View Full Version : so whats your thoughts

John ED Renstrom
10-04-2015, 08:26 PM
when this 67 showed up here I checked all of the fluids and toped them were needed. the car sounds and acts like it has a vacuum leak so we have been changing hoses and tighting things up. discovered that today the master cylinder is dry both sides with no visible leaks under the car or on any wheel. we have about 40 miles on it now. it was stopping all right with out any brake fade and the peddle held firm. the question is do I need to change the booster and the master cylinder or just the booster?

Joe Rackov
10-04-2015, 11:54 PM
If it was my coach I would replace both. At minimum the master cylinder if it actually leaking into the booster. You could look for signs that the fluid is leaking past the cylinder bore and into the booster as there should be some witness marks at the rear bore and or signs of fluid entering the booster.

In the 70's we had a problem with GM cars and trucks. A combination of low vacuum at the engine was drawing the air/fuel mixture into the brake booster. One sign was a witness mark of fuel running down at the joint of the booster and master cylinder. All cars got a canister filter added to the booster vaccum line and if any signs of vapor being drawn into the booster, those got a new booster. The air/fuel mixture would cause the booster to fail prematurely.

While normally the only result of a failed booster is a hard pedal, if there are signs of brake fluid entering it would be easier to do it once and for all and be done with it.

Paul Steinberg
10-05-2015, 01:59 AM
No question that the master cylinder needs a rebuild. Remember that the master cylinder is commercial chassis specific. They used both a Bendix master and a Moraine master, and they each use a specific kit, and the Bendix is a one year only part. The Moraine according to the book fits from 1967 - 1970, but I know first hand that it doesn't fit the 1968, so I believe that it is also a one year only part. The commercial chassis master has the lines coming off one side, and the regular car has them on the other. Don't remember which side for each of the cars. The commercial chassis uses the same kit as the Eldorado uses.
The Bendix booster is black and also a one year only part, and the Delco Moraine Original Boosters Are Usually Gold-Anodized. You can't switch brands without switching master cylinders to match.... Bendix master with Bendix booster, and Delco master with Delco booster.

John ED Renstrom
10-05-2015, 10:33 AM
thanks guys my booster is gold and of course the master is rust. so sounds like a delco is what we need. the lines on this one come out the on the left. I have discovered that brake fluid produces a lot of smoke as it goes threw the engine.