Technical Engine wants to die when brake booster is engaged

Good morning, hope everyone had a good weekend.

I have an older SBC crate 350 that I am waking up, it's running a Quadrajet and HEI so pretty standard set up. The issue I am having is that when I use the brakes the power booster engaging causes the engine RPM to drop and stumble and will someone kill the engine.

I did spray some starter fluid around the carb connections with the engine running and no obvious vacuum leaks were evident.

The brake booster is new and presumably good, presumably that is... From what I have able to find this behavior seems to be indicative of a bad booster but wanted to get some thoughts on what might be going on here.

Thanks in advance.

 

Do you hear a hissing noise when the brake pedal is held down?

 

Test the booster.... Put a vacuum pump on it and draw it down and see if it holds vacuum .... Then press on the pedal and see if the brake pedal is okay.... You can use a power or a hand vacuum pump... are Do you have a vacuum gauge you can hook up to the engine and watch and see what it's doing ??

 

Thanks for the responses,

@sunbeam - I do not hear a hissing when I engage the brakes. The mechanical fan on this thing is pretty loud so I will listen again to make sure.

@HotRod33 - great idea, let me get a vacuum gauge on it this afternoon and follow-up.

Have a good morning guys, and thanks again.

 

Pretty typical of a bad booster diaphragm.

 

I've seen the diaphragms crack in the center, at the seat of the M'cylinder, more than a few.
Also in behind, where the rod goes thru...Spray inside along the rod also.

 

Thanks - I'll test this darn thing shortly and follow-up. Won't be a shock, but still disappointing that a brand new booster was bad out of the box.

 

OK guys-I’m officially pissed off now. You all nailed it-the booster is bad, despite having less than 20 miles on it and having been properly installed etc. I put a vacuum gauge on it and it would not hold pressure ( you could watch the vacuum bleed down to zero on the gauge ) and was difficult to even get much of a reading on it

 

From experience New doesn't always mean good and you don't know how long it sat on a shelf in some warehouse before you got it.

 

I hear you, I've had this happen before too, but darn if it isn't enraging when you are working against a deadline.

BTW - I think I'm a member of your club. Grin.

Thanks for the help guys, very much appreciated.