RenaissanceMan

Question about brake fluid reservior cap...

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The cap on my 76 has a metal depressible contact on it, that closes the circuit when the float's little metal shaft comes into contact with it. (Hope that makes sense.) I believe it has gone bad, so I'd like to put a new cap on it. Looking at what's available, seems the most recent cap/float setups simply use at attached cap and float construction. Can I safely assume this will be interchangeable?

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(edited)

So after cleaning the contacts on the cap I've determined it's operating properly. The issue is that the little metal shaft on the float has broken off of it, so it's not making connection to the cap. Guess I will look and see if I can find the replacement float... Everywhere I look online says it's NLA or backordered. Anyone have an extra used one? :)

Edited by RenaissanceMan

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Bet you can fabricate something to replace the broken metal shaft on the float.  Since the shaft doesn't complete the circuit, but merely pushes two contacts together, I'll bet you could glue a plastic rod--or even another brass one in place.  All it has to do is hold the contacts closed when there's sufficient fluid in the reservoir...

 

mike

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Get a couple of these while you're at it:  51135676199

They will save you a beer can's worth of blood a year if you work on the driver's side of the engine bay a lot

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8 minutes ago, halboyles said:

Try this part number, still available:  34322225602

 

Here's a good source:  https://www.blunttech.com/searches/search

 

Yup, that's the one I found earlier that is a slightly different design. If I can't fix or replace the original float, I will just get one of those.

 

6 minutes ago, mike said:

Bet you can fabricate something to replace the broken metal shaft on the float.  Since the shaft doesn't complete the circuit, but merely pushes two contacts together, I'll bet you could glue a plastic rod--or even another brass one in place.  All it has to do is hold the contacts closed when there's sufficient fluid in the reservoir...

 

mike

 

I actually tried this before posting. I drilled a tiny hole through the center of the float and pushed the brass pin barely through it. Fit was tight enough to keep it from moving. However, it is only _just_ short enough to not actuate the switch in the cap. I'm going to fabricate something else that will work.

 

Thanks guys!

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3 minutes ago, halboyles said:

Get a couple of these while you're at it:  51135676199

They will save you a beer can's worth of blood a year if you work on the driver's side of the engine bay a lot

 

Those go behind the starter relay aft of the ignition coil also!

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2 minutes ago, ray_ said:

 

Those go behind the starter relay aft of the ignition coil also!

 

That is so funny..... You must have been spying on my computer... I threw a couple of those in my shopping cart earlier, remembering that I was missing one from my reservoir!!! However, I didn't realize they go behind the starter relay also. Thanks for the headsup!

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13 minutes ago, ray_ said:

 

Worked for me. it fit my '75 brake reservoir just fine.  At least you can have something working on your car, while you try and fiddle with the OEM replacement. 

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46 minutes ago, Vicleonardo1 said:

 

Worked for me. it fit my '75 brake reservoir just fine.  At least you can have something working on your car, while you try and fiddle with the OEM replacement. 

 

Thanks for the confirmation!

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(edited)

The E21 replacement cap and float assembly is clearly a simple choice,  However, I have a related question, for those who are partial to brake fluid strainers as originally found on earlier type 114s.  😉

 

Frankly, the cap is virtually indestructible and the metal plunger/contact/s are easily cleaned up (polished) to make functional.  The problem concerns a float that is no longer sealed or a rubber friction fitting, i.e., plug, that connects the metal plunge rod (linkage) to the float itself.  (That later part is a small piece of rubber that may degrade after a few decades.)

 

I have encountered two floats, both of which managed to hold fluid and thereby defeat the purpose of the float.  One of the floats appeared to have a micro crack at a seam.  After extracting the fluid from the float, the seam was resealed with a careful use of a soldering tip.  The second float has a pinhole leak in the center (or the donut hole) where the metal linkage contacts the float.  JB Weld or similar epoxy would seem to be a natural fix for this situation, since the cured product is resistant to Dot 3-4.  This even includes replacement of the rubber plug.  However, I believe that JBW, in particular, does not adhere well to polypropylene or polyethylene - and one of these plastics is probably used to form the float.  Short of melting some similar plastic to make the float airtight, is there any other sealant or adhesive that is both tolerant of brake fluid and sticks to the above-named plastics?  (I post the question mindful that occasionally someone is apt to try a similar fix for plastic brake fluid reservoirs and even windshield washer fluid reservoirs, where an epoxy might be an obvious choice, but for problems adhering to certain plastics, i.e., polypropylene or polyethylene.

 

 

 

brake fluid foat assembly  (1).jpg

brake fluid foat assembly  (2).jpg

brake fluid foat assembly  (3).jpg

Edited by percy

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It’s a pretty harsh environment. I would say try silicone but the concern would be it shedding bits into the fluid and on into the brake system. 

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I wonder if the float could be filled with appropriate closed cell foam...

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(edited)

Thanks. Thought about silicone/rtv but dismissed it for the same reason, potential contamination.  At least with the epoxy, it could be ground and finished ,  ,  , but that would not prevent "shedding" if it fails to permanently adhere to the base plastic.  One assumes there must be a commonly available adhesive/sealant that permanently adheres to polyproplyene and is impervious to brake fluid, but none comes to mind.

 

 

 

 

 

078143220456.jpg

 

 

 

 

 

Maybe fix-a-flat or flex-seal is the winning ticket?

 

 

 

c1e029b2-de26-454e-acac-ebe2a4cfb5a8.jpg

 

 

 

 

 

Wee Doggy!

 

F5E04E15AA4942DEB850C7CB17E9F225.jpg

 

 

CLEAR.jpg 

Edited by percy

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