Master Cylinder Cap is Seeping

[tubbedamx]

Like the title says one of the caps on the master cylinder is seeping.

I wrapped a little paper towel around the lid and looking at the pictures you can see it’s soaking up brake fluid.
I’ve tried ever so slightly shimming the rubber gasket in the lid and have tried a little less brake fluid. Always the same result.

Has any one ran across or have any ideas for a solution, Or know were to get replacement caps. I’ve had it for several years and I don’t have paperwork with part numbers.

Thanks

 

[Vaanth]

Like the title says one of the caps on the master cylinder is seeping.

I wrapped a little paper towel around the lid and looking at the pictures you can see it’s soaking up brake fluid.
I’ve tried ever so slightly shimming the rubber gasket in the lid and have tried a little less brake fluid. Always the same result.

Has any one ran across or have any ideas for a solution, Or know were to get replacement caps. I’ve had it for several years and I don’t have paperwork with part numbers.

Thanks

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The pictured master cylinder looks like a version of the Chrysler master cylinder, part number 3880289 (also 3766254, 3766275, 4205972, 4318738), although there are many similar master cylinders. The caps do not look like original Mopar caps, but could just be an alternate aftermarket version.

The cap rubber gaskets may be worn and need replacement, or the cap tangs have lost tension and need replacement.

Dorman has replacement caps and gaskets for the Mopar master cylinder and others as well. The replacement Mopar style caps and gaskets are as follows:

• 42044 Master Cylinder Caps
• 42081 Brake Master Cylinder Gasket

Dorman, and others, also make other caps and gaskets for other similar master cylinders.

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[tubbedamx]

That’s perfect!! Thank you so much.

 

[Ricks70Duster340]

I've used new aftermarket master cylinders with these caps and they leaked.

 

[Oldmanmopar]

Go to a salvage u-pull-it and grab a couple off of newer trucks . Thats what I did . nothing better then good use OEM parts . verses Chinese replacements. I took the whole tank and just slamed the whole thing on. Didn't even have to bleed it. Never leaked a drop after that.

 

[tubbedamx]

Thanks, I’m going to that too. There’s a yard 20 minutes from here

 

[CRUZE 418]

I did #2 two years ago. Stopped the leakage, and I even use DOT 5. The Dormans are inexpensive.

 

[matthon]

The caps that come with the master leak, the replacement caps don't, at least in my experience.
Go figure.

 

[RustyRatRod]

I did #2 two years ago. Stopped the leakage, and I even use DOT 5. The Dormans are inexpensive.

You haven't gone #2 in two years? They got stuff to fix that, you know?

 

[CRUZE 418]

Yeah, magnesium works pretty good!

 

[tonysrt]

I had the same problem and replaced the gaskets and no more leaks. You can buy new gaskets probably through Dorman.

 

[tonysrt]

I dug out the bill for the Master Cylinder gasket and it is Dorman #42081 about $12.00 on Amazon back then.