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| Master cylinder caps leak https://slantsix.org/forum/viewtopic.php?t=38182 |
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| Author: | the_shadow [ Wed Dec 02, 2009 10:15 am ] |
| Post subject: | Master cylinder caps leak |
On my '71 dart with front disc brakes, i've had one of those dual reservoir aluminum master cylinders with the plastic reservoir on top, that has 2 caps. The thing leaks like crazy out of the caps. Every weekend I open the hood and there's fluid everywhere, like it's poured out of the caps down the master cylinder, like a few tablespoons full or something. I've tried cleaning everything with warm water, even the caps and gaskets and put them back on, same thing. I got a different style of cap and gasket, no difference, still leaks I've also lowered the level of fluid quite significantly, no difference. Any ideas? I believe I got this master cylinder a while back from Rick Ehrenberg but I can't remember. It's been doing this for about a year now and I usually bungee-cord a terry cloth around the master cylinder so it doesn't leak onto the paint, but I would like to solve this before I paint the car. Thanks... |
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| Author: | SlantSixDan [ Wed Dec 02, 2009 10:36 am ] |
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Sounds like the reservoir is defective in some fashion. Is it the correct straight horizontal reservoir, or is it the type meant to be installed at a rearward slant (as on some brake boosters)? If the slanted type is mounted straight up and down, you can get leaks because the front cap will be below the fluid level. You ought to be able to get a new reservoir, but I can't give a part number without knowing exactly what master cylinder you have. |
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| Author: | the_shadow [ Wed Dec 02, 2009 8:07 pm ] |
| Post subject: | |
It's the straight-top kind, the front and rear caps are at the same level. Could there be a trick to putting on the caps or something sneaky I don't know about? I know someone with a nearly identical master cylinder and he has the same problem. |
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| Author: | radarsonwheels [ Thu Dec 03, 2009 2:10 pm ] |
| Post subject: | I got one too |
I got mine from Ehrenberg on ebay. It is the gold colored aluminum one. Big bore master, very lightweight. Plastic res. with two caps. I've seen some other threads on these things leaking I think on moparts? Also if you have the big bore m/c like me you probably have to stand on it to stop and can barely lock it up with your butt off the seat... I just ordered the smaller bore m/c (1 1/32?) from dr. diff so my problems will hopefully be over soon. My solution on the leaking was to just not top it off to the top. It leaked some when full, then stopped leaking once the level got a little lower. Did it get lower from leaking, or from disc calipers filling up as the pads wear? I don't know, but the level is staying pretty high and not changing much when I check it. The bigger theoretical problem I have with my m/c is that if it can leak dot3 out, then it can absorb moisture in. I have stainless lines, so that helps, but water in the juice always causes annoying recurring air in the lines... Anyway, sorry for not helping much. Let us know what direction you go and how it works out. Kevin |
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| Author: | SlantSixDan [ Thu Dec 03, 2009 2:28 pm ] |
| Post subject: | |
By and large, this style of master cylinder reservoir is really good at keeping brake fluid in and moisture out. It begins to sound to me as though whatever screamin' deal R. Ehrenberg got on those master cylinders he was auctioning off on ebay…might not've been so screamin' after all (defective reservoirs). |
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| Author: | the_shadow [ Thu Dec 03, 2009 7:52 pm ] |
| Post subject: | |
Quote: It begins to sound to me as though whatever screamin' deal R. Ehrenberg got on those master cylinders he was auctioning off on ebay…might not've been so screamin' after all (defective reservoirs).
I was afraid this would be the case. This is the only thing I bought from the guy, before I found out about his bad rep a while back.Dan, do you have a part number for a quality replacement reservoir? Quote: I got mine from Ehrenberg on ebay. It is the gold colored aluminum one. Big bore master, very lightweight. Plastic res. with two caps.
That's the same one I have, except I got mine directly from him.Quote: I just ordered the smaller bore m/c (1 1/32?) from dr. diff so my problems will hopefully be over soon.
Please let us know how this works, Doctor Differential is a great guy to buy from.
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| Author: | SlantSixDan [ Thu Dec 03, 2009 9:40 pm ] |
| Post subject: | |
There are various p/ns listed for the reservoirs in various year factory parts catalogues; I don't know which one would fit whatever master you've got...and prices from Chrysler are idiotic ($56 at discount). Y'might try grabbing some reservoirs from a wrecking yard. Also, is the leak definitely from the cap(s), or could it be from the front or rear rubber reservoir mount grommets that secure the reservoir to the cylinder? |
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| Author: | RickEhrenberg [ Fri Dec 04, 2009 11:49 am ] |
| Post subject: | M/Cyl caps leak? |
I guess an explanation of master cylinder operation is needed. At the bottom the reservoir (top of the actual cylinder bore) there's a pair of ports (holes) called "compensating ports" by the factory. I think a better name would be "refill ports". When the cylinder is at rest (pistons fully returned), these ports are open (uncovered), allowing fluid from the reservoir to fill the bore, replacing any fluid not returned on the last stroke (pad wear, evap., small leaks, etc.) When you step on the pedal, the piston(s) need to move a small distance before these ports close. During that travel, a mini-geyser of fluid squirts up from each compensating port. This is why, with the old iron master cylinders (as well as the new designs), there would be a mess if you bled or pumped the brake with the cap(s) off. I've seen this squirt up several inches! On the older cast iron reservoirs, there was a large "dome" (or domes) in the cap, and a very flexible diaphragm-type seal or gasket in the cap. This would pulsate (flex) up and down as you stepped on and off the pedal, to accommodate the volume change, even if you filled the reservoirs to the rim. The design changed with the advent of the alloy cylinders and plastic reservoirs. There's no longer a dome in the cap. Instead, there's a "fill to" split-ring line in the reservoir -- I guess this was supposed to be obvious to old-time mechanics who remembered similar "fill to" lines in lead-acid batteries. This is at least 1/2", maybe more like 3/4", down from the top. The reservoir is huge! If you ignore this and overfill it, it virtually MUST leak! The few of these that I had returned for supposed leakage went on my own personal cars. They don't leak a DROP. And I road race, autocross, drag race, etc. -- none of my cars are trailer queens! For the guys that wanna use my face on a dart board, go ahead, amuse yourselves. But I ask you to remember that I went ahead and got these as a service to the Mopar community -- I was in the right place at the right time. I made less than $6 each on them, and I laid out all the cash. I'm currently trying to get more, but, so far, NG, at least not at any kind of reasonable price. MoPar to ya! Rick Ehrenberg |
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| Author: | radarsonwheels [ Fri Dec 04, 2009 12:33 pm ] |
| Post subject: | For the record |
Trash talking people on the web sucks and I was thinking about posting this when I read the other comment about R.E.'s "bad rep", and haven't read his post yet I did have bad luck with the stuff I got from him, but his customer service was top notch. I never complained about the m/c because it works and its light and the kit he sent me bolted right up. I assume full responsibility for badly choosing my m/c bore. The leaking might be a way bigger deal to me if I didn't just have a rattle can spray bomb firewall. Also, even though I worry about moisture coming in, I never had a problem with it. I also ordered his 'upgrade' 8 3/4" rear wheel cyls. I waited much too long to put them on (maybe 6 or 9 months) and didn't expect a warranty when one of them failed immediately. I emailed him and asked to buy another to match my good one. He sold me one for his cost and apologized, saying they are brembo and should not fail. A week after putting in the replacement the 'good' one out of the first batch failed. I ended up ordering from rockauto getting stock replacements for around $15 or less a side. No problems since. It might seem like I'm badmouthing this guy, but actually every time I asked him to stand behind his parts he wrote back fast and shipped parts fast and was helpful answering questions. I just feel like I had bad luck with the parts I got. I don't know about any other people's experience but I am only telling my story, and in this case because I knew others had the same problem with the same part. I was naming names to ID the part, not to talk trash on someone's reputation. OK now I'm gonna go back up and read the BIG PRINT rebuttal. I just don't like the idea of badmouthing someone I don't know who seemed to try to do the right thing by me. Of course if everybody he dealt with had great customer service and beat parts there would probably be lots more trash talking? I only know my story and if I meet the guy I'll still drink a beer with him, not punch him out! Kevin |
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| Author: | RickEhrenberg [ Sat Dec 05, 2009 11:09 am ] |
| Post subject: | M/Cyl caps leak? <more> |
I should have added this bit of info: It is possible for one of the internal piston seals to fail on any dual master cylinder. I have never seen this on a new or OEM one with less than 150K on it, but it happens quite a bit on rebuilts. Here's the symptoms: pedal suddenly drops while pressing the pedal (i.e., stopping). On the next stroke, it may be OK, but it will happen again. When removing the reservoir cap(s), one chamber will be very low or empty, the other will be overflowing, pushing fluid past any type of cap and/or seal. If you have a master cylinder with this symptom, park the car until it is repaired! Rick |
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| Author: | magicdart [ Sun Dec 13, 2009 5:50 pm ] |
| Post subject: | cap leak fix |
hi. I just recently installed the modern master cylinders from ehrenburg on my two old cars. My charger with power brakes felt immediately better in stopping and did not leak. My dart with manual disc brakes feels much better stopping as well, but the rear cap leaked. I popped out the little rubber bit inside the cap, and stuffed a perfect size washer in there. Now the cap is much tighter and doesnt seem to leak. Rick E's customer service was great by the way. |
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| Author: | Wesola78 [ Mon Jan 18, 2010 7:14 pm ] |
| Post subject: | |
I didn't buy any master cylinders from Rick Ehrenberg, but I have been reading his articles for years. I don't know him personally, and I have not heard about any business deals that other people have had with him. However, I feel that he has made a very positive contribution to the Mopar hobby. Specifically, his great tech articles. I didn't want to get into any arguments or flame wars, I just wanted to say that. From me, thanks Rick! Wes Moeller |
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| Author: | gmader [ Mon Jan 18, 2010 7:50 pm ] |
| Post subject: | |
I am replacing one of Rick's master cylinders now myself. It also leaked, was too big for my calipers, etc. Pretty much all the other stuff that others have experienced. I, too, have respect for Rick's technical info, contributions, and down right passion for our brand ( but not our engine  ). I don't want to chase him away, but if anybody wants a gently used aluminum master cylinder, I am happy to give you a good deal.Thanks, Greg |
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| Author: | GregCon [ Mon Feb 25, 2013 8:27 pm ] |
| Post subject: | |
Hello....I joined the forum so I could post to this thread although I see it is few years old. I also had the leaking master cylinder reservoir issue on two 'Gold' master cylinders I bought from Rick. I don't know, but suspect, they had some defect that caused this. I don't buy his explanation above. It might be right, but it leaves a lot of questions unanswered. Why? Let's look at the facts: 1) I've had 20+ cars with the classic 80's style master cylinder of the type we are discussing. All were filled up with fluid, none leaked. I suspect many others have the same experience, right? 2) I don't know if they are OEM or not, but many of the reservoirs I own have a cast-in legend as part of the plastic which reads 'fill to bottom of ring.' It doesn't say 'don't fill up completely or it will leak', it says 'fill to bottom of ring'. 3) Show me a Mopar service manual or TSB that tells us to underfill the reservoir. With the millions of vehicles in service using this style of master cylinder it must be a common issue, right? 4) Most safety inspection stations here in Texas, if they are doing their job, will top off a low reservoir and won't pass a car with it low. And if you tell them "You have to leave it low or it will leak" they will fail your car and tell you to fix the leak. 5) On most recent 'Gold' leaker, I replaced the reservoir with a new one - still leaked. I then replaced the whole master cylinder with a Strange master, which is a copy of the Mopar unit. No leaks, and I even have it filled up to the bottom of the rings. 6) Rick points out that there is a 'geyser' of fluid when you step on the pedal. This is true, but it is under little pressure and 'should' be a small amount if the master cylinder is timed and ported properly. The 'big' pressure that the master produces only happens once the fill port in closed off - not when it is still open to the atmospheric pressure inside the reservoir. My guess, without spending any further time looking into the issue, is the 'Gold' master cylinders are either ported improperly or timed improperly and that is what causes the overage of fluid that wants to escape. A normal master cylinder doesn't behave that way. As for me, I tossed the 'Gold' master cylinders and am having great results with the Strange units that for $69 from Summit Racing are a great bargain to boot. We all love Rick but I think these 'Gold' cylinders are junkers. I'll add that the first unit that leaked did so on a 150 mile trip all over the freshly painted inner fenders of my big-buck restoration. By the time I saw what was happening the paint was damaged. |
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