Lexs400

I am posting this here as well hoping to get a response incase the LS forum doesnt result in any.
I'm trying to figure out why there is almost a 2 second lag in the brake effect of the 93LS400.
As an example, If i jam the brakes at moderate speeds, it almost takes 2 to 3 seconds of full pressure before something in the system kicks in and applies full force of the brakes and then the car has the full brakes applied with a rapid jerk. The rapid application is OK but it should happen the moment the brakes are jammed. Not after the lag period.
Once however, the brakes are jammed and ABS kicks in, from there on forward for about an hour or so the brake response does not have any lag in it.
Leave the car over night or drive without slamming the brakes and it goes back to the non-responsive, no crisp 3 second lag braking situaiton.
the car has traction. DOes this sound like a bad Master Cylinder or should I be looking at a different component ?
any ideas would be appreciated.

Lexs400

need some expert advice here !

Inabj2

Im no expert but perhaps your answers could provide clues to other posters.

Is there a brake lag if you were to SLAM as hard as you can on your brakes after sitting there overnite? Is the 3 seconds lag of NO breaking at ALL or is it weak braking for 3 seconds followed by a strong firm braking?

I take it moderate or normal driving braking also takes 3 seconds? Or is the 3 seconds apply only if you were to brake strongly? Does it matter what kind of conditions the road is?

Edit: Reading your other thread it looks like you already checked the obvious areas...

Tammy

I had this symptom when a brake vacuum booster diaphram was cracked and leaking. Mine failed intermittantly, but I noted less then normal manifold vacuum. The entire unit needed replacement; vacuum and braking returned to normal.

Lexs400

well here's a bit more explanation.
Initially when the brakes are slammed, the car does start to stop but from the moment the car starts to stop it's about 3 to 4 seconds lag from there on when the system kind of wakes up and realizes that the brakes have been slammed and that's when the car starts to take full effect of the braking system. ABS doesnt even turn on the first time the brakes are slammed because the car still keeps crawling as if the rotors were glazed. But once ABS kicks in the hour or so of braking after that period is perfect. Where the car doesnt experience the 3 second lag anymore. The brakes jam the moment the pedal is slammed.
THe booster is new, was replaced six months ago, so is the master cylinder that got replaced last year.
The rotors/callipers are new with new pads. The brake hoses have been replaced. All this to cure the brakes as the way they are right now (acting up intermittenlty) are not predictable.
I have already taken the car to 4 different dealers in the NJ area in the past one year and other than them repalcing all these parts, nothing positive came out of it.
I am now fed up with the dealers just wasting my money and therefore trying to find out if someone here could shed some light on this situation.
thnx again for all the replies.