28 replies to this topic

[McBrian]

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 that’s 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 ¼” 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. I’ll let everyone know how it gets fixed.

[wolfe10]

McBrian,

Vacuum to brake vacuum booster should be the same, whether using the throttle or cruise control (engine-generated vacuum would be the same and based on throttle position). Can't understand how it would be different based on whether the throttle is applied by your foot or cruise control unless the cruise control has a vacuum leak.

When you turn off the engine, comeback after 5 minutes and step on the brake pedal. Is it hard then or "normal"? That would be a reasonable leak down test for the vacuum (excluding cruise control circuit). If it is hard after 5 minutes of sitting with the engine off, start removing and blocking off vacuum lines until you find the culprit.

Brett

[McBrian]

Brett, under heavy acceleration there is a vacuum drop.

[wolfe10]

Brett, under heavy acceleration there is a vacuum drop.

Wonder if a vacuum reservoir would solve the problems. All gasoline powered vehicles have very low/zero vacuum under hard acceleration.

[McBrian]

I still think that a one way vacuum check valve would do the trick. I am really concerned that others who have the Invisibrake will encounter the same problem. There is nothing like having to hit your brake hard and finding a hard pedal.

I did as you had suggested and 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.

That was a very easy way to check for vacuum leaks. Thanks!

[wolfe10]

You have just confirmed that you do not have a vacuum leak through the Invisibrake system (engine off for 5 minute and no decrease in vacuum to brake booster).

Suggest you check the vacuum components of the cruise control, as they appear to be the issue. May be as simple as taking off the vacuum line to the cruise control and sucking on it-- no vacuum suggests you should get with Honda to troubleshoot it.

[McBrian]

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.

[wolfe10]

OK, but since you said you did not loose vacuum boost to the brakes even after 5 minutes with the engine off, but did loose it when the cruise control was operating, I would block the cruise control vacuum line as well (assuming it is vacuum operated). From your description, the cruise control is the variable.

[McBrian]

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.

[derh2o]

At last resort, I would recommend telling Roadmaster technical support you would like to talk to Mike Cannon. Mike is the developer of all the braking systems at Roadmaster. Technical support told me Roadmaster does not make a braking system for the 2012 Focus. I put a post on the forum for an alternative to a Focus, stating that the Invisibrake cannot be uses on the Focus. To my surprise, Mike Cannon reply to my inquiry on the forum stating his position and that they can put an Invisibrake on the Focus. Point being, he was very helpful. I purchased everything i needed to connect the Focus to a MH, and found Roadmaster a great group of people to work with. Lucky for me, I live in Vancouver, WA, and their site is just down the road.

[McBrian]

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.

[wolfe10]

McBrian,

Not sure from you post (particularly the "leak in my system that was repaired" part)-- do you still have a problem or is it solved??

If not solved, should be pretty easy to diagnose the source of the vacuum leak:

#1. Start by plugging the vacuum line at the engine. Drive and check for vacuum issue. That rules out both Invisibrake and the new vacuum line to it. Be sure to use a solid plug such as golf "T" rather than as screw, as vacuum will follow the threads of a screw or any threaded plug.

#2. Next, move to the Invisibrake and plug the line that goes into the brake unit. Any change? That rules out the Invisibrake.

If you good vacuum in tests #1 and #2 but loss of vacuum when the Invisibrake is connected, the next thing I would do is use a hand held vacuum pump to pull a vacuum on the Invisibrake. Determine bleed down time from, say 20" to say 5" vacuum. Call Mike Cannon at Roadmaster with the facts.

The good news is this should not be hard to diagnose.

[McBrian]

Wolfe10,

I am happy to report that I no longer have the hard brake pedal problem.

I put the following statement in to cover all possible causes. "Either the Invisibrake unit is malfunctioning, the design has a flaw or there was a leak in my system that was repaired."


I was really unhappy with the tech at Roadmaster. He couldn't give me a solution so he just brushed me off.

My feeling is that the invisibrake unit can leak vacuum when it is off or the line to the unit can be more that the car can compensate for when the engine is under a load.

The system works correctly now since I installed a one way vacuum stop in the line to the invisibrake.

[McBrian]

It was suggested to me that I should test the breakaway switch by pulling the pin. I did that this morning.

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 am trying to find out if the person who made the suggestion had a problem with their breakaway switch or not.

[wolfe10]

Don't know who made the suggestion, but testing all the functions of any supplemental brake is part of the installation process.

Did you use the PSI knob on the on the Invisibrake to set pressures for your toad?

[McBrian]

Yes, we did set the pressure with PSI knob on the intial install. We drove the MH with toad attached in a large parking lot for the intial adjustment. We then went on the road and did a few "fine tuning" adjustments. It works fine. I also check the toad brakes daily.

When I installed the unit I did test the connection and it worked. I know I should have tested the switch by pulling the pin.

[wolfe10]

The easy test I do on the brake-a-way switch is to go to a place with a gently sloping road with the back of the car facing down-slope.

With vehicle in neutral, engine off, start down the hill. As you start, have someone pull the brake-a-way pin. You should hear the compressor come on (with the Invisibrake) and stop within a couple of feet.

Brett

[McBrian]

I'm happy to report that the new breakaway switch arrived very quickly from Roadmaster. I installed the switch and tested it. It worked fine. As I mentioned in a previous post, I was trying to find out from the person who suggested the test if they had a problem with their breakaway. They reported that they did not have any problem. Thank you for all of your help! Brian

[karend]

We bought an Invisibrake for our Honda CRV at the 2012 FMCA Internatinal rally. Used it twice. The third time our brake lights on the car did not work and the brake seemed depressed (i.e. not totally released.) we called Roadmaster going down the road. No response. Still waiting and will pass on to them what you've said.

[McBrian]

Karend, your problem is much different from mine other than the lack of caring/response from Roadmaster. I would suggest you start a new thread to get some advice from the vast knowledge and experience of other members.