Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Master cylinder rubber boot question

In assembling my resleeved TD master cylinder I test fit the external accordianed rubber boot. This provides a snug fit to the master cylinder. While I have yet to fit the assembly to the push rod (which is still mounted in the car) there does not appear to be a way for air pressure in the boot to be equalized to atmosphere as the brake pedal is depressed and released. How is this accomplished?

I'm tempted to punch a small hole through the boot in a location where water and dirt infiltration may be less of a concern. What have other people done?

Larry Shoer

Don't think it was meant to be 'atmospherically balanced'...when the the push rod is in place...there should be a few natural places for air to escape. (Don't think mine really accordians all that much?)
gblawson - TD#27667

I painted my master cylinder with POR15. The surface is sufficiently smooth that the rubber boot provides a surprisingly air-tight fit to the master cylinder. I was partly wondering if pressurization in the boot might force a little air past the seal and into the brake fluid. I realize that while the rubber boot is being pressurized, so to is the brake fluid. That means this is probably not a significant concern.

I'm afraid the engineer in me is showing through!

Larry Shoer

Think the seal is way tighter then the boot could be...the rod on mine slides easily in and out of the boot.
gblawson - TD#27667

The Closure to the cylinder has a hole which allows the pressre in the cylnder equalize. The air hole must always be clear or the pressure contained will not let the fluid clear back

Ellis Carlton


My question isn't about the internal hydraulic system operation of the master cylinder. The rubber boot I describe is strictly to prevent road dirt and water from contacting the external moving parts which are otherwise exposed in the master cylinder.

Larry Shoer

Larry - I think that the air will just push past the rod as it is pressed. Cheers - Dave
David DuBois

This thread was discussed on 27/10/2006

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.