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 Post subject: Trailer hitch shunt
PostPosted: Sun Mar 16, 2008 3:55 am 
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Starfish

Joined: Mon Aug 07, 2006 4:28 am
Posts: 57
Location: Sydney, Australia
Hi all,
Have noticed just over the last couple of weeks the surge brake "shunt" has became a lot more excessive than previous times, wondering if there is some part in the hitch that wears to cause this, there also is a bit of a rrrrrrrrwww noise when the tow vehicle acelerates and the hitch is extended, after crossing a speed hump ect . Have read the post a few down "surge brakes" but this seems to refer to the shunting in general & not a worsening condition, any help is appreciated.

This is the type of hitch i have
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A couple of pics from today
Heading out
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At the beach
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2005 Four Winns Sundowner (Sold)
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 Post subject: Re: Trailer hitch shunt
PostPosted: Sun Mar 16, 2008 1:36 pm 
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email admin your custom rank

Joined: Wed Feb 13, 2008 10:11 am
Posts: 663
Location: Corinth, TX
Scott - Not sure I can help answer your question, but thanks for the "warm" photo's. Sure looking forward to summer.

David

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 Post subject: Re: Trailer hitch shunt
PostPosted: Sun Mar 16, 2008 1:53 pm 
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230 Mike
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Joined: Mon May 15, 2006 7:59 pm
Posts: 5141
Location: Kansas City, Table Rock Lake
Hi Scott, beautiful pics!

When you say "shunt," it seems you're talking about noise? (Shunt is an electrical term.)

The amount of noise from your coupler is very dependent on the level & condition of brake fluid in your trailer's brake system. If your fluid level is low or your brake lines have air in them, the coupler will slide farther with each stop & start, even to the point of the brakes no longer working.

Pop that large black plastic cap off. Under that you'll find a large plastic screw-in cap. That's the opening of the master cylinder. Make sure your brake fluid is up at the right level. Whether it is or not, consider bleeding your trailer's brakes. That's something that ought to be done every couple of years anyway. It gets any air out that might be in your lines, and gradually replaces the old fluid with new (brake fluid naturally attracts and absorbs moisture which reduces it's effectiveness).

Of course, all this assumes there's nothing loose or broken on your truck's hitch :) .

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2005 Four Winns 230/240
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1998 F-150 XLT
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 Post subject: Re: Trailer hitch shunt
PostPosted: Mon Mar 17, 2008 3:33 am 
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Starfish

Joined: Mon Aug 07, 2006 4:28 am
Posts: 57
Location: Sydney, Australia
Hey Mike,
Checked that brake fluid, not a drop in there :oops:
I guess i will have to bleed the system, looked in the FW owners manual, says take it to a dealer. Can this be done at home? I would imagine you would have a helper push the coupler while you backed off the bleed screws on the calipers until you got a continuos stream of fluid then tighten? Thanks for your help so far

Regards Scott

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 Post subject: Re: Trailer hitch shunt
PostPosted: Mon Mar 17, 2008 1:10 pm 
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230 Mike
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Joined: Mon May 15, 2006 7:59 pm
Posts: 5141
Location: Kansas City, Table Rock Lake
Yes, that's the idea.

It's completely dry though? The master cylinders on these trailers have an integral dampener, which helps to reduce the shock when taking off from a stop. These dampeners also use brake fluid from the master cylinder to operate, and if they run completely dry they can be difficult to get primed properly again. That could potentially be a reason to get your dealer involved.

The bigger question you should be asking, though, is where the fluid went. Normally the fluid deteriorates (because it sits without use for long periods of time, because it gets dunked in water, and - well, because it's in a trailer) - but if it's GONE, you have a leak somewhere.

Here's the bleeding instructions from Tie Down, the mfr. of your brakes & coupler (for model 70LP or 7000LP coupler):

2. Tie Down's actuators feature a shock dampener that uses brake fluid from the master cylinder. The dampener must be primed before bleeding or using trailer. To prime the dampener, fill the master cylinder with DOT 3 brake Fluid. Push the coupler into the housing and slowly pull out 3 times, then refill master cylinder.

3. Use only DOT-3 heavy-duty hydraulic fluid in the Model 70LP actuator. Use a pressure type brake bleeder to bleed brakes. (This type of brake bleeder is available at your local automotive jobber.) Follow manufacturer's directions. Or, manually bleed the brakes using a heavy-duty flat blade screwdriver inserted in the hole provided on top of the actuator near the front. Insert the screwdriver and use a pumping action to activate the master cylinder in order to bleed the brakes. See page 8 for more details.

To bleed master cylinder and brakes, install bleeder hose on first wheel cylinder to be bled; if tandem axle trailer, bleed closest axle first, and the closest brake on that axle first. Use a loose end of hose from the bleeder valve submerged in a glass container of brake fluid to observe bubbling (hose must be submerged into clean brake fluid to keep air from traveling back into the brake cylinder). Loosen the bleeder screw located in the wheel cylinder one turn, the system is now open to the atmosphere. The bleeding operation for that brake is complete when bubbling stops. Be sure to tighten bleeder screw securely. Each wheel cylinder must be bleed until all air is out of the lines. Replenish the brake fluid during the bleeding process so the level does not fall below half full level in the master cylinder reservoir. When bleeding and testing is completed, make sure master cylinder is filled to 3/8" below the top of the reservoir and filler cap is securely in place.

***********************************************************

The full document used to be on Tie Down's web site and probably still is. For anyone handling brake fluid around a painted trailer, be aware that a single drop of spilled brake fluid will almost immediately eat the paint off.

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2005 Four Winns 230/240
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 Post subject: Re: Trailer hitch shunt
PostPosted: Mon Mar 17, 2008 6:59 pm 
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Starfish

Joined: Mon Aug 07, 2006 4:28 am
Posts: 57
Location: Sydney, Australia
Mike,
I think you where right about the leak!!!!!!
The brake line has broken away from the caliper :shock:
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 Post subject: Re: Trailer hitch shunt
PostPosted: Tue Mar 18, 2008 1:16 am 
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230 Mike
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Joined: Mon May 15, 2006 7:59 pm
Posts: 5141
Location: Kansas City, Table Rock Lake
Whoa! Now that's a new one!

See, here's an example of how FW could improve their trailers. Those stupid steel brake lines really need to go.

From being in Australia and having a galvanized trailer, I assume you boat in salt water? If so, what I would do is replace your steel lines with flexible brake lines. Tie Down even sells them that will work with your other existing brake components, in fact you already have a flexible line running from the master cylinder back to the junction of the two main frame rails under your winch. At that point there's a brass fitting, and from there on back it's all steel lines. FW saves about $20 by using steel instead of continuing the flexible lines all the way back.

I don't know how mechanical you are, but replacing those lines with flexible lines should be simple. Once that's done, you're "only" left with the task of getting the dampener on your master cylinder re-primed. Given all of it together, it might not be a bad idea to just let your dealer take care of it, but I would not put steel lines back on.

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2005 Four Winns 230/240
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1998 F-150 XLT
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 Post subject: Re: Trailer hitch shunt
PostPosted: Tue Mar 18, 2008 5:40 am 
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Starfish

Joined: Mon Aug 07, 2006 4:28 am
Posts: 57
Location: Sydney, Australia
Think this job has got a touch out of hand.
I have got a particular helpful motor mechanic where i get my cars serviced, a block away, so he is going to come up and repair it in the garage.

Regards Scott

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