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MG TD TF 1500 - Master cylinder

Hey guys,
I'm restoring my Lockheed master cylinder (Q56). I cleaned out the feed hole in the supply tank. Then I noticed a second drilled hole ,about half the size of the feed hole. This second hole does not go all the way thru to the piston space. Does anyone know where it goes or what its function is?
Thanks,
Mike
MJG Mike

When you say you cleaned out the feed hole...do you mean the 'pin' sized pressure relief hole?
gblawson(gordon)

If you cleaned the main feed hole, the second one has a pin sized opening going down into the (?) piston tube below. It allows the pressure to back off... if it is clogged, you brakes won't release. It took me an hour or so to clean it out so i could see the head of a pin down in the chamber when i pushed it in (tiny...just the tip).
I found later that the little cleaners for welding tips are small enough to clean it out.

(this is assuming we are talking about the same hole)
gblawson(gordon)

Gordon,
Thanks for the info. I will continue the cleaning and see if I can get a pin to pop through. I thought that it had to go somewhere.

Thanks for helping me out.

Mike
Mike

Mike, a pin may be too large in diameter for reaming out the hole. As Gordon said, a welding tip cleaner is small enough. I used a piece of stainless steel safety wire.
Jim Merz

Actually, i think the pin 'was' too large...and went to a finer needle. It was later that someone showed me a set of welding tip cleaners and they looked to be perfect. My biggest problem was opening up the hole to get anything through.
Symptons... on a trip to Watkins Glen my brake lights started to stay on...after finding nothing, I noticed a bit of drag in the brakes.... after cleaning the master cylinder and reinstalling, i could only drive a few hundred yards and if I used my brakes, my wheels started to lock and stay locked (that was a fun drive back to the barn).
I now can remove the master cylinder by just kneeling beside the car and reaching under!!!!
gblawson(gordon)

MJG Mike,
That little hole is .024"-.025" in diameter. I found out by trial and error.
George
GF Metz

I have used a .060 drill to reopen that little hole.Just use a small hand held pin vise to hold the drill and twist by hand. Power drill migh be too much and then you end up with a broken bit in the hole.
Sandy
conrad sanders

Thanks guys,
I was able to clean the "pin sized pressure relief hole" with a used dentist's pic given to me by my dentist. The pic was smaller than a needle. Anyway, it worked and I'm grateful to all for the advice.

Let me suggest that you ask your dentist for old pics and old drill bits. I've found they come in very handy at times.

Mike

Gordon, "I now can remove the master cylinder by just kneeling beside the car and reaching under!!!! "
Remove master cylinder? without removing the floor board?
Or just clearing out the hole?
MGrogan

Remove the whole thing... reach under, undo the main line, undo the two bolts and slide it off the shaft...voila!!! Only thing i would have to remove the floorboard for is to get that pesky brake switch fitting out...my bolt goes into it from above?
gblawson(gordon)

This thread was discussed between 15/08/2008 and 18/08/2008

MG TD TF 1500 index

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