Hi guys, thanks in advance for any advice you can give.

When braking in the van there's an intermittent problem with the brakes. We'll be braking fine when suddenly the pedal will press right down and the brakes lose a ton of their effectiveness. Again, it only happens once in a while and after it happens, they work fine again for quite a while. It's only happened at slow speeds (so far). The wife says pumping brings them back.

The fluid level seems fine, I did top it up and I'm keeping an eye on it.

Some background: We bought the van earlier this year and replaced the front caliper. There was still a problem during the safety. The mechanic loosened a clamp on one of the lines saying it makes a pinch point over time, and it worked fine after that. The brakes have been great for months.

soooo... leak? air in the line? ABS sensor? What are your thoughts?

sounds like an internal leak in the master

You either have air in the system or a leaking cylinder (wheel or master). GET IT FIXED RIGHT AWAY! You have an accident just waiting to happen.

I used to have a car that was loosing fluid but the wheels were dry, come to find out fluid was leaking behind the brake booster running down the firewall. Check that area for wetness. But do something right away like other posts that is a problem waiting to happen and not to be taken lightly.

Van should not even be driven until fixed. Master cylinder failure is common on these vans as are sticky calipers. Your problem is most likely a failing master cylinder. For the little it costs to replace, it is cheap insurance that your wife doesn't lose braking while entering an intersection.

Not to sound overly dramatic, but this can easily lead to major injury or even death.

PS: Nearly impossible for the ABS to do this unless the ABS module itself is leaking. If there were a sensor failure the ABS light would be on and the ABS would be inoperable leaving the regular braking system fully operable.

Thank you all for your help. Looks like I'm changing the master cylinder tomorrow.