Draining Airtanks

johnnyw20

I recently brought a man 8.163 horse lorry and just passed the rigid test. There was question on the test about draining airtanks which I realise I dont have a clue how to.

Can anyone please let me know how to drain the airtanks on the lorry as I dont want to run into problems.

Thanks

Solnskaya

Open the drain bung on the bottom of the air-resevoirs? With the yoke turned off. Water builds up in the tanks, it rusts out and fecks up the braking system, you need to drain it off, etc etc.

johnnyw20

This is what is at the bottom of the tank. How do I open it?

Solnskaya

With a jar of Hellmans, or else a spanner, rightey tightey, leftey loosey. On some that pokey yoke sticking out of the nut can be backed off using a tommy bar through the hole until you get a flow coming out, much like bleeding a radiator.:) Personally, if it was mine, i'd whip off the big nut to allow the crud to come out better, the bleeder in the middle has a tiny hole and will probably be blocked solid anyway. When you have the drain plug off, give it a rub with a wire brush and put some copper grease on the threads to stop it siezing in future. Also poke a wire through all of its orifices to make future drainages less tiresome. A blast of compressor friendly lubricant up into the tank when the bung is off would also do more good than harm. A quick running of the engine with the drain bung out may also cause the better expulsion of a smattering of crud, but dont over do that as the compressor wont really like it for more than a minute or two. That washer also looks shagged, no doubt opening it will finish it off, so have a new copper washer to hand for when you replace the bung to help get a good seal. Also, when all back together happily, give the truck a bit longer to build pressure before setting off, just in case.

johnnyw20

Thanks very much for the reply. Much appreciated

Jim from Cork

If/when that bleeder valve is free:
You will often see those valves will a thin wire cable fitted and connected to a part of the chassis where it is more easily accessible. Then rather than having to bend down to access the valve it can be done easily from the side of the vehicle (hence the hole in the stem of the valve). You can also get an "auto" drain valve.
Your truck has an air dryer fitted to decrease the amount of moisture in the system. There is a filter on this unit that needs to be changed regularly, usually at oil change/service time. I'd read the maintenance section of the manual for further info.
There is layman info here:
http://www.lowestpricetrafficschool.com/handbooks/cdl/en/5/1
http://auto.howstuffworks.com/auto-parts/brakes/brake-types/air-brake3.htm

Slidey

There is no way I would touch that bung unless it is blocked.

With the air up on the truck use a spanner or something to push the valve to one side. You should get a blast of air and some water and maybe some gunk.

Then tie a bit of wire to the valve and run it out to somewhere accessable and give them a quick blast each morning before heading off.

Taking that bung could potentially open a can of worms for yourself.

As was also suggested, make sure and change the air drier filter on the truck when doing a service. These are designed to take the moisture out of the warm air coming from the comppresor by using desiccate. The problem is that they become useless when oil gets into them as can happen over time

911s

Solnskaya wrote: »

With a jar of Hellmans, or else a spanner, rightey tightey, leftey loosey. On some that pokey yoke sticking out of the nut can be backed off using a tommy bar through the hole until you get a flow coming out, much like bleeding a radiator.:) Personally, if it was mine, i'd whip off the big nut to allow the crud to come out better, the bleeder in the middle has a tiny hole and will probably be blocked solid anyway. When you have the drain plug off, give it a rub with a wire brush and put some copper grease on the threads to stop it siezing in future. Also poke a wire through all of its orifices to make future drainages less tiresome. A blast of compressor friendly lubricant up into the tank when the bung is off would also do more good than harm. A quick running of the engine with the drain bung out may also cause the better expulsion of a smattering of crud, but dont over do that as the compressor wont really like it for more than a minute or two. That washer also looks shagged, no doubt opening it will finish it off, so have a new copper washer to hand for when you replace the bung to help get a good seal. Also, when all back together happily, give the truck a bit longer to build pressure before setting off, just in case.

This sounds a bit complicated and may confuse the original poster. In the picture shown, the small protruding nipple just needs to be moved sideways to release the trapped water. The small hole in the nipple would have had a wire through it connected to an easly accessable location beside the air tank. Best do this task in the morning after water has had a chance to settle at bottom of tank overnight.

Solnskaya

911s wrote: »

This sounds a bit complicated and may confuse the original poster. In the picture shown, the small protruding nipple just needs to be moved sideways to release the trapped water. The small hole in the nipple would have had a wire through it connected to an easly accessable location beside the air tank. Best do this task in the morning after water has had a chance to settle at bottom of tank overnight.

In theory, but on most of the yokes that have not been drained regularily/for a fair while, the drain is blocked solid with crud and gunk- most of the call-outs to shunters etc are because the tanks are waterlogged and cant be drained due to clogged drain spigots. If the bung is removed and cleaned properly, lubed and replaced, no worms or cans need to be harmed. Around the transport yards we service I see an awful lot of tractor units getting expensive call-outs from mobile mechanics because the tanks are never properly drained and the spigots are never removed and cleaned properly. And an awful lot of air-dryers are solid/leaking as well due to never being looked at. Anyway, where were ye lot yesterday? Ye should know it's not safe to leave me here alone manning the advice desk, anything could happen:-)

doctorchopper

If you do decide the take the plug out, just be careful poking around in there with a rod, my father did something similar with a large air compressor tank, took the drain plug out, took a rod to poke up through the rusty crap, but there was still a lot of pressure in the tank (even though the gauge read 0) and one he broke the rust free it shot out of the drain like a shotgun blast and the rust embedded in his hand, had to get surgery to remove most of the particles but they had to leave some in.

johnnyw20

I can push the nipple in and air gushes out. Do I keep doing that until the tank runs out of air?

Hermy

johnnyw20 wrote: »

I can push the nipple in and air gushes out. Do I keep doing that until the tank runs out of air?

That's exactly what I would do.

Slidey

johnnyw20 wrote: »

I can push the nipple in and air gushes out. Do I keep doing that until the tank runs out of air?

Nah, there is no need to drain the tanks, once the air comes clean and there is no gunk or water it will be good enough

Hermy

Slidey wrote: »

...once the air comes clean...

+1