Need some help with my brakes, Ive got a5.7L TPI 4 wheel disc breaks and my pedal is hard as a rock. I know the problem is vacum as the fluid has been bled to no avail.

The problem is i dont think the vacum lines are right . All my plenum and runner gaskets have been changed and new bolt kit and I have a new EGR valve etc, but when I bought the car most of the vacum lines were disconnected or plugged, there wasnt even a line coming off the vacum fitting on the throttle body wich Im pretty sure aint right.

So Ive done the best I can but obviously not good enough. I have a shop manual but I cant seem to find a diagram for the vacum lines. Maybe Im blind. Im not to concerned with any vacum for the AC, or cruise control right now Just want the major stuff to work right. What have i got brakes, EGR, distributer right? Can anyone post some pics and instructions on the vacum routing for the break booster and other important vacum lines? or at least point me in the right direction in the shop manuel?
Thanks

 

On the break booster there is a vacumn line that runs from it to the manifold. is it hooked up at both ends? One end with a 1 way valve is at the booster and the other end goes to the manifold for full vacumn signal.

 

I have 2 General Motors manuals from the mass air flow sys to the density sys, and I agree with u that it does NOT show any diagrams for the routing of these lines but only from stright lines to each part? Yea I can't figure it out myself. So I bought a Haynes manual, and guess what? Same issues, not showing anything how to dial this all in properly,

But when asking your please include the year that u have? Because mass air flow has a regular diagram, and then the 90-92 Tpi motors has a little bit different routing diagram for the vaccume's,

I know this- the EGR has to go to the passangers side pentium port hole 2 that's closer to the from motor, the same side port 1(closest to the passangers side back) goes into the fuel pressure regulator if I can remember correctly, but other members will charm in to correct this if I'm wrong,

The front 48mm throttle body has a small vaccume line under the throttle body that u could easly miss to see, actually u can't see it at All, so take the long vaccume line from there that goes under the pentium intake and run that back into the same location of the 1 & 2 ports by a plastic small tubbing, this one has the bobble fat tube into the 3 inlet and also the outlet to convert into 1 line,
There is also a LONG plastic tube that comes from the cat, this is also directed under the runners of the pentium all the way down to the canister, this is a very critical vaccume that must be done if your running A.I.R, without this? U may be heating up the car with out u never knowing it at all, because of this 1 plastic vaccume most 3gen guys never know why there car over heats? So they end up changing everything to cool down there Iroc, Gta formula, ect.... Because of this vaccume line,

What u can do if no diarram is found on your search,

Connect all your lines into the plastic rubbing (chep at any auto store less then 3 dollars at home depo, yes home depo) and start up the car and just see the ideling and spray some carb fluid to make sure your good to go, won't hurt nothing what so ever and should be safe if u don't have any other issues tben just vaccume diagrams,

I'll try and post u some Picts here but with my phone I just can't figure it out, so just email me for Picts that I have saved into my phone and ill just send them to u or anyone who needs this help with actual Picts,

I have the density diagrams Picts only
And have a few Picts of the mass air flow ones to

Email me any time at:

johnjohninht@gmail.com


I'll do my best to help u guys out as this is a pain that I don't want your car to just sit and wait on the know how for a vaccume lines,

Hope this helps
Will work for any Trans am, Gta, formual, Iroc z, z28 and also the corvettes to from all 1985-1992 models only with 305 to 350 Tpi - l98 models only -

If u need more info on this thread? But don't like to turn u guys away from our site here, but go to:

Corvettesc4.com

C4corvettes.com

Superchevy.com

These sites are for any Tpi needs and they are the same motors with the same diagrams to,
They also have some great build to at super chevy, just type in Tpi and u get the wonder world of all l98 motors ever made to date

Good luck and hope this all works out for you guys

John
Iroc z parts and supplies
Houston tx,

 

find a big vacuum hose nipple on the intake plenum and hook the brake booster there.