BLKTOPTRVL

Car sat for nine years.

• When it is started, If I wait about a minute before moving I get a little brake boost, when I let up on the pedal, the next press is hard as a rock and I get almost no boost.
• Moving out into the street, If I drive for about half a mile, I will build up a little more boost, and then the pedal goes hard again.
• Driving longer periods without pressing the brake gives me more boot and more presses of the brakes before I lose assist again. When I build more vacuum, I get more boost.
• This pattern continues with no change...

These are my thoughts...

• The line going to the intake manifold may not be getting enough air at a rate to replenish vacuum fast enough because it has a little kink (not the OEM molded hose). I have ordered a new hose, it will arrive next week.
• The check valve in the booster hose may be malfunctioning. I took it off and I can blow as hard as I can and I get no air through in the check direction. When I blow in the opposite direction, I have no problem moving air through - there is a rattle sound as the air moves past the check valve. I am thinking the check valve is OK.
• Since the brakes stop the car OK when there is boost available, I consider the calipers OK and although it will not hurt, I see no need to bleed the brakes to fix this issue - however, I do have speed bleeders on the way.
• My conclusion is that the must be something wrong with the booster itself, somehow it is not collecting and holding enough vacuum and needs to be replaced. I would prefer (cost wise) to get a rebuild kit for the booster, but I have never done this job, I have no frame of reference as to how difficult it would be to do this, and I can find no instructions anywhere.

Anybody have any thought at do not jibe with my suppositions? I'd appreciate hearing.

RotaryEvolution

iTrader: (30)

grab the rubber line from the lower intake to the firewall and bend it, i bet you find a big gnarly crack in it.

if not, the banjo that goes into the lower intake manifold is usually carboned to hell and back, blocking most all if not all airflow. this is a less known secret, but a very common issue.

BLKTOPTRVL

The line is new, so no crack... As for the banjo, I'll pull it out tomorrow and take a look Are you only seeing carbon in the banjo itself, or in the manifold too. If the manifold, I am guessing a pipe cleaner should do the job. I have a spare in the garage, I'll take a look to see how thick the metal is where that air is routed.

Than again, this is in the intake tract... do you worry about dislodging a huge chunk of carbon that gets swallowed by the engine?

RotaryEvolution

iTrader: (30)

banjo, pipe and manifold all should be cleaned out.

10TH_ANNIV_T2

Hi, so I'm having similar brake boost issues, slightly different though. So first-- thank you both for the post and ideas! Did you get your issue fixed (either replacing the booster or rebuilding it)? Was it the vacuum booster?

I'm pretty sure my check valve is good, I can blow through it only in the arrow direction. I checked the banjo and hose on that end, banjo was excellent, I replaced the hose as it had some cracks and I couldn't tell if they went all the way through.

I presume that the check valve is what allows a slight vacuum to be retained in the booster when the engine is off, so you still have one/two "power" brake applications.

The FSM has 3 tests:
First is press pedal with engine off (using up any vacuum boost), start engine while holding brake pedal down. If the pedal moves down (mine does not) once started (vacuum is applied and the booster is working), the unit is functioning. So, I fail that one.

Second test-- run engine for 1-2 minutes. Stop the engine, Press pedal with usual force. If the first push is longer than subsequent pushes, then the unit is functioning. Mine-- no change, hard and high each time. So I fail test 2.

Third test-- run engine, press pedal with usual force, stop engine with pedal being held down for about 30 seconds. If pedal height does not change, unit is OK. Mine pushes right back up. So I fail test 3.

I don't have vacuum gauges to do the more thorough procedure described in the FSM, but the above tests seem to be comparitively similar.

Greg O.

misterstyx69

iTrader: (142)

..make sure that the rubber hose from the brake booster is going in the proper direction as it has a check valve built into it.. It says "ENGINE--> "

10TH_ANNIV_T2

Yes, the arrow on the hose is the only direction I can blow through it, so the check valve appears to be working properly, which is good as it looks like this hose with valve is no longer available.

Greg O.

clokker

iTrader: (2)

Not that it matters to you now, but for future reference, any hose with a standard check valve will work. The OEM part is nicely formed and uncluttered but easily and cheaply substituted.