Brake Problem...

OKCM38CDN · Post by **OKCM38CDN** » Tue Jun 16, 2009 5:48 pm

In an earlier posting I said I was having brake problems... the brakes work; but the pedal looses all of its play and is hard to push.

I brought the M-38 home this afternoon from storage and pulled the wheels they are very hard to spin like the brakes are applied softly... I could not spin the drums without the tires or using a screwdriver as a lever...

I drained a little bit of fluid from the cylinder using the bleeder screw and suddenly the drums are loose and spinning freely... I checked the level in the master cylinder and it is about 3/4 full...

I am thinking I have lost the master cylinder and that it is not allowing the fluid to go back into the cylinder when the brakes are released... Has anyone else seen this? Am I on the right track... Master cylinders are not super expensive but do not want to change it if I do not need to...

Comments Please... Need to fix this by Friday so I can participate in a convoy / Parade near Tulsa, OK this weekend...

TIA

reddog · Post by **reddog** » Tue Jun 16, 2009 9:13 pm

I had the same problem and found that the master cylinder linkage rod jam nut had come loose some how and the rod that pushes on the master cylinder was pushing on it taking away the freeplay in the linkage. So the brakes were being applied even without touching the pedal.

Post by **wesk** » Wed Jun 17, 2009 12:54 am

Hal, Red Dog is correct. You should check pedal free play first, then cylinder rod travel next then suspect the check valve in the master cylinder. I wouldn't suspect bad hoses since yours are only a couple of years old and you indicate all wheels were dragging. If none of the above seem to be your problem check that heat shield isn't missing causing fluid expansion problems.

OKCM38CDN · Post by **OKCM38CDN** » Wed Jun 17, 2009 5:50 am

Will check the freeplay tonight...

I know it is not fluid expansion problems as it is happening when cold... before I even start the engine...

Post by **wesk** » Wed Jun 17, 2009 8:27 am

This is just a general note for all readers, not a chastising of anyone in particular

This is the disadvantage of trying to troubleshoot over the phone or web. Without being there we must rely entirely on the owners description of the event and the surrounding circumstances. Without 100 % of the data that occurrs we can never be able to approach 100 % of the appropriate advice. We all will forget little tid bits but I just want to remind all that "the quality of what comes out is only as good as the quality of what goes in."

acengraver · Post by **acengraver** » Wed Jun 17, 2009 8:32 am

I had a car that did a similar thing and it turned out to be deteriorated rubber brake hoses. The inside was crumbling and formed a "Check Valve" the held pressure when the pedal was released. The pressure would slowly release over a few hours and then after a couple of stops would build up enough pressure to keep the shoes from releasing.

OKCM38CDN · Post by **OKCM38CDN** » Wed Jun 17, 2009 3:35 pm

I checked the adjustment this morning and nothing has changed...

What ever the problem it is in the master cylinder... it is not allowing the fluid to return to the cylinder...

Will take it out tonight and go from there...

OKCM38CDN · Post by **OKCM38CDN** » Wed Jun 17, 2009 8:16 pm

Found the problem...

The master cylinder was clogged with what looked like mud... I rinsed it out and the inner portion of the MC is clear of rust...

I have the vent system hooked up and am wondering if it was pulling dust into the MC...

I replaced the MC and will need to bleed the system; but that can wait till tomorrow, ran out of daylight.

Post by **wesk** » Wed Jun 17, 2009 9:41 pm

It should be getting clean dry filtered air. If your oil level is high in the cleaner she may be foaming and the mist may be making it's way thru the vent plumbing. I thought you installed a new master cylinder during the resto? What are you using for brake fluid?

OKCM38CDN · Post by **OKCM38CDN** » Thu Jun 18, 2009 5:51 am

Wes,

It was a brand new MC during the restoration; but that was 4 years ago... I have been driving it as I can and have done several parades and both Arkansas convoys (100 miles each).

As for brake fluid, I have been using a Valvoline type that comes in a Bronze colored plastic bottle... Thouht I had some left but don't so need to see what it is... I do know it was not DOT 5 or silicone... I want to say DOT 3 or 4

I am going to check the air filter tonight and go from there...

Will let you know...

4x4M38 · Post by **4x4M38** » Mon Jan 19, 2015 7:49 am

What can happen if you have too much oil in the master cylinder?

skyjeep50 · Post by **skyjeep50** » Mon Jan 19, 2015 8:11 am

I suspect the "mud" you saw was rust. Check your brake lines and wheel cylinders for contamination. Flush everything with new fluid.

Post by **wesk** » Mon Jan 19, 2015 9:03 am

Any oil in any master cylinder is an issue. Brake systems and their fluids are incompatible with any petroleum products. Note the date of the posts!

4x4M38 · Post by **4x4M38** » Mon Jan 19, 2015 9:14 am

I'm sorry Wes. Bad choice of terms.

Can I have a stiff pedal issue if I overfill the master cylinder
with fluid. Pedal free travel is 1/2" plus. New shoes, new wheel
and master cylinders, new steel and flexible lines, bled master
and lines at the wheels.

The pedal travels through free, then applies, moving a little
more, then stops. I have adjusted the shoes to spec. I may
have overfilled the master in the process. The brakes will stop,
but it seems like they take longer than they should.

Tks,
Brian

Post by **wesk** » Mon Jan 19, 2015 10:47 am

New brakes require a seasoning or running in of the shoes against the drums.

The two most important systems on the jeep from a safety standpoint are brakes and steering. They must be repaired, rebuilt and maintained precisely IAW the appropriate manuals. This usually requires a troop with serious mechanical savvy/experience who is familiar with all the industry standards that apply to these job tasks. I am often hesitant to add advice when I am unsure of the savvy of the person asking the question. None of us want to hear after advising someone on brake/steering repairs that they failed to operate properly and someone got seriously injured or killed.

It would be my advise to get some fully qualified over-the-shoulder local assistance with your brake troubleshooting. There are many issues of non-compliance with industry standards that would cause your system issues with all those new components.

If your drums are brand new (NOT RECONDITIONED) and shoes are brand new and all hydraulics are brand new and all manual directions have been followed to the "T" then with the correct run in of the shoes to the drums she should brake just fine.

If you have old or turned /reconditioned drums then all bets are off and you really will need to study proper industry procedures to follow with these reconditioned parts. This includes but does not mean all inclusive that you insure shoe's are shimmed to match new drum ID and surface contact is correct.

You need to insure that the play measurement you are making is based on master cylinder piston travel only and not cumulative slop in the linkage.

Brake Problem...

Brake Problem...

over fill master cylinder