HELP! PTO won't disengage...2000 Freightliner Century Class

Maybe the "mechanic" had valid reasons for changing all these items (I'm not there to see), but he honestly sounds more like a "trial & error parts changer", than a true mechanic. I never (emphasis on never) change any part unless I know that part to be faulty, worn beyond specs, or a cause of the problem. That is a golden rule for any good mechanic. Any monkey can be a parts changer and sooooner or later (after your $$ are exhausted) he'll hit on the right faulty part.

PTO troubleshooting is one of the simplest problems to solve, compared to other truck/engine/driveline problems.

 

New check valve to PTO? A check valve could be causing the problem, if he installed a check valve so air can engage the PTO, but not let the air out to release it, then bingo. I have never seen a check valve on a PTO.

 

Bingo is right!! (still baffled how I missed seeing that "neon sign" in her last post)
Yep, if that check valve is in the PTO air line... I believe you nailed it GrapeApe!
And if so, their mechanic would really be a first hand "accomplice" to the problem.

 

one more quation, electric (with clutch pedal switch) valve ore simple air valve?

 

Thanks for letting us know the status/outcome so far.
It's still a bit "troubling" for me, and maybe you too, as the "fix" doesn't appear to have an "ahaa" moment where anything definitively defective was found. Kinda just another "parts change".

The "check valve" you describe is really a pressure supply valve, and it is fine & correct to install at the supply tank port. But when you said "installed new check valve to PTO", as GrapeApe pointed out (and I agree with), there should be NO, zero, nada, check valve anywhere in the air line from the PTO selector (engage/disengage) air valve to the cylinder or PTO itself. If there's a check valve in that part of the line/system, that's a major problem.
It's ok to have the supply tank pressure protection valve, tho. It's actually a pressure valve, not a true check valve. It just prevents PTO engagement/operation if the supply pressure is too low (below 65 psi).

The fork we referred to does not shut off air (as you worded via the mechanic). It is simply a shift fork, which is attached to the inside of the PTO's air unit side cover. The air cylinder unit on the PTO case slides this fork back & forth (to engage pto & to disengage pto), according to your PTO air switch position. The ends of the fork rest inside the smooth groove of the slider unit, alongside the engage/disengage output gear.
You usually never see any pics of this fork, because once you take off the side cover (on cable or air shift), the fork comes off with the sidecover. Most pics of the PTO show just the PTO box with the sidecover and shift assembly already off.

Here is a pic of the Chelsea PTO fork (Item #55 in your Parker pdf, page 5):


I hope you can continue on troublefree, and the PTO ends up working fine. But was really expecting an "Ahaa" kinda fix. Good luck!

 

I agree with Baha...ck not proper gasket PTO 2 trans its easy 2 add 1 gasket drain into clean 5 gal. bucket pump back in after adding 1 gasket gear clearance a must 2 work

 

I have a feeling they already have it fixed since this thread is over a year old.