Strange Brake Issue

[Ralph Pearce]

So I pull into a service station to check my tire pressure. The surface near the compressor is uneven, and as drive across the uneven surface with my foot on the brake, the pedal suddenly drops near the floor. I immediately check the backing plates - no leaks. Then I check the m/c reservoir - fluid level fine. It then happened again a couple times before getting it back home. Talking it over with different folks, it sounds like a m/c issue, so I have it replaced with a new Raybestos m/c.  After picking it up from the shop, it happened three times during the circuit back around to the shop.  I'll have my foot on the brake applying pressure, then the pedal will suddenly drop near the floor, possibly triggered by some unevenness in the road. 

 

I remember when we installed new lines, cylinders, and pads, that we had a heck of a time bleeding the brakes. I finally had some guys with a mobile unit come out with a pressure bleeder.  The shop is going to check for any issues at each wheel, but if everything looks good, I'm wondering if this could be a caused by air in the lines....

 

As always, your wisdom is appreciated... 

[Jeff Balazs]

Ralph;

Sure sounds like a defective M/C. You might want to look into doing a conversion to a dual chamber M/C. Lots of us with trucks have Cherokee M/Cs and it is a pretty easy job.

Hth, Jeff

[Ralph Pearce]

Thanks Jeff, though we just put a new one in and still acting the same...will search the topic further though, thanks.

[Plymouthy Adams]

light pedal pressure and loss of pedal with no obvious leaks is as Jeff says, MC problem.  The event taking place is internal by passing of the seal...often you can feel a bit of wet fluid within the dust cover of the MC   The pressing of the pedal with a bit more force causes the lip of the seal to be against the MC lining and therefore prevent the by pass..most folks notice this while at a stop light and panic.  It is a sign to perform a bit of maintenance and try to eliminate future body work to your car or someone else's.

Edited March 27, 2018 by Plymouthy Adams

[Ralph Pearce]

Hmm, it's sure sounds like this is a m/c problem, yet rather frustrating since this one is brand new and seems to have the same problem.  Is there anything I can do to correct the issue with the cylinder other than returning and trying again??

[lonejacklarry]

If you paid for a new functioning master cylinder then that is what you should have received.  Apparently, it did not work out that way.

 

Take it back and get a new one and try it again.  I've had more problems with new/rebuilt stuff than simply used stuff.

 

The reason this occurs on a rough road is that your leg, foot, etc., weigh a little more at the bottom of a deep bump.  

[NiftyFifty]

Are you running all stock brakes? Mine have done the same thing, so I swapped MC's and it did it again...what honestly think is happening is I don't run a rear residual valve and I think the pressure on hot days was bleeding back...all it took was a second pump of the brakes and they were right back...but I am running front discs, rear jeep yj diff with updated drums and a Cherokee master cyl.  Now I always pump long before it's needed...hasn't happened in a couple years, so not sure why it would come on suddenly.

[Jeff Balazs]

Ralph;

It is totally frustrating.  But it is part of a problem that is becoming more and more common. It has to do with a general lack of quality in many replacement parts that are now being made overseas. I know you think you did the correct thing by replacing this M/C with a new one. And that certainly would have been a likely fix for the issue 30 years ago. Back then the replacements were being made here by reputable companies. But these days a name on a box doesn't begin to insure true OEM quality. Really the next one you put in may fix the problem....or just as likely not. I myself have no confidence in these sorts of replacement parts these days. Particularly anything from China.

 

When I began building my truck I started to go down this path on the braking system. But the more I thought about it.... stuff like what you are going through now scared me off. Instead I decided to completely update the braking system on my truck. Since I planned all along to use it as my daily driver this more than justified the $1500 I put into the 4 wheel disc upgrade I did. Ten thousand miles later I am totally convinced this was the best money I spent on my truck. I am not saying you need to do everything I did but at least consider a more easily maintained solution for the braking system.

 

One more thing I think bears mentioning is that the brake pedal linkage adjustment on these trucks can contribute to this problem.

Because of the way this linkage works if it isn't adjusted very carefully you can have issues with the M/C bypassing with either an OEM M/C or a more modern type replacement like the Cherokee M/C. This is generally not a issue with most M/C's that are firewall mounted but it certainly is with the under floor mounted ones like is on our trucks.

 

Jeff

[59bisquik]

I bought a brand new master cylinder when I first started getting my truck on the road. The old one was leaking and pitted, so I bought new from one of the few Dodge vendors. It leaked immediately out of the bore and was hard to bleed. I ended up going with the Corvette dual after that. The 54 later trucks can’t use the Cherokee. That being said... pretty common the get them bad out of the box.

[Ralph Pearce]

I decided to pick the truck up from the shop (they hadn't done anything further). I drove it home carefully, of course, and discovered that it will not only sink to the floor, but will jump right back up and then down (and then up...) all under constant pressure.    

[NiftyFifty]

I would 1st check your push rod adjustment, but sounds like you need another master cylinder 

[Dodgeb4ya]

I think the Chinese are trying to kill us all off!

Failing deadly brakes.... more US property for sale!

[lonejacklarry]

14 hours ago, Jeff Balazs said:

 . Particularly anything from China. 

 

The folks in China have the same technological expertise as does the US.  The offshore people are building parts just exactly to specifications laid out by US companies.  All the chain auto parts stores and suppliers have to compete financially with the store up the street.  The only way to do this and still make a profit is to specify a less than quality product.

 

If you are old enough to remember when "Made in Japan"  meant junk then this will be self explanatory.  Same story..

[Todd B]

I am old enough, and it still is junk. 

[FlashBuddy]

I call it the Walmart Effect. Suppliers needing to get the price down for Walmart results in sneaky changes to products. Take the typical Walmart lawnmower. Rubber wheels replaced with plastic, pull cord 5 inches shorter, push bar 8 inches shorter. Shampoo, cream rinse and hand lotions in pump bottles now using skinnier springs that have difficulty returning the pump to its uppermost position.

 

My recent wheel cylinders purchase netted me lighter castings; less steel and more ??? As long as they can hold up under the pressures and mechanical forces involved I'm cool with them, but the machining being off center and incomplete is not cool. To 

@Todd B's point, Takata air bags are made in Japan, aren't they?

 

I see Kim Jong-Un is meeting with Chinese President Xi Jinping - probably to discuss quality control 

[Jeff Balazs]

2 hours ago, lonejacklarry said:

 

The folks in China have the same technological expertise as does the US.  The offshore people are building parts just exactly to specifications laid out by US companies.  All the chain auto parts stores and suppliers have to compete financially with the store up the street.  The only way to do this and still make a profit is to specify a less than quality product.

 

If you are old enough to remember when "Made in Japan"  meant junk then this will be self explanatory.  Same story..

Could they make the same quality parts as were made here years ago? I kinda doubt it. You have to know right from wrong and they seem to have a genuine problem with that concept. My take on this is that we are ultimately at fault. "We" lifted them up out of the stone age. "We" encourage and reward profiteering on our side of the planet. And "we" continue to accept things as they are these days. Until there are some fundamental changes in "our" collective behavior we are going to have to live with this. Wanna start a war? How about a boycott on all chinese imports? I am game if you are.

 

And Todd your comparison of Japanese products to this crap isn't really valid IMO. I have a 40+ year old Kenwood stereo and a Yamaha graphic equalizer that is almost that old and they are still see daily use and are working fine. Try that with anything similar that is made in China.......

 

Jeff

[lonejacklarry]

52 minutes ago, Jeff Balazs said:

Could they make the same quality parts as were made here years ago?

 

Yes, they actually could but would you want to pay for it?  I'm guessing that most people, instead of paying $50 for a quality part, would simply buy the Walmart or AutoZone specified part at a lower price.  If it happened to be bad then one could get it replaced on warranty.  Does this sound familiar?

 

Right or wrong does not enter into the equation.  They are building exactly what the US distributors are specifying---no more, no less.

[Plymouthy Adams]

two edged sword.....yes the standards could be better and yes better at a still competitive price..however, build an item to last 20+ years and you just produced yourself out of business.  The product needs to be a solid working item, with a parts rebuild/repair stream available after an average built in 3 year normal usage.  The life expectancy would be in the wearing parts, in case of MC and cylinders, the seals.  Seems many here are reporting issues however with the seating/sealing of the attaching lines and bleeders, to this end there is no excuse for poor product or shoddy workmanship.   It may get better, other countries will rise up to challenge the predominate market, some garnertheir share by building the better mouse trap, some garner it by low bid and often the resulting of lowering the now low standard of quality.   If a new item has good threads and seats, a kit is just a couple dollars more.  It would be my advice to anyone buying a modern offshore replacement item to tear down and inspect and actually clean the assemblies and reassemble before use.  Dirt and debris during the process of manufacturing is often overlooked on an assembly line.  Yes is a pain that we should do this but could make a lot of difference in end performance and longevity.  Just a bit of food for thought.

[Dodgeb4ya]

At the beginning of new production... yes the parts are made exactly as spec'd.

later .... the not quite as specified parts production enters production...poorer fit and design. Quality control drops.

Saw this on 20/20 several years ago.

Seems if people came same a dime over safety.... they will and ... importers love it.

I have dealt with a lot of this offshore white box garbage  way too much....

I want to pay more to do the job right and only one time otherwise the customer pays twice.

[motterso]

Just to make sure - you might inspect all the brake drums and see if one might be cracked. Pedal movement (with steady pressure from your foot) can be a sign that a brake drum is out of round or broken. Another good reason to upgrade to a dual master cylinder when time allows.

[RobertKB]

I have sent four different master cylinders out to White Post Restorations for resleeving for my various brake repairs and restorations. All were old and worn out master cylinders and they came back looking like new and beautifully functional. I recommend this process if you want to keep your original master cylinder. That way you avoid off shore products and keep quality OEM or high quality North American made replacement master cylinders.

 

There are other companies out there that resleeve as well but White Post is the one I am familiar with.

[ggdad1951]

make me want to dig out my originals for future use...after a rebuild.

[Ralph Pearce]

I have tomorrow through the weekend off, so I'll get her up on stands in the morning, get the hubs off and go from there...will keep you guys posted.

[48Dodger]

Rebuild, refurbish, regrind,renew,redo....it's why I can't bring myself to throw stuff away....just ask anyone who's been to my place....I would rather have a shot at an original part first.

 

48D

[johnsartain]

Rebuilding and refurbishing through American and local R&R shops is about the only way to keep your  American Made parts, American. After my rebuilding of my 1950 B2B, I discovered on the many trips to NAPA, O'Reilly, Auto-zone, Rock Auto, etc... everything is made overseas. I can't recall any part I bought at these retailers not being made in Japan, China, Korea,  or Taiwan. I did find that the Corvette Master Cylinder I purchased was made in Canada. I don't think that there are any parts houses other then the ones selling NOS and Re-manufactured.
Most of the parts on my truck were so rusted that getting them apart impossible. The wheel cylinders cracked under the stress. Grease Gunning them wouldn't budge them. Generator, Starter, Carbs were all missing. At the time I needed them, I could find everything but the starter. Wilson Auto Electric had the best deal on a re-manufactured starter through O'Reilly for i think was 225.00.