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Mack was building air to 150 PSI now it won’t go past 40 Psi


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We had a line break on this truck 2 weeks ago, we replaced it and it would stay at 130 PSI, yesterday it started building to 150PSI, we changed the governor it built to 50 PSI temporarily now no air. 
 

I was thinking there’s an obstruction. The mechanic has gone over everything and said he found no leaks or obstructions.
 

I’m going to head there to see if I can figure it out, I’m thinking the unloader valve was stuck closed now it’s stuck open?  Didn’t know if anyone else might have different ideas? 

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I would put my money on hard discharge pipe coming off the compressor..  They clog up with carbon...  PITA to replace.. unhook the far end of it and start the engine,  i bet flow will be low.  jojo

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  • 2 weeks later...
On 2/19/2024 at 8:08 AM, Kolehamilton said:

 

Sprayed WD40 into the compressor intake and blew air into it with a shop compressor. It’s building now. 

Good job! The unloader on these used to stick common issue! You can buy a head replacement kit for the single cyl compressor!

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