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Old 08-08-2012, 06:12 PM   #1
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Roadmaster Invisibrake hard brake pedal

Last November/December I had installed a Roadmaster Invisibrake on my 2012 Honda Fit with automatic trans and cruise control. I have had no problem while towing the Honda Fit BUT when I am driving the Honda with the cruise on and it is accelerating and I have the need to hit the brakes, I get a hard brake pedal. It only last a second or two. (But thatís a lot!)
Now, I turned wrenches for many years and thought it seemed like I was not getting adequate vacuum to the brake booster. I called Roadmaster tech support and followed his list of things to check. The hoses were tight and the cruise cancels when I hit the brake pedal. Tech support did not resolve the problem.
I suggested that a check valve was needed in the ľĒ vacuum line that went 12 to 15 feet to the Invisibrake controller. He said it was not needed.
Has anyone else had similar experiences? Any thoughts on something overlooked?
I intend to take the car to the Honda dealership and have them diagnose the problem next week. And yes, I will not be using the cruise control until the problem is resolved. Iíll let everyone know how it gets fixed.
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Old 08-08-2012, 07:44 PM   #2
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I tested the vacuum hold of the system by running the car for a minute and then letting it stand for five minutes before trying the brake pedal. It was normal.
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Old 08-08-2012, 09:07 PM   #3
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I do admit it sounds like loss of vacuum

Can you splice a vacuum gauge in the line and monitor it.

You can also try this.. Next time you drive, "hemostat" the line to the Invisi brake box, (I have 3 genuine hemostats here for jobs like that) or otherwise close off that port.

But it sounds like a low vacuum issue to me too.
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Old 08-09-2012, 05:44 AM   #4
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I am going to disconnect the vacuum line and plug the one going to the invisibrake and attach a vacuum gauge on the brake booster side. I will then try to recreate the problem.
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Old 08-09-2012, 07:01 AM   #5
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McBrian:

Did your Invisibrake (IB) come with one or two vacuum check valves (Circle 15 on the Components page of the install instructions)?

Maybe RoadMaster (RM) tech covered this with you but just in case:

I received my IB last Dec 2011 and it only had 1 one-size fits all check valve. Before installing IB in Mar 2012, I looked at the install instructions on the RM site and noticed that RM was now including two check valves for different sized hoses: use the one that fits your hoses. Called RM; tech said they'd had probs with the single valve; told me how to test; test failed; tech sent me new check valve.

Have had no probs with IB, either towing or driving the toad.
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Old 08-10-2012, 09:09 AM   #6
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Yes, it came with two vacuum breaks. I wish I could find the other one. The tech at Roadmaster said I had the new version.

I disconnected the invisibrake vacuum line and attached my vacuum gauge for a test drive to get a baseline. I discovered two things.
First, my vacuum gauge, which has been sitting idle for a few years, no longer operates. Second, I could not recreate the hard pedal problem.

I have been testing on a section of highway near my home which has a steep grade and I can get three or four tests while on it. I reconnected the invisibrake line and the problem returned.

I am now putting together a vacuum break using a pvc valve. I'll not be able to test it because of the heavy rain today.
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Old 08-10-2012, 03:50 PM   #7
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Well.. The good news is you have narrowed it down to the Invisible Brake.

I'd replace the check valve.

If it's leaking then the vacuum in the brake booster can "Bleed down" while you drive, when you lift your foot off the gas it starts to build up again, but you are quick to hit the brake (A good thiung by the way) and get there before it builds.

I'd replace the check valve.. That is the problem.
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Old 08-10-2012, 05:40 PM   #8
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It's not the check valve that is supplied. The one that is supplied goes on the engine side of the brake booster line to prevent the invisibrake from trying to cause a vacuum in the engine when the invisibrake is applied. That one was checked and is ok.

The problem I am/was having is that the engine vacuum now has to also create vacuum in the invisibrake control and the 12 or so foot of vacuum line. I placed my makeshift vacuum break at the tee going to the invisibrake line.

Although I haven't tested the makeshift valve, I am happy that by disconnecting the line to the invisibrake the problem disappears.

My concern is Roadmasters position that it cannot happen. A hard pedal in a panic stop can lead to disaster. I'd bet that there are other cars out there with the same problem, just waiting for an accident.
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Old 08-22-2012, 08:10 AM   #9
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I finally had the opportunity to test the make shift vacuum stop I installed on the line to the Invisibrake. I am happy to report that I no longer have the hard brake pedal problem. Either the Invisibrake unit is malfunctioning, the design has a flaw or there was a leak in my system that was repaired. Everyone with an Invisibrake should test their car for this potentially dangerous problem.
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Old 08-22-2012, 05:27 PM   #10
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McB:
Please clarify: After your mod, does the IB still work OK when the breakaway switch pin is pulled when the car is not attached to the MH? Does the IB still work OK when you're towing the car?
Thanks.
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Old 08-23-2012, 06:14 AM   #11
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I did not pull the pin on the breakaway in my tests. I will do that this morning and post the results. Thanks for the good idea.
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Old 08-23-2012, 08:30 AM   #12
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Wow, I'm glad I tested the breakaway switch. I pullled the pin and nothing happened! I then disconnected the wires to it and connected them together to bypass the switch. It worked.

I will call Roadmaster when they open this morning and get a new breakaway switch. I will admit that I never tested the brakaway when I installed the unit.

I have been happy with the performance of the invisibrake when I am towing. I tested and adjusted the brakes when I installed the unit and we always test the unit daily before starting on the road. I think they may still have a bug or two to work out though.

My invisibrake is just that, invisible. I have the control unit sitting inside my spare tire rim on a piece of plywood which I cut to fit snug. The wires and hoses are run through the same channels as the car wires. You wouldn't know it was there.
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Old 08-23-2012, 08:42 AM   #13
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View2a.thril, did you have a problem with your breakaway switch?
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Old 08-24-2012, 07:16 AM   #14
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I have not had any problems with IB including the break away switch. I was just curious if your modification had any unexpected impact on the IB when towing or on the break away.
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