Help! Complete brake failure
I purchased a used 1998 Sportsman 500 about 8 months ago. It sat in a older guys garage for years but was in great shape and only had 1500 miles. I used it to plow snow last winter with no problems. A few weeks ago i took it camping for the first time. While on a very short ride with my 3 year old son in front and wife on back, (combined weight approx 320 lbs) and descending down a fairly steep hill I suddenly lost all brakes. My hand brake would pull all the way to the grip with no pressure and the foot brake also lost all pressure. Needless to say that without an engine brake, shiftable transmission, or any sort of emergency brake I had absolutely no way to stop 500 lb. machine on a steep descent. Long story short we're lucky to be alive, particularly my 3 year old. I absolutely cannot believe that whoever designed this ATV made it possible for a single part failure to result in complete brake failure, especially on a machine without engine brakes or gears. Strangely after we thundered down the hill and finally crashed to a stop brakes mysteriously began working again (but not for 5-10 minutes after this whole ordeal).
I got the ATV back to camp, bled all the lines (there was no air in any of them), checked fluid (completely full in both reservoirs), checked pads (all we're good). I'm at a total loss. My best guess is that something went wrong with the rear caliper since that is the only place the hand and foot brakes intersect. Each have their own master cylinder & bleed screw on the rear caliper. I just can't believe that there is any chance both brakes could fail at precisely the same time, and then both mysteriously begin working again at the same time.
Had anyone here ever heard of or seen this in another machine? I I've been around and worked on ATVs my whole life. Now I don't dare take my son on it anymore, which kind of defeats the purpose for me. I've been thinking of plugging off the rear brake line at the 4-way junction in front of the fuel tank to completely isolate the hand brake from the foot brake, any thoughts? Has anyone done this successfully? I spoke to three different dealerships about the problem but none of them exactly inspired confidence. I feel like I need to be 120% sure I the brakes won't fail again before I will let any of my family anywhere near it again. I'm also reluctant to sell it for fear of someone else getting hurt. A $2000 machine just isn't worth it.
Apologies for the novel, I know there are a ton of experts on this forum. Any thoughts or help would be very much appreciated! Thanks in advance!!