diamond t 1 Posted March 20, 2014 Share Posted March 20, 2014 Hi All getting ready for new season and took truck out for a run round , started ok [after battery charge]and seamed to run good ,cannot remember about the brakes though . They work fine , but pedal goes right to the floor , and also it hisses all the time the pedal is pushed , and I cant remember if that was how it was last year . Any advice gladly received , or any other Diamond T owners comments on their braking system.:undecided: Thanks Diamond t 1 Quote Link to comment Share on other sites More sharing options...
Gordon_M Posted March 20, 2014 Share Posted March 20, 2014 Gauge pressure on dash while this is happening? Could be a stuck check valve somewhere or the pressure relief valve might be stuck open. It's been 20 years since I had to look at T brakes tho. Quote Link to comment Share on other sites More sharing options...
TooTallMike Posted March 20, 2014 Share Posted March 20, 2014 It could be a sticky foot valve. Is the hissing coming from under the cab floor? I'd suggest running the engine up and wedging the foot pedal down with a piece of timber so you can crawl under and see where the air is coming from. - MG Quote Link to comment Share on other sites More sharing options...
wwiitrucks Posted March 21, 2014 Share Posted March 21, 2014 If you have a air compressor hook it up to your truck not running to keep the system charged. listen for the leak,If no leak that is good. Use a board as Mike said to hold brake pedal down, Hunt for leaks. Are all the glad hand and drain valves closed ? The pedal will go to the floor with air brakes, You will not have a solid pedal like hydraulic brakes. The valve that the brake pedal is attached to is regulating valve 0 psi. to 100-120 psi. depending on what your governor is set at ,the farther you push on the pedal the more presser on the brake diaphragms. A common leak is the relay valve (between the rear axles). and diaphragms (made of rubber, old, hard,crumbly) Are all the valves on your truck the original type ? Just let us know where it leaks with the brake pedal OFF and ON. Jeff Quote Link to comment Share on other sites More sharing options...
42 chevy Posted March 21, 2014 Share Posted March 21, 2014 If the relay valve leaks with the pedal up it is the intake valve leaking in the relay valve, if it leaks with the pedal depressed, it is the diaphram. If the leak is in the brake acuation valve, at rest (meaning your foot is not pushing the pedal) check the exhaust valve. As Jeff stated there is no "feel" in the brake pedal. If it is leaking out of a glad hand conection check your 2, 2 way valves, they might be stuck in one position. John G Quote Link to comment Share on other sites More sharing options...
diamond t 1 Posted March 21, 2014 Author Share Posted March 21, 2014 Thanks for the advice , will have a look over the weekend when I get to the truck , From what I have read, it seems that the pedal going to the floor is normal . When the pedal is pushed I will have a look at the gauge on the dashboard and see what it does . There does not seem to be a leak without the pedal pressed , and when the pedal is pressed you hear the air as the brakes are applied , but this sound continues until the pedal is released . Sounds as though there maybe a diaphragm gone or a leak between the pedal valve and 1 or more chambers do You think. Thanks again Diamond t 1 Quote Link to comment Share on other sites More sharing options...
42 chevy Posted March 21, 2014 Share Posted March 21, 2014 If a brake chamber diaphragm has gone bad, it usually makes a loud hissing sound. When you get the system sorted, be very careful when applying the brakes, the tech manual says to apply the brakes gradually, if you do not, any passengers you have on board will be meeting the windshield unexpectedly. John G Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.