99' U320 air brake high pressure

Topic: 99' U320 air brake high pressure (Read 1894 times) previous topic - next topic

99' U320 air brake high pressure

July 30, 2010, 01:48:06 pm

Our '99 recently started showing higher then normal PSI readings on the front air gauge. Normal should be 90-120 psi.
Goes to 147psi before the pop off valve opens. Rear goes to 115-118 psi before the pop off valve opens.
Cycle the brake pedal 3 times reduces the front to 110 psi (rear to 85 psi) then back to 143 psi (rear back to 115 psi).

Note: these reading were in our driveway this morning, but on our recent trip, similar reader were noted. Current Odom is 108900.

What should I be looking for?

dick & Sue U320 '07 Escape toad, getting ready for a Northern & UP, Mich. trip in a few weeks.

Re: 99' U320 air brake high pressure

Reply #1 – July 30, 2010, 02:04:03 pm

Either the air governor has failed and needs replacing or sensing air line into the governor has broken off.
Have had both experiences.

The pressure goes up until the main pressure valve lets off the excessive pressure.
If the line has broken, you can hear it very easy when the engine is shut down,'
Good luck
Dave

Re: 99' U320 air brake high pressure

Reply #2 – July 30, 2010, 02:20:05 pm

Quote

Our '99 recently started showing higher then normal PSI readings on the front air gauge. Normal should be 90-120 psi.
Goes to 147psi before the pop off valve opens. Rear goes to 115-118 psi before the pop off valve opens.

The air compressor is located on the engine and operates only when the engine is running. Clean, filtered, turbocharged pressurized air from the intake manifold is force-fed into the air compressor. The compressor maintains the air system whenever the system's pressure falls below preset parameters. When the maximum pressure is reached, the compressor output is diverted. An air governor is used to maintain the air pressure from 85 to 125psi.

Air pressure build up test.
Continue to let the air pressure build; it should not take more than four minutes for the air pressure to go from discharged (5-20 psi) to between 120 and 130 psi.

Governor cut-in/cut-out test.
When air pressure gets between 120-130 psi, the governor should cut out. The dash gauge needle stops moving. When the needle stops, pump the brake pedal to reduce the air pressure to 80 psi, release the brake pedal, the compressor starts pumping air (cutting in)! watch for needle movement. The air governor causes the air compressor to cut in between (85-90 psi).

Governor Service:
Haldex D2 Governor Service Data

Re: 99' U320 air brake high pressure

Reply #3 – July 30, 2010, 02:41:33 pm

Sounds like the first thing I would check is the air governor. It is on the right side of the engine as you face it about halfway up. It has a cover over a screw that you can use to adjust the pressure. The bladder sometimes fails and if you do not have one you can screw it in and out and see if it helps. I carry one with me. You will need one that will turn on at 95 lbs. It is an easy fix.

Dave M covered the other possibilities.

Re: 99' U320 air brake high pressure

Reply #4 – July 30, 2010, 03:05:51 pm

I've been carrying this part around and really do not know what it is for. Is it the air governor?

Re: 99' U320 air brake high pressure

Reply #5 – July 30, 2010, 03:12:01 pm

Quote

I've been carrying this part around and really do not know what it is for. Is it the air governor?

It looks like an air check valve ??

Governor is a little bigger.

Re: 99' U320 air brake high pressure

Reply #6 – July 30, 2010, 03:40:03 pm

The rebuilt runs from about $15.00 to $30.00 outright, last one I purchased for my FT was from a
TSA truck stop, $25.00 and they installed it for $45.00 after they looked to see how hard it would be, they would have not done it if it were very hard. They were very happy.
My old governor became erratic, so I replaced it, now happiness.
Dave

Re: 99' U320 air brake high pressure

Reply #7 – July 30, 2010, 08:20:46 pm

Barry,
Would the haldex model in your picture be the correct one for my 99 U320?

Re: 99' U320 air brake high pressure

Reply #8 – July 30, 2010, 08:40:22 pm

Quote

Would the haldex model in your picture be the correct one for my 99 U320?

I would not know that Part number for sure, but here is a photo of one on a 1997 to see if it looks like yours.

Re: 99' U320 air brake high pressure

Reply #9 – July 30, 2010, 09:17:46 pm

Thanks Barry. Mine is working ok. Would just like of get a spare. Will look at mine in the morning to see if it looks like either of your pictures.

Re: 99' U320 air brake high pressure

Reply #10 – July 30, 2010, 10:08:36 pm

I carry a spare but if you do not have one. You can take the rubber cap off and screw it all the way back then all the way down and try to get it back to where it was. I did that with Don Sprouse after a Rally we had in WV and he got home. He went and bought a replacement and a spare. In fact he go a deal and bought about ten of them so our mid Atlantic group was mostly supplied.

Re: 99' U320 air brake high pressure

Reply #11 – July 30, 2010, 10:28:55 pm

The Governor is refered to as the D-2 Governor, Mine is made by Bendix but there are most likely many brand names. They all are the D-2 Model
Ask any truck parts house for the D-2 and you have it, no matter who made it.
Dave

Re: 99' U320 air brake high pressure

Reply #12 – July 30, 2010, 11:53:30 pm

Thanks, I will ask for a D2 model.

Re: 99' U320 air brake high pressure

Reply #13 – July 31, 2010, 01:30:36 pm

Just a quick update and thanks for all of the input.

Our friendly Detroiter Truck Stop has D-2 Governors in stock @ $31.79.
He suggested that it could also be the gauge, so with that, I removed the air lines to the front gauge.

The gauge bottomed out at 30 psi, just about the amount that it read over normal range.
Several taps with the wrench and the needle moved to Zero.
Re hooked everything and now the front and rear track exactly each other and the pop-off is at 115 psi.

So now, either I have a defected or sticky gauge that needs to be replaced.
The manufacturing # is 150 077 006 and the VDO # is 150112. Just found one at Perry, Mi., almost on our way North for $32.50.

Monday morning I'll be at my parts store to buy a spare governor, just in case.

Once again, thanks for all the help.

dick & Sue, heading for Northern Mich and the UP starting next Sat.

Re: 99' U320 air brake high pressure

Reply #14 – August 01, 2010, 10:45:18 am

In an earlier comment, July 30th, you had mentioned the pressure went up and the pop off relief went off. If that is the case, I can not see where the gauge was all that incorrect.

Of course something else could have caused the sound of the pressure relief going off like a high speed leak in a tire. air conditioner line blowing off.

Cheers
Dave

Re: 99' U320 air brake high pressure

Reply #15 – August 01, 2010, 11:16:39 am

Dave,
What I said was "Rear goes to 115-118 psi before the pop off valve opens." May be I should have said that when the pop off goes off, the front gauge was at 147 and the rear was at 115-118 at the same time.
Since removing the air lines from the front gauge and "tapping" the gauge back to zero, both gauges tracked each other on a restart. During this test, we were parked in our driveway, no tire leak & no AC on.

Just rechecked a few minutes ago, both gauges were in sync with each other at 60 psi.

We have located a new VDO gauge and the D-2 governor (keep as a spare). Will pick them up this week.

Thanks for input. I always like to go back and recheck what I did, just the old "engineering" in me.

dick

Re: 99' U320 air brake high pressure

Reply #16 – August 01, 2010, 11:37:19 am

Dave, most off over pressure pop off valves go off about 140-150 psi.
Looks like the first step would be get a good working governor installed, then check out where you are with the gauges.
It is always nice to have a solid starting point from where you can make all your calculations.
I read that some where in the engineering books
Had it happen due to sensing line to governor had broken off while on I-95 is FL. Fixed at first rest area.
Good luck
Dave

Re: 99' U320 air brake high pressure

Reply #17 – August 01, 2010, 11:45:07 am

Dave,
Thanks for the update. That'll be my new plan. So much easier to repair in our driveway than on the road side.

dick

Re: 99' U320 air brake high pressure

Reply #18 – August 01, 2010, 01:02:28 pm

Quote

We have located a new VDO gauge and the D-2 governor (keep as a spare). Will pick them up this week.

Found a Governor for $16.93 at http://tinyurl.com/2fj554o

Re: 99' U320 air brake high pressure

Reply #19 – August 01, 2010, 02:42:38 pm

Barry, Yup, the D-2 governors have been in the $15-$30 range for years. And they are real simple to replace, if you have the right tools and some mechanical sense. Not "Rocket Science"
Dave

Re: 99' U320 air brake high pressure

Reply #20 – August 01, 2010, 02:48:12 pm

Quote

Barry, Yup, the D-2 governors have been in the $15-$30 range for years.

Quote

Our friendly Detroiter Truck Stop has D-2 Governors in stock @ $31.79.

I was just offering to Dick where he could find one cheaper than the one he is looking at.

Haldex D2 Air Governor

Reply #21 – August 01, 2010, 09:54:50 pm

Barry,

How do I know if my Bendix system uses the D2 Governor? Is it pretty universal, even for old (19 years) coaches like mine? I really like the price from Ryder Fleet products and have purchased from them a few times before.

Re: 99' U320 air brake high pressure

Reply #22 – August 01, 2010, 11:38:21 pm

This is a photo of my air governor. Hmmm, guess i will have to do something about that rust.

Re: Haldex D2 Air Governor

Reply #23 – August 02, 2010, 12:17:59 am

Don, Take a look at D2 on the Internet and look at yours. If they are similar, you have a D2. http://www.google.com/images?num=100&hl=en&rlz=1Q1DLUS_enUS354US354&q=d2+governor&um=1&ie=UTF-8&source=univ&ei=UkZWTOy3DsX_nAfVyfSUBA&sa=X&oi=image_result_group&ct=title&resnum=4&ved=0CDIQsAQwAw

Re: 99' U320 air brake high pressure

Reply #24 – August 02, 2010, 10:12:30 am

Quote from: Dave M – August 01, 2010, 02:42:38 pm

And they are real simple to replace, if you have the right tools and some mechanical sense. Not "Rocket Science"
Dave

Not for the "mechanics" at the TA Truck Stop in Brunswick, Ga. It was not a D-2 governor, but it was very similiar but had extra air outlets and was one of the Bendex governors replacing sob. They said it would not fit. I had to show them how to install it and plug off the extra outlets, cause they were clueless. Then they charged me labor. I should have charged them for instruction time. Too boot, they paged me from the restaurant when I was eating, and when I got back there, my meal was gone. It was one of those days.

Affiliate Notice