Author Topic: Leaky reproduction brake reservoir?  (Read 4598 times)

wwheeler

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Leaky reproduction brake reservoir?
« on: February 21, 2017, 05:55:55 »
I purchased one of the newly reproduced dual reservoirs for the later cars a couple of years ago. I am just now installing it and discovered a molding flaw in the part. This area is where the float switch is inserted into the plastic shell. There is an O-ring that seals the switch body to the shell. Where the O-ring fits, this flaw is present. It is sort of a half circle shape. I discovered it when I was using my pressure bleeder and I could not get it to hold any pressure. Sure enough, it was leaking at that spot. O-ring is in good shape, BTW.

I had the angled Mercedes replacement reservoir on there prior and had no problems with pressure bleeding that. I only use 5 to 10 PSI when bleeding. Anybody run across this that pressure bleeds?       
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Tyler S

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Re: Leaky reproduction brake reservoir?
« Reply #1 on: February 21, 2017, 15:34:13 »
I had a similar issue with a reproduction a year and a half ago. The opening was too big and the float assembly with o-ring was loose in the bottle. The cap also did not screw down correctly. I had to file the threads on the bottle to get the cap to fit. Used a thicker o-ring on the float switch.
Dont know if these issues have been fixed with the newer offerings.
1968 (67) 250sl. 4 speed manual. DB180 Silver
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wwheeler

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Re: Leaky reproduction brake reservoir?
« Reply #2 on: February 21, 2017, 15:44:20 »
That is good news, bad news I suppose. Being a rubber molder, I know that area is difficult and not surprised there are problems. My O-ring fit was actually very tight and I had to carefully chamfer edges to get the O-ring to fit w/o damage. I first thought I had cut the O-ring, but turns out it was the molding itself. There are many Metric O-ring cross sections and I will see if maybe a thicker one may help. I will also try to smooth the area to eliminate any excessive voids.

The threads on my cap/bottle weren't as good as the factory issue, but good enough.

Misery loves company....   
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Shvegel

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Re: Leaky reproduction brake reservoir?
« Reply #3 on: February 23, 2017, 01:54:39 »
I bought one when they first came out.  It has sat in a drawer waiting for my body to come back ever since.  I pulled out out last night and I have the same mark in the same spot only less pronounced than yours.  I am pretty sure they are roto-molded as opposed to blow molding so it my be from some sort of blemish from ejecting the part from the mold.

wwheeler

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Re: Leaky reproduction brake reservoir?
« Reply #4 on: February 23, 2017, 04:43:01 »
Mine too were from the initial offering. Even before they came out with the correct screw caps. I noticed one side only has a slight indentation, whereas the other side is more pronounced. The indentations vary a bit from the two that I have. So could be from ejecting. The other bad thing is that the indentation is exactly where the point of the O-ring seals.

I am trying EPDM (must be that) 1/8" O-rings (.139") which are fatter than the 3mm (.118") O-rings that are normally used. I am also going to try 1/8" O-rings that have a smaller ID. My hope is that stretching the fat O-ring will thin out the cross section some and maybe make it easier to install. I am hoping the wider cross section will fill that gap and create a seal. Quad (X) rings and square rings are not available in EPDM in that size, or I sure can't find them.

If you do not fill the reservoir to the max line and do not pressure bleed, you may not ever see a leak. I hate to go back to the Mercedes replacement reservoir, but it never leaked. I have not heard from the seller to see if there has been a fix or how to remedy the issue. I will let you know what comes of the experiment.
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

Shvegel

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Re: Leaky reproduction brake reservoir?
« Reply #5 on: February 23, 2017, 07:00:54 »
Thanks.

JPMOSE

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Re: Leaky reproduction brake reservoir?
« Reply #6 on: October 04, 2017, 20:04:07 »
Is anyone aware of mfg. corrections since this posting?   I would be curious if the issue has been addressed before purchasing one.   Also, are there simple mods that can seal it from leaking out the sides of the reservoir?   I don't care about bleeding with a pressure unit, as I can do it the old fashion way.
Best Regards,

J. P. Mose
1968 250SL
1970 280SE 3.5 Cabriolet
1987 560SL

wwheeler

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Re: Leaky reproduction brake reservoir?
« Reply #7 on: October 05, 2017, 04:16:13 »
I do not know if any changes have been done since my last post. Admittedly, I am a sealing engineer and am hyper-sensitive to leaks.

I still have the reproduction piece on my car and have no leaks. But, I ended up sanding areas with fine sandpaper to minimize the depressions in the plastic where the O-ring seats. I then added an 1/8" EPDM O-ring (actually measures .139") which is a bit fatter than the 3mm standard O-ring. All of this almost resolved all of the leaks when tested with air. The leaks were minimal enough now that I could pressure bleed @ 10 psi. 

So I doubt the reservoir would leak fluid during normal operation. Air is harder to seal than fluid. But given how caustic brake fluid is to paint, I still keep the fluid level low enough that it does not touch the O-ring when the car is at rest. My W111 mount has the reservoir at a slight angle towards the back. If I filled it to the max, the fluid would touch the O-ring in the back cavity. I just don't want to risk it.
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6

mdsalemi

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Re: Leaky reproduction brake reservoir?
« Reply #8 on: October 05, 2017, 20:54:57 »
I then added an 1/8" EPDM O-ring (actually measures .139") which is a bit fatter than the 3mm standard O-ring.

Wouldn't you be more comfortable with a Viton O-Ring? I wouldn't trust a cheap O-Ring these days since who knows where they come from and what they are really made with, even if they say EPDM. I think Viton would be better?
Michael Salemi
Davidson, North Carolina (Charlotte Area) USA
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JPMOSE

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Re: Leaky reproduction brake reservoir?
« Reply #9 on: October 05, 2017, 22:47:53 »
Thanks guys.....I hope you’ve been well!!
Best Regards,

J. P. Mose
1968 250SL
1970 280SE 3.5 Cabriolet
1987 560SL

wwheeler

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Re: Leaky reproduction brake reservoir?
« Reply #10 on: October 06, 2017, 04:53:27 »
Wouldn't you be more comfortable with a Viton O-Ring? I wouldn't trust a cheap O-Ring these days since who knows where they come from and what they are really made with, even if they say EPDM. I think Viton would be better?

Most O-rings at the big box stores, I couldn't tell you what they are. Nitrile (NBR) is the most common and is great for oil and ok for water. Viton is generally known as a high temperature, chemically resistant material. However for brake fluid, it is NOT good. The best for brake fluid (dot 3 and 4) is EPDM.

When selecting rubber materials, the best source is on-line for compatibility charts. McMaster is a good source for O-rings (metric included) and having different materials. Yes, you have to buy 100 pieces. But generally are cheap and you know what you are getting. I would say that if an O-ring package spells out what the actual material is, there is probably a good chance it is what it is. When it says nothing, like at the big box stores, who knows.
Wallace
Texas
'68 280SE W111 coupe
'60 220SE W128 coupe
'70 Plymouth Roadrunner 440+6