Big brake problems

[woodyjeep]

Ok, here is my deal. I changed my front left caliper today because of problems with it, but I also have been having soft pedal/low braking power. Now, since I've changed it, I've bled the brakes and I get great pedal when the Jeep is off. BUT, right when I turn the jeep on, the pedal goes to the floor and I have no power with it. It will stop me, but it is like fred flinstone braking power.

What could my problem be?!

[BingBing]

Leak in the system?
Bad master cylinder?
Water contamination?

[woodyjeep]

Leak in the system?
Bad master cylinder?
Water contamination?

Out of curiosity, how would any of those make the problem I'm having? I have great pedal when it is off, but the SECOND the vehicle turns on, my pedal is weak as hell.

[BingBing]

It sounds like your losing pressure somewhere. If you pump the brakes with the vehicle off the pedal should get stiff, that means the master cylinder is working properly. Did you bleed the brakes correctly starting with the wheel farthest from the master cylinder? There might be air in the system still. You should replace both calipers at the same time too.

[woodyjeep]

It sounds like your losing pressure somewhere. If you pump the brakes with the vehicle off the pedal should get stiff, that means the master cylinder is working properly. Did you bleed the brakes correctly starting with the wheel farthest from the master cylinder? There might be air in the system still. You should replace both calipers at the same time too.

yes, I bled from the right rear, left rear, rf, lf.

Now, I may have caused a problem when I was working on it. I was pumping my brakes up when I just got done puting the caliper on and I may of (not sure, there was a little fluid in the master cylinder) sucked air into the master cyl. Could that cause this. Yes the pedal does get stiff when the vehicle is off.

What way can I get all the air out? I bought a one man bleeder kit but the damn hoses are too small to fit over any of the bleeders.

[BingBing]

That'l do it. The only good one man bleeders are the vaccuum type and those aren't cheap. The best way is to get someone to pump the pedal and you release the bleeder. Always keep it topped off, check after every wheel. This may be your problem so start there if you are unsure if air got in there.

[woodyjeep]

would bleeding the master cylinder help? How do I do that?

[BingBing]

Its done by bleeding the brakes like you did before but before you bleed each wheel check the fluid and make sure its full. You can bench bleed new master cylinders before you but them in the vehicle, but thats not your case.

[AZ Jeff]

The pedal is SUPPOSED to go down when you start the engine. That's the sign of a good brake booster.

You STILL have air in the system somewhere.

[bustednutz]

I went out a few years ago to AutoZone and got a one man vacuum pump. It was about 35.00 I think. It was well worth the investment. I used it to bleed the brakes on an Audi Quattro I had at the time.
Its easy to use. Just slip the hose over the bleeder (it also has adapter fittings) but I never used those. And pump, pump, pump. It has a small containment cup, but I used a 2 liter soda bottle to drain mine it. I flushed it alot.
Just be sure that after a series of pumps you add fresh brake fluid to the master cyl resevoir. It works great.

[woodyjeep]

I went out a few years ago to AutoZone and got a one man vacuum pump. It was about 35.00 I think. It was well worth the investment. I used it to bleed the brakes on an Audi Quattro I had at the time.
Its easy to use. Just slip the hose over the bleeder (it also has adapter fittings) but I never used those. And pump, pump, pump. It has a small containment cup, but I used a 2 liter soda bottle to drain mine it. I flushed it alot.
Just be sure that after a series of pumps you add fresh brake fluid to the master cyl resevoir. It works great.

ya, I looked those up earlier. I'm buying one tomorrow. This air will come out!

[bustednutz]

Let us know how it turns out.
Thanks

[woodyjeep]

no change. The brake is great with the vehicle off, no pedal power once started.

[old_man]

Make sure the hose to the vacuum booster is not leaking. A quick check for a leaking vacuum booster is to watch the rpms and take a pair of pliers and crimp the hose going to the booster. If the rpms drop, the vacuum booster is leaking. If you have pedal with no engine, the MC is fine. You are fighting a vacuum booster problem.

Mine crapped out while I was driving. I slammed the brakes in traffic with no effect and rear ended a Ford Explorer and totaled it.

[woodyjeep]

ok, gonna check that