Air Leak or what?

[fortwayne]

I drive a 1999 FL-70 and have heard what I believe maybe some sort of air leak or something.

Here is what is happening.

When I sit and idle about every 1-1 1/2 minutes a loud release of air is discharged from under the truck.

Now I don't know if this is normal, since it does it in the same time span, if its some sort of safety device etc for the air tanks or whatever OR if I am failing to do something and that is what is triggering this constant issue.

**** - it bothers the heck out of me when I sleep and erks me off when I park beside someone that has the same thing going on....(at least it erked me when I was driving another truck that didn't do it.)

And yes I do believe it does it when I drive as well. Pressure for the airbrakes is fine is constant - no alarms, nothing to indicate a problem.

I really wish I knew more about trucks and repairs etc....

 

[stamp11127]

Either this is a joke or you have forgotten about the pressure release valve.
How often do you purge the water from your air tanks?

 

[fortwayne]

Either this is a joke or you have forgotten about the pressure release valve.
How often do you purge the water from your air tanks?

No funny man this is not a joke!

If there is a release valve on these older trucks I can not find it. There are two cords near the rear, which could be the release valves, but they are not your standard pull and release - they may have to be 'unscrewed.'

Like I said I am no mechanic but I do know about the release valves, maybe it is more about locating them on this ole' beast if nothing else - if that is the problem.

 

[Moot]

No funny man this is not a joke!

I'm just a van driver but I'd put money on beans for dinner or your air dryer is purging like it is suppose to.

 

[fortwayne]

thanks moot!

yea I have no clue on these older trucks, newer ones i reached underneath and there is the 'pully' or whatever the heck you wanna call it and you pull it and the thing does it's trick to release water out of the lines, etc etc - but the older ones like i said i don't know.

the whole air dryer thing makes a little more sense to me...

 

[fortwayne]

anyone else have other thoughts or suggestions on this matter?

thanks.....

 

[Moot]

thanks moot!

newer ones i reached underneath and there is the 'pully' or whatever the heck you wanna call it and you pull it and the thing does it's trick to release water out of the lines,
the whole air dryer thing makes a little more sense to me...

When you pull on the cable you are operating a spring loaded valve on the underside of the air tanks. On older trucks a pet**** valve was used to drain the tanks.

I'm sure what you are hearing is the air dryer purging. Every 1½ minutes seems excessive. Is your compressor running constantly? Or it could be the desiccant cartridge in the dryer needs service or replacing.

 

[bayouhotshot]

I have the same truck mine use to do it after the compressor shut off even if the truck was not running

I had to change the air regulator on the side of the moter (cold weather I think) now my air pressure is at 160 and the new regulator is staying open and the compressor wont shut off can you ajust them? And how?
Im not trying to spend anymore time outside than i have to

 

[Moot]

On older trucks a pet**** valve

That should read petćóćk valve. Silly censor.

 

[fastman_1]

Moots on the money, also back in my big truck days I would drain the air tanks completly once a week, to get all the water out.

 

[nightcreacher]

if your air dryer is doing the job,when you tried to drain your tanks,no water came out,if you still have condensation,your air dryer isnt doing the job.That pop he hears is the air dryers pop off valver.

 

[stamp11127]

Fortwayne, no insult intended. The wording of the thread is perfect for a leg pull.

Since the valves in your tanks have the lanyards I'd yank on them and see how much water comes out. Why have a lanyard on a valve that unscrews? I got in the habit of pulling them daily. I know it is overkill but what the heck it is a habit....

 

[bluejaybee]

I have the same truck mine use to do it after the compressor shut off even if the truck was not running

I had to change the air regulator on the side of the moter (cold weather I think) now my air pressure is at 160 and the new regulator is staying open and the compressor wont shut off can you ajust them? And how?
Im not trying to spend anymore time outside than i have to

Most air compressors have what is called a governor. It is in fact a regulator of sorts. Most are preset at factory and some are adjustable. I have never seen one set to allow more than 135 lbs. of pressure on a truck. There may be instances that it would be necessary for more pressure, but not on your basic truck. The governor in all cases I have seen, is mounted on the compressor itself. It is usually what your lines screw into. There should be a plastic (bullet shaped cone) cover on the side of the governor. Unscrew the cap and if there is a screw under it, it is adjustable. If no screw, you will have to replace the whole governor. I would set it to 125 lbs.

 

[bluejaybee]

I drive a 1999 FL-70 and have heard what I believe maybe some sort of air leak or something.

Here is what is happening.

When I sit and idle about every 1-1 1/2 minutes a loud release of air is discharged from under the truck.

Now I don't know if this is normal, since it does it in the same time span, if its some sort of safety device etc for the air tanks or whatever OR if I am failing to do something and that is what is triggering this constant issue.

**** - it bothers the heck out of me when I sleep and erks me off when I park beside someone that has the same thing going on....(at least it erked me when I was driving another truck that didn't do it.)

And yes I do believe it does it when I drive as well. Pressure for the airbrakes is fine is constant - no alarms, nothing to indicate a problem.

I really wish I knew more about trucks and repairs etc....

What you are hearing is the air dryer purging. But there must be a small leak somewhere if it does it that often. And it could be alot of things. But it should not pop off that often if you have a tight air system. Mine was caused by a defective air dryer cartridge. It had become full and let gunk build up around release valve on air dryer thus causing a small loss of air. Therefore, it set there and cycled and at the end of each cycle, air dryer would purge and you would hear the big hiss of air. Any air leak, big or small, will cause your air compressor to kick in and out. You should be able to see your air dropping on your gauge when it is doing this. Depending on your application, it should kick in (on) around 90 PSI and kick out (off) around 125 PSI.

 

[fortwayne]

I finally after digging through 11-years of grease and road soot found the plugs to drain the air tanks of any water, etc..............man was it dirty.......don't think the other guy every drained the thing!

I now believe that it is the dryer, but the whole system should be drained. The reason I say that is that I have three plugs near the rear axle. I pulled on all three and only two continue to give me any air after draining.......would that mean the other is just so full of junk and dirt etc that it is actually clogged?

Shouldn't I being hearing air out of all three after I drained them of water etc?
And why do I only see three?

Sorry to ask these stupid questions, but, we you ain't a mechanic you just ain't a mechanic...


Thanks for the pointers and any additional help you can provide. Bored at the Oak Grove-70 Petro Plaza!

 

[greg334]

Doesn't everyone know where their drains are?

Replace your cartridge, it is not hard to do.

It doesn become defective but it does lose the ability to pull moister out of the air in the system as time goes on. Maybe replacing it every 2 years is a good thing.

I would also just as a precaution pull the drain plugs to make sure there isn't any crap in the tanks.

 

[bluejaybee]

I now believe that it is the dryer, but the whole system should be drained. The reason I say that is that I have three plugs near the rear axle. I pulled on all three and only two continue to give me any air after draining.......would that mean the other is just so full of junk and dirt etc that it is actually clogged?

Shouldn't I being hearing air out of all three after I drained them of water etc?
And why do I only see three?

If you are referring to three seperate air tanks, yes, you should get air from each one when you pull on the drain valve cable. But, if it has been that long since it has been drained, I wouldn't be surprised if the drain valve itself isn't corroded inside the tank. You may need to replace it but I caution you to consider where you are and what you will do if you go to replace it and it breaks off in the tank. Like, do you have an extractor if it breaks off. All I have seen are made from brass and when deteriated they are very likely to twist off. Otherwise, they are no trouble to replace, if you determin that is why no air comes out of tank. I seriously doubt the whole tank is full of junk. And just a word to the wise. If you don't know when the air dryer cartridge was replaced, it might be a good idea to do that also. Especially if you see any traces of oil coming out when you drain tanks.

 

[fortwayne]

thanks bluejay.....yea we have a mechanic back at our docks in michigan so i will have him replace the cartridge.....I will also have him pull that plug and take a peak there as well....once again thanks!

 

[bluejaybee]

I guess I am a scardy cat, but I always think of what could happen if I try to do this or do that while on the road. While I carry a pretty good assortment of tools, it is not practical to carry enough for every scenario. My thinking while out on the road is, if it ain't broke, don't fix it. If I break down, then it is broke, and if I can fix it fine, but if something else breaks or gets damaged, at least I was already down. What I guess I am referring to is, don't put yourself out of service because you were trying to do a little maintenance.

 

[fortwayne]

Bluejay, you are right. I drained them and that is about all I can and will do at this point. Don't plan on unscrewing the drain just incase it did snap off then I am out of service....besides I haven't had any air pressure loss and the brankes have been working fine......like you said it is a maintenance issue and I will get it fixed when I return to Michigan...........at this point all it is to me is a maintenance issue that can be resolved back at the shop and its just annoying as heck to listen to when trying to sleep....thanks again.