Les, not only in place but I fabricated a dual layer aluminum shield, with 3/8 air gap, twice the size of original to account for the large collector on the stainless headers. It is wider and taller than stock. I did have the same thought though. I shot the master and servo with temperature gun when the brakes were in fail mode, and they were around 100-110 degrees. Didn’t seem excessive for under bonnet temp.
HI Les,
Yes, I always had the heat shields in place. All I can say is, I cleaned the small piston and bore and reassembled twice using red rubber grease without permanent fix, but when I bought and installed a new small piston it worked fine. I believe it was related to the elasticity, or stickiness, of the little seal on the piston.
Just to wrap up. Bought a new MC, put it in yesterday evening, bled brakes this morning, and took it for a shake down. Ten miles of twisty braking road, no drag!! So glad that’s done with. I guess I’ll have to blame the rebuilder…me!.
Thanks so much to all that chipped in with solid advice. I learned a ton about this system.
Now back to the eternal SU tuning…
Congrats. Small victories make the world go round.
Remember; It’s been said Carburetor is a French word meaning “Leave me alone”. Once they are set up resist the impulse to keep fiddling with them 
Maurice Chevalier once said to me, Karl, he says…there are two kinds sexy women in this world… I say, " only two"?, he says yes, really smart ones…and really dumb ones…he didn’t mention carburation…
Well, I followed the advice of some of the listers and bought a new servo and master cylinder. They are both installed, and I’m in the process of connecting all the brake fluid lines and vacuum hoses. In the back of my mind I vaguely recall a discussion about “bench priming” the master cylinder and possibly the slave cylinder, too. Is this something that’s recommended, or can I simply connect the lines, fill the reservoirs, and bleed the brakes?
At some point I may disassemble the servo and MC to see what failed. Future fun.
I’m hoping to have things wrapped up by the time some good driving weather arrives here. This morning it’s wet and 40 degrees!
Randy
Ithaca, NY
Randy, when I rebuilt my master and servo, I just installed and bled them. Takes a while but worked fine. On my recent replacement of the master, I put it in my vise and bench bled it to save time. It’s a pretty easy one as they go. Did save time too.
That is what I did after replacing both. Sometimes it helps to crack the hard line to the servo open just enough to allow air, then a bit of fluid to escape - but i cannot recall if I needed to do that on the E.
Now that the new master cylinder is installed, the new servo is installed, the brake fluid hoses are connected, and all the vacuum lines are installed it still seems that there is very little assist in braking. The Jag stops, but you have to basically push pretty hard on the pedal.
To test the power brake booster I put my foot on the brake pedal, then started the engine. There was no depression of the brake pedal…none. It’s my understanding that is the way to tell if your’e brake booster is working.
I did check the reaction valve. With the car running there is ample suction at the pipe coming off the hose connection on the white plastic. When the brake pedal is pressed, the vacuum stops immediately.
I also tested to see if the vacuum system was holding air by running the engine for a couple of minutes, the turning off the engine and depressing the brake pedal several times. There was an audible whooshing sound each time the pedal was pressed, lasting about five pushes before the vacuum was depleted.
Is there any other way to check to see if the brake booster is working as it should?
Randy
Sounds like a failed booster. Have you checked vacuum from the front booster pipe?
I have not checked the vacuum from the front booster pipe. What’s the procedure for doing the test? Randy
The front pipe is what provides the vacuum and energy to assist braking. The front and rear halves of the booster both have vacuum under normal conditions. When you hit the brakes, the rear half loses vacuum, allowing the front half to assist brakes. If you have no vacuum at the front half, you have no assist. If you remove the the back pipe, so the front half should be the only side with vacuum , then remove front to see if you get a woosh of air into the booster.
Karl, what you are saying is not the best way to describe it. The old saying “vacuum is nothing and nothing can do nothing” comes into play here. Vacuum does not provide the energy to assist braking. It is the atmospheric pressure that enters the back chamber and pushes the diaphragm (since there is vacuum/nothing in the front chamber pushing back) that provides the energy to assist braking.
Tom
Yes, the same way the atmosphere shoves a milkshake up a straw…
Yes, that is correct.
Good, so we agree. However it’s really only relative. As vacuum isn’t nothing, it’s just relatively lower barometric pressure.
Now considering that the creation of the differential in the pressures of an automotive power brake system is generated by the engine, in the form of vacuum, I would be laboring a point to suggest it is nothing.
Karl, yes, it can be argued in various ways. The reason for my quote is that a vacuum, a perfect vacuum, is a lack of anything, no dust, no nitrogen, no any molecules of any type, therefore it is nothing. What it is, I guess is a condition.
Tom
Including dark matter and dark energy?
A couple of things,
a lot of people have said that brake sticking with DOT5 is caused by the seals in the system swell up as they are not compatiable with silicon and the brake calliper pistons are unable to retract causing the brake drag?
Where did the fluid go? well there is enough suction going on that the fluid will find its way back to the intake mainfold and will be burnt off through the engine in extreme cases white smoke blowing out the tail pipes.
On the “no servo assist” I have found that the little 5/16" piston at the end of master cyl. that opperates the air valve can get rusted into the bore, but with two people it can be fixed in situ, one to press the pedal and one to catch the piston, careful cleaning with a cloth is all that is needed. although if the seals have swollen up then you will be into a reseal job on all cyls and complete flush out and back to DOT4.