04 Liberty braking question

[04Roadglide]

I tow my 04 liberty behind my class c motorhome. The tow bar has a built in surge function that pulls the brake pedal via a cable run through the firewall. While towing the jeeps transfer case is in neutral and the key is ìn the first position. Does this seem correct? I'm assuming the brakes get boosted only with the engine running? The pedal is hard in this set up, but still provides braking? I think it's assisting with braking but it's hard to tell.

 

[Shankster]

One of the more interesting questions I've read - anxious to hear if anyone can answer. For sure the brakes only get power assist when the engine is running though.

I don't know if this helps, but when I'm towing WITH my Liberty, to check if my trailer brakes are working I push the button on my brake controller to apply the brakes on the trailer without touching the brakes on my Liberty - if I feel braking happening I know my trailer brakes are working. Does your motorhome have any such button?

 

[04Roadglide]

One of the more interesting questions I've read - anxious to hear if anyone can answer. For sure the brakes only get power assist when the engine is running though.

I don't know if this helps, but when I'm towing WITH my Liberty, to check if my trailer brakes are working I push the button on my brake controller to apply the brakes on the trailer without touching the brakes on my Liberty - if I feel braking happening I know my trailer brakes are working. Does your motorhome have any such button?

No, it's all from the surge device in the tow bar. As the hitch compresses on itself a lever on top pivots forward which in turn pulls on a small cable that runs back through the engine compartment. The cable is fastened to the brake pedal and physically pulls/ depresses the brake pedal.

 

[04Roadglide]

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[Shankster]

No, it's all from the surge device in the tow bar. As the hitch compresses on itself a lever on top pivots forward which in turn pulls on a small cable that runs back through the engine compartment. The cable is fastened to the brake pedal and physically pulls/ depresses the brake pedal.

Pretty slick!

One way I can think of to test it is for someone to be in the driver's seat of the Jeep, foot lightly on brake pedal, brake with the motorhome and try to get a feel for how far the brake pedal gets sucked in, then, while coasting the motorhome on a level or downhill road have the person in the Jeep duplicate the movement of the brake pedal with their foot and see if you feel any braking.

Not as informative, but another way would be to brake with the motorhome for an extended period on a longish, steepish downhill. Then pull over and feel (or better yet, use an infrared temp sensor) all of the Jeep's wheels (or rotors if you have the IR temp sensor) to see if they've got hot. Prior to the test get a baseline temp on all wheels - sun beating down on one side could make wheels on that side hot with no relation to brake operation.

 

[04Roadglide]

Pretty slick!

One way I can think of to test it is for someone to be in the driver's seat of the Jeep, foot lightly on brake pedal, brake with the motorhome and try to get a feel for how far the brake pedal gets sucked in, then, while coasting the motorhome on a level or downhill road have the person in the Jeep duplicate the movement of the brake pedal with their foot and see if you feel any braking.

Not as informative, but another way would be to brake with the motorhome for an extended period on a longish, steepish downhill. Then pull over and feel (or better yet, use an infrared temp sensor) all of the Jeep's wheels (or rotors if you have the IR temp sensor) to see if they've got hot. Prior to the test get a baseline temp on all wheels - sun beating down on one side could make wheels on that side hot with no relation to brake operation.

The IR Temp sensor is a great idea. I have one in the cab of the rv. Next time we travel I'll check that. Thanks

 

[eric1514]

Do you have the optional DL-300 monitor? At least then you can tell if the brakes are being applied. Whether they are doing something or not is just a feel at that point.

I use a portable braking system in my Liberty when I tow it. As part of the set up procedure, the unit will apply the brakes 3 times to deplete the vacuum in the boost. I also have sensitivity and force adjustments so I can control when and how hard the TOAD brakes are being applied along with an indicator light in the cab of the motorhome. I can definitely feel a "tug" when the brakes in the Jeep come on.

 

[JeepJeepster]

I've never heard of or seen a setup like that.

You are correct, no assist without the engine running. The brakes will still work if you push (or pull?) the pedal, obviously not as good.

Key in first position, tcase in N, trans in Park.

 

[04Roadglide]

Yes that's it. The tow bar manufacturer recommends a bit of slack in the pull cable, but I think I'll tighten it up a bit.
I also have a bungee cord inside the jeep to pull the pedal back

 

[burntkat]

I'd leave a little slack in that cable. There is a reason the manufacturer specifies some slack. You don't want to ride your brakes in the towed car.

You absolutely are not having any mechanic or hydraulic advantage added to the Liberty in this condition. All you have is 'dead stick' brakes.... Meaning, exactly as if you were to lose the engine at speed and apply the brakes a few times... You have enough vacuum assistance (assuming an airtight vacuum system, no leaks) for 3 or 4 applications of brakes. After that it's simply the little bit of mechanical advantage you get from the architecture of the brake pedal to the hinge, to the actuation rod into the cylinder. Also, the fact you are running a hydraulic brake system gives quite a bit of MA as well.... This can be compared to an old cable-pulled mountain bike brake system vs hydraulics.

I could go a lot farther into this subject, but it isn't necessary.

TLDR - you have some mechanical advantage to the braking system, but no boosting (because the vacuum or hydraulic booster <depending on the build I- think the diesels had hydroboost?> due to either the hydraulic system <PS pump> or vacuum system <gas engine is a huge vacuum pump, remember> not running. The pull cable from the towbar manufacturer is likely providing less braking than you would if you were to press the brake pedal, as it is pulling from the other side of the lever/fulcrum that is the brake pedal assembly.... Which IIRC, is not as long as that same fulcrum to the brake pedal.

 

[burntkat]

Also, IIWY, I'd look into some sort of bracket or brace that locks the t-case into the neutral position. I have seen too many towed Jeeps have the t- case lever vibrate into gear..... With the result being a catastrophic (and literal) *EXPLOSION* of the t-case and transmission. Most of the automatics are going to need the engine to be running to pump the transmission fluid around the transmission if they are in gear, and without that (only done by the running engine inputting torque into the transmission pump at the input shaft) you WILL be rebuilding a transmission (if you're VERY lucky)... And more likely, replacing it entirely owing to case and hard part erosion and/or fragging out.

EDIT - not just some dude on the Internet being paranoid.... Here's the receipts (ignore the AI horseshit, as one should) -

Google Search

 

[nmbluept]

04Roadglide,
Go to irv2.com and look at the ClassC or ClassA Motorhome Discussion forums. Join the group - it's free, then you can search for supplemental braking info. There are a ton of discussions on supplemental braking systems. Your NSA system is pretty popular, I'm sure you will find a bunch of useful information there. You could also post your question there.

Good luck & safe travels

 

[04Roadglide]

04Roadglide,
Go to irv2.com and look at the ClassC or ClassA Motorhome Discussion forums. Join the group - it's free, then you can search for supplemental braking info. There are a ton of discussions on supplemental braking systems. Your NSA system is pretty popular, I'm sure you will find a bunch of useful information there. You could also post your question there.

Good luck & safe travels

Thank you. I'm a member @ IRV2. I'll have to get on and do some reading

 

[Robochop]

I tow my 04 liberty behind my class c motorhome. The tow bar has a built in surge function that pulls the brake pedal via a cable run through the firewall. While towing the jeeps transfer case is in neutral and the key is ìn the first position. Does this seem correct? I'm assuming the brakes get boosted only with the engine running? The pedal is hard in this set up, but still provides braking? I think it's assisting with braking but it's hard to tell.

Just mt 2 cents, but when I tow a Liberty with my 2 wheel tow dolly I always put the transmission (not running) and the transfer case in neutral. I have never had any issues after that. I use a Yukon when I tow..

 

[burntkat]

Just mt 2 cents, but when I tow a Liberty with my 2 wheel tow dolly I always put the transmission (not running) and the transfer case in neutral. I have never had any issues after that. I use a Yukon when I tow..

It's on a tow dolly. Why are you worried about having the transmission/transfer in neutral? If the wheels aren't turning it's nothing to worry about.

 

[Robochop]

It's on a tow dolly. Why are you worried about having the transmission/transfer in neutral? If the wheels aren't turning it's nothing to worry about.

2 wheel tow dolly. Rear wheels are on the road. I have towed several different Liberty's for repair.

 

[burntkat]

Ah, yeah, I was picturing that wrong. Sorry.

 

[Robochop]

No worries, were all here to help each other with our experiences!