I would like to know what the correct vacuum pressure reading should be at the tube that connects to the power brake booster. (93 ls400 w/trac)
I'm trying to fix a brake pedal that requires almost double the effort to brake effectively and before I replace the booster I want to ensure that the vacuum that the booster is being supplied by the engine is of the correct reading.
any help would be appreciated.
more over, is there a way to check this without using the mighty vac vacuum readers etc ?

 

It should be the same as engine vacuum since the manifold only has one vacuum reading.. At idle should be around 15-20 in/hg.

 

the reason i ask this is because the brake pedal on the ls400 seems to be pushing back everytime i press on the brakes. at the same time the braking power is reduced quite a bit where the 'bite' from the brakes just goes away. at the other times the brakes act perfectly normal. it's intermittent about 50% of the time.
given the booster and master cylinder are new, i was guessing this could've been caused by intermitten vacuum issues. not sure but i'm curious to find out if such a brake problem has been experienced by anyone else.