ImWildBill

I have a 1990 LS400 and all of a sudden the break peddle went to the floor and I had almost no brakes. They wouldn't pump up by repeatedly pressing the peddle down, so would that be the master cylinder? The fluid level was down just a little, isn't leaking anywhere I can see under the car. Any ideas?

deanshark

Before just saying "it's the master" you should take the tires off and check all the lines. Even though you don't see anything leaking under the car it could be leaking and spraying all over inside the rim but not dripping.

lex2001

Yep. My son had the same issue and there was no puddle or drips under the car. Same symptoms as you. Very little loss of fluid in the cylinder but no pressure at the peddle. I took each wheel off until I found a small leak in a line. I cut it out and replaced it. I've been told that once one line rusts through the rest will follow soon, although I don't know if that's true or not. Something to consider on a 21 year old car.

ImWildBill

I was under the car while my fiance was pumping the peddle and watched all the lines and calipers to make sure they weren't leaking, cause that was my first thought is that there was a leak. But with no leak found, I figure it's the master cylinder. Does that sound right? I haven't had a chance to diagnose break issues other than replacing pads when worn for quite a few years....

lex2001

I don't know how to check the master cylinder. If no one chimes in here I'd google "how to check master cylinder". Did you look closely at the brake lines? The reason I ask is that on my son's car the brake line was wet for only about 4 inches even after I pumped the brakes in the driveway. If you have a leak in the lines it may not be very obvious. Look for anything wet, not necessarily dripping.

sethjon

When were the brakes done last? Aside from a line leaking, it could also be a piston moved in too far because the rotor was turned too thin. It happened to a friend of mine. If thats not it, you must have a leak somewhere. The master cylinder needs to be looked at but that would be too obvious. Look under the car and see if its spraying backward while you were driving.

jb2wheels

Could a bad booster cause this?

PureDrifter

iTrader: (10)

no. bad booster would cause the pedal to stiffen, not drop.

you either have a MASSIVE air bubble, or a leak.

ImWildBill

Ok, I work graveyard so when I get home in the morning I'll get back under the car and see if I can see if there are any leaks, any wet spots again. I hope I can fix it with minimal trouble...

deanshark

Don't crawl under it to look, you wont see much that way. Take the wheels off so you can get your head right in there and look around everything. Also that way you can get a good look at the inside of the rims to see if it's sprayed in there. Did you try just adding fluid to see if the pedal came back at all, or try bleeding the brakes? That's where I'd start.

AussieAuto

I agree with above about a thorough check because those lines can leak and be hard to find unless you put it up on a hoist to inspect, however if there is no leak evident then I reckon the master is probably toast, I have changed a couple over the years...

ImWildBill

Well, found a very small leak in the front passenger rubber line this morning, had to order the line. We picked it up this afternoon but couldn't install it due to having to get some sleep so I can work tonight.

I did add more fluid, it really wasn't that low just under the min line. I'll have the line swapped in the morning and bleed the breaks. I found while looking for the leak that the front drivers caliper isn't releasing all the way. It's still rubbing the rotor some so it looks like a new caliper will be needed sometime soon.... I'll swap it out when I replace the break pads in a month or so.

FrankReynoldsCPA

Dang man, were you on the road when this happened? I lost my brakes once coming up to a red light on my way home from work......I don't think my butt has puckered so tight in my life. Was driving my 89 Firebird with a manual transmission. I shifted down and grabbed the handbrake.....slid through the intersection......didn't wreck thank heavens. There were 2 cops behind me, but they acted like nothing happened, lol.

Bled my brakes the next day and it worked out fine.

Rey

Did your lines have cracks in them? Ive noticed cracks in mine, I think its time to upgrade to stainless.

ImWildBill

The brakes actually went out when my fiance was driving home from work. I did have brakes go out on me when I still had my 77 El Camino, yeah it'll make your butt pucker up so tight you can't shoot a greased bb up there!

None of my lines look very old at all so I was surprised to find that leak, none are cracked.

Well the other day I replaced the front passenger line that had the pinhole leak in it, bled the brakes and I now have brakes again! Thanks everyone for your help, I'd have just replaced the master cylinder and still had no brakes without the input.

If anyone lives in the Kansas City area and wants to stop by for a beer and Chiefs football on Sundays just drop me a message!