Brakes on 1997 Dodge Truck - Where's the fluid going?

[rtimgray]

So I've got a new problem with my old truck. Early in the spring, I was driving home and noticed the brakes were getting spongy. When I got home, I checked my resevoir and sure enough, it was low. I topped it off and tried to find a leak, and found nothing. We went on vacation the following and week and I decided I would work on it when we got back. After we got back, I forgot that it had happened and I didn't have any problems for the rest of the summer.

About a month ago, I was driving back home and the same thing happened, except this time, pretty much all of the fluid leaked out pretty quickly. I was fortunate and had some extra fluid with me, so I slowly made my way home. Again, I topped of the resevoir and had my boy pump the brakes and I couldn't find any leaks. No noticeable difference for the last month.

Last night, I checked the resevoir before I drove the truck, and it was down a little. So I topped it off, and off I went. This morning, it is lower again. However, it's raining, so I don't have any chance of finding a leak right now.

The only common thread that I can think of is that I seem to notice that it leaks if I really have to stomp on the brakes, rather than normal braking. It doesn't appear to be leaking from anywhere around the master cylinder, resevoir, or booster, nor any of the lines in the engine compartment. I've wondered if I might have a leaky wheel cylinder that only leaks sometimes, but I never find any leakage running down the tires after it sits.

This truck is not a daily driver, but it is driven three or four times per week for 30 or 40 miles, so it's used fairly often.

Any ideas where my fluid disappearing to? I would appreciate any experience or suggestions.

Thanks.

Good luck and take care.

 

[Gem99ultra]

Don't mistake me for an expert... But it's possible that your master cylinder is defective. In some cases it will allow the fluid to leak past the seal and be sucked into the vacuum line going to the engine. That would allow the fluid to go into the engine and be burned, probably without notice.

One tell-tale sign, if you can hear it, it to listen for a low sound from the booster while apply the brakes. Also, usually the pedal will go down, sometimes only a small amount, when you hold constant pressure on the pedal.

I did experience this once with my Chevrolet p/u. Also had the same experience with transmission fluid on another car. Never knew where the fluid was going until someone noted that I had a plume of white smoke coming out of the tailpipe.

It's worth checking on the vacuum booster though. A sudden total failute of the booster could be a really bad situation.