1974 brake booster parts help

[Joel A.]

Hey folks. Need some input/ideas on parts vendor. Going thru the brakes on my '74 again. Installed new o-ring style pistons in all 4 calipers, then rebuilt the master cylinder. Once I was ready to reinstall the master, I found a seal/boot on my booster that is torn. I suspect this is a nagging vacuum leak I have been chasing for a while. Anyway, I cannot find anyone that can supply a boot/seal for this booster pushrod. I do NOT want to buy a reman booster, either. Does anyone have a lead on a supplier for booster parts that I could get this boot from? Thanks!

booster2a.jpg boostera.jpg booster3a.jpg

[Patrick H.]

Not exactly the same, but...

https://www.ebay.com/itm/264968450071

[Joel A.]

Thanks, but that goes on the other side of the booster. Close, but no seegar. 😉

[Joel A.]

Well, I seem to be in the middle of a conundrum here. I have searched many places for info on this seal, but it is NOT showing up anywhere. Not in the FSM, not in the Overhaul Manual, not in the GM Parts fiche, not even in a parts diagram from several booster rebuild kit suppliers. I have a new "front seal" ordered....can get them pretty much anywhere. WHY does MY car have this seal, but it not show up anywhere else? The booster has never been removed from the car, and as far as I can remember, the pushrod has never been pulled out either. Where the heck did it come from? It obviously fits into the hole on the front of the booster, as it fits just like the headlight actuator seals do on the actuators. I checked...the headlight actuator seals are smaller in diameter, so it's not something someone rigged up on this booster. Story of my life....touch ONE thing, and fall into the never ending pit of repairs...

booster1a.jpg booster5a.jpg

[David M.]

Give Mike a call. He should be able to source anything booster & master cylinder related.
If that seal is shot the booster will blatantly leak. I think the old design is long obsolete.
The new design is better and its hidden no one but you will know its there.

He just did brake parts for my "other" car.

[Joel A.]

Thanks David. I think I have already checked that company...I'll look at my notes and see.

[Joe L.]

Well, I seem to be in the middle of a conundrum here. I have searched many places for info on this seal, but it is NOT showing up anywhere. Not in the FSM, not in the Overhaul Manual, not in the GM Parts fiche, not even in a parts diagram from several booster rebuild kit suppliers. I have a new "front seal" ordered....can get them pretty much anywhere. WHY does MY car have this seal, but it not show up anywhere else? The booster has never been removed from the car, and as far as I can remember, the pushrod has never been pulled out either. Where the heck did it come from? It obviously fits into the hole on the front of the booster, as it fits just like the headlight actuator seals do on the actuators. I checked...the headlight actuator seals are smaller in diameter, so it's not something someone rigged up on this booster. Story of my life....touch ONE thing, and fall into the never ending pit of repairs...

booster1a.jpg booster5a.jpg

Joel------

The seal you seek was GM #3910048. It was discontinued without supercession about 20 years ago and is VERY difficult to locate. It was also known as Bendix # 2501325 which, as far as I know, is also long-since discontinued. This is a "dual element" seal consisting of a metal plate and an elastomer

However, there must exist an aftermarket replacement for this seal whether configured as original, or not. If there were not, commercial rebuilders would not be able to rebuild these boosters. It is very possible, though, that these seals are not available through normal retail automotive parts sources. You may be able to obtain one through one of those rebuilders as others have suggested. Better yet, you might consider having one of those sources rebuild your booster.

[Joel A.]

and is VERY difficult to locate. ..

You're tellin me!
Thank you, Joe, and thanks for the part numbers, too. That will help somewhere down the road if I keep searching. You never know. I intend to contact Brake Restoration, mentioned above, tomorrow, and see if they can offer any help. I do have a new "front housing seal" on the way, and that will definitely help eliminate a vacuum leak there. My plan is to install it along with the torn "boot" seal. It needs both so the master will press them tight against the booster front, and make a seal.
Thanks again for the help, folks.

[Joe L.]

I finally got around to digging one of the 3910048 seals out of storage. Here are some photos of it [not for sale]:

[David M.]

I concur on the unobtainium status of the Bendix part. 30-35 years ago I had one let go in my 68 442. I had to go to a brake specialty supplier (in town) and he dove deep into the dusty bowls of the place to unearth one.

I cant imagine Mike wont be able to assist you. Be interested to know.
Be patient with Mike. Its him and his wife running the operation. She generally answers the phone. He is well respected in the industry and knows his stuff.

[Owen L.]

I finally got around to digging one of the 3910048 seals out of storage. Here are some photos of it [not for sale]:

The Bendix number on that part looks like 2500932 - a replacement seems to be available, though it's got a different appearance.

[Joe L.]

The Bendix number on that part looks like 2500932 - a replacement seems to be available, though it's got a different appearance.

Owen-----

The Bendix number that, as I previously mentioned, I have for the seal is 2501325. However, that may be an old number that has been replaced. The Bendix number on the GM #3910048 seal that I have does appear to be 2500932. So, the Bendix seal of that part number should be the right one. I just knew that a replacement for this seal had to be somehow available and, as it turns out, it is!

[Joel A.]

I have that seal. It is readily available from several vendors. The seal I am/was looking for is the BOOT that fits into the front of the booster, and seals on the pushrod.
frontseal2.jpg boost4a.jpg