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Topic: No Rear Brake Pressure (Read 719 times) previous topic - next topic

No Rear Brake Pressure

Leaving next Wednesday for Williamsburg. Coach has sat for couple weeks, so decided to start it up. Fired right up and front brakes pressured up to 125#. Rear brakes won't come up to pressure on gauge. Goes up to 10#. Didnt hear any leaks. Probably need to replace dryer. On my to do list. Confused why front would pressure up but not rear. Recent new D2, safety valves, pressure regulator on tanks and multiple fittings/ leaks repaired. Where should I start?
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #1 –
Maybe a check valve into the tank is stuck or maybe only a bad gauge. Try reversing the lines at gauge to see if you have the same condition or if it changes.
previous 1984 35 ft ORED 250 HP 3208 Cat       
previous 1998 40 ft U295 CAI 325 hp Cummins
previous 2003 40 Ft u320 build #6140 450 Cummins M11.                                                         
1999 Mazda Miata
Ron, Nancy, Tipper the cat, Max The dog
1997 U 270 36 ft build number 5174 8.3 Cummins

Re: No Rear Brake Pressure

Reply #2 –
The drier would affect both tanks. You have a major leak in the rear brake system. If you can use an air compressor and hook it to your air chuck for airing tires you might be able to hear the leak. Too many possibilities to list them all until you can say which end of the coach it is leaking from.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: No Rear Brake Pressure

Reply #3 –
Will block up and put air to coach tomorrow.  Time to start crawling around underneath
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #5 –
I put in an air chuck at dryer so I can hook compressor to coach and trace leaks. Found leak at hose from coach compressor. Actually at nut to compressor. Looks like leaking at threads to housing.
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #6 –
That leak would not explain one tank with normal pressure and one with just 10 psi.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: No Rear Brake Pressure

Reply #7 –
Its handy in this type scenario to be able to know for a fact what pressure you have in each brake tank.

I put a male quick connect fitting on the drain valves for both brake tanks.  Stuck a female quick connect fitting on a pressure gauge.

Pop the gauge on the drain valve, open the valve, you see exactly what pressure you got in that tank.

Easy way to diagnose a faulty dash air pressure gauge.

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: No Rear Brake Pressure

Reply #8 –
Chuck will follow up on your suggestion. Tank had pressure will configure new so gauge can attach. One of my new tank drains i replaced in February already leaks. Everything seems to be crap these days(chinese). Bonus is finding 2 air leaks.........so far
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #9 –
120# at drains on both tanks. Gauge?
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #11 –
I may have found out it is is the PSI sender unit. On order should know soon
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #12 –
Replaced sender unit on rear tank. Now show 140# at dash gauge for rear and between 105-110# on gauge for front. Both tanks test at 120#. WTH. How do I get accurate or close to accurate readings at dash.
2001 4010 U320
Build 5875

Re: No Rear Brake Pressure

Reply #13 –
Quote from: Spiderhitch –
Replaced sender unit on rear tank. Now show 140# at dash gauge for rear and between 105-110# on gauge for front. Both tanks test at 120#. WTH. How do I get accurate or close to accurate readings at dash.
I believe on your model year coach the dash air pressure gauges are electronic.  As you already know, there is a pressure transducer on each tank.  What you may not have discovered is the magic box that translates the signal from the pressure transducers, and sends the info to your dash gauges.  Your problem may be located in the magic box.  Some of the magic has leaked out.    :headwall:
 
See thread linked below for more bad news:

02 U320 Air gauge stopped working

1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"
 

Re: No Rear Brake Pressure

Reply #14 –
Quote from: Spiderhitch –
Replaced sender unit on rear tank. Now show 140# at dash gauge for rear and between 105-110# on gauge for front. Both tanks test at 120#. WTH. How do I get accurate or close to accurate readings at dash.
My front and rear gauges consistently have a delta of around 20psi too. I assume it's the magic box chuck mentioned. Direct-read gauges are somewhere on my to-do list but I have forgotten where.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.