Reservoir cap

[Graeme 1978]

Hi all should these caps have a hole in them to vent them or not.
Cheers

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[EmilysDad]

which reservoir?

 

[Graeme 1978]

Sorry brake reservoir.
Silly me

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[EmilysDad]

Sorry brake reservoir.
Silly me

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Yes ... it should so that the level can move.

 

[Graeme 1978]

A have checked mine and there's no hole in the cap and so a had a look at some on Web sites and those don't appear to have holes in either that's why am wondering should it have a hole in the cap.
Are Mercedes ones made differently were as they don't need holes in.
Thanks graeme

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[EmilysDad]

There needs to be a vent in the cap somewhere because the fluid drops very slowly falling due to pad wear. If it didn't vent, it'd try and draw a slight vacuum in the reservoir.

 

[Graeme 1978]

So would you say a need to drill a small hole in the cap or NOT

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[EmilysDad]

So would you say a need to drill a small hole in the cap or NOT

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I'd leave it as it is cos I'm sure it must be vented in some way .... I'll look at one of mine later.

 

[Graeme 1978]

Thanks

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[Graeme 1978]

Am only trying to workout if there's something wrong.
When the cap is tight securely tight the brakes are let's just say they are OK.
So a undone the cap just to brake the air tight seal so the cap is not off but just undone.
Since a done that my god the brake peddle has come up and by god they work just touch the peddle and am nearly head butting the windscreen to me that's the way the brakes should be.
So if the cap is undone slightly and the brakes work amazingly is that right or wrong.
If a tighten the cap down properly and the brake peddle has travel on it and not as good is that right or wrong.
So should the cap have a small hole in it or not that's the moral of the story.
Thanks graeme

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[Doug1234]

Take the cap off and look and see if it has cling film under it.
Sometimes when brake parts like callipers and hoses are being changed people put cling film under the cap to stop air getting in as this slows the escape of fluid.

 

[Graeme 1978]

Defo no cling film there cheers

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[Doug1234]

It does seem odd and I’m quite sure the caps do maybe have a diaphragm of some kind but my years of driving have me thinking master cylinder seals because of the pedal staying down

 

[Graeme 1978]

The pedals not staying down the brakes are working it just they work better when the cap is loose not tight.
Am just wondering if other people have had similar issues.
But thanks for your input.
Or should there be a breather hole in the brake reservoir cap

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[Doug1234]

They let air in but not out as far as I’m aware , so as pads wear down they let air in to compensate for fluid level dropping down.