On the way home tonight, had almost complete brake failure. Fortunately was in a Walmart parking lot when the brake pedal went to the floor. Checked all around but could see no leaks and from the side, the master cylinder reservoir looked full. Need a emoticon for scratching my head. Drove the truck a bit and found that it appeared that at least one back brake was working, but only for a few seconds before the pedal hit the floor. With that small amount of brake remaining, decided to drive home very slowly and pray that no bozo forced his way in front of me.

As I could not see any leaks, my guess at that moment was that due to me flushing the brake fluid last month that somehow the new fluid had eaten the seals in the master cylinder and that under pressure it was bypassing. I used good quality DOT 3 fluid, so doubted my own reasoning, but that's all I could come up with on the spur of the moment.

Got home and discovered that now the inside of the RH front tire was covered in brake fluid, as was the inside of the rim. The reservoir was now empty. Pulled the wheel off and discovered that the banjo bolt holding the brake line to the caliper was loose. Took almost a 3/4 turn to make it tight. Now I am really puzzled. How on earth could that come loose? The only thing that comes to mind is that when the guys installed the new front suspension on the truck a few weeks ago, that one of them leaned on the metal portion of the hose and moved it enough for it to start working loose. This is a huge stretch of the imagination, but I can't think of anything else. Anybody ever seen or heard of a banjo bolt coming loose on the brakes?

Tightened the banjo bolt and topped up the reservoir. Pumped the brakes a few times and the pedal is solid. Don't have enough brake fluid on hand to bleed that brake, so will do that tomorrow. Question for you brake experts; should I bleed the entire system from scratch, or will just bleeding that bad brake be enough?

 

Stan, I had a 97 f450 ford service truck, came to me brand new, right out of pdi. Drove it off the trailer, and almost right through the back wall of the shop. All 4 banjo bolts were loose, resulting in one brief shining moment of almost stopping, then some serious cursing while trying to stall it out.

Nobody ever came good on that one.

I've also had loose fitting after guys having the calipers off for one reason or another. So I check them every time there's work done.
I've also seen dirt caught in the copper washers, doesn't always leak right away, but after a time it will manifest itself. Normally at about the worst possible time.

 

pind, thanks for the response. These calipers have never been off. Last month when I flushed the brake fluid everything was bone dry, hence my puzzlement over why the leak now. Guess this one needs to be chalked up to one of the unknowns. Checked the opposite side and it was tight and dry.

 

Stan,
If the reservoir went totally dry, I would not take any chances on air bubbles and bleed the backs and then the fronts. All you need is one heavy panic stop and an air bubble stands between you and possible havoc.....

Gary

 

Gary, I totally agree. Have just finished bleeding the entire system. First bled the bad brake, then did all four brakes in the usual order, furtherest first and closest last. Have good solid brakes now. Started the engine and stood hard on the brakes a few times and held the pedal down hard for quite a while. The pedal does not slowly bleed down and no signs of leaks anywhere.

Was surprised at how dirty the fluid was considering that I flushed out the entire system about 6,000 miles ago. It was not black like when I did the flush, but had a distinct black tint to it. Now have good clean fluid everywhere once again.

 

Crazy ex-girlfriend?