M1078 air leak behind grill

Baja2dakar · Jun 8, 2014

When driving air began leaking from a fitting above and behind the grill. All similar fittings have lines attached. As you see from the photo there is nothing there. I'm wondering if some sort of pressure valve should be there and fell off or is there something inside that needs servicing. Any ideas?

DSD277 · Jun 8, 2014

I can't be sure from the pic but that may be the air vent for the CTIS. Does it vent only while the CTIS is going though it's system check?
I was told from an ex-S&S employee that they would screw with "newbies" by blocking the vent during the system check and have the controller go into fault mode, and have the newbie freak out. :lol:

jtron79 · Jun 11, 2014

that's the vent end. it's connected to air brakes and CTIS, did your pressure gauge start dropping or did you just hear the air?

Baja2dakar · Jun 12, 2014

jtron79 said:
that's the vent end. it's connected to air brakes and CTIS, did your pressure gauge start dropping or did you just hear the air?

Everything was fine, went over a speed bump and then the next time I applied brakes, I heard the air. Later inspection found that it does not leak when the parking brake is applied, but does leaks slowly while driving but lot more when the brake is applied. The gauge is running 90-100 psi while driving but obviously drops when brakes are applied multiple times, to the point the low pressure alarm will come on in city stop and go driving.

jtron79 · Jun 12, 2014

It is normal to hear air venting out of it when you pull the parking brake because it is actually venting the pressure away from the spring brakes, and that is where the air will vent to. It would be a good idea to check both your trailer supply valve and parking valve as my trailer valve was bad from sitting. It could be the brake application valve is venting when it shouldn't, best test there would be to apply brakes and have someone listen at vent, it should only vent as you let up on the pedal from an application and not during. if your parking or trailer valves are bad you may get air at the gladhands as well.

Baja2dakar · Jun 12, 2014

jtron79 said:
It is normal to hear air venting out of it when you pull the parking brake because it is actually venting the pressure away from the spring brakes, and that is where the air will vent to. It would be a good idea to check both your trailer supply valve and parking valve as my trailer valve was bad from sitting. It could be the brake application valve is venting when it shouldn't, best test there would be to apply brakes and have someone listen at vent, it should only vent as you let up on the pedal from an application and not during. if your parking or trailer valves are bad you may get air at the gladhands as well.

It is leaking out of the vent during normal driving then a lot more when pressing on the brake pedal. I will check the brake application valve. No leaks when the parking brake is applied. Thanks.

auctionaddict · Jun 23, 2014

My LMTV did the same thing, It was the brake pedal air diaphragm.
There is a vent line on the brake pedal assy. under the dash.
Pull the hose off and you will hear the leaking, Its routed behind the grille
I took mine apart and cleaned it.

Overdrive · Apr 22, 2016

Resurrecting a VERY old thread...

Just FYI this is the exhaust port for both the park/trailer and the brake pedal valves (when they release). The connections are made just behind the heater.

These are the only two things connected to this fitting and it is NOT a one way valve just open to elements all the way back up to the park/trailer valves and brake pedal valve. So don't spray water up there!

OD

scottmandu · Apr 22, 2016

If your trailer/parking brake valve leaks air can exit that orifice.

rjoffrion · May 9, 2016

Ok I have a truck leaking out there when I push the parking brake button in. also when I step on the brake pedal it exhaust air through the parking brake button assembly. I have cleaned and or replaced all the valves I can find. it is a M1079A1 van body. any help would be great..

Suprman · May 9, 2016

If air is venting around the control knob shaft on the parking brake valve I would start by replacing that valve. You may get a slight puff when operating the control but air should never vent out from inside the valve body along the shaft. The TM has follow me flow charts for air leak issues. As long as the lines are connected correctly the TM troubleshooting works pretty well. If someone switched a line or two around then you may end up going in circles though.
Will

coachgeo · May 10, 2016

Suprman said:
If air is venting around the control knob shaft on the parking brake valve I would start by replacing that valve. You may get a slight puff when operating the control but air should never vent out from inside the valve body along the shaft. The TM has follow me flow charts for air leak issues. As long as the lines are connected correctly the TM troubleshooting works pretty well. If someone switched a line or two around then you may end up going in circles though.
Will

Guess we need a pic in here to refer too since it's been mentioned several times that airline swapping happens and that the TM does not show clear picture/drawing of proper locations. Superman or anyone else would you please consider shooting and maybe labeling a pic to help everyone out? Or a drawing? I'd shoot a pic for everyone myself but my rig is 150ish miles away.

JD4044M · Aug 3, 2021

Darn My truck just started this??? Went for a 30 mile drive after putting the old Speedometer back in and it now works right. The new Alternator solved that problem when the voltage was right. Was talking to a guy on the road while truck was running and my air buzzer came on idling? Only had 1/4 mile to get back home. Pulled in parked the truck and heard air leaking even with bad hearing!! Found it before it quit. It was a 3/8" Air Hose Drivers Side right at the frame and fan blade. It was worn thru paper thin and blew thru!! So I cut the bad spot out and used a Air Hose Compression Fitting to splice the hose back up. Easy fix started truck and air went up fast and the pump shut off, cab lifted ect.

Shut off the truck and dam air is now coming out the hole in the picture above in the post. Venting for some reason and just started sitting there turned off? Nothing I seem to do at the dash or brake pedal stops this leak. Have not went out to see if I have any air left but will do right now and see which tank is empty. I replaced both Dash Push/Pull Air Controls with new ones and a air valve near the steering up on that side wall to stop the Emergency Brake Glad hand air leak once. What would be causing air to come out that drain like hole in the center of the dash. I can plug it with my finger and the air just come out above it. Can't see above it to tell. Man I hope I don't have to pull my dash apart to fix this!

Check all 3 tanks pretty even but low around 60-70 PSI what is interesting is if I watch the Cab Air Bags they lift about 1/4" then go back down while the truck is shut off? Just lifts a little and settles a little. My Tire Air System also started working again and if I remember right the Hwy is 55-58 lbs and I am at 62 PSI by my air hose. They never seem to leak or change over time I do check. Did look at the Heater Dash might be able to get in from the here

un/bolting a cover to look?

Man for 26 years it sure is nice and clean up there including the radiator fins!

chucky · Aug 3, 2021

JD4044M said:
Darn My truck just started this??? Went for a 30 mile drive after putting the old Speedometer back in and it now works right. The new Alternator solved that problem when the voltage was right. Was talking to a guy on the road while truck was running and my air buzzer came on idling? Only had 1/4 mile to get back home. Pulled in parked the truck and heard air leaking even with bad hearing!! Found it before it quit. It was a 3/8" Air Hose Drivers Side right at the frame and fan blade. It was worn thru paper thin and blew thru!! So I cut the bad spot out and used a Air Hose Compression Fitting to splice the hose back up. Easy fix started truck and air went up fast and the pump shut off, cab lifted ect.

Shut off the truck and dam air is now coming out the hole in the picture above in the post. Venting for some reason and just started sitting there turned off? Nothing I seem to do at the dash or brake pedal stops this leak. Have not went out to see if I have any air left but will do right now and see which tank is empty. I replaced both Dash Push/Pull Air Controls with new ones and a air valve near the steering up on that side wall to stop the Emergency Brake Glad hand air leak once. What would be causing air to come out that drain like hole in the center of the dash. I can plug it with my finger and the air just come out above it. Can't see above it to tell. Man I hope I don't have to pull my dash apart to fix this!
[/QUO My truck does that in the winter only at the brake release valves and i just keep pushing them in and release them a few time then it stops but i thought maybe it had some trash in the valve or ice maybe

JD4044M · Aug 3, 2021

Report so far? Checked all 3 tanks pretty even but low around 60-70 PSI what is interesting is if I watch the Cab Air Bags they lift about 1/4" then go back down while the truck is shut off? Just lifts a little and settles a little. My Tire Air System also started working again and if I remember right the Hwy is 55-58 lbs and I am at 62 PSI by my air hose. They never seem to leak or change over time I do check. Did look at the Heater Dash might be able to get in from there?

JD4044M · Aug 3, 2021

NOPE took the cover off the heater and controls and I stopped there. Bet there is nothing back there except 2 hoses? Had to put it together a wildfire broke out near us now out. Least I can drive it still the leak is not that bad and the compressor can keep ahead of it. Thinking this has to do with the CTIS venting all the time? Push the brake pedal dose not stop and the Brakes vent thru there also at the same time pushing the pedal. Seems to stop leaking at 60-90 PSI not sure just can't hear it and the tanks all 3 have enough air still that should make noise??? Need to figure if the CTIS Control is under the fuse panel foot kick area not behind the heater? My CTIS Control works off and on for no reason at all just glad my tires never loose air just checked!

Ronmar · Aug 3, 2021

That port has nothing to do with CTIS.

That is where the air from the treadle and park/trailer valves vent when you release the park/trailer air to set the park brakes, and when you release/let-off the brake pedal.

There is a hose on the treadle that runs into the center dash, that is the treadle vent line To that port. You can disconnect it from the treaddle and see if any air is coming out the port on the treaddle where the line connects. Leaking air there means it is the treadle, no leak means it is coming from the park or trailer valve. Since y0u just replaced those recently, it is most likely the treadle which will need to be overhauled or replaced…

JD4044M · Aug 3, 2021

I hope the Treadle Valve is not to much of a job to do? I will have to look that part up. Darn fires keep popping up here can't be down long fixing it. I will do a search on this part and see what it looks like at least. Thanks it is a start!

Mullaney · Aug 3, 2021

JD4044M said:
I hope the Treadle Valve is not to much of a job to do? I will have to look that part up. Darn fires keep popping up here can't be down long fixing it. I will do a search on this part and see what it looks like at least. Thanks it is a start!

.
Guessing you have your water tank loaded if you need it...?

You know about firefighting from past experience. What about the grass?
Do you need to be running the bushhog on the field down below your place?

JD4044M · Aug 3, 2021

Mullaney said:
.
Guessing you have your water tank loaded if you need it...?

You know about firefighting from past experience. What about the grass?
Do you need to be running the bushhog on the field down below your place?

Were pretty mowed they have had 4-5 new fires in the last hour with the lightning and high 50 MPH winds?? Has calmed down a lot no fires within 5 miles or so right now. It RAINED in the storm just enough to make spots. I stood out and watched for ground strikes and nearby starts. Do this every storm till it is over.

We got a couple big ones going on not that far away! About 100,000 acres plus total around us so it is smokey real bad!! Our VFD is on a fire right now from lightning in the trees. Guess the strike found a clump not burned good from last year. Just heard 5-6 fires on a hillside. The guys are jumping!

M1078 air leak behind grill

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