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Hi Danny, No real work on the brake system other than pulling the booster to get at the steering box. I did have the front hubs off at one point and the brakes look like they have been done in the last 10 years as everything was very clean. I suspect that something I did something with the booster when I took it out that enhanced whatever was wrong with it. The car was “biting” real hard when I was driving it and I thought it may be a rear brake grabbing, but now I think
it was at the dash end. One interesting note. While I had the booster off and the two halves apart, I noted that the internal boot was held on by a large hose clamp. Not the flat steel one that crimps at the top that was done at the midland factory. So, I know
that unit was worked on at some point. The spare booster I have from a New Yorker has the factory, crimped on, band still holding the bellows on. What stood out was that the pushrod from the booster to the master cylinder on these two units were NOT the same. Makes me wonder if I am having a compensator port issue. Also, the inside of the MC in the car has a casting that is of junk
quality. If you look closely you can see some casting sticking up out of the floor near the compensator bleed. The unit from the New Yorker in the plastic bag has much better machining in it. This is why I am asking for some help from folks so that I can nail down what should be there as opposed to what is there. The thickness of the eye on the push rod at the brake pedal and some photos of the bolt-nut. I also need to find
out about the differences in the push rod to the MC. You can see that the lengths of the booster to MC rods are different.
Someone did a repair at some point, and I need to clean up this mess. Then if I still have problems, I will dig onto the wheels. I suspect that all the issues are up top. I am thinking of ordering a dual MC and then seeing if I can get one of the booster houses to rebuild a booster and then “match” the pushrod to the new MC as a unit. My other option is to rebuild the booster myself and match the MC to the
booster by creating a test bench with a old brake plate assembly and drum to simulate actual use. But I really do not want to have to go down that road of hooking up a vacuum pump and everything. James From: Dan Plotkin <dplotkin@xxxxxxxxxxxxxxxxxxx> James- I recall a situation in which a friend had a Treadle-Vac rebuilt for his 58 Fleetwood. No Cadillac has a brake pedal return spring under the dash but this one did because the pedal would not come back all the way. In that case the problem
was that the pivot from pedal to pushrod had been plated and its dimensions altered sufficiently to cause binding. If your attachment hardware is wrong you really cannot blame anything else until you are certain that everything is moving freely in the direction
it should. No idea if this is operative but check to see if anyone has a residual valve in the brake line. I have one on the rear circuit of my F and if I purposely stand on them I can lock the rears and they take a bit to unlock. Have you flushed
this system to be sure the lines and cylinders are not munged up? Danny Plotkin From: 'James Douglas' via Chrysler 300 Club International [mailto:chrysler-300-club-international@xxxxxxxxxxxxxxxx]
Something else is bothering me. When I went to place the bolt in place that holds the rod coming from the booster to the brake pedal, the steel lock nut went on the shoulder bolt and down to the shoulder, but the nut thread was only about ½ way in the nut. It did not
make it to the end which is the “lock” part. Is it possible that at some point someone swapped the bolt? Is it possible that the plunger coming from the booster is not the correct one and it is thicker that it is supposed to be and… Perhaps the linkage is binding and not swinging free. If anyone has on the shelf a known correct booster would you measure the thickness of the plunger where the bolt goes through for me? Perhaps it has a too thick pushrod. The bolt is a shoulder bolt and is supposed to float. Also, if anyone has a bolt, would you measure the total length from under the head to the end of the shoulder and the length from under the head to the very end of the bolt? I want to make sure something is not going on with that. The end of the bolt looked like it was cut after it was made. Perhaps someone did it to get that cobbled up return spring and bracket to clear. I tossed it out so I cannot see if
that was it. I hate it when I find that some idiot worked on a car and messed it up. Thanks, James From: 'James Douglas' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
The answer is yes and no. Let me explain. Sometimes if I sit there for 10 seconds it will come back up. Sometimes it does not. I took it down the block and came to a stop. It stayed down so I shut the engine off and waited. After about 15 seconds or so it popped back up. What was interesting is that I could hear at the same instant one of the AC vacuum cans make
noise like the linkage arm moved. I highly suspect that someone had the MC and the booster done at some point and the job was junk, hence the return spring BS. I REALLY want to get this thing out to see if the temp steering box is going to be ok and test the car generally to see what I really got for my money. In any event, I think I am going to punt and head back to San Francisco today. I will take the spare booster I picked up off that New Yorker and ship it off to get rebuilt. I am also going to get a dual MC from a 1968 to 1971 drum-drum
car and have it sleeved and then send it along with the booster so they can make sure the pushrods are properly adjusted. It is not that big of a deal to take the “Tee” out and put to 90’s on the lines and cut some short sections up to the new dual MC. I really do not want to stress my back under the dash to pull that booster to play with it when I suspect I will end the end need to put a quality rebuild in it. Best to cut my losses for this weekend and be patient. James James From: dplotkin <dplotkin@xxxxxxxxxxxxxxxxxxx> James, I once experienced a similar failure on my 60 Buick. Pedal went to the floor seemingly held by vacuum. Pedal came up with engine off. Is your pedal returning with no vacuum, when engine is off,? Most master cylinders have a spring inside to bring it back. I see this external spring and bracket stuff when boosters or cylinders are wrong or poorly repaired. I see lots of Treadlevacs that way. Say whether the pedal is held by vacuum or gravity. Dab Sent from my Verizon, Samsung Galaxy smartphone -------- Original message -------- From: 'James Douglas' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Date: 1/22/23 1:12 PM (GMT-05:00) To: "Chrysler 300 List Server (chrysler-300-club-international@xxxxxxxxxxxxxxxx)" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: {Chrysler 300} 300K Midland Booster
I just went to pull the 300K off the rack, I have the steering all back in with the temp box. I went to back up and the brakes were locked. The pedal did not return. Now I had the booster off. It looked like it had been rebuilt at some time in the last 20 years. There was some surface rust on the can and also some on the plunger. I took the can apart, just the two shells and
I cleaned everything on a wire wheel and gave the parts some zinc paint. Nothing on the inside. I put it back together and that was it. I reinstalled it after the steering was in. Now one thing that has not worked well is the brakes since I picked it up. I do plan on an entire rebuild, but that is after the steering. There was a funky return spring and bracket on the brake pedal arm that I took off. It did not seem
to affect anything. But now I see why. Anyone have any ideas? The service manual does not have anything on pressing the pedal down and and it staying there. I can pull it back with my foot. I doubt it is the MC but anything is possible. Help! James -- -- --
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