air compressor slow to build air

Discussion in 'Trucks [ Eighteen Wheelers ]' started by heavyhaulerss, Apr 23, 2010.

  1. heavyhaulerss

    heavyhaulerss Road Train Member

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    I noticed my air compressor had a good size leak on top of it, where the 4 1/2" bolts & 1- 9/16 bolt hold down a small top plate. I took the plate off & put new gasket on. no leaks, but now my air pressure gets to about 90-100 & then takes 20 30 min to get to 120 the cut out pressure I have govenor set to. before it used to get to 120 fairly quick. I did not touch the springs or the other things that wer in the holes. just cleaned & replaced gasket. took Nothing out. dont know why my pressure is extremely slow to build now. especially after it gets about 90p.s.i. it sorta stays right there. I had to do something cause it just changed wihtin 30 min, as long as it ook me to change gasket & try out. HELP!!:biggrin_2552:
     
  2. heavyhaulerss

    heavyhaulerss Road Train Member

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    I have a ser 60 det with the t.f 550 bendix compressor
     
  3. Longhood379

    Longhood379 Medium Load Member

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    My guess would be that you got a piece of gasket stuck in the intake valve , the first thing I would try is take the outlet line off and see if the free flow of air would disslodge it (if that is the problem):biggrin_25515:
     
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  4. speedyc-16

    speedyc-16 Light Load Member

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    Check the air govener (d-2valve) maybe some junk got in there?
     
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  5. lovesthedrive

    lovesthedrive The Confuzeled

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    Check the torque of the bolts. Also if the bolts are like Chevy they are only to be used once. Otherwise most mechanics know that after a first 20 hour rebuild to retorque head bolts as the gasket compresses the torque loosens.
     
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  6. JohnP3

    JohnP3 Road Train Member

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    With the air preasure low remove the hose that goes to the unloaders, or if the governor is mounted there unbolt it. see if the build rate is better do it at 1200 RPM. put you finger over the outlet port and feel when it starts to pass air. That is the cut out preasure. If you still get slow air build up try removing the unloaders, and see if they are free. Clean the bores with a bright pad and blow out the bores then install a new unloader kit. If the governor and unloaders are OK then you could have a bad valve. Put shop air into the discharge hose and see if you get blow by into the crank case when the compressor is unloaded. That would mean you have a leaking valve, and the head has to come off to the clean, the valves and inspect them. You need a special tool sometimes to remove the valve set up. Just a thought!
     
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  7. heavyhaulerss

    heavyhaulerss Road Train Member

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    I think I have it fixed. what is the cut in pressure supposed to be? mine cuts out at 120 p.s.i. hovers mostly at 100 p.s.i & when it gets about 90 p.s.i it tips back toward 100-120 p.s.i. 90 seems to be the min pressure before the compressor kicks in. does this sound right? the num 1 gauge always shows 10-15 lbs less than the num 2 tank gauge.
     
  8. lastgoodusername

    lastgoodusername Medium Load Member

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    if my memory ain't making a liar out of me, mine starts at around the 90 mark as well. both tanks should go to your cutoff pressure (120). gauges correct?
     
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  9. JohnP3

    JohnP3 Road Train Member

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    Actually now a lot of localities want cut out preasure set to 100 lds 105 lds area but yes you are correct. If you anything other than a Ford, then the build time for a properly working air system should be, alow the system to go to cut out preasure, bleed off to 50 lbs, with the motor at 1200 rpm it should take 1 minute 50 seconds to build to 120 lbs. If it is lower than that then there is a problem.
     
  10. lovesthedrive

    lovesthedrive The Confuzeled

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    90 psi is a fair setting on the recover point. During training we were told if it takes longer than 3 mins to recover from 50 psi, or 5 mins from a cold (empty) reservoir that it should be a concern.

    Not sure about why your guages are showing different pressures. They should be the same. Only time you will see a difference is when your charging the trailer tank.
     
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