Checking for proper brake booster operation

[Grumblebuns]

Despite my better judgement, I've decided to check out the TC advertised on Craigslist:

http://www.lotuseuropa.org/LotusForum/index.php?topic=3034.0

I talked to the seller and I'm going to take a closer look at the car later on this week. One of the unknowns on the car is the status of the brake boosters. The engine supposedly starts up and will run but the car can not be driven. So in this condition how does one verify operation of the brake boosters.  I vaguely remember  that stepping on the brakes will cause a whooshing sound that can be heard in the cabin when my booster were working on my TCS. I can't think of any other way except to drive the car.

Joji Tokumoto

   

[BDA]

I can only point out that they have (or at least the top one has) been rebuilt at least once. Given the dry climate, I would be hopeful that they are still good but beyond that, I'm not any help. Sorry.

[EuropaTC]

One of the older methods was to start up the engine and run it for a few minutes, operate the brakes. Then switch off, press & hold down the pedal whilst re-starting the engine. If the servo is working you'll feel the pedal move slightly as the engine vacuum builds & operates the servo. Maybe not the best indicator on a car that's been standing because of course the calipers might be seized, but it's a start.

Brian

[tedtaylor]

should NOT be a deal breaker.    one should NOT fear rebuilding boosters anymore, since the kits are readily available, detailed rebuild instructions abound, and even the 3rd party hydraulic rebuilders can also do the job for you.
I don't recall hearing any hissing sounds while operating my boosted brakes, but then again, i'm hard of hearing in that mid-frequency range!!! 

[Arizona]

I discovered a problem with my booster when I disconnected the vacuum line and saw brake fluid dripping out. Brake fluid injection?

[jbcollier]

Pump the brakes until the pedal is hard, at least 10 or 15 times..  Start the engine, the pedal should be now noticeably softer and lower.  This will tell you if the booster is "working".  It won't tell you if it leaking, hanging, or any other ailments.  Look in the manual, every 40K, every brake rubber and seal was supposed to be replaced.  These cars are now coming up on 50 years old.  I would replace or completely overhaul the boosters regardless if they "work" or not.

[tedtaylor]

I discovered a problem with my booster when I disconnected the vacuum line and saw brake fluid dripping out. Brake fluid injection?

If you have brake fluid in the vacuum line, it usually is sucked into the intake and would make a running engine smoke big time.   Accompanied by a noticeable loss of brake fluid too.