Sorry if this subject has been brought up before but I could not find my answer. I just took my 49 3100 out for its first ride and after about a mile I started to loose power. I quickly turned around and brought it home. noticed that both front wheels were super hot. I jacked it up and the front wheels were locked up (could not turn by hand). I have floor mounted master cylinder corvette style with duel bowl. power booster, 78 Camaro sub frame with disc front drum rear powered by 307 small block v8. the prop valve is mounted directly under the master. I installed 2lb residual check valves for the front and a 10lb residual valve for the rear. I took the 2lb residual valves out of the system and re plumbed the lines without the 2 lb valves now the brakes need bled before I test drive. the wheels unlocked as soon as I cracked the valves loose. my truck sits low in the front and looks to be that the calipers are slightly lower than the master or right at the same hight. Question is will I get flowback issues and if so what will be the result?
You didn't say, but I assume you have drums in the rear? Do you have a prop valve? The reservoir that faces the rear of the truck is for the front lines, and the reservoir that is closer to the front supplies the rear. Are you plumbed that way?
You might check to see if the actuator rod from the pedal to the master cylinder has some free travel in it. If it doesn't it won't let the fluid return to the MC and holds the brakes on. Intentionally shorten it too much and then lengthen back out to desired pedal height.
Thanks Evan, this is actually the first thing I had tried. I unbolted the master from the power booster to free it up a bit and make sure the push rod was not making contact. the front brakes were still locked up. then that is why I had opted to remove the residual check valves. I am now concerned with what may happen without the valves installed. It is funny that from what I am reading a lot of people seem to think its a must have and a lot of people seem to think they are not needed???? I figured I would ask around here being that this site deals with my make and model truck.
I had the same issue this summer when I first got mine on the road. I also thought it was the residual valves and removed them but it made no difference. I had 2 lb for the front and rear and have a disk / disk setup. Even though i thought i had the booster plunger rod short enough into the master cylinder i did not. It felt like i had free travel in the pedal but in reality you can push in the master cylinder plunger sometimes just a bit before you get some real resistance on it. Being unable to even release the master cylinder all the way out will cause the brakes to pump up and cause the locking / dragging. As a test try this...... Take the truck out again for a fast run so you get the brakes to drag. Park the truck and don't touch the brake pedal at all. Quickly get under the truck after safely parking it and blocking it up and try to loosen the 2 bolts that hold the master cylinder to the booster. If when the master cylinder is unbolted it might pull away on it own or if you pull it away a bit the front brakes loosen the rod being too long is your issue. Another thing to look for is pedal bounce. If your return spring is worn or undersized the pedal can actually bounce up and down when driving thus slightly always pumping the brake. I never noticed this when the truck was not running because the booster was not getting vacuum and the pedal was stiffer overall. Once the truck was started the pedal got nice and soft it would take one finger on it to push it down. I added another return spring and now it does not bounce. Hope this helps.
As for needing the residual valves........my thoughts is you actually don't unless your master cylinder is at or below the level of the brake calipers. Unless your slammed way down i doubt you need them. My truck works perfect without them installed and im dropped 3".
