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GrahamH

problem bleeding brakes

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GrahamH

Tried to bleed the brakes on my 05 Extreme tandem trailer today. Purchased a Vacula vacuum bleeder for this purpose (and a few other jobs). Started on the farthest wheel from the master cylinder and worked to the closest. Repeated the process. After pulling over a quart of brake fluid through the system there still seems to be a lot of air present. So much air was coming out at each wheel brake that I thought it must have been getting in at the bleed screw threads?? The amount of air never subsided.

I tested the brakes by jacking up one wheel and using a tie down, I winched the actuator to the full brake position. The jacked up wheel spun freely.

Before I started, the fluid level in the reservoir was ok. No leaks evident in the brake lines or at the wheels. I can't be sure if the brakes were working or not. I tow with a 3/4 ton Chey pickup with a Duramax, I don't really feel the boat when pulling or braking.

Any help is greatly appreciated.

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Pistol Pete

If you think air was getting in through the bleeder screw threads then, you probably had the bleeder open too much. It only needs to be opened 1/2 turn. Also, before you close each bleeder, you have to let the vacuum rest and wait until you see a solid line of pure fluid coming out before you close the bleeder.

People new to vacuum bleeding brakes tend to go over board and pump, pump, pump, then shut the bleeder.

Are you sure you never let the master cylinder reservoir go dry? There's only a couple of ml of fluid in there. Were all other bleeders closed when you had any 1 bleeder open? There's a lot of ways to mess up bleeding brakes on a trailer especially if you have 4 bleeder points.

edit, now that I re-read your post, are you saying you used an air powered vacula like the one in this pic.? If you did, I bet you ran into the problem of not letting the vacuum come to a rest before closing the bleeder. I've seen that a lot.

post-29-12577282515692_thumb.jpg

Edited by Pistol Pete

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GrahamH

Thanks for your reply. I think it is a combination of issues, the most frustrating one being that it seems impossible to seal the threads of the bleed screws. Even if they are only open 1/4 of a turn, they leak. Tried grease, did not work, tried telfon tape and it worked for the first time but not the second. I thought everything was going really well and then unfortunately on the last wheel I let the level get too low in the reservoir. So I started again, but could not get the bleed screws to seal.

Please expand on the reason for letting the vacuum come to a rest before closing the bleed screw. Do you mean to disengage the air and let the vacuum dissipate to zero?

Thanks again.

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Lance B. Johnson

You may have to bleed them by pumping the tongue if you cant keep the air from coming around the bleeders. Never had that problem before but then I gravity bleed almost everything.

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Pistol Pete

Graham,

If you are using that vacula I have in the picture, that thing is pulling a massive amount of volume of vacuum. If when you've got it connected to the bleeder all you see is airated fluid, the reason is because the vacula is pulling more vacuum than the fluid can come out of the bleeder fast enough. So the vacula is creating a negative dead space just inside the bleeder that you will only get rid of by taking your hand off the vacula's "on" lever and letting the fluid go back to a solid line. This should take about 20-30 secs.

That vacula is really overkill for this kind of job. And, BTW, like Ruffdawg mentioned, I seem to have more success with pumping the trailer tongue. I do it with a bar clamp.

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GrahamH

The Vacula bleeder that I bought is very similar to the picture you posted. You may well be right in that the negative pressure zone just inside the bleed screw may be too strong, hence sucking air past the threads. Teflon tape on the threads helped. I'll try creating a vacuum then turning the unit off and letting things settle. I am also going to make sure that nothing is restricting the outflow of the master cylinder. If flow out is limited, it would exacerbate the problem. I called UFP today and they said that the tongue should be all the way forward to ensure unrestricted flow.

Thanks for your help.

Graham

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GrahamH

Took the A-60 UFP Actuator out of the tongue and apart tonight. Major carnage inside unfortunately, which is probably why I could not bleed the brakes successfully. I'll find out in the morning if the parts add up to more than the cost of replacement. Luckily no rush at this time of year.

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Pistol Pete

Just as a side note, I've had nothing but problems with the UFP hydro. surge brake system. I've probably replaced every part in the system, some of them twice. Good luck.

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beef

I just completely rebuilt my brakes from the master cylinder on back. I found the best ufp component prices (by a wide margin) from a place called rvdirect.com. Replacement parts at the wheel from easternmarine.com. Spent a lot of time shopping. Hope this helps.

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