

iTrader: (1)

I got 3 bad calipers one day all they had at the store.


That is one of those things I only ever bled one Master Cylinder and tried once to bleed a LSPV

Despite having to replace it seems miles of brake line and other hydraulic brake parts .

You got one bad one another one is quite possible

With those plastic fitting and hoses routed back into the reservoir master cylinder mounted in a vise or secured some other way .

Reservoir filled with enough fluid to cover fill things 1/2 way or so

Slowly move piston fluid should be pushed out of both ports back into the reservoir

Who can say they might be boxed wrong they may have given you the wrong one.

Terrys87

iTrader: (1)

Like wyoiming9 does his. I clamp the edge in my vise and with a dowel or screwdriver, with the rubber hoses running back into the tank, I pump the piston.

2 days ago, I had a clutch slave cylinder to go bad. I had to get a part store replacement as I need the truck for work. I put it on and it leaked around the threads. Up on looking further into it, it is either the end of the factory line not sealing against the nipple in the slave cylinder or maybe the slave cylinder is SAE threads and the factory metal line is metric.

What I did in a pinch and is working until I can get one on line in, is I took the piston out of the part store cylinder and installed it into my Aisin housing. Not sure if that will work in your case and I may have just lucked out, but I had to get my truck on the road again.

old87yota

Quick update:

After trying to get the third NAPA master cylinder to work properly (it locked up) I decided enough is enough.

I decided to to this right so I ordered an Aisin master cylinder. I took apart my original master cylinder to see if I could find what caused it to leak in the first place. Nasty brown sludge was caked to the inside of the pistons and the bore had a gritty sludge by where the seals sit.

wyoming9

iTrader: (1)

Like other fluids Brake fluid needs changed as well.

The thing is when things work it is never touched for the most.

Who knows how long it might have been in there.

AKHeathen

i used to have a bench bleeder. used it twice, just because, but it was as useful as a quick clamp, socket, and bucket of fluid, or a vice and the hoses in the case of toyota cylinders. i think a 70's ford (don't quote me on that) was the only one that it might have been better than doing it installed with someone topping it off. (on other vehicles where the ports are at the bottom).
don't take this wrong, but if you couldn't get one of 3 napa cylinders working, there is a chance you either did it wrong, or something, like the instructions or lspv, is getting in the way. heck, even a seized drum brake adjuster can get in the way of a bleed on-vehicle. did you try putting the shipping plug in the rear port while it gravity bleeds to get the front pumping, like i suggested? it should hold enough pressure for a bench bleed (but not in the vehicle with foot power). can you explain more how it locked up?

old87yota

Yeah, I don't think the fluid was ever changed before I changed it last year. It was my great grandmother's truck that was barely driven, especially before she passed away. I did not flush the system, just gravity bled until all the fluid was clear.


Yes I did try that, fluid will drip out the front but still won't push any fluid out when the cylinder is pushed in or try to suck anything back in when I release the pistons. It looks like there is no difference between just letting it drip naturally and pushing the pistons in and out.


After the first master cylinder didn't work I was trying to figure out if I did something wrong as this is my first time replacing a master cylinder. These devices are fairly simple so I am not sure what is going on. I tried to see if anything I did could possibly cause the problem but could not think of anything.

I got to thinking, with the way it is acting, it seems like the front piston doesn't move at all. Is it possible that after sitting on a self for a while has caused the front piston to get stuck?

I figured out that my third master cylinder "piston stopper bolt" was loose which caused a jam. I tightened it up and moves freely again (still have the problem).
I have not put any of the master cylinders in the truck. I wanted to get a good bench bleed first.

highonpottery

iTrader: (1)

there are several youtube videos on how to bench bleed a toyota MC - perhaps watch it and see if your method varied somehow.

AKHeathen

I just thought of something. ... most of the master cylinders came without resivoirs.... is your front passage plugged?

old87yota

Guess what....



UPS delivered the new Aisin Master Cylinder today!!

Started the bench bleeding 5 minutes ago and I am happy to report that the new master cylinder seems to work great! Now time to install it in the truck!


Upon further inspection of the NAPA MC's, I think the front piston seals got pretty stuck to the bore after sitting for years. When I thought it was bottoming out, I was just feeling the front piston. before returning the MC, I pushed the MC pistons harder to see if I could get it to move. It did move eventually but I think I ruined the front seals trying. Fluid would get pushed out but not in the volume that the rear port did.

The Aisin MC did not feel like it was sticking at all when I started bleeding like the NAPA ones did.


Now I have the peace of mind of having a solid reliable master cylinder for years to come.

Thanks for everyone's help!

Here is a video I found on Youtube showing the bench bleeding of the same Aisin MC I have.

This is not my video.

I did shorten the tubes a bit to make the bleeding easier. You can see the guy bleeding the MC in the video has longer tubes which doesn't allow the air to exit when you push the piston in all the way.

osv

glad to hear it's working.

fwiw, you don't need to bench bleed mc's, all it does is provide an opportunity for dirt and junk to get into the mc.

what i did was bolt everything up in the truck, pump the brake pedal, then use a 2x4 that was long enough to hold the pedal down, from the front seat.

put rags under the mc, then crack the brake lines to bleed it off, pump and prop again, etc.

obviously easier if you have an assistant instead of a 2x4 :-)

Terrys87

iTrader: (1)

Glad to hear you got it.iI know it was probably getting frustrating after 3 part store brands but now with your Aisin, you are good to go.

AKHeathen

good deal..... however, ditch those grease line/air line brass compression fittings...... i don't even know why they sell them in the automotive market. they are for groenfield and similar systems on industrial trucks, and in no way safe to use on hydraulic brake systems. a flare kit is cheap, and the proper 3-5kpsi line compression fittings are far different, and generally not available outside of truck shops, if they even have 3/16" line option. to give you an idea, those are rated for 1/10th of line pressure of a hard breaking lockup working pressure, and rule of thumb is 3x that burst/failure pressure. if you keep them, and need to lock the brakes up, keep pumping till the front brakes grab when they do let go.

old87yota

Sorry but I have no idea what you are talking about.

If you are referring to something in the video, this is just a video I found on Youtube to show how to bleed the MC for people viewing this thread in the future.

This is not my video or truck.

My truck has all of the factory lines and fittings.

Here is what my truck looks like now:









Sorry for any confusion...