Air brake issues, Foot valve makes a squalking noise when pressed

Foot valve makes a squalking noise when pressed and sounds like back pressure in foot valve. Replaced foot valve and no change. Tractor protection valve behind sleeper where blue and red lines connect is working fine but have to pump brakes to get good stopping power. Truck brakes feel like they are doing most the work. I'm stumped. Please help.

 

What kind of truck

 

Check for a split air line that is causing the sound. You might have to jam a stick or something to hold the brake pedal down while you chase the noise. If not, you might have to start blocking off air lines until you find the one that is causing the noise.

 

Mine does it when cold goes away Real cold worse. All my Trucks did it when cold normal . Not saying that’s your problem unless it showed up on a real cold day

 

2014 KW T660

 

Noise I can deal with but the brake issue that it's symptom of, I cannot

 

Similar issue with mine now. Any info would help

 

Honestly this sounds pretty normal. If your unsure about brake application pressure to the trailer and are concerned with the tractor doing most of the work you can always test to verify the right amount of air is heading to the trailer. I would make a dummy glad hand and put a guage on the other end of the dummy. Make sure someone holds full brake application pressure and check the guage.air the truck up fully. Should be while holding the foot pedal down about 90 to 120 psi.... the squaking noise can be from the foot valve exhausting air through the diaphragm check to make sure it's not for abunch of dirt on it. If you have an issue with not enough air getting to the trailer and don't have an obvious leak you might want to trouble shoot from the tractor protection valve to the foot valve....

 

Normally noise through an air valve is something leaking. If it where silent and you don’t think the trailer is helping I would look at the tractor protection valve.
Since there is noise I would look to an air leak. Find a quiet area away from noise, open your hood (Block wheels and other safety stuff). Run the truck up to air drier cutoff pressure with park brake released. Shut truck off and Jam a stick on the brake pedal to hold it down as hard as you can get it wedged in there and walk around listening for the air leak.

 

I agree with you but a squaking noise when applying a brake application sounds different then an air leak on a brake application. Use soapy water to check all the valves as well.