When this happens the peddle wont go down normally if I try to push on the brake it fights me it usually takes a cuple of times pumping the brakes and then the peddle depresses but wheels do lock up then. I had the front brakes and front rotors done and the rear brakes done and had new brake springs put in thje rear also when just doing normal braking the peddle pulsates. I am not getting any fault codes either with my sun pro by actron Gm scanner. On the dashboard it has written s10 sport and blazer on the 2 front doors. 1992 with 155,124 miles 4wheel abs 4 wdrive fronts are disc and the rears have drums, could one loose caliper bolt cause this Thank You in advance

Could be a few things. Brake booster could cause a hard peddle. Also, I seen brake rotors warp very quickly if there is a caliper sticking or a blockage in the hose. Also will make the peddle hard. Jack up the front and spin both fronts. See if the one is harder or has more drag. If you find that one is dragging take the wheel off. Crack the bleeder open for a few seconds. close the bleeder off. See if the rotor spins more freely now. If it does it is most likely a brake hose on that caliper. If it still turns hard it is most likely the caliper is frozen. Also look for blueish discoloration on the Rotor, that is a sign of something dragging and overheating it. Hope this helps