Very odd rear brake problem

1945 - 196*, Willys CJ series, questions, discussions, regarding anything related to the post war jeep.®
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Bob Bell
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Re: Very odd rear brake problem

Post by Bob Bell » Sun Sep 25, 2016 9:12 am

Well, I hang my head in shame at my incompetence.

I do have a question however. Why was it, if my pedal was out of adjustment, that when I replaced the DOT 5 fluid with the regular (and yes, I did flush it out when I got the vehicle home - I did know that it was a NO NO to mix the two), why was it that my brakes operated perfectly thereafter, WITHOUT MAKING ANY ADJUSTMENTS to the pedal travel.

Thus the only difference between using DOT5 and normal fluid was that with the DOT5 the fluid expanded, and the normal fluid didn't. I humbly submit, that my assumption, even if it was wrong, was a reasonable appraisal of the situation give the facts as I saw them.

Incidentally, I committed the big NO NO of mixing the fluids because I had no DOT5 available, and the reservoir was too low to safely drive the jeep. I was 30 miles from home, and wanted to get home.

Thanks for the links to the truly excellent pieces on differing methods of bleeding brakes - great stuff.

This next bit of info might infuriate the purists, but it was something I had to do on my jeep - I fitted a vacuum booster to make braking more effective. I understand that by doing so I didn't really make my braking necessarily more efficient, as the drum size was not increased. Thing was I broke my right foot and did not have the strength to exert enough pressure on the pedal to stop quickly. I was understandably worried of causing an accident. The booster has worked very well - I am very happy with it.

Once again, I tip my hat in gratitude for all the info and good advice.

Bob
Bob Bell

1946 CJ2A 36116
Have owned dozens of flat fenders over the years including 1945 CJ2A 10011 which I sold in 2002.
First 4WD was an Austin Champ in 1965, and then a GPW UK license number HRO 443, sold in 1974.


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Re: Very odd rear brake problem

Post by Joe Gopan » Sun Sep 25, 2016 10:06 am

When the Army was converting to DOT 5, even with proper flushing, there were problems with some vehicles with the Master Cylinder and Wheel Cylinder cups swelling. This was late 70's thru early 80's.
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Re: Very odd rear brake problem

Post by artificer » Mon Sep 26, 2016 7:24 am

No need to hang anything or to take fence anywhere. These threads are not individual but lead others to discover the meaning of in this example brakes locking up after a few applications & Why is it so?

Heated up brake fluid will not cause this to happen, doesn't matter what type of fluid.
I have seen more Jeeps without the heat shield than with & no issues.
SIMPLY:
When the brakes are applied there is a little hole in front of the piston called the by pass or compensating port.
This hole must be uncovered.....
When the pedal is pushed down the piston rod free play is taken up then the piston & primary cup move forward covering this small hole creating a fully closed hydraulic system.
When the brakes are released the piston rushes back so quickly the pressure inside the closed system becomes less than atmospheric.
The reservoir has atmosheric air pressure on top of the fluid & there is another [this time relatively big] hole through into the cylinder called a fill or charge port.
Fluid under atmospheric pressure rushes through this charge port collapsing the primary cup & filling the low pressure area in front of the piston.
As the piston comes to rest the by pass or compensating port opens & excess fluid returns to the reservoir through that small port.
If the there is no piston rod free travel or the end washer shim is too thick the piston & primary cup may be too far forward & excess fluid is trapped in the still closed system & brakes will drag.
As Joel indicated swollen master cylinder rubbers can cause dragging/locking issues but your problem went away so that was not the problem. Also very rarely the compensating port may become blocked & that may have been cleared when bleeding/flushing.

So what do you think you did that altered/eliminated your problem?

Nothing wrong with fitting a servo or booster & if that was in play originally that also may have been the culprit & not the master cylinder @ all.

Another tid bit....the reason the compensating port needs to get fluid to the low pressure area in front of the piston is so if one needs to make another panic stop the hydraulic system has a full charge, otherwise the pedal might go to the floorboards.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Very odd rear brake problem

Post by Bob Bell » Mon Sep 26, 2016 8:13 am

So what do you think you did that altered/eliminated your problem?
Let me say first of all this problem with the DOT 5 fluid happened getting on for twenty years ago. I just mentioned because I thought it was interesting, and someone had asked about using DOT 5.

The interesting thing is that other than draining the system, and refilling it with regular fluid, I did nothing. I repeat, nothing. And after that i never had the problem again. And let me also repeat that withe DOT 5, the problem would slowly creep up. I had said every 100 miles before ... it may have been more than that. After all this time, I cannot remember exactly how much time, or miles passed between the pressure building up to the point that the jeep both slowed down, and the pedal became harder and harder. I do know that often I drove the jeep many times without the problem becoming apparent, although that may just have been because those periods consisted of just a few very short trips. Like I said, it was a long time ago.

At the time, I found it baffling, and thought that the proximity to the exhaust system was the cause of the fluid expanding. And expand it did. Although I still have the same jeep (kinda, any how, as I totaled the frame in an ice storm in Rhode Island, and thus completely rebuilt it in 2002), most of the braking system was replaced at that time. All hoses and cylinders, anyway. Thus at this point in time, it would be both hard, and pointless to try and replicate the problem. I am just glad it is in the past. I fitted the servo a couple of years ago.

Once again, thanks for the interest and comments.

Bob
Bob Bell

1946 CJ2A 36116
Have owned dozens of flat fenders over the years including 1945 CJ2A 10011 which I sold in 2002.
First 4WD was an Austin Champ in 1965, and then a GPW UK license number HRO 443, sold in 1974.

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Re: Very odd rear brake problem

Post by artificer » Mon Sep 26, 2016 8:45 am

Without doing this topic to death....the point I would stress for Bob & those interested is that if the compensating/by pass port is open when @ rest as it should be....the temperature of any type of brake fluid in the brake system can't cause brake drag or lockup.
John GIBBINS Member Institute of Automotive Mechanical Engineers [Ret], ASE Master Medium/Heavy Truck & Auto Technician USA -2002 Licensed Motor Mech NSW MVIC 49593 Current 2015
TO DIAGNOSE, TROUBLESHOOT OR FAULT FIND ANY AUTO SYSTEM....
Understand how system parts interact with one another. GOOD parts can then be established & the NOT GOOD problem/s part/s isolated for repair or replacement.

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Re: Very odd rear brake problem

Post by Joe Gopan » Thu Nov 10, 2016 6:52 pm

Facts are facts, and are further confirmed by those having long time experience with the type.
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Re: Very odd rear brake problem

Post by Bob Bell » Tue Aug 29, 2017 8:29 am

Just realized I never posted the finale to this problem. Turns out it was a sticky wheel cylinder, and now the jeeps stops in the correct manner. The rear driver wheel still squeals upon the first two ore three brake pedal applications, and then is silent. When I last had the drum off I de-glazed the shoes, and made sure there was no dust in there, but it made no difference. Not a big deal in the grand scheme of things, but a bit irritating. The linings, by the way, are still pretty much 'as new', so I can guarantee it is not a metal upon metal sound.
Thanks again for all the help and support.
Bob
Bob Bell

1946 CJ2A 36116
Have owned dozens of flat fenders over the years including 1945 CJ2A 10011 which I sold in 2002.
First 4WD was an Austin Champ in 1965, and then a GPW UK license number HRO 443, sold in 1974.

Bob Bell
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Re: Very odd rear brake problem

Post by Bob Bell » Sun Nov 05, 2017 10:06 am

I was a little premature in publishing my last report. Very shortly after the last post, the rear driver's wheel started to come on just a smidgeon before the passenger wheel. After two or three applications of the brakes, the braking becomes even. BUT the hideous squealing has returned with a vengeance. If I come to a stop sign with pedestrians present, they clap their hands to their ears and give me a dirty look.

I have taken both rear drums off, cleaned them, cleaned the linings with a wire brush, switched drums from side to side, used a spare drum, all to no avail. The problem persists on the rear driver's wheel regardless of which of three brake drums are on it. Once again, I emphasize the linings are in as new condition, there is NO grease present. I have used a tiny bit of 'brake parts lubricant' on the anchor pins as I was told that squeal might emanate from there, although I personally cannot see how that would be so.

The shoes are not scraping on the backing plate anywhere. I have adjusted the shoes over and over and the vehicle does indeed stop in a very straight line once the obligatory two or three brake applications have occurred.

Any suggestions?

Thanks,

Bob
Bob Bell

1946 CJ2A 36116
Have owned dozens of flat fenders over the years including 1945 CJ2A 10011 which I sold in 2002.
First 4WD was an Austin Champ in 1965, and then a GPW UK license number HRO 443, sold in 1974.

Joe Gopan
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Re: Very odd rear brake problem

Post by Joe Gopan » Sun Nov 05, 2017 10:17 am

All's well, that ends well. :wink:
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HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: Very odd rear brake problem

Post by Bob Bell » Sun Nov 05, 2017 10:43 am

it would just be better if it ended silently! The noise is horrendous.
Bob Bell

1946 CJ2A 36116
Have owned dozens of flat fenders over the years including 1945 CJ2A 10011 which I sold in 2002.
First 4WD was an Austin Champ in 1965, and then a GPW UK license number HRO 443, sold in 1974.

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Re: Very odd rear brake problem

Post by Rus Curtis » Mon Nov 06, 2017 3:27 pm

It doesn't sound like its ended well to me...

To me, it sounds like you've eliminated the drum as a cause. I don't have the depth on how your jeep is set up as I've never owned a 2A - let alone an early one.

Without knowing for sure or not being able to touch it, it would be easy for me to make the assumption that you could go through each component and remove/replace, i.e shoes, cylinder, backing plate, etc., -one by one - just like you did with the drum and give it a test drive. Surely you'd be able to identify what's squealing.

Through my limited experience, I want to chase the rabbit down a couple of different holes but can't guarantee any results - I'd just be guessing. So, I'll continue to monitor but hold my opinion.
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Re: Very odd rear brake problem

Post by Joe Gopan » Mon Nov 06, 2017 5:24 pm

Sounds like one wheel is not releasing, causing the shoes on that wheel to drag on the drum. Feel your drums after a short drive, if the shoes are dragging, it will be warmer than the rest.
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HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
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Re: Very odd rear brake problem

Post by Steve Webb » Mon Nov 06, 2017 7:07 pm

A non contact thermometer could be a help in this. You can really get a good read for hot spots.I use one as an electrical contractor a lot. Pretty inexpensive now also. I used it on my engine to check temps of heater hoses to see it the T- stat was opening a long time ago
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Bob Bell
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Re: Very odd rear brake problem

Post by Bob Bell » Mon Nov 06, 2017 7:39 pm

My initial thoughts were that the brakes were not releasing, thus causing the squeal, but it only occurs WHILE I am pressing on the pedal. The moment I let up, the squeal disappears. So that seems to disprove the 'not releasing' theory. I drove it today, through city streets, and for half an hour the squeal practically disappeared. But then it returned .....

I'll check the temps over the next few days. I don't have a thermometer - will have to use the 'burn my hand' method.
Thanks for the interest fellows.
Bob
Bob Bell

1946 CJ2A 36116
Have owned dozens of flat fenders over the years including 1945 CJ2A 10011 which I sold in 2002.
First 4WD was an Austin Champ in 1965, and then a GPW UK license number HRO 443, sold in 1974.

Joe Gopan
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Posts: 49841
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Re: Very odd rear brake problem

Post by Joe Gopan » Tue Nov 07, 2017 2:11 am

Glazed shoes? They can squeal.
2011 MVPA PIONEER AWARD - MVPA #1064
HONOR GRAD-WHEELED VEHICLE MECHANIC SCHOOL 1960 - US ARMY ORDNANCE SCHOOL(MACHINIST) ABERDEEN PG 1962 - O-1 BIRD DOG CREWCHIEF - 300,000+TROUBLE FREE M-38A1 MILES
LIFE MEMBER AM LEGION-40/8-DAV
7 MIL SPEC MAINTAINED MV'S
COL. BRUNO BROOKS (ARMY MOTORS) IS MY HERO


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