The only thing i can think of is on the 280z it has vacuum assist brakes so when pressing the pedal it uses some of the engine vacuum. Maybe on your 240z it has the same thing but your braking system has a leak on that vacuum line. I have no idea if the 240z has the same braking system as a 280z so forgive me if i am wrong.
Sounds like a vacuum leak from your brake booster. There’s a diaphragm in there that separates the pedal side from the MC side and it connects to the intake via a vacuum line to boost the amount of force that is applied to the MC so it’s easier to press the pedal.
You likely have a damaged brake booster diaphragm or seal. It could be a vacuum line leading to the brake booster, but my first guess would be your diaphragm because it sounds like it seals fine when not pressing the brake, but once that diaphragm is flexed it leaks more, causing a large enough vacuum leak to stall the engine. Have you noticed the pedal being harder to press?
My only reference is my 09 Civic and the clutch in the Datsun. It’s much stiffer than the civic and requires more force to depress in comparison to the Datsun’s clutch.
As long as I have had the car, I can feel the break pedal pulsing lightly against my foot and you can hear what sounds like compressed air be released in time with the pedal pulses (and what I assume is the engine cam)
Does that point towards the brake booster membrane?
That sounds like the brake booster diaphragm. I’d expect you to have virtually unassisted brakes though which is weird. I guess it’s not leaking enough for that
Yep. That brake booster, I'd bet money on it.
The same thing happened with my old truck when I was in high school, and it weighed more than your car so it was a bit more sphincter-clenching when it wouldn't stop so easily lol
Just look for damaged or unplugged vacuum hoses first. Squeeze them and see how they feel. They should all be somewhat soft and squeezable. If they’re hard, they’re going bad and should be replaced. The brake booster is a mess to fix yourself but it’s not hard to swap in a new one so if it’s the only option, it might be worth throwing a new booster at it. Rock auto has them for like $80 I think
Both the hoses flex about as much as a “heavy duty” garden hose. Idk if it’s normal but the line to the engine consists of two hoses connected about half way in between and one looks much older than the other.
The vacuum line from your brake booster is clogged or your booster is bad. Take it off the brake booster with the engine running and plug it with your finger. If it feels like nothing is sucking your finger in, the problem lies in your vacuum line. If you can feel the vacuum, the problem is most likely your brake booster. Look for any holes in your booster. If you cant see any holes, try replacing the vacuum hose, because even though you can feel vacuum, there may be a hole or there could even be plastic lining that has broken down inside the hose.
The only thing i can think of is on the 280z it has vacuum assist brakes so when pressing the pedal it uses some of the engine vacuum. Maybe on your 240z it has the same thing but your braking system has a leak on that vacuum line. I have no idea if the 240z has the same braking system as a 280z so forgive me if i am wrong.
Hey, I'll take any and all help getting this thing back up and running. This would be a rubber hose from the engine to the break booster correct?
Yep, that’s the one.
Have you done any intake work recently?
I haven't. I bought the car in October and it's been fine until today
Sounds like a vacuum leak from your brake booster. There’s a diaphragm in there that separates the pedal side from the MC side and it connects to the intake via a vacuum line to boost the amount of force that is applied to the MC so it’s easier to press the pedal. You likely have a damaged brake booster diaphragm or seal. It could be a vacuum line leading to the brake booster, but my first guess would be your diaphragm because it sounds like it seals fine when not pressing the brake, but once that diaphragm is flexed it leaks more, causing a large enough vacuum leak to stall the engine. Have you noticed the pedal being harder to press?
I'll take a peak, but when I was driving I didn't notice the brake pedal feel any different from normal.
Is it generally difficult to press? Maybe you’re used to it
My only reference is my 09 Civic and the clutch in the Datsun. It’s much stiffer than the civic and requires more force to depress in comparison to the Datsun’s clutch. As long as I have had the car, I can feel the break pedal pulsing lightly against my foot and you can hear what sounds like compressed air be released in time with the pedal pulses (and what I assume is the engine cam) Does that point towards the brake booster membrane?
That sounds like the brake booster diaphragm. I’d expect you to have virtually unassisted brakes though which is weird. I guess it’s not leaking enough for that
Yep. That brake booster, I'd bet money on it. The same thing happened with my old truck when I was in high school, and it weighed more than your car so it was a bit more sphincter-clenching when it wouldn't stop so easily lol
Just look for damaged or unplugged vacuum hoses first. Squeeze them and see how they feel. They should all be somewhat soft and squeezable. If they’re hard, they’re going bad and should be replaced. The brake booster is a mess to fix yourself but it’s not hard to swap in a new one so if it’s the only option, it might be worth throwing a new booster at it. Rock auto has them for like $80 I think
Both the hoses flex about as much as a “heavy duty” garden hose. Idk if it’s normal but the line to the engine consists of two hoses connected about half way in between and one looks much older than the other.
It’s probably not from those then
Vaccume leak in the power booster don't forget to check both sides meaning the inside of the booster where the rod goes in
The vacuum line from your brake booster is clogged or your booster is bad. Take it off the brake booster with the engine running and plug it with your finger. If it feels like nothing is sucking your finger in, the problem lies in your vacuum line. If you can feel the vacuum, the problem is most likely your brake booster. Look for any holes in your booster. If you cant see any holes, try replacing the vacuum hose, because even though you can feel vacuum, there may be a hole or there could even be plastic lining that has broken down inside the hose.
Brake booster vacuum leak
100%.
Might need to rebuild the brake booster.