Brake Master Cylinder Rebuild gone awry....piston stuck

[robacarp]

Greetings from the other side of the Atlantic!

 

I am finishing up some restoration work on a 1976 TR7 and have run into a bit of a snag. I've been rebuilding the brake components and gotten all the wheel cylinders rebuilt and working only to notice (about a week after bleeding out the system) that the master cylinder was leaking. So I pulled it off, sucked out the pistons with a shop-vac, replaced the seals and put it back together. When I tried to bleed the brakes I was getting nothing out of the circuit that feeds the rears, even at the master cylinder.

 

Now when I assembled the rear wheel cylinders I made a mistake and put the seals in backwards....led to all sorts of odd fluid-disappearing problems. So when I found out that I had a non-functioning rear circuit on the master cylinder I assumed I had made another such mistake. Instead of doing the smart thing and trying to bench bleed the master cylinder, like the book suggests, I decided I'd just tear it apart again and check the seals. I am now thinking that I had a more minor problem until I dirtied things up with my meddling.

 

Nevertheless I was able to pull out the front-circuit (rearmost when in the car) piston but not able to remove the rear-circuit (frontmost) piston. I pulled out the dinky placeholder pin and I tried to suck it out with the shop vac...no luck. I borrowed a compressor and tried to blow it out to no avail I tried upwards of 100psi. It doesn't budge, though my hand hurt after trying to cover the reservoir hole.

 

I should add that I can compress the piston with a long rod and the spring pushes back, but only to the point that it sits at now, where it stops moving.

 

Anyways, I can't figure it out. Anyone have any other ideas on how to get it out?

 

Thanks in advance.

Robert L. Carpenter

[TR8IAN]

Greetings from the other side of the Atlantic!

 

I am finishing up some restoration work on a 1976 TR7 and have run into a bit of a snag. I've been rebuilding the brake components and gotten all the wheel cylinders rebuilt and working only to notice (about a week after bleeding out the system) that the master cylinder was leaking. So I pulled it off, sucked out the pistons with a shop-vac, replaced the seals and put it back together. When I tried to bleed the brakes I was getting nothing out of the circuit that feeds the rears, even at the master cylinder.

 

Now when I assembled the rear wheel cylinders I made a mistake and put the seals in backwards....led to all sorts of odd fluid-disappearing problems. So when I found out that I had a non-functioning rear circuit on the master cylinder I assumed I had made another such mistake. Instead of doing the smart thing and trying to bench bleed the master cylinder, like the book suggests, I decided I'd just tear it apart again and check the seals. I am now thinking that I had a more minor problem until I dirtied things up with my meddling.

 

Nevertheless I was able to pull out the front-circuit (rearmost when in the car) piston but not able to remove the rear-circuit (frontmost) piston. I pulled out the dinky placeholder pin and I tried to suck it out with the shop vac...no luck. I borrowed a compressor and tried to blow it out to no avail I tried upwards of 100psi. It doesn't budge, though my hand hurt after trying to cover the reservoir hole.

 

I should add that I can compress the piston with a long rod and the spring pushes back, but only to the point that it sits at now, where it stops moving.

 

Anyways, I can't figure it out. Anyone have any other ideas on how to get it out?

 

Thanks in advance.

Robert L. Carpenter

[TR8IAN]

Hi Robert,

 

welcome to the forum - a very usefull place!

 

For what its worth, dont do it!

Its your life at risk - the new master cylinders are Im sure still available- you know all the seals should be correct and in the correct places.

 

Great news you are saving a really great car.

 

Cheers

Ian

[robacarp]

For what its worth, dont do it!

Its your life at risk - the new master cylinders are Im sure still available- you know all the seals should be correct and in the correct places.

 

I appreciate your sentiments but if I can save US$300 its worth it to me....I've rebuilt brake components before and its really a simple process, so long as you can get the pistons out :-). Not that I don't agree...it is my life at risk and I'll do everything I can to make sure all the cylinders function properly and brake well. But I'm hoping to do that for the $25 cost of the seal kit instead of the $300 replacement (and, I might add, rebuilt) cylinder.