RD6michigan Posted January 19, 2022 Share Posted January 19, 2022 Hey guys, I have an 2001 Rd 688. Started it up today and I'm only building about 90 psi on the guage, but the low air buzzer isn't building any pressure at all. The green needle on the guage reads about 90psi. The orange needle reads 0 psi and obviously the buzzer is going off. I'm in Michigan, could it be frozen? Where do I start. I normally would call my buddy, but unfortunately Covid took him way to soon...... Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/ Share on other sites More sharing options...
67RModel Posted January 19, 2022 Share Posted January 19, 2022 The orange needle is for the secondary air system. Usually the low pressure indicator (buzzer) is tapped of the secondary system supply tank. There is a one way check valve at the inlet of the both primary and secondary tanks to prevent supply air coming from the compressor from flowing back into the compressor and/or air dryer and/or wet tank. It sounds like the check valve at the secondary tank is stuck or failed. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487406 Share on other sites More sharing options...
RD6michigan Posted January 19, 2022 Author Share Posted January 19, 2022 67 RModel, I will check that out today. Thanks. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487407 Share on other sites More sharing options...
67RModel Posted January 19, 2022 Share Posted January 19, 2022 Or maybe there is break or leak in the line feeding the secondary system supply tank. It may be hard to hear or unnoticeable with the engine running. Look for the simple stuff first. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487408 Share on other sites More sharing options...
RD6michigan Posted January 19, 2022 Author Share Posted January 19, 2022 Yes, I put it in the shop yesterday so it would defrost. I'm going to check it out after lunch. I just needed some pointers to start with. Thanks. I will update. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487409 Share on other sites More sharing options...
Onyx610 Posted January 19, 2022 Share Posted January 19, 2022 Sometimes the check valve will have a metal bracket around it and it says “check valve” or it’s a large elbow fitting with an arrow on it. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487413 Share on other sites More sharing options...
RD6michigan Posted January 20, 2022 Author Share Posted January 20, 2022 So figured it out yesterday. The outcome is I better start draining my tanks more often. Rookie mistake I guess. The secondary tank had an enormous amount of water in it after it unfroze. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487482 Share on other sites More sharing options...
Onyx610 Posted January 20, 2022 Share Posted January 20, 2022 That will do it, maybe replace the dryer cartridge too. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487483 Share on other sites More sharing options...
fjh Posted January 20, 2022 Share Posted January 20, 2022 26 minutes ago, Onyx610 said: That will do it, maybe replace the dryer cartridge too. Good call Ony ! This comment applys To the newer vehicle's specially! The magic transmissions and after treatment crap needs dri air to operate correctly We see more failures to the 7th injector dowser modules attributed to water than almost any other failure on the after treatment setup ! and the stuff aint cheep! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487486 Share on other sites More sharing options...
RD6michigan Posted January 26, 2022 Author Share Posted January 26, 2022 On 1/20/2022 at 9:58 AM, Onyx610 said: That will do it, maybe replace the dryer cartridge too. Where would that be located on the truck? Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487936 Share on other sites More sharing options...
Onyx610 Posted January 26, 2022 Share Posted January 26, 2022 Let the truck build air pressure and stand outside of the truck and look to see where the air purges at. That’s where your air dryer is at and the cartridge is on top of it. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487947 Share on other sites More sharing options...
Onyx610 Posted January 26, 2022 Share Posted January 26, 2022 Let us know if you can’t find it. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487955 Share on other sites More sharing options...
Onyx610 Posted January 26, 2022 Share Posted January 26, 2022 Also if you get one, ask for the purge valve too. It’s held in by a snap ring on the bottom. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-487956 Share on other sites More sharing options...
RD6michigan Posted February 24, 2022 Author Share Posted February 24, 2022 I ended up replacing the complete air dryer. Quote Link to comment https://www.bigmacktrucks.com/topic/69083-air-pressure-problems/#findComment-490176 Share on other sites More sharing options...
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