240z break booster death?

[240zness]

Been on this forum a lot recently , lurking, but not posting about cars. Would like to post a build thread or an introduction but just lost brakes in my stock 71 z , and a few of you guys I see on most threads have plenty of info for any topic it seems.

 

Just wanted to give a few thoughts and see if you all are interested. I noticed revs were affected by foot on brake as I left my garage , revs were up 500 rpm after getting if freeway and stopping at light . After a big corner and some urgent breaking the pedal pushed back and started to hiss as I slowed to 5-10mph. Traffic started moving and I limped to work. So now parked brakes make revs go up, and there is no stopping power pedal doesn't depress and you hear the vac leak not just manual

 

Any way just replace booster.. ok. Any other vacum system checks , my vac advance has been sticking.

 

If all sounds normal for a failure just say so.

 

If distributor issue separate, etc. I don't mess with it cause it does 110, and a mec does most of my work.

 

Again so much experience here I had to ask

 

Thanks

Bret

[datzenmike]

Take the distributor cap off and watch while you suck on the vacuum advance hose. It should advance (turn clockwise) half an inch or so and hold until you release it. If it won't hold, you have a leak in the vacuum can or the hose, so look for it. If sticky twist the rotor by hand to clear any tightness. You may have to take the distributor out and partly dismantle it to lube the moving parts of the vacuum and mechanical advances.

 

 

Step on the brakes several times to exhaust any residual vacuum that may be present in the system. Depress the brake pedal and hold. Start engine. What you should feel normally, is the pedal will drop slightly as soon as the engine starts and the intake vacuum builds. This would indicate that the booster is working ... even if it does have problems. If you suspect anything look at the larger vacuum hose from the intake to the booster for splits or leaks, clamps tight.

 

There is a felt pad or ring inside to muffle the sound of vacuum being vented when the pedal is depressed. Not noticeable with the engine running but you may hear it when off. A constant hissing is not normal. Stepping on the brake should not affect a warm idle. 

[240zness]

Thanks for the walk through , I assumed you would be a responding member

 

I'll work on the distributor, as for brakes the lines looked good , and tight.

Pedal does not drop on start up , air leaks out immediately and is purged with slight pedal depression after motor is shut off.

 

Original booster due to fail at 45 yrs right. Did read about capping lines to booster to allow manual braking, can't stop with the brake pedal at all now.

 

I'll check the hoses again, was driving hard may have loosened -thanks again

[datzenmike]

Just remove hose and seal the intake end. Braking will be severely lessened without booster. Severely lessened.

 

Check in-line one way valve. You should be able to suck air through on the intake side. You should not be able to blow air through from the intake side.

[Stoffregen Motorsports]

Mike's advice on how to diagnose a brake booster is always spot on.

 

What to you do for a living, Mike?

[datzenmike]

I give advice....

[Stoffregen Motorsports]

I am the wolf...

[datzenmike]

Well you know what they say about free advice.... it's worthless.

[240zness]

I can PayPal you something

[Stoffregen Motorsports]

Holy cow. Someone's willing to pay for advice...!

 

Take the money, Mike!

[Cheetahking]

Holy cow. Someone's willing to pay for advice...!

 

Take the money, Mike!

Careful - you might have to pay for that advice.....