I am going to replace all my soft lines and calipers. I want to use a power bleeder. Can I just zip tie the vent caps on the master res down to keep brake fluid from pouring out when power bleeding the system?

Interesting question, but I've never had to secure the vents.

Please post your results...thanks!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Isn't the vent in the fill cap? I believe you are refering to the level sensor caps. Those could leak if cracked in which case should be replaced.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10

You need new caps if they leak. Will also need to make a cap to go onto the MC to let the fluid into the MC that doesn't leak. I'm remembering vents in the main cap that got liquid steel since it's what was in the tool box.

I make a cap for each vehicle and have a plumbing fitting on the hose that connects to the bleeder. That makes the change between vehicles easy. The hose is long enough to take care of the Dodge truck. Changing fluid every couple of years seems to help the caliper and MC seals last longer but I don't have scientific documentation.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

It helps to know the vehicle involved.....

Those little black caps shouldn't leak, they're available new if they do .

Yes, pressure bleeding is the easiest way to go, I bought the basic one and it comes with a screw on cap that fits most modern vehicles .

Only 5 # is necessary, don't go crazy over pumping it .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I am talking about the level sensors for clarity. I have a power bleeder with the correct adapter for most german cars. My experience has been the level sensors leak on most of these 123s when a power bleeder is hooked up. I have never tried to zip e these down when bleeding. I am understanding that these should not leak when using a power bleeder?

Yes, that's what we're talking about ~ they're replaceble, I got mine from.....

? ******** AZ? some OnLine place in Arizona .

Easy to install and no more weeps / leaks .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Vwnate,

Can I trouble you for a link? Are you into old Vws? I have loads of old bus parts.

Good morning here you go : https://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?SUPERCAT_FLAG=Y&command=DWsearch&description=Brake%2520Fluid%2520Level%2520Sensor

Yes, I've been into vintage VW's since the 1960's, I only have one left, a well used but not yet dead 1959 # 113 DeLuxe, not pretty, I'm needing to install a freshly rebuilt 36HP engine into it .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I used a pressure bleeder on my 85 W123 which replaced the standard fill cap with the bleeder's fill tube. Nothing leaked out the level sensors on the master cylinder reservoir. You should be good to go unless your sensors leak.

Pump your bleeder to 15psi. No more is needed You may have to freshen up the pump pressure from time to time.