2007 Camelot 40' PDQ Slow to Build Air Pressure

[chip4872]

My 2007 Camelot 40' PDQ is slow to build air pressure on startup when tanks have drained to zero pressure.  Once the tanks reach 40 psi, they fill normally, and air systems seem to operate as they should. 

I'm mostly ignorant about the air system in this coach, so would appreciate any pointers as to where to look.

I do have a new park brake valve that I need to install since mine has a slow leak, but I'm not sure that is related.

Thanks for any pointers.

[Mocephus]

Hi Chip,

I recently did a brake system check with the help of Frank and Tom, our site Administrators. They provided the comprehensive brake system checks cited below.

Not sure how long it is taking your system to build, but the Compressor Build-up Test below will guide you on what is acceptable. 
 

Motorhome Air Brake Pre-Trip Check Step 1 – Secure Motorhome
1) IMPORTANT - Chock rear wheels.
2) Visually inspect air brake components.
3) Start engine. Monitor air pressure. At >100 psi (690 kpa), shut off engine.
4) Retract leveling jacks and then retract all slides (follow owner’s manual for correct order).
Step 2 – Park Control Valve (Park Brakes)
With engine shut down and key in “Run” position.
5) Push in Park Control Valve to release parking brake.
6) Open air system drains (should be 2 or 3) to bleed off air.
7) Monitor air pressure.
a. Confirm that low air pressure warning activates at ~ 60 psi (414 kpa).
b. Confirm that Park Control Valve pops out at 20 – 40 psi (138 – 311 kpa).
😎 Shut drains.
Step 3 – Supply Circuit
You will need a watch or timer for this step.
9) Start engine and run at fast idle (1200 – 1500 rpm).
a. On some coaches, turn on cruise control and then push set button.
10) Perform Compressor Build-up Test.
a. When pressure reaches 50 psi (345 kpa), mark time.
b. Confirm low air warning shuts off (resets) at 60 psi (414 kpa).
c. When pressure reaches 90 psi (621 kpa), mark the time.
d. Time between 10a and 10c must be less than 3 minutes.
11) Confirm governor cut-out and cut-in pressure.
a. Build up air pressure to system maximum.
b. Pressure should hold at 120 – 135 psi (828 – 931 kpa). You should hear a brief release of air that signifies the governor has stopped building air. Note/record pressure.
c. Pump service brakes to reduce system air pressure.
d. Pressure should fall by 15 – 25 psi (103 – 172 kpa) BELOW cut-out pressure observed in step 11b before starting to increase. Note: check owner’s manual for normal range if actual values differ from above standards.
Step 4 – Air System Leaks
12) Push in park control valve (release park brake).
13) Turn off engine. Note/record pressure.
14) Depress and firmly hold brake pedal down for 2 minutes.
a. Confirm that air pressure does not drop more than 4 psi (28 kpa). 15) Release brake pedal and pull park control valve to apply park brakes.
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Motorhome Air Brake Pre-Trip Check Step 5 – Service Brake Response
16) Start engine. Ensure air system pressure is within normal operating range.
17) Release park brake.
18) Set automatic slack adjusters.
a. Step hard on brake pedal and depress fully, then release.
b. Repeat 3 – 4 times to ensure slack adjusters are properly adjusted.
19) Remove wheel chocks.
20) Perform brake response test.
a. Depress and hold down brake pedal.
b. Put motorhome in gear.
c. With brake pedal depressed, push accelerator pedal to ensure motorhome does not move forward.
d. Release accelerator and pull park control valve to engage park brake.
e. Push accelerator pedal to ensure motorhome does not move forward.
f. Release accelerator and put motorhome in neutral.
21) Shut off engine. Do not operate motorhome if one or more of the following are true:  Park control valve did not pop out at 20 – 45 psi (138 – 311 kpa).
 It took longer than 3 minutes to build up pressure from 50 to 90 psi (345 to 621 kpa).  Governor cut-in and/or cut-out pressure was out of allowed range.
 System leakage is greater than 4 psi (28 kpa) in 2 minutes.
 Motorhome failed the brake response test (service brake or park brake).

 

[Frank Bergamo]

I would start with the air governor. It looks like this, https://www.napaonline.com/en/p/TWDH284358?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Brakes&campaign_id=8659198719&adgroup_id=106304766654&adtype=pla&gclid=CjwKCAjw-b-kBhB-EiwA4fvKrNmr8CCVhX96BAaKB4vEpsldnF3tSOAkP-bPnP2g0Z5mKxyOwx4M7xoCGbcQAvD_BwE&gclsrc=aw.ds&. 
Hope this helps.

[Bruce S]

I would like to add a qualifying statement to the initial pressuring test.  If you have dumped your air bag suspension it will of course take longer to get up to the 90 psi point.  Our bags are not fully pressurized until about 80psi.  Then again I'm told there are low pressure bags available for some applications that are fully charged at about 50 psi.   If the test above assumes the bags are ready for travel then of course the time factor would not be affected. 

[TommyL]

Chip ,had similar problem 08 camelot, below 40 psi slow to no air up . Above 40 air up normal, we were losing air faster than I liked. Fixed several small leaks, replaced governor, no luck. Bypassed air drier with pipe fittings we had in stock, bingo, aired up normally, held pressure. Replaced with new air drier and filter,all good. R&R auxiliary air drain, now only runs once every couple days. I spray slide seal conditioner in intake of auxiliary air once a year, goes from noisy to quieter. 15 years old still going strong.

Tommy 08 camelot tag isl 400

[chip4872]

Thanks, all...

I have to go to NAPA tomorrow for a pickup, and will try to get an air governor and get it installed. 

I'll also work through the pre-trip process, and then start on the air dryer.

Am currently on a tour in Alaska so parts may be an issue, but will advise of the progress.

Thanks again.  This is a valuable resource, and I'm glad I found it.