I have a Chinese floor jack that I bought new 27 years ago at a "tool store" at an indoor flea market. It's been great, never a problem. Now it will only go down with the weight of the car on it, or me! Which makes it difficult to pull out from under the vehicle when using it. Can I fix it? Flush? Clean a valve? Which? Where? How accessible is the valve? I hate to get rid of something that can be fixed.