1967 Cadillac BENDIX Vacuum Booster and Master Cylinder?

[www.eldorado-seville.com]

Hi,
I replaced the original BENDIX Vacuum Booster and Master Cylinder on my 1967 DeVille about 2 years ago.
http://www.eldorado-seville.com/files/67brakebooster.php
I bought a unit from rockauto.com and installed it. Since then my brakes never felt really satisfying.
I need to apply way too much pedal pressure to stop the car compared to how it was before and compared to my other cars.
Also the pedal travel seems to be too long as well. Everything was bleed multiple times. The vacuum hose is new and hooked up pretty well, the check valve seems to work perfectly as well.
The unit I got from rockauto is one from Delco. Its either defective or its simply not suited or powerful enough for this car. I cant imagine that I did anything wrong during the installation process.
I now checked my original booster and its a Bendix unit. I would like to replace it once again with a Bendix setup or have my original booster rebuilt.
Unfortunately I did not have any success in locating a rebuilt Bendix vacuum booster so far. Any suggestions?

regards,
Gerald

[cadillactim]

Gerald

Is the rod from the booster to the master cylinder adjustable?  If so, it may need lengthened for the brakes to reduce pedal travel. You may also need to check that the wheel cylinders are moving properly. Any bad rubber lines can restrict fluid flow and not allow the wheel cylinders to have enough pressure applied to the brake shoes.

Also make sure the brake shoes are adjusted properly, as that will cause a low pedal.

You can check the brake booster to see if it is leaking vacuum. First, with the car off, gently put your foot on the brake pedal and start the car. The pedal should drop a little because of the vacuum in the booster. Next, have the car run a few minutes, turn it off and wait about 3 minutes. Then pull the booster vacuum line check valve out of the booster. You should hear a loud gush of air leaving the booster. If not the booster is leaking. 

Tim

[www.eldorado-seville.com]

Tim,
thank you very much for your expertise - its highly appreciated!

Gerald

Is the rod from the booster to the master cylinder adjustable?  If so, it may need lengthened for the brakes to reduce pedal travel.

That was my first thought as well! The rod is only adjustable on the original Bendix unit - not on the Delco I got from Rockauto...

You may also need to check that the wheel cylinders are moving properly. Any bad rubber lines can restrict fluid flow and not allow the wheel cylinders to have enough pressure applied to the brake shoes.

The wheel cylinders are new as well - and they seem to work properly - they also worked well before I replaced the booster.

Also make sure the brake shoes are adjusted properly, as that will cause a low pedal.

I even tried to over adjust them so that the wheels could hardly spin - it did not change anything - they are now adjusted to shop manual specs. I also replaced all the adjusters, springs and everything else - also worked fine before I exchanged the booster and master cylinder...

You can check the brake booster to see if it is leaking vacuum. First, with the car off, gently put your foot on the brake pedal and start the car. The pedal should drop a little because of the vacuum in the booster. Next, have the car run a few minutes, turn it off and wait about 3 minutes. Then pull the booster vacuum line check valve out of the booster. You should hear a loud gush of air leaving the booster. If not the booster is leaking.

I tried to start the engine last fall with the pedal slightly pushed in - and not much happened at all. There was only a slight drop. The power booster feels totally underpowered.
Will have to try the other test you mentioned when I can pull the car out of winter storage - I cant start it at the moment in the overcrowded garage.
This test sounds very interesting - never heard about it before - will do it asap.


Thanks again!
Gerald

[Rob Troxel]

Gerald,

How are things in Austria?  I see you still have that great looking Eldorado.  I did break down and have the trans rebuilt on my 68 Eldo.  The seals came apart like a brittle cookie.

Regards,

Rob Troxel

[www.eldorado-seville.com]

Rob,
I´m very sorry to hear about the problem with your Eldorado! I hope it will be fixed soon and you can enjoy your 68 again.
Everything is well over here - the cars are in winter hibernation until the end of April and I will try to fix the brake issue on my DeVille until then. I will also install new front wheel bearings soon. The 58 Eldo also needs new front wheel bearings and my new L*ncoln Mark III will get a new vinyl roof.
So a lot of things to take care of during the much too cold winter... Unfortunately my garage is not heated...

[cadillactim]

Gerald


Are you sure the master cylinder is a Delco? The Bendix and Delco parts are not interchangeable with each other. Has to be Bendix master and Bendix booster, or Delco master and Delco booster. Compare the old parts with the new ones. Should be noticeable differences. The Delco brake parts are definately a lot easier to come by than the Bendix, as you have discovered.

Tim

[Gene Beaird]

^^ This.  I've heard good and very bad things about parts from Rockauto, so I'd hold the MC suspect.  But I'm guessing you're already returned the core?  That 'slight drop' when you started the engine with your foot on the pedal can be all you may feel.  As long as it's a little movement, you should be good there. 

And boosters can leak a bit, and still work, but if you're getting no vacuum boost with the engine running, the booster may be defective.  Pull the vacuum hose and plug the port on the engine and try to move the car in the driveway.  If there's no difference, you have a defective booster.

What condition are the brake hoses in?  While I have yet to experience it in a GM vehicle (it seems to be an issue with some Dodge products), hoses can apparently collapse internally and look okay externally.  The ones on our '68 Calais were seeping at the swedged area at each end of the rubber part, so I replaced all of them when I recently replaced the MC.  The wheel cylinders on our car looked good, and seem to function well. 

But with all this, I suspect your MC is the wrong part.

[dadscad]

This summer the Bendix booster and master cylinder unit in my 63 gave up. I replaced it with the Delco unit because of local availability. The Delco unit I put in does not produce the same assist boost that the Bendix unit did. I experienced the same effect as you have, to stop the car, the Delco requires more pedal pressure than the Bendix did.

Rather than pulling the vacuum check valve out of the booster and taking a chance of damaging the seal grommet, to see if it holds vacuum, it would be better to let a little time pass after turning off the engine and then actuate the brakes. You should get two or so brake applications before the vacuum is exhausted. Some boosters will hold vacuum for a short period of time and some for days on end. Give yours 10 minutes or so and test it, then start the car to draw another vacuum. Shut it down and come back several hours later and step on the brake pedal.

David

[www.eldorado-seville.com]

Thanks gentlemen for all your tips!
As we had a very sunny and dry day today with temperatures just above freezing I decided to take the cars out of storage to do some of the tests you suggested.
When I start the car while gently pushing the pedal in - there is some very slight pedal movement - maybe half an inch or even less.
The car produces a strong vacuum at the vacuum hose. I let the car idle a couple of minutes and then first removed the vacuum hose. After about 5 minutes I carefully removed the check valve without damaging the seal grommet and I heard that air was sucked in. So the booster seems to hold vacuum...

I´m pretty sure that the booster and the master cylinder are both Delco products - its easy to tell on the booster as "DELCO" is embossed. There is no embossing or part number on the MC though - but as it came as one unit I *think* its the Delco as well...
I just have the feeling that the Bendix unit might just be stronger and the Delco is a little underpowered for my car.
The brake hoses are pretty new as well - and everything worked perfectly well before I exchange the booster and the MC. I replaced it as the MC was slightly leaking.
Tomorrow I will drive the car without the vacuum hose attached and see how much difference it will make, but I suspect that there will be a little difference...

Btw - I still have my original core - I did not return anything - so I could have this one rebuilt - any sources?

USA Parts Supply carries rebuilt units but they are not sure if they are Delco or Bendix...
They sent me two pictures of the unit they are offering though - anybody can identify them? The MC looks slightly different on my car...


the pictures USA Parts Supply sent me of their unit they have for sale - can you identify if its a Bendix or Delco?


and this is the original Bendix from my car...



Thanks again everybody!

[Bob Hoffmann CLC#96]

I don't want to hijack this thread but I have a similiar problem. I need a Bendix MC rebuild kit for my 68 Eldo. No one seems to have it. Any ideas?
Thanks, Bob

[www.eldorado-seville.com]

I don't want to hijack this thread but I have a similiar problem. I need a Bendix MC rebuild kit for my 68 Eldo. No one seems to have it. Any ideas?
Thanks, Bob

Bob,
would this one fit??
http://www.caddydaddy.com/BRAKE-ITEMS/Master-Cylinders/Rebuild-Kits/1968-Cadillac-Bendix-Master-Cylinder-Kit-p5018.html

[www.eldorado-seville.com]

And boosters can leak a bit, and still work, but if you're getting no vacuum boost with the engine running, the booster may be defective.  Pull the vacuum hose and plug the port on the engine and try to move the car in the driveway.  If there's no difference, you have a defective booster.

Went down to the garage once again and did your test - pulled the vacuum hose and plugged it.
After hitting the brake 2 times I could hardly stop the car. So the booster is working - there is a huge difference with the hose connected or not. It also seems to hold vacuum for a longer period of time.
I think the MC and booster are just too weak compared to what I´m used. Everybody else who drove my car seems to be very happy with my brakes, but they had no before/after comparison...
It seems to be the same as to what David experienced with his Delco booster...

[cadillactim]

Gerald


I have a Delco assembly on my 67, and the cars stops fine, but I never had Bendix to compare with.

The Bendix master cylinders are easy to identify. If you look on the bottom middle there is a "hump."  Delco's are straight. Both units from USA are Delco. If you look where the brake boosters halves are joined togther you will see the difference between Bendix and Delco boosters. The way the Delco halves lock together are different than the Bendix.

Tim

[Gene Beaird]

The USA Parts MC does NOT look like the OEM MC.  That's not to say it won't work.  Additionally, it looks like the RockAuto assembly you installed on the car has a different MC than what came off.  The MC bleeder screws do not look correct.  Again, that's not to say that replacement MC won't work. 

I'm betting that the hydraulics and vacuum assist are functioning properly, but you have a replacement MC with a smaller bore than your OEM MC.  You can probably verify by removing the nuts that hold the MC to the vacuum booster and gently pulling the MC away from the booster so you can get some calipers on the back of the MC to measure the bore of the cylinder.  Then pull the MC off the OEM assembly and compare. 

It may be better to first pull the MC off the OEM booster, so you can see what and how to measure, then do the one on the car.  Hopefully, you have enough flex in the brake lines that you can move them without having to bend things much.  Either that, or just disconnect the brake lines off the MC and pull the MC.  If you do that, you may want to suck as much fluid out of the MC as you can so you don't pour fluid over everything ruining paint.   

The assembly you pulled off your 67 looks just like the MC I replaced and the booster I restored on our 68 Calais. 

[Bob Hoffmann CLC#96]

Guys,
 I'm glad that Gerald is getting closer to solving his problem.
Thanks to all the good info posted,I'm getting some insight also. My car is a 68 Eldo.
From the pictures posted, it looks like I have a Delco unit in my car even though the MPB says that they were all  Bendix.
I had this car since new & had the booster/MC rebuilt once years ago. I know it has the original booster because I asked them not to paint it. It still has the original stencil which says 93D. Is D for Delco?  It looks like the 2 halves are Delco style also. The MC does not have the bump on the bottom. The MPB also refers to a 2 letter stamp on a Delco MC. Does anyone know exactly where it's located? Thanks again for all the help so far.
 Bob

[www.eldorado-seville.com]

It still has the original stencil which says 93D. Is D for Delco?  It looks like the 2 halves are Delco style also. The MC does not have the bump on the bottom. The MPB also refers to a 2 letter stamp on a Delco MC. Does anyone know exactly where it's located? Thanks again for all the help so far.
 Bob

Bob,
my 67 Eldorado also has the 93D stencil - and according to the Master Parts Book only Bendix MC´s were used for the Eldorado in 1967 and 1968 as you already mentioned. I just had a look at my 67 Eldorado - the original booster and MC still have the factory applied black paint on them - indicating that they are made by Bendix. The shop manual mentions that Bendix units are painted black whereas the Delco units were zinc plated. Another way to distinguish them as long as they are still original...
The MC on my Eldorado also does not have the bump on the bottom - but as there were no Delco units produced for the Eldorado in 1967 and 1968 I´m sure its made by Bendix.

[www.eldorado-seville.com]

The USA Parts MC does NOT look like the OEM MC.  That's not to say it won't work.  Additionally, it looks like the RockAuto assembly you installed on the car has a different MC than what came off.  The MC bleeder screws do not look correct.  Again, that's not to say that replacement MC won't work. 

I'm betting that the hydraulics and vacuum assist are functioning properly, but you have a replacement MC with a smaller bore than your OEM MC.  You can probably verify by removing the nuts that hold the MC to the vacuum booster and gently pulling the MC away from the booster so you can get some calipers on the back of the MC to measure the bore of the cylinder.  Then pull the MC off the OEM assembly and compare. 

It may be better to first pull the MC off the OEM booster, so you can see what and how to measure, then do the one on the car.  Hopefully, you have enough flex in the brake lines that you can move them without having to bend things much.  Either that, or just disconnect the brake lines off the MC and pull the MC.  If you do that, you may want to suck as much fluid out of the MC as you can so you don't pour fluid over everything ruining paint.   

The assembly you pulled off your 67 looks just like the MC I replaced and the booster I restored on our 68 Calais.

Gene - thank you very much for these excellent tips. I will measure the bore on the OEM MC and the one I got from Rockauto. (you are right the original ones did not have any bleeder screws on the MC) I´m pretty sure that you are right and that the OEM MC has a larger bore and that will make the difference which I´m experiencing.
You mentioned that you restored the booster on your 68.  Where did you get replacement parts?
I would love to restore my original Bendix booster as well.
Any lead to a professional rebuilder where I could send my booster and MC to? Or should I do it by myself? The shop manual mentions a lot of special tools which I do not have...

Special thanks to Tim for pointing out the difference on how to identify Delco and Bendix units!

[Scot Minesinger]

I drive my 1970 Cadillac quite a bit for a classic (4 to 5k miles per year) and the quality of new replacement parts is a huge problem.  Generally the discount auto parts stores, such as Napa, Rock Auto, Advanced Auto carry parts where price is the sole selling point.  Installed a new starter in 2010 and had to replace it in 2011 (re-built a used one this time).  Replaced power steering pump and new one is now an audiable tachometer for me-going to replace it this weekend.  Gone through two alternators, it is just ridiculous.  I drive the car at least one a week even in winter, just drove it today.  Suspect that the booster is no good.  USA Parts, which can be expensive often is worth the price.  Re-built parts have given me better service than cheap China made new parts.  If you are satisfied with the installation, a defective part is certainly a likely culpret.

Good luck, Scot

[Gene Beaird]

Gerald,

The 'restoration' of our booster was strictly a cosmetic restoration.  The booster worked, so I didn't need to rebuild it (although it really amazes me at the items the service manual shows how to rebuild, including the booster).  I'm not sure one can even get a booster rebuild kit any more. 

The booster exterior had a fair amount of rust on it, especially under the MC where the MC was leaking brake fluid.  I simply removed it, knocked the rust off with a wire wheel on a bench grinder and re-coated it.  Yes, it is not the way I'd refurbish a car I plan to show, but this will be a driver, I have other cars to show.  The booster still has some rust pits that I'd putty over if I were to try to make it look better, but it's down in the corner of the engine bay and it looks TONS better than it did before.  Careful observation can reveal the pits in the finish and the non-OEM finish. 

I didn't opt for a new cadmium coating, another thing I'd go to if the car was going to be a show car.  Instead I opted to use this kit:

http://www.eastwood.com/golden-cad-kit.html

It's not perfect, but very close if you're interested in making the booster look a little better.  Additionally, it's painted, so less likely to rust again.  I did clear-coat it after letting it cure for a couple of days, and it looks very nice.  Probably a little more shiny then the factory cadmium coating, but I'm cool with that.

It's a crummy cell phone picture, and the picture doesn't have a 'this end up' stamp in the picture data, so it doesn't post proper-end-up, but that's kind of what things look like. 

[www.eldorado-seville.com]

Gene,
thanks a lot for the info and the pictures you posted.
Its looking great! As mine is a Bendix booster its at least easier to restore appearance wise as Bendix units were painted all black ;-)
The shop manual states that only the Delco boosters were zinc plated.

thanks again!
Gerald