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How do you find those air leaks?

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My 2007 Volvo 670 has a pretty good air leak and I don't know where to start looking. It will not hold any air overnight and drops pretty quickly to 100 psi while it is running. The compressor kicks in and the pressure comes back up to 140, the air dryer cycles like it should then it starts going back down again. I shut it down but don't hear anything. I have had air leaks since I bought this truck and the dealer I purchased it from replaced a valve on the drivers side frame close to the transmission and that took care of the leak pretty well at that time. Since then I have moved the axel and reconnected everything. I have sprayed the fittings on the new air bags and all of the lines that were disconnected but have no bubbles. I did connect the two air lines from the rear air bags together instead of capping each one separately. Other than that everything else is as it was. I have replaced both brake cans as well. I am at a loss for where to look. I would appreciate any help you all can give me. I don't like the rapid air loss especially while driving.

 

Thanks Quentin

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Don't forget to have a good listen around the air tanks. They do rust in between each other. I changed my tanks about two years ago in my 06.

 

Nigel

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Sometimes the "soapy water in a spray bottle" trick doesn't work....try using shaving cream on the are of a "suspect leak" and watch it for a minute or two and look for bubbles. As already mentioned look at tanks, seats , airbags, height control valves, D-2 air governor, turbo control valve, just to mention a few areas of known issues.
Sometimes a leak will come and go...I have a few of those. I have found some of my leaks had to have 125 psi on the system to reveal themselves.
Good luck and let us know what you find.

Scott

Edited by MrSeas

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This is what some of us have purchased and used. Mine got passed around at the national rally and seemed to work impressively. Expensive but worth the investment when you think what a shop would charge to hunt down and repair a leak.

 

http://www.amazon.com/Inficon-711-202-G1-Whisper-Ultrasonic-Detector/dp/B000TRJA8M/ref=sr_1_2?ie=UTF8&qid=1420686375&sr=8-2&keywords=ultrasonic+leak+detector

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If you have a shop style airline connector on the truck, and have access to an air compressor, use it to air the truck up without it running, Leave it hooked up so you have a continuous 125psi going to the truck. Search under the dash, the seat control valves, the airbags on the hitch, etc.

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On my antique, the most difficult to pinpoint air leak for me was a transmission range piston. Maybe the new fangled trucks don't have 'em, or they're way different. Just a thought.

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I have the ultrasonic leak detector and it does work pretty well. Just don't expect miracles. It will HELP you find them, but you still have to hunt them down. Anything significant will show up pretty fast,though. Just expect to crawl around a lot.

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I am not sure I have one of those testers in the budget but I sure can check all of the rest of the things mentioned. I do have shop air and will make myself a setup to connect it to the front air tank. I do hope that will help me locate the worst leaks. I have not changed the air bags on the cab but that is in the plans in the very near future since I am starting on the bed and they will be very difficult to do anything with after the bed is in place. I will check the front suspension bags as well. Even though the weather outside is miserable I have to continue on if I am going to have this truck ready to hit the road in by April. I have found out that the price of steel has gone up a bunch since the last time I purchased any and that may limit how far I go on the bed for this year since I am doing my own build. Lots more to do. Thanks for the input all is appreciated.

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After replacing the cab air bags, axle air bags, then the cab air leveling valve, axle air valve most rapid leaks were gone, I never heard any air leaks or found with soap, but as you stated better to replace the cab bags before the bed goes on.

As for the price of steel, I just ordered my bed steel yesterday at the tune of 5,700.00.

Broke the bank budget this month for truck repairs.

 

Roger

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My 2007 Volvo 670 has a pretty good air leak and I don't know where to start looking. It will not hold any air overnight and drops pretty quickly to 100 psi while it is running. The compressor kicks in and the pressure comes back up to 140, the air dryer cycles like it should then it starts going back down again. I shut it down but don't hear anything. I have had air leaks since I bought this truck and the dealer I purchased it from replaced a valve on the drivers side frame close to the transmission and that took care of the leak pretty well at that time. Since then I have moved the axel and reconnected everything. I have sprayed the fittings on the new air bags and all of the lines that were disconnected but have no bubbles. I did connect the two air lines from the rear air bags together instead of capping each one separately. Other than that everything else is as it was. I have replaced both brake cans as well. I am at a loss for where to look. I would appreciate any help you all can give me. I don't like the rapid air loss especially while driving.

 

Thanks Quentin

There are different components to your air system.

 

You can have a leak in the service line that you won't hear hissing unless someone is stepping on the pedal.

 

If you have a leak in the emergency line, this will only leak when the dash button is pushed in.

 

The thinks like the air bags and the air seat are also possible leak areas and those are not supposed to consume any air in a static condition. Your rear tractor air bags can be isolated bu flipping the dump valve.

 

Most all of the air systems leak a little, but as these get worse you need to track down the leaks and fix them otherwise you can get into real trouble.

 

With your rig parked on level ground and with the wheels chalked, release the parking brakes. Now go around to each wheel and listen. Wiggle the air lines and if the hissing gets worse there is the problem. If you don't hear air escaping then you can use some soapy water in the squirt bottle. Also check the glad hand seals and give a good listen to the dash area.

 

Next set the brakes and have someone step on the brake pedal. Again listen and wiggle the brake lines at each wheel and the glad hands.

 

Look at the air compressor also. The belt should be tight and the hoses should not be leaking. Often air leaks at compressor hosed can be seen by oily stains where it has been leaking.

 

Doing it this way you will find most major leaks.

 

Prior to driving you should do your leak down test.

 

THE "IN CAB" AIR BRAKE TEST

 

First thing to do is to break the test down into the different categories! You can do this easily

by using the Acronym L-A-B (Leaks, Alarms, Buttons)

 

 

Chock the wheels! if you have not yet! Some states will require the truck to be chocked BEFORE you even start the walk around

 

With the engine still running, check the air pressure. You are looking and or listening for the air systems governed cut out pressure to be reached. This happens when the air tank pressure reaches 100 psi -125 psi. When the "cut out pressure" is reached, you will hear the air compressor stop pumping air (sometimes hard to hear) or you will hear the air dryer exhaust air with a loud PSSSSHHHTTTT!!!! NOW you can start the air brake (L-A-B) test.

 

 

Turn off the engine and TURN THE KEY BACK ON!!

 

Why? Most trucks low air pressure warning buzzers will not work with the key off!!

 

The first required task in the L-A-B test is to check for LEAKS

 

Release ALL the brakes! Push in BOTH brake buttons! (Remember, the truck is chocked so don't panic) There WILL be an initial DROP in air pressure! This is normal and it?s basically the air leaving the tanks and going out to the rest of the system! After this initial drop, watch the air gauge and listen for any leaks.

 

?L? to test for LEAKS:

 

Push in and HOLD the brake pedal. Tell the examiner what your doing and he/she will be probably be asking you what you're looking for. just tell them that you are holding the brake pedal down for 1 minute and looking for an air loss of LESS THAN 4 psi in that minute. (straight trucks require LESS THAN 3psi).

 

Make sure you have some way of TIMING yourself!! and that you keep your foot on the brake for the WHOLE MINUTE. And move you to the next part of the test.

 

"A" NOW you will test for ALARMS

 

Firmly and pretty quickly pump or fan the brake pedal and watch the gauge again, at around 60 psi the low air alarm or buzzer and/or the warning light will come on.

 

If you forgot to turn the key on the alarms and warning lights will not work!

 

"B" The next task is to check the BUTTONS

 

AFTER acknowledging the ALARMS, Continue to Pump the brake pedal (SLOWER BUT MORE DELIBERATE) until BOTH of the Air supply buttons ?POP? out.

The buttons should "pop" about 30 psi.

 

After the buttons pop, you will need to start the engine and build air pressure.

 

There are TWO final tests for the brake system

 

Parking Brakes:

 

After you build the air pressure back to ?normal? range, The brakes are still set from the air brake test so all you need to do is put the truck in a low gear and attempt to pull forward. Use light pressure! Do not release the clutch fully, you could damage the drive train. A slight ?TUG? against the brakes is what you want.

 

Service brakes:

 

To test the service brakes, release ALL the brakes (while covering the foot brake of course) pull the truck into LOW gear, check to see that the area ahead is CLEAR and slowly get the truck moving forward S-L-O-W-L-Y. After you get the truck moving push in the clutch and apply the foot brake, the truck should stop without pulling to either side!. Some states will require you to remove your hands from the wheel for this test.

 

This video is pretty good at explaining the air brake system.

 

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^ Do you fail the test if you run over your chocks doing the last two tests?

 

:-)

 

When applying brake pressure to the service brake tests how much air pressure should you be applying to the system to check for pressure loss during your 3-4 minute time period?

Edited by GoldRush

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Guest Lostinaz

You'd have to look pretty hard to find a belt on an air compressor these days.

???

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We got our T2000 late in 2012, it held it's air like a champ. 20,000 miles later we were able to shake a few things up a little.

 

Found leaking around the shaft of rear suspension leveling valve, which got changed in the sand of that fine Quartzite event.

 

Next one was really hard to find, was the hydraulic looking hose running from the air compressor to the drier, but not the fittings,

it was leaking right thru the side of the braided hose all along it's length.

 

This last one has also been tough. Short of driving the beast into a pond and looking for bubbles, I tried everything. Soap/leak detector,

mechanics stethoscope, and Carl's ultrasonic detector at the national rally. Carl's little toy is the ticket, on a quiet non-windy day that

pup will hear kids blowing bubbles in their milk at 20 yards. This last leak, I hope, was so large soap wouldn't work, and was on top of

the compressor, not at a fitting but instead under and around a plate that contains what they call an "unloader valve". A $60 Bendix kit

and a couple of minutes under the hood now has us holding 50psi for more than a week again.

 

Keep after these leaks as it will help in the bonding with your baby, the grime that moves from her to you and your clothes makes her better.

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Anyone looking for leaks needs to find a 12 year old junior gearhead. Their hearing isn't degraded by time (or ear hair), and it's a great chance to spend some time with the next generation.

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There are different components to your air system.

 

You can have a leak in the service line that you won't hear hissing unless someone is stepping on the pedal.

 

If you have a leak in the emergency line, this will only leak when the dash button is pushed in.

 

The thinks like the air bags and the air seat are also possible leak areas and those are not supposed to consume any air in a static condition. Your rear tractor air bags can be isolated bu flipping the dump valve.

 

Most all of the air systems leak a little, but as these get worse you need to track down the leaks and fix them otherwise you can get into real trouble.

 

With your rig parked on level ground and with the wheels chalked, release the parking brakes. Now go around to each wheel and listen. Wiggle the air lines and if the hissing gets worse there is the problem. If you don't hear air escaping then you can use some soapy water in the squirt bottle. Also check the glad hand seals and give a good listen to the dash area.

 

Next set the brakes and have someone step on the brake pedal. Again listen and wiggle the brake lines at each wheel and the glad hands.

 

Look at the air compressor also. The belt should be tight and the hoses should not be leaking. Often air leaks at compressor hosed can be seen by oily stains where it has been leaking.

 

Doing it this way you will find most major leaks.

 

Prior to driving you should do your leak down test.

 

THE "IN CAB" AIR BRAKE TESTFirst thing to do is to break the test down into the different categories! You can do this easily [/size]by using the Acronym L-A-B (Leaks, Alarms, Buttons) [/size]Chock the wheels! if you have not yet! Some states will require the truck to be chocked BEFORE you even start the walk around [/size]With the engine still running, check the air pressure. You are looking and or listening for the air systems governed cut out pressure to be reached. This happens when the air tank pressure reaches 100 psi -125 psi. When the "cut out pressure" is reached, you will hear the air compressor stop pumping air [/size](sometimes hard to hear) or you will hear the air dryer exhaust air with a loud PSSSSHHHTTTT!!!! NOW you can start the air brake (L-A-B) test.[/size]Turn off the engine and [/size]TURN THE KEY BACK ON!!Why? Most trucks low air pressure warning buzzers will not work with the key off!! [/size]The first required task in the L-A-B test is to check for [/size]LEAKSRelease ALL the brakes! Push in BOTH brake buttons! (Remember, the truck is chocked so don't panic) There WILL be an initial DROP in air pressure! This is normal and it?s basically the air leaving the tanks and going out to the rest of the system! After this initial drop, watch the air gauge and listen for any leaks.[/size]?L? to test for LEAKS:Push in and HOLD the brake pedal. Tell the examiner what your doing and he/she will be probably be asking you what you're looking for. just tell them that you are holding the brake pedal down for 1 minute and looking for an air loss of LESS THAN 4 psi in that minute. (straight trucks require LESS THAN 3psi).[/size]Make sure you have some way of TIMING yourself!! and that you keep your foot on the brake for the WHOLE MINUTE. And move you to the next part of the test.[/size]"A" NOW you will test for ALARMSFirmly and pretty quickly pump or fan the brake pedal and watch the gauge again, at around 60 psi the low air alarm or buzzer and/or the warning light will come on.[/size]If you forgot to turn the key on the alarms and warning lights will not work! "B" The next task is to check the BUTTONS [/size]AFTER acknowledging the ALARMS, Continue to Pump the brake pedal (SLOWER BUT MORE DELIBERATE) until BOTH of the Air supply buttons ?POP? out.[/size]The buttons should "pop" about 30 psi. [/size]After the buttons pop, you will need to start the engine and build air pressure. [/size]There are TWO final tests for the brake system[/size]Parking Brakes: [/size]After you build the air pressure back to ?normal? range, The brakes are still set from the air brake test so all you need to do is put the truck in a low gear and attempt to pull forward. Use light pressure! [/size]Do not release the clutch fully, you could damage the drive train. A slight ?TUG? against the brakes is what you want. [/size]Service brakes:

 

To test the service brakes, release ALL the brakes (while covering the foot brake of course) pull the truck into LOW gear, check to see that the area ahead is CLEAR and slowly get the truck moving forward S-L-O-W-L-Y. After you get the truck moving push in the clutch and apply the foot brake, the truck should stop without pulling to either side!. [/size]Some states will require you to remove your hands from the wheel for this test.

 

This video is pretty good at explaining the air brake system.

 

 

The only thing I will add is on Volvos you have to start the motor for the alarms to go off. Most trucks you don't and the tester can get confused about that. Mine understood and went with it no problem.

 

Volvo does this as a convenience for drivers who have the key on when stopped and don't need to hear the alarms go off in the middle of the night.

 

JC

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One good tip I have seen is to use children's bubble blowing solution (or make your own) to exaggerate the bubble size of leaks making them easier to find or at least narrow your search

good luck,

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