SaleenS7

I'm driving back home today and start coming to a stop and realize I've lost a lot of braking power and the brakes seem as if they are hard to push/not enough stopping power. I feel like I've lost about 70% braking power. I stopped and looked over the brakes but I realized I had a hissing sound coming from the engine compartment. Probably a vacuum leak of some sort. I was able to get home safely keeping a large gap between myself and the cars in front of me. Thank goodness I didn't need to do any emergency stops...

I snapped a picture. The little tube in the center of the picture seems to be missing whatever hose that was probably attached to it. I'm assuming this HAS to be the reason for all of this.

Does anyone know where the hose connects to and if this is an easy DIY? I tried searching and couldn't find anything related to this. Any info well be helpful. I'll keep the car parked for now just to be safe.

LScowboyLS

yes, you have a vacuum hose missing or else just come loose

search around and see if you can find that tube flopping around lose nearby in the engine compartment and re-attach it

this is *definitely* the cause of your braking issue, you have lost the vacuum power boost for your brakes, you just have manual braking right now

until you are able to find or replace the missing vacuum tube, you can take something like a small cork or stopper of some sort and plug the hole where the vacuum tube is missing, that will get rid of the hissing and restore the braking as a temporary fix

SaleenS7

Thanks for the quick response LScowboy. It seems like you're always giving me golden information here.

I think you ought to be nominated for moderator here.

I shall try to find this tube. If I can't find it I'll plug the hole and stop by the dealership tomorrow. I'll keep you all updated.

SaleenS7

I could not find the tube... I even took the engine cover off and still couldn't find anything. I wonder how in the world it got disconnected. So I blocked the hissing sound as per your suggestion LScowboy. (picture attached) Hissing sound is gone but the brake pedal still feels the same. Very hard and not enough braking power.

I'm thinking this is really something simple. I can probably but the tube myself from autozone or something and reinstall it myself.

I have no idea where the tube would connect to. I tried searching everywhere to see any possible locations it would connect to but to no avail. Does anyone have a diagram or a real world picture of where the tube connects to?? This would be invaluable.

LScowboyLS

I don't have a 98-2000 car handy to take a pic of, but there is a vacuum hose routing diagram under the front of the hood!

on my 96, that vacuum line goes to a vacuum switching valve on the driver's side of engine, near the top, about 3/4 ways back towards the firewall, above cylinders 5 & 7

SaleenS7

I just couldn't find that diagram.. bummer. I'll try again tomorrow when there's light out.

Thanks again LS, I'll keep you updated

halojereme

I'll try again tomorrow when there's light out.

SaleenS7

huh? I'm confused by your response

python

iTrader: (4)

im surprised the car would even idle

SaleenS7

I took off the engine cover again today and still couldn't find any diagrams for the hoses. Perhaps the 98-00 did away with that.

Could anyone with a 98-00 model LS please post a pic of where the tube will connect into or at least the approximate area? As soon as I know where it goes to I can buy the right size tube and fix it myself.

The closest lexus dealership to me is about 50 miles away and I don't want to have the car towed there for something that seems as simple as this.

python

iTrader: (4)

i would think it goes to your brake booster..u said the pedal is hard to push...check your booster

SaleenS7

Oh god, the missing hose in question was literally in both the pictures above with the silver clip on it... It was simply just hanging down. I thought that hose went into the engine block for some reason.

Herp derp moment... problem fixed. Thanks all!

Dutchy

Why shouldnt it idle? If theres a vacuum leak, idle becomes higher! (False air)

+10 for fixing it yourself !

steve2006

The brake booster vacuum pipe can be seen connecting to the LHS of the booster reservoir and then passing over and behind the brake master cylinder.The other end of the pipe attaches to the intake manifold/Plenum chamber.
The engine vacuum is supplied to the booster reservoir and is stored there until needed by the brakes.
There is also a one way valve fitted in the pipe to prevent loss of stored vacuum so even if the engine stalls when driving you have back up for one or two applications of the brakes before you lose the power assistance.
To test the operation of the brake booster start the engine then after 10-20 seconds switch the engine off, press the brake pedal several times and the pedal will become harder to press as the reserve vacuum is used up.Keeping your foot on the brake pedal start the engine again.If the booster is working correctly you should feel the pedal drop slightly as vacuum is restored to the booster.
Picture below is from a 1997 Toyota Celsior albeit RHD but it shows the major components obviously LHD models are reversed.

PureDrifter

iTrader: (10)

No idea how your main brake vacuum line became disconnected. The car will idle without it but will have a really really lumpy idle (similar to a very aggressive cam).