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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2662
Experience:  Journeyman TechnicianWorked on small to large engines for 30 yearsGas,LP,Diesel
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I am losing air pressure on my brakes, it has becoming worse

Customer Question

I am losing air pressure on my brakes, it has becoming worse to the point of not moving
until I build the pressure up. I have an Iveco E17 tipper 7.5 tonne. I will be taking it to the
Maintenance company who checks it every 12 weeks and I only picked it up yesterday and it passed it's brake test. When finally getting back to my yard I release the air pressure from
the air tanks and water came out first for the first 5-10 seconds, but still the air pressure
Wouldn't build up very fast. I was told by a friend it could be the brake filter. Do you have any ideas.
Submitted: 4 years ago.
Category: Medium and Heavy Trucks
Expert:  spankyjr1 replied 4 years ago.
Hi and Welcome Thank You for your question

Sorry for long delay

First thing is the air tanks should be drained daily they say but once a week is sufficient if the air drier is working correctly.

Whoever is doing the maintenance is not doing a good job because draining air tanks is part of the service.
5-10 seconds is about normal for a month of not draining it's from heating and cooling of compressed air and normal condensation.

Yes the air drier may need a new filter but let's check everything.

Start by draining tanks,then start engine and raise rpm to 1500 and time how long it takes for air drier to purge.
Should be under two min.
Next shut truck off and look for a drop in air pressure should be none.
Fix any leaks.

Next release brakes and check for air pressure drop should be about 10lbs and stop dropping.
If it's dropping check brake chambers for leaks and replace as needed.

Next have someone hold brakes down while park brake is released and check for leaks,repair any leaks.

Let me know the results and we can go from here.
Also what psi does it stop building air?

One other thing to check is while it's building air feel around hose from air compressor going to drier and spray with soapy water to check for leaks.
A common problem is a leak in this line and causes slow air build up times.

I'm usually on line from 6am - 6 pm US central time.

Talk later

Customer: replied 4 years ago.
hi there , thanks for the reply, I have checked for leaks, there is none,
Sprayed soapy water around the chambers, still no leaks. We have air
Coming out the compressed as we checked it going to the drier. The air pressure now will only get to 8 and that is as far as it will go up, so tomorrow
I will be buying an air drier I am hoping that will do the trick or do you have any further suggestions.
Expert:  spankyjr1 replied 4 years ago.

Hey Jason,
You can try by passing drier and run compressor line directly into tank, that will tell you if it's the drier or the air compressor.

Also at air compressor there should be a small air line, take that off and make sure no air pressure is coming out line.
That tells the compressor to stop pumping.

So you either have a bad compressor,drier,or governor.

If you have modal number of drier I could try and look up.


Better yet take an hook up shop air directly to air compressor discharge line and see if it builds air, if it does you need a air compressor if it does not you need a drier.


Let me know if you have any problems