brakes, or lack thereof

[bkahler]

On our 79 Cherokee we are experiencing what I would consider poor braking. We've replaced the booster, master cylinder, front pads, turned the rotors, turned the drums, good rear shoes.

The symptoms are having to apply what I consider to much pedal force to stop. With a load in the back or towing a trailer without electric brakes we have to be careful to start braking early to make sure we come to a stop. It can be a little nerve wracking to have to make a sudden stop because you have to stomp on the pedal pretty good.

Any suggestions on what to check next?

Thanks!

[Dan G]

Check brake hoses front and rear.

Did you purge the fluid? If you're not aware brake fluid is hygroscopic (it likes water, sucks it up actually) and the water degrades the brake fluid to the point that the fluid then compresses (like a gas/vapor) as opposed to having the proper hydraulic properties you want.

[bkahler]

Dan, I forgot to mention that I had the front and rear brake hoses replaced which would likely mean that the fluid was reasonably well purged when the brakes were bled.

[smithhl]

Cool, you've got an Amphicar! How did you, Where did you, How much was, WWAAAHH I want one! A true go anywhere vehicle. Don't hold us in suspense tell us about it.

[BostonWagoneer]

When you say too much pressure, do you mean the pedal is too hard and doesnt move much and you have to really lean into it, or the pedal is mushy and goes down really far?

I am going to guess it is the former and I suggest you check the vacuum to the brake booster. If the booster doesnt get enough vacuum, braking will feel like you have manual brakes.

[MtnNate]

I had the same problem with mine for a while. I found out that the vaccum hose wasn't connected to the booster.
TOO MANY VACCUM HOSES!!!!!
Fixed my problem though.

[bkahler]

Sorry about the long delay in responding, to many projects, to little time!

Anyway, the pedal travel seems to be about right for stopping but it just seems like the jeep doesn't want to stop. You can really apply a lot of pressure to the pedal and only feel a marginal response change. Don't get me wrong, the brakes do work, the only way to describe it is they don't feel right. They certainly aren't mushy.

The vacuum lines have been checked and there is plenty of vacuum. Can't find any leaks either.

All of the fluid was purged when I had the shop replace all of the rubber brake lines. Add to that the new pads, turned rotors and drums (shoes were fine) and I can't see any reason for the poor braking ability.

As for the Amphicar, yep, we have one! Not much has been done to it as yet since we're waiting to take pocession of our shop (25'x 65') and that won't happen until the 1st of march. Until then all we can do is sit in it and pretend....! smile.gif

[Baldy]

Seein as we're talking about brakes...I went through this same procedure. Brake lines, pads, shoes, calipers, flushed the fluid, vacc leaks, etc...Now my next step will be a double diaghpram brake booster off a J20. Any thoughts? My thinking is that maybe the jump up from stock to 35" tires is my problem.??...don't think this system was designed for such a size of tire. Any suggestions will be appreciated/taken into consideration. Thanks

Laz

[Sgt. Dave]

If you think about it, that's lots of leverage and energy to dispurse with that big a tire. Be sure and use a premium quality set of pads and shoes. Performance Friction carbon metallics or some copper metallics. Follow the finish directions closly. Believe it or not they need a VERY smooth rotor to work. The more polished, the better. The dual diaphram booster is a good idea. It may be time to do some research on a larger bore master cylinder (more line pressure for the same pedal pressure) Another possibility is rear disk brakes. Are you having any fade problems, or just poor braking action. You should be able to lock all 4 wheels up if the system is adequate. This seems to be a common problem. Maybe someone with a full set of factory shop manuals can look up master cyl. specs. A bigger one may have been used on a J truck. One other thing, just because the rear shoes look good doesn't mean anything. Pull the wheel cylinders out and rebuild or replace them. Then be sure all the adjustor assembly is up to specs. Replace the hold down springs, and all the return springs. Be sure the drums are true, and within diameter limits. Stopping is more important than going! Yes, I am fanatical about brakes!

[bkahler]

Interesting thought about tire size and stopping ability. I'm fairly certain we have larger than stock tires. I'll have to verify that this weekend when I get a chance. What with the holidays it seems like everything is being put on hold.

I do have the factory shop manual but again, its won't be in hand until the weekend.

There was someone on ebay selling disc brake conversions for the big jeeps. Price for the adapters wasn't all that bad but you still had to buy the rotors and calipers, still it might be worth considering. My only concern there was how that would affect the front to rear brake biasing as designed by the factory. Any thoughts on that?
Also, good points on the quality of the brake shoes/pads. I don't know what they used for the fronts when they replaced them but I know the brake shoes have been on there for quite some time. The rear wheel cylinders have been replaced as recently as last year with new off the shelf units.

Thanks!

[will e]

I had a similar problem with my brakes.

A PO had installed an 'emissions control device' that would acutally cause a vacuum leak to run the engine lean. It actually helped with the MPG but every once in a while I seemed to have trouble with the brakes. Not mushy, you just had to push real hard as if the engine was not running. I disconnected the unit and the problem 'went away'.

I would guess your booster is the problem.

The rear disk set up looks nice. There is nothing wrong with a good set of drums (excpet when they get wet). Anyways, lots of people make adjustable proportioning valves.

[Sgt. Dave]

The difference in pads and shoes will amaze you. Shop slipped some "cost effective" (translates into cheap) organic shoes and pads in on us a few years ago. Those things must have been made out of recycled grease. They wouldn't stop my Grandmother! Good pedal feel, but you could push so hard you literally broke the seat back, and couldn't get a wheel to lock. Same cars, put Performance Friction pads on, and they stop like you've thrown an anchor out! Unbelieveable difference! Price difference? about $20 a set higher. But, what's your life worth? :rolleyes:

[bkahler]

I have found the brakes to be consistantly the same no matter what the engine speed or load is. Only real difference comes when pulling the trailer and if I don't have the trailers brake control module turned on the braking ability of the jeep is evn more dismal. You have to plan your stops well in advance without the controller on. We have replaced the booster and the MC itself and found zero difference in the stopping ability.

I suppose if we did switch to the rear disc we could add an after market proportioning valve. No different than those used on race cars.

Thanks!

[bkahler]

You've got a good point there Sgt Dave! I honestly don't know what brand/quality the shop put on them. I guess its time to shop around for some new pads. Hopefully over the christmas holiday week I can get these changed out.

Thanks for the tip!

[Baldy]

All good points guys..

Sgt.Dave - I do skimp on such things as paint, and any cosmetic items :D ,when it comes to performance..ie stopping, motivation I buy the best. As for wheel cylinders....duh, I honestly never even thought of em! I'm experiencing general poor braking, little by little everything will be replaced but I'm looking for better than stock performance. Want the best brakes possible for out on the trails...don't like roll overs! :eek:
bkahler - rear discs are an attractive idea, however I like the "when all else fails" feature of the e-brake...don't know how that would work with discs.
Could always throw an anchor out the back :D

[Retro93]

Interesting. I have the exact same problem with my '79 Cherokee. No matter how much pedal pressure I apply, there is no increase in stopping power. Even in a panic stop situation, I have never experienced wheel lock. Everything in the system has been replaced except the proportioning valve. That is going to be my next stop. I have one on my 77 parts Chero that I'm going to switch out. I have a feeling that the valve is or has failed and is restricting the line pressure, hence the extremely hard pedal. We're pushing against the valve. Make sense?

Anyway..I'll post with the results when I make the valve switch.

Regards,

Kim

[bkahler]

Kim, I'm definitely looking forward to your results. I've been wondering about that valve. Some of our Triumph sports cars have a similar valve and we've never had problems with them. But, that doesn't mean a whole lot when you're dealing with a vehicle that weighs twice what a Triumph does.

And....Baldy brought up a good point about parking brakes. Just how would a person add parking brakes to a Cherokee converted to rear disk? Might that be a good exercise in futility?!!

Thanks!

[will e]

I have a set of really good carbon brakes in my cabinets. I will put them on in the next couple o weeks to see if they make a difference. Preious owner may not hae gone for the best type of pad.

I will try a few 'controlled' tests in a parking lot and see if I can measure a difference.

Lots of rear brake kits come with parking brake abilities.

I have seen some kits where a 'third' rotor is added to the drive shaft to be used as a parking brake. May not be good for a FSJ with lots of wheel travel.

[bkahler]

Will, if you find a set of brake pads that seem to do the job I would definitely like to hear about them, brand and part number.

I don't remember any mention of a parking brake with the rear disc kit that I came across. Guess I'll have to contact the guy about what the feasability of that is.

Thanks!

[reddog]

I have always had good luck/performance with the performance friction pads. The proportioning valve may be one place to look, it maybe not getting enough pressure to the front.

Can you lockup any wheels? Where do you get the vacuum for the booster from? Have you hooked up a vacuum gauge to the booster hose and checked it while you drive? If the petal is good and firm then it is not the lines/fluid.

Kerry

[TPICherokee]

Well, bkaler and retro93, you are not alone. I have that exact same problem with my '79 Cherokee and the same with the '79 Waggie I had at one time.

When I first got my Chero the brakes were great then after a couple of months they went "bad" with a bad pedal feel so I adjusted my rear brakes and magically my brakes came back to life!! But that only worked for 2 weeks and then they went to hell again. I have tried to adjust them again, but to no avail... the brakes still suck. I get no lock-up in a panic situation and no matter how hard I press them, I get the same braking performance. I even replaced my proportioning valve and it didn't help.

I hope someone comes up with a solution.

[Bob Barry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by TPICherokee:
When I first got my Chero the brakes were great then after a couple of months they went "bad" with a bad pedal feel so I adjusted my rear brakes and magically my brakes came back to life!! But that only worked for 2 weeks and then they went to hell again. I have tried to adjust them again, but to no avail... the brakes still suck. I get no lock-up in a panic situation and no matter how hard I press them, I get the same braking performance.<HR></BLOCKQUOTE>

It sounds like your auto-adjusting hardware on the rear drums is frozen up. It's cheap to replace them.

[River Beast]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Bob Barry:


It sounds like your auto-adjusting hardware on the rear drums is frozen up. It's cheap to replace them.<HR></BLOCKQUOTE>

I have a hard pedal, too... :(

This is what I thought on mine...yea they were frozen... so I fixed them... got some braking back, but not enough.. I still have a hard pedal as well... even added a vac resevoir.. that helped a little but not enough... now I am going to replace the booster with the dual diaphram setup from a 78 J20... it's $75 from AutoZone...not til after X-mas.... I have low vacuum as well... can't get it above 11 at all!!!. The booster duz hold vac though according to my gage.

I think I will replace the res too while I'm there.

I haven't had time to do much to my rig for a while.... after the holidays I should get rollin' :D...

Here's a weird situation:

When I start up (pressure applied to pedal).. the pedal is hard...I pump it with no change...then hold it down, I throw into drive and the pedal drops about 1/2" and 'feels' almost like a brake pedal should feel but immediatley gets hard again when still applying pressure.

WHATS UP?!?!

I'm no brake engineer... ;)

Seems like we have a brake digest started :D

[Retro93]

I don't think the rear adjusters are the problem since I have replaced them. Everything has been replaced in the system except the proportioning valve.

I have a Hydo-Boost unit off of a '76 Cadillac Eldorado that I am going to intall after I change out the prop. valve. It is an "exact" bolt up, replacing the vacuum booster. :D The stock master cylinder also bolts up to the unit with no modifications. All of the critical measurements [pedal rod length, master cylinder bore/depth] are within acceptable tolerances.

I intend to get this thing to stop even if I have to weld a plow on the back that I can drop on command. smile.gif

Anyone who wants pictures of the Hydro-Boost unit along side the stock Jeep parts let me know and I'll email them to you.

Regards,

Kim

[ December 19, 2001: Message edited by: Retro93 ]

[Tony Rio]

Me and my '78 just checkin' in here to say we have the same issue...

[bkahler]

In a way,its reassuring to see other people having the same problem and then again its disheartening to hear of so many people having the same problem! So far, at least in my case, replacing the brake pads seems to be the most likely course of action. Barring brake pads it points towards the proportioning valve. I'm keeping my fingers crossed that its the brake pads. Next week I hope to put that theory to the test.

Thanks for all the replies....! smile.gif

[Retro93]

bkahler,

I have tried different pads on the front discs..no improvement. Currently I am using premium synthetic/bronze pads, replacing the compostion units I had in place. It just keeps getting better and better. :eek:

[bkahler]

Retro93, from what I understand from your last post that your braking has not improved from changing pads. That certainly doesn't make me happy to hear that!

I have been able to lock up the back brakes on the jeep, but that was only after I adjusted them manually for tigher tolerances. They locked up for a little while upon stopping but eventually wore themselves in and no longer do that. So I no longer can get brake lockup either.

The only items that I have yet to replace are the proportioning valve, brake shoes and steel brake lines. Everything else has been replaced. The shoes had good linings on last check (maybe a month ago?). My understanding of the proportioning valve leads me to think it shouldn't really be the problem either. All its doing is trying to balance the pressures between the front and rear circuits. I would think that if it was faulty one or the other circuit would lockup when the pedal was pushed hard enough. But I'm certainly no expert at this as is obvious by my inability to fix the problem as yet!

Keep those ideas coming folks....!

[Sgt. Dave]

Looks like the common ground is insufficent line pressure. Perhaps someone can do a little research & see what the Master cylinder bore is. I have a line on some larger bore cylinders thay may work.

[Tony Rio]

Just out of curiosity, anyone have any idea what it would cost to just re-place the entire brake system less the disks and drums?

What all would be involved for an entire replacement.... p-valves, hoses, master cylinder, booster, et.

I keep hearing all these posibilities, so I'm considering not even futzing around and just replacing everything from the get-go.

Rather than nickle-and-diming myself to death with parts one at a time until it gets better, and spending all the weekends to do it. I am playing with the idea of just paying my mechanic to rip it all out and replace it all.

Thoughts? Expensive and a little overkill (I should be doing my own work, after all) but of anything on my truck, a 100% functioning braking system is number 1 priority on my list.

[Marvin Gates]

Has anyone thought about, all the people that are having brake problems, what size are your tires? are all of you running large tires?
My 75 Wag has 2.35X 15 tires and the brakes were changed by the p.o. about 5 years ago and I can lock up all 4 wheels any time, with no problem. Just a thought!

[91GWag]

I have the same problem on my 91 wag good stiff pedal but can't lock them up and my right leg calf muscle looks like popeye's forearm!!!

[Tony Rio]

<BLOCKQUOTE>quote:</font><HR>Originally posted by Marvin Gates:
Has anyone thought about, all the people that are having brake problems, what size are your tires? are all of you running large tires?
My 75 Wag has 2.35X 15 tires and the brakes were changed by the p.o. about 5 years ago and I can lock up all 4 wheels any time, with no problem. Just a thought!<HR></BLOCKQUOTE>

I thought about that... and were I running 35's or so I could see it, but with only 31's? Imean... mine is not just marginally bad... it's BAD in capital letters. I don't stop unless my foot is to the floor, and even then I can't panic stop.

I find myself being a better driver though... I have to plan to stop, and sure don't follow people closely! :D

[Rogue]

i don't know without looking or researching if they are adjustable but a definite possibility could be a misadjusted pushrod that goes between the brake pedal and booster, some models have an adjustable rod between the booster and master cylinder, i know this because i didn't check the adjustment on one on a customer's vehicle when i replaced the master cylinder and he sure noticed the difference in a hurry! if this rod is adjustable and misadjusted then you would only be using half of your master cylinder's abilities. there is a tool out there i've never met anyone that had one but you place it between the pads and stomp the pedal and and it takes a reading of the clamping force. one last thought is do the caliper slides move freely? you should be able to slide the caliper back and forth on the slides with just your hand, good luck

[Retro93]

I'm running 31" tires...I don't think that they are contributing to the poor braking.

As far as the pushrod that goes between the vacuum booster and master cylinder, it is not adjustable.

I was looking at the prop. valves on my vehicles this afternoon and there is one thing I did notice. The pin valve that has to be depressed to bleed that back brakes appears to be frozen on my '79, while it moves freely on the '77 unit. I wonder if there is some internal corrosion that is binding up not only the bleeder [pin] valve, but the other moving parts as well. I do know that when I first started working on the brakes the brake fluid that came out of the system was so "contaminated" that it had turned black. Just more information for us all to digest. :rolleyes:

Regards,

Kim

[Sgt. Dave]

Found a rear disc brake kit with emergency brakes http://www.stainlesssteelbrakes.com/pages/Results.asp?carMake=Jeep&carModel=27&car Year=74-91 (http://www.stainlesssteelbrakes.com/pages/Results.asp?carMake=Jeep&carModel=27&carYear=74-91)

Think I'll call them tomorrow and see if they have any ideas. Good products, great reputation. They also have an adjustable proportining valve with a built in pressure gauge

[ December 19, 2001: Message edited by: Sgt. Dave ]

[will e]

when I did my first rear brake job on my FSJ "will e" I noticed that the adjusting star pressed against the spring. (drivers side only). Both the old and new spring were this way. Basically it kept the adjuster from turning and opening up.

I ended up bending it more to clear the 'star'. I am sure the po took it to a shop to get the brakes done. They didn't even notice this problem.

Has any one else noticed this?

Also, I assume these brakes work like my ford brakes. They adjust when you are in reverse.


Mike

[Retro93]

bkhaler,

I have brakes now. :D I replaced the vacuum booster with a Hydro-Boost unit. Amazing results...my Jeep stops rapidly and straight, even during a panic stop. The pedal feels normal now. It doesn't have the hard pedal that we have all noticed with the stock set up. I've had it running for 2-3 days now and haven't noticed any bad habits. All I know is that I have normal brakes for the first time. Good feeling knowing that I can stop now.

Regards,

Kim smile.gif

[bkahler]

Kim,

Thanks for the feedback on your solution! Where did you get the Hydro-Boost unit and how much was it? Is it much work to replace the booster?

Thanks!!!!

Brad
:D

[Marshmountain]

Speaking of Amphicars...

My Dad bought one brand new in 1967 when the company was going out of business... had it for many years, very sad when he sold it.

Took it across the Hudson River many times, local lakes, etc. He replaced the original Triumph Herald motor with a beefed up Spitfire motor for a little more pep. I actually have a red and white front seat for an Amphicar in my workshop. Where did you pick your up?, and what kind of shape is it in?

[Retro93]

Brad,

I pulled the Hydro-Boost setup from a '76 Cadillac Eldorado sitting in the local Pick A Part.

It was a pretty simple installation since most of the attachment bolts were in the same location as my Jeep. I did have to move the brake pedal up 1" to center the pedal rod on the HB unit.

Total cost for the swap..approximately $25. :D

Hope this information helps.

Regards,

Kim

[River Beast]

Kim,

Did you use your PS pump or the one from the Caddy.... and did the lines all match up for connection?

Starting to hunt down a Caddy this weekend! ;)

[Retro93]

Todd,

I used the stock power steering pump on my rig. It's handles both the p/s and HB with no complaint. The Caddy pump had a double inlet for the return lines. I got around this by adding a "T" fitting in-line with the outlets from the the power steering box and HB unit. Just to be safe, I also added a Ford p/s cooler to the return to lower the fluid temps. a little.

Regards,

Kim

[River Beast]

thanks for the info Kim... wondered how you did it....let's get this straight....

HP side of pump goes to where?

it is now in the gearbox...

can you explain the routing of the hoses for peice of mind? thanks

[ January 16, 2002: Message edited by: River Beast ]

[Sgt. Dave]

Good info! BTW, those Ford P\S coolers are a good addition to any rig where you work the steering hard. They also make good fuel coolers.

[Retro93]

Todd,

The HP side of the hose goes from the pump to the inlet side of the HB unit. From there, you connect a HP hose to the outlet side of the HB which goes to the power steering box. The return hoses go from the HB and power steering box to a "T" fitting, then through the in-line cooler and back to the pump.

I was able to use all of the HP hoses from the Cadillac for this install. They were all long enough..nothing else to buy. :D

Hope this helps. If not, I will be on #FSJ [UNDERNET] this evening. We can cover any other issues you may have.

Regards,

Kim

[Retro93]

Hi All,

Just an update on the Hydro-Boost set up. It has been installed for a couple of weeks now. Still working fine with no problems to report.

Regards,

Kim smile.gif