Classic/Antique Car Repair: 1954 Chrysler New Yorker, power brake booster, chrysler new yorker

Question
Dick:

Please let me apologize for such a long span of time, from our last contact.

I just recently was able to determine the possible cause to the rough idle I was experiencing.

During a routine servicing, the mechanic discovered that when I step on the brake pedal, the rough idle occurs, and when I remove my foot from the brake, it goes away.

His conclusion initially was that there might be a vacuum leak in the Power Brake Booster device, however, he later thought it could be an electrical drain in the brake light or other electrical components.

I am hoping you can shed some light on this, and as always, offer a possible solution or advice, as to what you believe this problem to be.

I want you to know, that in every instance that I have contacted you for advice, you have always been completely accurate, and I have always advised my mechanic of your diagnosis, and he has always agreed with it.

Thanking you again for your courtesy and kind consideration with this matter, I remain,

Respectfully,

Anthony J. Vitale  Retired Police Detective/ Shield # 246

P.S. I will be at the Chrysler Nationals in Carlisle PA this weekend to show off my 1954 New Yorker, that you have been instumental in keeping her running like a Swiss Watch.  THANKS!!

Answer
I'm about 99% certain that this is a vacuum leak caused by a faulty power brake unit.  

I cannot think of any electrical problem that would be severe enough to cause a rough idle, yet the vacuum leak  is a common symptom of a failing power brake booster.

To sort this out for yourself, remove and plug the brake unit end of the vacuum hose from the intake manifold to the power brake unit, then step on the brake pedal with the engine running.  I think you'll find the rough idle has disappeared (and if you drive the car that way, you'll have to press much harder on the brake pedal to stop!).

If this is the case, you need to remove the power brake unit and send it off to a competent rebuilder to be repaired.  While I know of some vendors out here in the west who can take care of it for you, I think you can probably ask around and find one much closer to you.

A NAPA store can often send it out for you for rebuilding, also.

Many of my friends from the on line Imperial club will be at their booth at the show this weekend - if you see the booth (and the collection of Imperials and other Chryslers), you could stop by and tell them hello for me - they all know me.  It's a little far for me to travel (about 3000 miles!).

Dick