Why is there a puddle under my car?

September 1, 2016 | By Staff


I have a 1993 Corvette 40th Anniversary with 27,000 miles on it. I have noticed a brake fluid puddle on the floor and a little fluid weeping between the master cylinder and the booster. I have filled the reservoir with DOT 4 fluid and checked it regularly to see if it loses fluid. The reservoir does not seem to lose any fluid but the puddling continues. Is the seal between the booster and the master cylinder leaking or is there another problem with the system I am not aware of? Do you think the master cylinder or booster is bad or do you think changing the seal between the booster and master cylinder will solve the leaking?


A car that old with only 27,000 miles on it has done a lot of sitting in the garage and that is worse than if the car had been driven more. If the brake hydraulic system has not been serviced in all that time, I would purge the entire system and replace all the seals. DOT 4 brake fluid is hygroscopic, which means it attracts and absorbs moisture. Also, seals dry out when a car is idle in storage and are perishable in any case.

The puddling may be a slow accumulation or it may happen only when you depress the brakes. In any case, assuming the hydraulics have never been done on the car, I would purge the system, replace all seals, and have the master cylinder rebuilt. That may sound drastic but remember, when it comes to the condition of a braking system, your life may be at stake.