Master Cylinder is weird. Anyone else ever have this happen?

[jackal]

I have a 78 Cj7. When I bought it the master cylinder was leaking around the firewall. I replaced it with a rebuilt one. It leaked out around the cover. I replaced it with another one and it leaks, too ,around the cover or "lid". I bled both of them as I usuallly always do on other cars. I also bench bled them. I even bled the front brakes on the Jeep first to align the plunger in the proportioning valve as they say to do in the JEEP BIBLE.

I recently ran across an old Chilton Shop Manual. The BIG book . It says in there to use a clip tool of some sort to hold open the proportioning valve while bleeding. It doesn't show a close-up but it gives an explanation. There are even part #'s for the clips depending on which year model you own.

Has anyone ever run into this problem? If you have let me know.


I really appreciate it.


Later,
Jackal

 

[Inspector-Gadget]

Hello jackal,

jackal wrote:

I recently ran across an old Chilton Shop Manual. The BIG book . It says in there to use a clip tool of some sort to hold open the proportioning valve while bleeding. It doesn't show a close-up but it gives an explanation. There are even part #'s for the clips depending on which year model you own.

Has anyone ever run into this problem? If you have let me know.

jackal, you are in luck as regards the second paragraph of your post. We recently covered the proportioning valve “clip” thing.

Click on the following link and scroll down to the second to last post in that thread.

http://www.jeepz.com/index.php?name...t=320446&sid=055f9df64eced2d3b6350c6b30683ce8

I don't see how this is related to the problem of the master cylinder leaking around the cover though.

Regards,

Gadget

PS: I don't see why those special tools would be needed to depress the P-V pin. Seems as though same thing could be accomplished using a C-clamp or wide-jaw Vice-Grips.

 

[BakedAlaskan]

Dude I am on my 3rd master cylinder. ALL reman from Napa, and they all leak around the top. My Jeep currently has only front brakes. I have been pissed off at this delima. I have swapped out many masters and never ran into this.

I know one of the leaks is my brake line needing to be reflared or replaced but it still leaks out of the top very badly.

The two options are buy a brand new one Napa does carry them for about 50+ bucks. Or take that POS reman and file the top smooth and hope that is the problem. Neither I have tried due to pure laziness and now it's 17 degrees outside.

So needless to say I doubt anything is wrong accept the top of your master cylinder is pitted and uneven. They don't mill them like a cylinder head they just clean them and put new guts in them.

Good luck, and when you get yours working email me I will pass on my address so you can fix my next. :lol:

 

[jeepngeo]

I had that same problem with a "new" reman master cylinder. After multiple bleedings and reconnecting the lines with still no fix. I purchased another "new" reman, but instead of swapping out the whole MC I just swapped the newer lid onto the older installed MC and the leak stopped. It may not work but it is a simple troubleshooting technique. Good Luck! :wink:

 

[Inspector-Gadget]

Keith and jackal,

I can only give sketchy details of a possible fix because it wasn’t my Jeep and what follows took place about three years ago, but maybe it will help:

My son had a similar problem with an 83, CJ. He bought a new master cylinder lid gasket at a local auto-parts place. I believe at Pep Boys. He cut out and removed the two flexible pockets of the new gasket. He then placed the new and trimmed gasket into place on the master cylinder lid while leaving the original lid gasket in place.

The end result was double-thick gasket around the perimeter of the master cylinder and the wall between the two brake fluid reservoirs.

As I recall, it took the strength a guerrilla to move to the master cylinder wire bail into place and latch down the lid, but that was the end of the master cylinder lid leak.

Given the low effort and cost involved, this fix might be worth trying.

Regards,

Gadget

 

[BakedAlaskan]

I have personally tried to stack the gaskets and swap out the lids (Since I have three........... :roll: ) But had no luck. I do however have a monster file and the ability to flat plane the top surface. I will win it's just a matter of time. I tell my Jeep all the time "don't mess with me,.........I have lots of tools!!"

 

[Inspector-Gadget]

ARB Lockers (air compressor)

HAHAHAHA @ Keith...

Atta Boy!!!

You gotta show your Jeep who the garage alpha-male is going to be! Otherwise, the Jeep will try to take over.

:mrgreen:

Gadget

 

[LBR]

Jackal - have you taken the MC top off and operated the brake pedal? When braking, a little spurt from the get go is normal, but if a substantial amount of fluid shoots up, it might be possible that the distance between the pedal and MC is too short. When you let off of the pedal and the master cylinder returns all the way back, the fluid from the reservoir will fill up the cylinder, if need be. The next time that you press on the pedal (if that distance between the pedal and MC is too short), the travel from the cylinder cup to that reservoir intake port will force fluid back up that same port that feeds "the business end" of the MC (pressurizing the reservoir area, eh)? If you keep working the brake with stop-N-go driving, that pressure may be getting so great over time (with a super full reservoir) that it seeks the path of least resistance.... out the top. Seems that a lot of the fellows above are having the same problem. Is "super sealing" the lid the cure or just a bandaid? Could be that todays rebuilds need that rod lengthened a touch compared to OEM MCs due to machining tolerances - I've not had this prob on my jeep, but have run into it on another vehicle. If this helps, SOBe it, if not, drink a sixer and I'll be the SOBer

 

[jackal]

Thanks LBR. That sounds more like it. I did have to modify the pushrod to fit the new master cylinder. The first MC was really presurized under the cap. I could pump it with the cap off and it would stream 2 foot. It looked like the Beverly Hillbillies " up through the ground come bubbling crude" . This one is not that bad. I knew it wasn't spillage. I have seen cars that lost the MC cap and it didn't lose fluid like I do.

Now for the bad part. My steering is getting looser, due to the fluid washing rust from the steering joint directly under the MC. Also the fluid smells a little when it hits the fenderwell headers.


[siThanks LBRze=18][/size]

You helped a lot,

Jackal

 

[LBR]

With a little fabrication, you could replace a non-adjustable MC pushrod with a home-made adjustable type. Then start lengthening out the rod until when the MC is pressed you get that sought after "little spurt" from the rear fill port. The MC should be pre-loaded juussssstttt right now. Word of caution: over design it for strength like Tim The Tool Man would do; you don't want to bend or break it in that one panic stop that is always lurking around the corner.

 

[jackal]

Thanks again LBR. I have searched all over the net looking for this kind of information . I knew by the pressure it had to be something else. I wondered about the proportioning valve and everything else. I am a machinist ,so I will mwke a nice adjustable pushrod with Heim ends and a large turnbuckle adjustment.


Thanks a million for the info.


LAter ,
Jackal

LBR is the man with a plan!!!!!!!!

 

[BakedAlaskan]

3rd times the charm, or post should I say. I love this site........... :evil:

I like the theory of pressure building up in the cylinder. I am sure that is the problem. I will double check it tonight. I was hoping this would have a real answer to it since I have doubted the leaky cap issue. Although I did take a considerable amount off of my original master cylinder to make it flat. It was very uneven and full of pits.

Hey Jackal, if it turns out to be a pressure problem how about making an extra adjustable push rod, and I will send you the cash for it?? I have searched for hiemi joints in this area and never came up with any.( I planed on making a set of adjustable clutch rods at one time)

Thanks guys, Keith

 

[BakedAlaskan]

OK I tested out LBR's theory and studied up on the insides and workings of the master cylinder. The rod length to the pedal is not too short, although an adjustable rod will fix the problem. The rod is held in with a snap ring and has a small part of the shaft that rest on and pushes the cylinder cups through their cylinders. This portion of the rod has become shortened with years of use and allows the cups to pull too far back. This allows too much of the stroke of the cups to be BEFORE the holes to the main resivoir. And since pressure takes the path of least resistance it forces a ton of pressure into the resivoir. Although an adjustable rod will work it still seems to be a bandaid to the real issue. I will buy a "new" master cylinder and fix this. Being a 24 yo Jeep I am trying to keep the bandaids to a minimum (it has plenty already :wink: ) Awesome idea BTW!!! I hate to say bandaid with your idea since yours would of at least worked. Where making the cylinder top seal would have not.

I will admit your post made sense to me yet I couldn't make it work in my head. But after checking everything out I GET IT NOW!!! LOLOL!!! I pressed the pedal with the top of the master, first pump 1 little burble, second pump, Gusher!!!!! third,.....well lets just say it almost hit the hood!!. I held the pedal from traveling back all the way, and presto, one little burble each pump.

Thanks a million for the info and help on this. This has plagued me since I have owned this Jeep. 3 remans and same issue. Now I can cure this once and for all, and fix my steering shaft bushing and power steering seals that the fluid has ruined. Not to mention having brakes without having to baby sit the fluid level.

As for the loss of rear brakes almost over night I put this on the pressure problem as well. After all that pressure "does" release out the top it creates a vacuum and pulls fluid back through the brakes lines and into the resvoirs. Making the back brakes pull even father back from the drum making them never really hit the drums and giving the impression they are out of adjustment. (This is really noticable with the use of the
e-brake) I also noticed a murky brown fluid showing up in the resivoir, which proves this vacuum theory and tells me I also need to flush the entire brake sytem when I get this cured.

OK long enough post, Thanks again.

 

[BakedAlaskan]

Well here is an update. I filed the top of my other reman leaking master cylinder. Got is nice flat and smooth. I also took it apart and lengthened the push rod using simple washers between the end of the plunger and the rod. I put it so that almost any pressure shows the the seals passing the two pin holes in the bottom of the master. I then bled the brakes for the ump-tenth time. My brakes are at the absolute top of the pedal. PERFECT, with all four wheels helping in the stopping. But it still leaks.........................

I have priced NEW masters they range from $55-$130 for a Wagner. I have yet to check inside the rear drums. I have replaced both calipers, all three hoses for other reasons. I guess buying a new master is the only true answer. Although I am a wee bit jaded that it will leak too. I hope it won't since this seems to be the main problem. But still I have worked on this so long I am doubtful of any fix. My firewall is peeling badly and the steering shaft/gear box is suffering. Beside pissing me off to the point of thoughts of explosives. :evil:

 

[Robo983]

Re: Master Cylinder Spurting/Shooting Fluid

Well, this post is serveral years old and I can only hope some of you are still around to finish this story for me.

I am having this same problem. The last post was to replace with a new master cylinder but you never said if that fixed the problem for you. My problem is identical. I purchased a remanfactured cylinder and a month later as my pedal was going to the floor I decide to pop the hood.....!@#K all the paint on the inside was pealed away on the fire wall and various other parts. I took off the hood of the master cylinder and depressed the peddle and found that it was shooting a stream of fluid 4" in straight up.

I found my way here via google search as I had bled my brakes at least 5 times and didn't fix the problem. After finding this thread I too tried not letting the peddle return all the way back to the stop and presto no more spurt. Since the last post never got updated I purchased a new not reman Master Cylinder, re-pained the firewall, and bled the brakes. Guess what it is still shooting/spurting fluid 4" in the air.

Help please if anyone actually did find the solution to this.

 

[LBR]

Robo983 - Can't speak for Jackal or BakedAlaskan hangin' here, but I make my rounds occasionally. It blew me away reading this old, old post and seeing my replys to it. Hopefully they will respond 'cause I'm curious as to their outcome as well. If you don't get a reply from them here, check their member profiles and PM them directly to respond....hopefully on this post rather than just to you directly so we all can learn. LBR

 

[Robo983]

I tried to email BakedAlaskin and got a return to sender email. I didn't try anyone else. I plan to reply to this as soon as I know anything. I bought another new MC and two more rebuilt ones. I put the second new one in and it only spurts up about two inches. I put the lid back on and pumped the pedal probably 50 times and never saw any leakage around the sides. I just do not remember having anything ever shoot up like that but can't say I ever tried it with the lid off. I started to order an adjustable push rod from Mopar Performance, http://www.mopartsracing.com/parts/dtrain.html. After talking to that 25yr veteran modding cars I was talked out of that being the problem.

I have the gas tank out now putting in a new VDO sender and gauge so I can't drive it around to find out if it is still leaking. I know I am going to wrap it in rags until I find out for sure the Bi?ch doesn't leak again. I'll get back hear and post if I find out for sure.