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Author Topic: have hard brake pedal, lousy brakes  (Read 328 times)

idahored

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have hard brake pedal, lousy brakes
« on: August 05, 2017, 04:16:46 PM »
Ever since I bought my 1995 Itasca 23rc two years ago, (P30 chassis), I've figured it must need a brake job. The pedal goes down half way but hardly slows the coach down, but let off and hit it again and I have double the braking which I still feel, I could never bring it to a fast panic stop. So I take it to a commecial truck tire center and tell them to check it all out. They said that two of the most experienced techs drove it, and feel it just stops like any motorhome they have driven. I figured they would wind up doing a complete brake job so I was ready for the big bill. What the brakes feel like, is like years ago driving some of the older model cars wth drum brakes that have oil on the brakes shoes, you have good pedal, lousy braking. Maybe there is a power brake assist that could be installed ? Needless to say, I give plenty of room to any vehicle ahead of me :)
1995 Itasca 23RC Class A
TOAD:
Mountain Home, Idaho

Paul & Ann

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Re: have hard brake pedal, lousy brakes
« Reply #1 on: August 05, 2017, 04:31:38 PM »
My first thought is that the booster is not working correctly.
Paul & Ann  Iowa
2005 Winnebago Voyage 38J
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scottydl

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Re: have hard brake pedal, lousy brakes
« Reply #2 on: August 05, 2017, 05:27:32 PM »
Commercial truck places usually know their stuff... is there another one in the area that can possibly give you a second opinion?  If they say the same thing, then perhaps the first 2 guys were right.  ;)  But the way you describe it does sound like a pressure-building issue of some kind.

Needless to say, I give plenty of room to any vehicle ahead of me :)

Always a good idea for sure!  These rigs will never stop like cars, which does take some getting used to.
Scott, wife, 3 boys... and the dog
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Charlie 5320

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Re: have hard brake pedal, lousy brakes
« Reply #3 on: August 05, 2017, 06:44:58 PM »
If this coach has rear drum brakes, they may not be adjusted right. They didn't stop so good with rear drum, but if it has 4 wheel disc then there is a problem. I would start by bleeding the system. Start with the right rear, left rear, right front, left front. Keep the master full and run the fluid till it runs clear when bleeding. The coach should have hydroboost brakes, and if somebody has changed the power steering pump, and didn't bleed the booster, then that maybe the problem. There is a lot of reading on the net about that system, and just anybody can't work on it.
2003 National Dolphin 5320
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Lou Schneider

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Re: have hard brake pedal, lousy brakes
« Reply #4 on: August 05, 2017, 09:51:13 PM »
Like Charlie said, most if not all P30 chassis use the Hydroboost braking system.  Instead of using a vacuum diaphragm like most power assisted brakes the Hydroboost uses hydraulic pressure from the power steering pump to provide the assist.

One way to test this is to try to turn the steering wheel with the engine idling while the motorhome is sitting still to put a load on the power steering system.  While doing this step hard on the brakes - if you feel the steering wheel run out of power boost or the brake pedal vibrates you have the HydroBoost brakes.

This also means the power steering belt has to be tight and you need enough fluid in the power steering system.

It requires specialized knowledge to correctly set up a HydroBoost system. You may have to go to a performance shop as it's also popular on the speed circuit.
« Last Edit: August 05, 2017, 10:06:25 PM by Lou Schneider »

Gary RV_Wizard

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Re: have hard brake pedal, lousy brakes
« Reply #5 on: August 06, 2017, 08:52:43 AM »
I'm of two minds on this one. The old P30 chassis was poor on braking (and the Ford F53 of that vintage wasn't much better), largely because the 16" wheels simply don't have a lot of brake capacity for that size/weight of rig. It ain't never gonna stop fast. However, the change of pedal feel after pumping once indicates a problem to me. Air in the hydraulic lines, maybe a weak hydroboost pump, that sort of thing. 

The heavy truck shop guys are probably more  familiar with air brakes and the much greater braking capability of the big trucks they work on daily. No 1995 vintage gas chassis is gonna come even close to those.
Gary
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Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Charlie 5320

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Re: have hard brake pedal, lousy brakes
« Reply #6 on: August 06, 2017, 09:02:13 AM »
Gary, NOT all P30 chassis of that area had 16" wheels and drum brakes. The 4 wheel disc brake chassis had pretty good brakes. I pulled an 18ft trailer with a race car for 7 years and never had a problem getting it stopped. His coach has a problem ! It should NOT have a hard pedal.

Air in the lines causes a soft pedal, not a hard pedal.
2003 National Dolphin 5320
496  8.1  Workhorse

98 Damon Daybreak 3130
GM Vortech 454  4L80E
SOLD

56safari

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Re: have hard brake pedal, lousy brakes
« Reply #7 on: August 06, 2017, 11:47:05 AM »
I'd lean toward either a failing hydro-boost or power steering pump.  When the next shop checks it out, have them check the brake line pressure - it should be well north of 1000 psi.  If it's not, be sure the power steering pump is providing adequate pressure.  Either could be the culprit.  The hard pedal is usually a sign of inadequate power assist whether hydro-boost or vacuum boost.  It's also possible to have glazed linings that don't provide much friction regardless of the pressure applied, but the improved braking one the second pump of the pedal sounds more like a boost problem. 
Jim & Lin
1999 Rexhall Aerbus

John From Detroit

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Re: have hard brake pedal, lousy brakes
« Reply #8 on: August 26, 2017, 03:31:53 PM »
Let me ask a question based upon experience.

Disc brakes or Drum?

The story: My first towed was a `1992 Chevy Lumina APV, Front DISC Rear Drum. Had exactly the same problem (not the first car I've had with that problem but first one I fixed).

Pedal dang near hit the floor every time.

Dealer, had his "Factory Trained" technician look at it 3 times.. No joy.

Finally I put my trained mind to work.. I visualized the system.. NO drawings in front of me, NO hardware, Just my mind.. And a thought came to me.. So the next morning I drove to Belle Tire (They do brakes) and ask them to have the technician measure the drums (Mic (Micrometer) the drums was the request).. I watched as he measured them (From outside the shop) and went in and ask George (The assistant manager) "How much for new drums"

Drove out and ... MAN  LIke new.

Now I'm not saying that is YOUR problem.. But here is how I visualized it.

Since the drums were way and I mean WAY beyond spec it took a lot of pressure to fully engage the brake shoe.

Why factory trained Dealer guy could not figure that out.... I DO NOT KNOW.
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