Can't Stop!!

Topic: Can't Stop!! (Read 1671 times) previous topic - next topic

Can't Stop!!

December 10, 2013, 08:54:47 am

This is a new phenomenon. My brakes act perfectly normal running down the road. But when coming to a complete stop, the coach wants to continue creeping forward. I have to really stand on the brake pedal to finally stop it. What is going on?

Re: Can't Stop!!

Reply #1 – December 10, 2013, 09:02:10 am

just a thought, is the engine idling a little too fast? That would require more braking.

Re: Can't Stop!!

Reply #2 – December 10, 2013, 09:13:43 am

I don't know but I would check the drive belt to your hyd pump . Sounds like you lose your power brakes at idle.Gam

Re: Can't Stop!!

Reply #3 – December 10, 2013, 09:47:01 am

These are AIR brakes, so hydraulic pressure would not be an issue.

Is your air pressure normal?

Slack adjusters properly adjusted?

And, as Charles asked, is engine idle speed set properly?

Re: Can't Stop!!

Reply #4 – December 10, 2013, 10:11:31 am

If air pressure, idle speed are OK and slack adjusters within specs, I would check disc temperatures. You could have one not releasing. HF has a IR gun special for $24 now so is an easy way without burning fingers. Check pad wear while you are at it.

Our brakes work fine but our driveway is so steep, I have to come down slowly in neutral or I can't even stop it with the service brakes. The big diesels generate a lot of torque at idle and if idle is even a little too high, it can really test the brakes while stopped.

Pierce

Re: Can't Stop!!

Reply #5 – December 10, 2013, 10:48:13 am

Are you using the retarder while driving or have you tried the brakes without the retarder? You should have good braking with the retarder off. Also how well does the parking brake hold? If the rear wheel slack adjusters are out of adjustment the parking brake will not hold very well. On level ground my coach will not move with parking brake on until the engine exceeds 1000 rpm. Sounds like a good time to have all the brake components checked. I agree with previous suggestions. Really having to stand on the brakes should cause the slack adjusters to make an adjustment.

Re: Can't Stop!!

Reply #6 – December 10, 2013, 11:39:36 am

Please disregard my last transmission!Gam

Re: Can't Stop!!

Reply #7 – December 10, 2013, 12:12:00 pm

Sounds like you have experienced the old foot on the accelerator and the brake at the same time!! Took me a while to get to where I would get my foot over far enough to keep it off of the accelerator. Stops well when I do that!! ---- Fritz

Re: Can't Stop!!

Reply #8 – December 10, 2013, 01:44:42 pm

Quote from: Jerry Whiteaker – December 10, 2013, 10:48:13 am

Are you using the retarder while driving or have you tried the brakes without the retarder? You should have good braking with the retarder off. Also how well does the parking brake hold? If the rear wheel slack adjusters are out of adjustment the parking brake will not hold very well. On level ground my coach will not move with parking brake on until the engine exceeds 1000 rpm. Sounds like a good time to have all the brake components checked. I agree with previous suggestions. Really having to stand on the brakes should cause the slack adjusters to make an adjustment.

I noticed the same thing you are alluding to. The brakes glaze on the coaches I think from never getting to proper pad tempature IMO.

So on non heavy traffic drives I will turn off the retarder and REALLY use the brakes repeatedly to wear off any buildup from light or no use.

Cold and glazed they are not very powerful.

Second issue I fixed was the chassis main air controller valve was worn and partially plugged up. 90-110 was its range.

Replacement is 110-130. More air pressure. Stronger brakes.

Bob

Re: Can't Stop!!

Reply #9 – December 10, 2013, 08:46:17 pm

Shift to neutral to eliminate engine driving forward while trying to stop with brakes.

Re: Can't Stop!!

Reply #10 – December 10, 2013, 09:01:32 pm

Air pressure OK, idle speed OK, slack adjusters OK, disc temps OK, parking brake OK, foot only on brake pedal. I could be guilty of excessive retarder use, so I'll try driving without it to see if symptoms change. In the meantime, Barry's suggestion is worth a try.

Re: Can't Stop!!

Reply #11 – December 11, 2013, 05:55:39 am

Our 1998 M11 also 'pushes' the coach more than I'd like at idle. Is there a way to lower the idle RPMs via the computer? We've tried the 'set and resume' switches for the cruise with no effect.

Re: Can't Stop!!

Reply #12 – December 11, 2013, 08:05:39 am

Bill, it sounds like you have the same issue as I did on my '99. I also tried to reset the idle speed via the cruise buttons, but to no avail. Then, during a visit to FOT last year, I asked one of the tech's if they knew of a solution for my coach. A little research later ...... and yes, they also tried to use the cruise buttons ...... someone recalled that the '99's didn't use the cruise buttons. Instead, idle speed was set by one of the two rocker switches behind the drivers side dash cover. (the one that hinges up toward the windshield) The one you are looking for is the one that returns to center. Momentary up push increases RPM by 50, and a momentary push down lowers the RPM by 50. The second switch is on/off and controlls access to dash fault codes. I was unable to get any documentation for either of these buttons. But that's how they work on my rig. Hope it's the same for yours. My M11 idled at 850 when I got it, and I struggled at the stop lights for years. Now it's set at 700, and all is good.

Dave VanAmburg

Re: Can't Stop!!

Reply #13 – December 11, 2013, 09:38:39 am

Thanks so much Dave. I'll check for the rocker switches this w/e. Is 700 rpm the accepted tach reading at idle? It seems I remember some folks were running 675 or even lower. What is too low?

Re: Can't Stop!!

Reply #14 – December 11, 2013, 12:39:52 pm

Quote from: bill & jan velting – December 11, 2013, 09:38:39 am

Thanks so much Dave. I'll check for the rocker switches this w/e. Is 700 rpm the accepted tach reading at idle? It seems I remember some folks were running 675 or even lower. What is too low?

Have to look but mine I think is 650 or less. Had to turn it up from lower as a rattle showed up in the dash.

Bob

Re: Can't Stop!!

Reply #15 – December 12, 2013, 11:44:54 am

I can't find those rocker switches. Can someone show me a photo?

Re: Can't Stop!!

Reply #16 – December 12, 2013, 03:56:47 pm

Brett, this is where they are on mine. We have the same year and model ....... you would think they would be in the same place!

Dave VanAmburg

Re: Can't Stop!!

Reply #17 – December 12, 2013, 06:36:59 pm

Wow! They're not there on mine. I wonder if someone unscrewed that plate. I'll have to go searching behind the HVAC hoses.

Re: Can't Stop!!

Reply #18 – December 12, 2013, 06:43:24 pm

Brett,

Let's back up.

What is your idle speed, once warmed up? That will determine if this is something that you need to pursue or just ignore.

"The other Brett".

Re: Can't Stop!!

Reply #19 – December 12, 2013, 06:45:20 pm

700 rpm.

Re: Can't Stop!!

Reply #20 – December 12, 2013, 06:51:23 pm

that is about the right idle.

Re: Can't Stop!!

Reply #21 – December 12, 2013, 11:47:41 pm

Quote from: John S – December 12, 2013, 06:51:23 pm

that is about the right idle.

Not in my coach but I think my tech buddy went to 550 and for the rattle I went up to 600

Re: Can't Stop!!

Reply #22 – December 13, 2013, 10:22:23 am

I found the rocker switches in the same place as Dave's. Can't wait to make the adjustment. Our M11 would lurch forward when placed in gear if the foot brake wasn't applied strong enough. This small rocker panel could be attached in numerous places under the dash.
thanks again Dave for posting your experience.

Re: Can't Stop!!

Reply #23 – December 13, 2013, 10:47:02 am

It's a huge pleasure to finally be able to give something back to this group. I've taken, and used so many of the wonderful ideas posted here ...... I will be forever in your debt.

Dave VanAmburg

Re: Can't Stop!!

Reply #24 – December 13, 2013, 04:07:52 pm

Adjusted idle a while back. Engine at idle in neutral, cruise control off, resume button to increase and set button to decrease idle.

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