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Master Cylinder Woes


Taylormade

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As I mentioned in a previous posting I discovered my brakes were gone after replacing the clutch in my 48 P-15. The car sat for about eight months. Before this my rebuilt (2006) master cylinder was working fine. Now I discover that the MC is the culprit. Each time the brake pedal is pressed, fluid shoots out the rubber boot on the front of the MC. There is a lip on the shaft connected to the pedal – the shaft that pushes the plunger back into the cylinder and compresses the brake fluid. The end of the rubber is supposed to stay seated in this lip, but it doesn’t – it stays put while the shaft moves backward.

I figure something dried up or hardened inside the MC while it sat and this leak developed. Now the pedal goes to the floor and the brake system develops no pressure at all, just a squirt of fluid each time the pedal is tried. Guess I’ll have to buy another rebuild kit. Anyone rebuilt theirs while it was still bolted to the frame? The manual says you can do it, but I have my doubts.

RT

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Just re-did mine while on the car.

1drain the cyl as best you can- turkey baster works.

2remove the brake lines-outside one first - cover the ends with something- I use alum. foil.

3 remove the nut that the brake lines attach to.

4 pull out spring.

5 unlock the plunger-run the locking bolt all the way up the threaded part or the eye bolt .

6 now run the plunger all the way down and it will come off the eye bolt

remove the the plunger rod by pulling it out and down.

7 now using 1/4 inch socket remove the nuts(7/16) holding the rubber boot in place.

then push the plunger inside the master to the far end and remove.

Now you are ready to to hone the cyl.

However, what this really sounds like to me is the fact that the master has a rust spot in it deep enough to let fluid pass thru. I that be the case honing is necessary but I bet it will not get the depression out- I have honed 4 with NO success- all failed.

I haggled with Napa and got a new one last week for 210 bucks. I am actually going to take an old one to a machinist here and see if they can sleeve it

will keep the board posted on how that works out cost wise and if feasible

LOu

Edited by Lou Earle
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I honed mine when I rebuilt it three years ago. I worried about some rough spots caused by rust then and showed it to a local mechanic who said it had cleaned up fine. I think he was a bit optimistic. I'm sure sitting for all those months has caused more rust and the problem I am experiencing.

Did you get a gasket for the large nut on the back end of the MC in your rebuild kit? I didn't and never took it off when I rebuilt mine. I did everything from the front of the MC since it was off the car at the time. Maybe that was the problem.

Have you installed your NAPA MC yet? I'm curious as to the quality now that everything seems to come from China or Mexico these days.

RT

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I honed mine when I rebuilt it three years ago. I worried about some rough spots caused by rust then and showed it to a local mechanic who said it had cleaned up fine. I think he was a bit optimistic. I'm sure sitting for all those months has caused more rust and the problem I am experiencing.

Did you get a gasket for the large nut on the back end of the MC in your rebuild kit? I didn't and never took it off when I rebuilt mine. I did everything from the front of the MC since it was off the car at the time. Maybe that was the problem.

Have you installed your NAPA MC yet? I'm curious as to the quality now that everything seems to come from China or Mexico these days.

RT

Not sure about the napa rebuild kits but the raybestos kits I have purchased come with a large aluminum washer which would fit the top plug or end plug as they are both the same size. However I have reused the original end plug washer and have not had problems. Just about everything comes from china theses days so that is a hard battle to win. You may be able to fine a nos or nosr mc at a swap or on ebay and install a rebuild kit for less then the prices of a new mc. Rockauto does have the new raybestos mc for $182. plus shipping country of origin is a crap shoot.

http://www.rockauto.com/catalog/raframecatalog.php

If you use rockauto here is a 5% discount code good until july 26

17924351413745

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the napa part is just fine as far as I can tell used one about 2 years ago does fine in order to really hone it well i think both ends should be off so you can go all the way from either direction but the smallest imperfection can cause problems- I hav e had 2 brake failures both due to bad master cyls- and both resulted in serious damage _ now try not to take any chances especially with the brakes!!!!!

y

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