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Master Cylinder for Atwood Brake Actuators

Atwood Accessories and Parts

ratingratingratingratingrating (33 reviews)


Code:   85841

Retail:$75.99

Price:$56.95


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Shipping Weight: 5 pounds

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Atwood Accessories and Parts - 85841

Features:

  • Replacement Master Cylinder for Atwood Brake Actuators
  • For drum brakes only

85841 Atwood Replacement Master Cylinder

Replaces 85736





Video of Master Cylinder for Atwood Brake Actuators


Videos are provided as a guide only. Refer to manufacturer
installation instructions and specs for complete information.

Video This Old Trailer Master Cylinder Install 2
This Old Boat Trailer: Master Cylinder Installation

Video Transcript for This Old Boat Trailer: Master Cylinder Installation

Today on This Old Boat Trailer we are going to rebuild the hydraulic actuator on here and we are going to be using part number 85841, the master cylinder itself, and then we are going to use a master cylinder replacement cap part number A87478, and the cable push rod replacement kit part number 85852, all from Atwood. The first thing we need to do is remove the old master cylinder itself. This is going to require taking off the cap which we have already done. We have disconnected the line back here already and then we can see our factory line, lets disconnect that and then we are just going to undo these four bolts right here. There is probably going to be some leftover brake fluid in there so it will be a good idea to wear some gloves or something. We are going to pull out the back and then underneath there is a little push rod you may want to pull away from it too to help knock it out. 01:09

The gasket for your old master cylinder sits on the bottom here. Most of the it came off with the old master cylinder but it is a good idea to run a scraper over it to make sure you get all of the junk out of there. Now we have got the master cylinder out, lets check the condition of the shock absorbents on the inside of here. Basically you should be able to move it but you should not be able to move the fast. It should be a slow, even, steady pace like this. In this case I think the shock is in good shape so we will not worry about replacing that. The next thing we are going to do is remove the old push rod part right here. We are going to have to take apart this bolt and the nut on the other side. Take it apart and get this out. Remove the bolt. There is a little spacer on the other side and hang on to that. This will come forward and the block, you will want to save that too and this part will get replaced. Lets pull the rest of that cable out from the top and down and lets go get our new parts. 02:28

First we are going to reinstall a new push rod cable. Push it back up the original opening and push that into place. Put the block in. We have got a few pieces to line up here get the location and run the bolt back in. Once you have got it through put the spacer back in to place and then reinstall the nut. We will use one of the new placement lock nuts on the outside and then we will tighten it back down. You do not have to crank it, just get it snug. This is our new master cylinder. We installed a little angle piece for the line to go into. On top we already installed the gasket which is kind of neat. We spent some time cleaning off the top of it so it adhered good because the gasket itself is basically like a sticker. What you also need to do is add a little rubber boot right here and that is going to slide on over the metal and it has its own little pocket that it goes in to. What will happen is that this push rod will end up going inside of here. If we can we will try to push everything up inside there and work it into place. One quick look and make sure it is all lined up and we will install the new bolts that came with the kit to hold everything in place. When you tighten these down you just want to get them snug, we do not really have to torque them down or anything. The next thing we are going to do is work on our catch for our cable. This one is in pretty decent condition but we will replace it. We are going to grind off the top of the rivet and to keep the sparks and junk and shavings from flying into the master cylinder we are going to put a paper towel in there just to plug it up to keep stuff from flying in. We are going to try to punch this out to see if we can get anywhere. If not we can grind it down and punch it some more. The next thing we need to do is remove the bolt for our shock right here so that way we can just push it out of the way and have plenty of room to install the nut and bolt. If you can not get this nut removed it might be easier to open up the master cylinder once again and then just put your hardware in and reassemble it. Put the tab into place and then we will sneak the nut underneath and run a new bolt through. Now we will tighten the master cylinder back up again. 05:24

Lets turn our attention to the other end of the cable now. We will put our hook on here and we are going to take a pair of channel locks and squeeze it down. Back to our master cylinder lets hook up a line going out to the trailer brakes. We will run it up until it stops. Maybe about 1/ 8 of a turn more and that should snug it up just fine. We are going to turn our attention to the hydraulic lines at the slave cylinders right at the hubs. We are going to disconnect the lines. We are going to put a cap on one end and then a line on the other so that way we can use a master cylinder to flush out the old fluid and get new fluid in there. It would be just like bleeding the brakes except we will be removing old fluid. We will fill up the master cylinder and we will pump fluid through. All we have got to do really is just move the hydraulic actuator in and out a few times to get things going. To make it easier put vise grips on the end here to give it more leverage. Draw in some more and that will push out fluid out back. We will repeat the same process from both sides of the lines. Next we will reconnect our lines to the slave cylinders in the hubs and then we will bleed the slave cylinders again and we should be good to go. We are going to do the other side. We can start them and then we will tighten them down with a wrench. Now we can start bleeding the slave cylinders. We are going to take the bleeder valve and open it up and we are going to slide a rubber hose over that and run it into our container. Then we will bleed the brakes. This will take two people to do. One to activate the coupler itself and one to shut the valve when you have gone through the stroke and it stops. We have got some fluid in the bottom of our container here. We want to keep running fluid until we get all of the bubbles to come out. This will take quite a while to do too. We will repeat the same process on both sides of the axle. When we are finally done we can install the cap and then we will be finished. With that, that will finish it for This Old Boat Trailer using part number 85841, part number A87478, and part number 85852.


Customer Reviews

Master Cylinder for Atwood Brake Actuators - 85841

Average Customer Rating:  ratingratingratingratingrating4.8 out of 5 stars   (33 Customer Reviews)




- 85841

ratingratingratingratingrating by: Jeff C.08/21/2012

Is this review helpful?


I R&R'd not only the master cylinder but both wheel brakes (I actually just replaced the entire backing plate on both sides, it is much quicker, and I needed the full meal deal on one side anyway after some problems on the road). The whole project went quickly and works great. There are no install instructions included with the master cylinder, but if you watch the online video etrailer offers, and pay attention while removing the old master cylinder, it is really pretty easy. Key items are: make sure the old gasket comes off completely and has left a clean surface (a wire brush is needed otherwise); make sure the new gasket is properly aligned atop the new master cylinder (it is adhesive but doesn't stick very well), and above all, keep the new reservoir clean during install. I needed to save and re-use a 90 degree fitting between the master cylinder and the brake line, but your install may be different. If you use it, clean it! 52547


Comments

I also had to reuse the 90 degree brake fitting. The new master cylinders do not come with it and there are no instructions showing it either. I order brand new brake lines and had to learn the hard way!

comment by: Ryan L - 9/10/2013


2055


Comments

Does the ball end of the cable go in the slot on the front of the master cylinder? The video does not show this, looks like it should in the schematic.

comment by: Bill S - 5/1/2013


1469

Check out the picture on part 85852. The cable attaches to the push rod assembly. In the event the trailer comes free of the tow vehicle, the cable will engage the push rod and the trailer brakes will activate.

Patrick B - 5/2/2013





- 85841

ratingratingratingratingrating by: TJL11/10/2013

Is this review helpful?


Worked like a champ. If the overall surge brake assembly is bolted on to the trailer frame rather than welded, it is easy to dismount the whole assembly then remove the old cylinder and install the new one. Ordering and shipping were reasonable. Installation video presents clear pictures and simple directions--well done!106906



- 85841

ratingratingratingratingrating by: Richard M07/18/2013

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I received the brake parts for my trailer right on time. The installation was simple and straightforward and the videos really helped. The surge brakes on my boat trailer work better than ever. You have a totally satisfied customer. Thanks.90206



- 85841

ratingratingratingratingrating by: Gary C.06/09/2013

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Looked all over the web for this master cylinder and e-trailer had it and all of the other parts that I needed to rebuild my brake system on my bass boat trailer. E-Trailer has everything you need and they have great service.83899



- 85841

ratingratingratingratingrating by: DMAC11/23/2012

Is this review helpful?


Order shipped almost immediately arrived at my door in 2 and 1/2 days I installed the master cylinder and other brake parts in about 3 hours. The video was good for info I may or may not have known or done. Quick service and exact product match on a 20 year old trailer. Locks also work great59956



- 85841

ratingratingratingratingrating by: James C.08/18/2012

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I would recommend Etrailer to anyone. I ordered several parts late at night and got an email notice early the next morning that said not only did my order ship already, but my shipping was upgraded for free! Also, The instructional videos on the site were extremely helpful. Thank you Etrailer. 52202



- 85841

ratingratingratingratingrating by: Randy G06/18/2012

Is this review helpful?


We have a 20 year-old boat trailer and the master cylinder was rusted out. After reviewing the installation video from etrailer, I was confident I could easily replace the master cylinder and bleed the brakes in just a couple of hours. The parts arrived right on time and after just an hour, I had brakes again! The only problem was removing the backing from the gasket adheasive. The backing stuck in one spot which caused the gasket to rip. Other than that, it was a very simple project. 44680



- 85841

ratingratingratingratingrating by: DB Cooper08/22/2011

Is this review helpful?


My only criticism is the the brake line fitting in this requires a fitting before the brake line can be attached (referenced as "an angle piece" in etrailer's installation video). it is not provided in any of the atwood kits. other than that its an easy installation.22483


Comments

For Atwood 85841 Master Cyl, there is a small 90 deg brake line adapter. Video calls it an angle piece. Does eTrailer sale that?

comment by: Jess P - 6/3/2013


1595

We do have one 1/8 NPT brass 90, but I am not sure if that is the right part. Different hydraulic couplers use a variety of different small parts and not all of them are available to us. We have to keep a stash in our shops for when we do repairs. If the 1/8NPT fitting I have linked will not fit the threads properly, good hardware stores or auto parts stores should be able to help you.

Patrick B - 6/4/2013





- 85841

ratingratingratingratingrating by: Wendy W07/07/2011

Is this review helpful?


All the parts ordered were exactly correct and job went well, other than I sure could have used a 3rd hand on the installation of master cylinder to keep everything aligned before the gasket fell off so I could get the bolts installed. Consequently I did not get any pix to submit, but everything is perfect with new boot and cap also. thanks to you all... WW18801



- 85841

ratingratingratingratingrating by: KG07/06/2011

Is this review helpful?


This master cylinder was a perfect replacement for my old popup camper that was full of rust and chunks. I really appreciate the video that walked me through the steps of replacing the part with an actual person working on the actual parts I ordered.18525



- 85841

ratingratingratingratingrating by: Jay09/24/2013

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Customer service is outstanding, product is great, and delivery was fast! Highly recommend etrailer.com!101230



- 85841

ratingratingratingratingrating by: Kenneth A07/19/2013

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A++++++++++++++++++++++++ 90561



- 85841

ratingratingratingratingrating by: Marty06/14/2013

Is this review helpful?


This was easy in install after I watched the video. Very positive way to promote an item. Bleeding wasn't a problem, and everthing fit perfect.84587



- 85841

ratingratingratingratingrating by: Mike L05/29/2013

Is this review helpful?


Exactly what I needed. Worked great. Fast Shipping!82323



- 85841

ratingratingratingratingrating by: Steve02/04/2013

Is this review helpful?


Super fast shipping and exactly what I ordered. Only wish that the parts breakdown of my whole surge assy was linked in the web site because I need more parts.64968



- 85841

ratingratingratingratingrating by: Craig F12/16/2012

Is this review helpful?


I received the items ordered very quickly. It all went together just like they showed in the video. The video was excellent and made the job easy. Thanks Much!!!61589



- 85841

ratingratingratingratingrating by: STU NEW JERSEY10/22/2012

Is this review helpful?


PART WAS CORRECT RECEIVED IT FAST AND IT WAS THE CORRECT PART THANK YOU,57835



- 85841

ratingratingratingratingrating by: Ron S10/12/2012

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As advertized. Fast delivery. When I need trailer parts I now know where to get them. 57043



- 85841

ratingratingratingratingrating by: Fred L06/22/2012

Is this review helpful?


I ordered two separate parts to refurbish my boat trailer. The parts arrived very quickly and were exactly what I needed for the job. I found Etrailer to be an excellent source and will use them again.45215



- 85841

ratingratingratingratingrating by: eric04/15/2012

Is this review helpful?


i have never replaced a master cylinder or anything else for that matter on a trailer but this website with the video and quality easy to find products made the repairs very easy and saved me on labor cost. 37297



- 85841

ratingratingratingratingrating by: Terry H.02/21/2012

Is this review helpful?


delevery was very fast, great service 32099



- 85841

ratingratingratingratingrating by: mfh11/04/2011

Is this review helpful?


just the right part . good price fast service thank you 26567



- 85841

ratingratingratingratingrating by: Steve C08/23/2011

Is this review helpful?


Received parts whilst on holiday in the USA. Fantastic service and delivered exactly when promised to my hotel. Will fit on my 30 year old trailer when I return to UK.22553



- 85841

ratingratingratingratingrating by: mikey07/22/2011

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great product, easy to do transaction, shipping was faster then expexted. I will diffently use and recommend e trailor again.19838



- 85841

ratingratingratingratingrating by: Michael W.07/11/2011

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Parts got here fast. Videos were great. Had no problems. Thanks19168



- 85841

ratingratingratingratingrating by: EG07/09/2011

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Great products 19009



- 85841

ratingratingratingratingrating by: Rebecca Nevel07/07/2011

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This is the second time we have done business with you, and I have to tell you everything has been perfect! We received everything on time and all was correct as ordered. When we need anything else we will be in touch. Thank You18836



- 85841

ratingratingratingratingrating by: Randy R.05/19/2011

Is this review helpful?


Product shipped fast. Customer service updates me via email through the process. Love the how to videos. Etrailer earned my business.14795



- 85841

ratingratingratingratingrating by: Tim M.04/18/2011

Is this review helpful?


Exact part I needed.They shipped it right away. Fair prices.11953



- 85841

ratingratingratingratingrating by: Dan03/16/2011

Is this review helpful?


The cross referenced master cylinder appears to be an exact replacement of the original and for a very fair price. Shipping and follow up were finest kind. I would recommend e-trailer to all of you who are rehabilitating old equipment.9470



- 85841

ratingratingratingratingrating by: Fred02/21/2011

Is this review helpful?


fast shipping 7603



- 85841

ratingratingratingratingrating by: Bobby Looper04/26/2013

Is this review helpful?


Works great 77985



- 85841

ratingratingratingratingrating by: John B07/22/2011

Is this review helpful?


My order came allot sooner than I had expected and the order was correct. I installed the product and I have no complaints. I look forward to doing business with eTrailer again!19941



Ask the Experts about this Atwood Accessories and Parts
Expert Answers about Master Cylinder for Atwood Brake Actuators - 85841                                             Do you have a question about this Accessories and Parts?


  • Does the Master Cylinder Cap and Gasket Come With the Atwood Master Cylinder, part # 85841
  • You will also need to order, part number A87478, to receive the replacement cap and gasket that goes with the Atwood part number 85841 master cylinder.
    view full answer...

  • Master Cylinder for Atwood is a Replacement for Hydraulic Surge Brake Actuators
  • This Master Cylinder for Atwood Brake Actuators, part # 85841, is a replacement master cylinder for surge brake actuators, which are used with hydraulic brakes. This master cylinder is for use with drum brakes only.
    view full answer...

  • Will The Atwood Master Cylinder, # 85841, Replace The # 85736 Atwood Master Cylinder
  • I called the manufacturer (Atwood) and they said that they did not have an Atwood coupler with the part number of 61101 (they thought it might be the date code on the coupler) but if it has the # 85736 master cylinder on it you can use the Atwood Master Cylinder, # 85841. The Atwood Master Cylinder, # 85841, is the exact replacement for the # 85736 master cylinder. The # 85841 master cylinder does come with the mounting gasket, but does not come with a replacement master cylinder cap and cap
    view full answer...

  • Replacement Master Cylinder part # 23361 for Model 60 Actuator Recommendation
  • It looks like you would need a Dico Replacement Master Cylinder for Model 60 Actuator, part # 23361. You may also be interested in purchasing a Master Cylinder Cap and Gasket for Model 60 Actuators, part # 23388.
    view full answer...

  • Troubleshooting No Hydraulic Fluid Reaching the Trailer Brakes After Installing New Master Cylinder
  • The small red/orange plug in the Master Cylinder for Atwood Brake Actuators, # 85841, cannot be easily removed and the part is not available separately. There could be several other problems that are causing the issue you are experiencing. There could be a lack of fluid in the system, a kink in line somewhere, or air in the system. With a full reservoir, I recommend bleeding the brakes to release any trapped air in the system. I have included a link to a video showing how to bleed trailer bra
    view full answer...

  • Atwood Master Cylinder # 85840 Recommendation
  • The replacement master cylinder that you would need for your 1993 trailer is the Replacement Master Cylinder, part # 85840. This will be a direct replacement for the # 85778 that you have on your trailer.
    view full answer...

  • Does a Trailer Surge Coupler Return to Normal Position on Its Own after Braking
  • When manually bleeding the brakes, you will need to push the coupler in and out by hand as it will not necessarily return on its own. If it seems that your trailer brakes are not working as well as they should, the brakes may need to be adjusted due to wear. There could also be air in the lines and bleeding the brakes should remove any air. I have included a link to a video that demonstrates the brake bleeding process.
    view full answer...

  • Master Cylinder Boot Replacement for an Atwood Trailer Brake Actuator
  • We do have a replacement boot for Atwood actuators. It is the Replacement Boot Kit, # 84258. The boot is also available in the Replacement Push Rod Kit, # 85852. I have included a link to a video showing a master cylinder installation for you.
    view full answer...

  • Replacement Parts for the Atwood Brake Actuator and Replacement Assembly
  • We do carry replacement parts for our Atwood Brake Actuators. Part # 85841 that you referenced is a replacement master cylinder for the Atwood Actuator, part # 82541. I have included a link to the available Atwood actuator replacement parts, many of which fit the Atwood actuator # 82541. I have also included a video of a technician replacing the master cylinder and the push rod assembly, part # 85852, on the Atwood brake actuator.
    view full answer...

  • Is it Better to Replace or Repair a Welded-on Trailer Surge Coupler
  • In most cases where the coupler is welded to the trailer frame, most owners find that it is easier to replace worn parts, rather than try to remove and replace the coupler. If you are not opposed to removing the old one and re-welding a new coupler in its place, I would go that route. The reason is because couplers can be tricky to work on and replacing some parts might reveal that you need other parts. With a new coupler, you get all new parts and will not have to worry about something else
    view full answer...

  • Hydraulic Drum Trailer Brakes are Locking Up on Boat Trailer with Atwood Brake Actuator
  • I agree with your diagnosis. It does sound like the worn parts of the actuator are causing some kind of issue with the master cylinder. It may be sticking and unable to pull back and it could be getting air in the lines or other problems. Also, check the break-away cable and assembly to see if it is partially engaged. There should not be much play in the system so I do recommend going with new parts to get the system back to good working order. When looking for replacement parts make sure tha
    view full answer...

  • Testing A Hydraulic Coupler and Bleeding a Hydraulic Brake System
  • If you look at page # 4 of the instructions I linked, you can see the typical procedure and a diagram showing how to test a surge coupler. The procedure involves using a 4 foot long 2 x 4 as a lever and the safety chains as a fulcrum. We have a video that shows how to bleed a brake system, click on the link provided. You will need a helper, a length of rubber tubing that will fit onto the bleeder valve and a clear plastic or glass bottle. I prefer a glass bottle because it is easier to see th
    view full answer...

  • Comparing Atwood # 84132 and Titan # T4339700 Trailer Brake Actuating Couplers
  • The Atwood actuator # 84132 comes with a manual reverse lockout and it has a 2-year limited warranty. On the other hand the Titan actuator, # T4339700, does not have a reverse lock out and it has a 1-year warranty. It will also fit on 1-7/8 inch, 2 inch, and 50mm balls whereas the Atwood only fits 2 inch balls. The Atwood coupler has an electrodeposited enamel finish and is rated over the 96 hour salt spray test requirements for corrosion resistance. The Titan actuator is steel with zinc pla
    view full answer...

  • Difference in Atwood # 85736 and # 85841 Master Cylinder for Atwood Brake Actuator
  • The Atwood Master Cylinder # 85841 you referenced is a replacement for the part # 85736 that is no longer available. The cost of the product is located at the link I have provided, not including any applicable sales tax and shipping and handling. I have included a link to an installation video for this product.
    view full answer...

  • Right Side Hydraulic Trailer Brake Locks Up After Braking
  • You may be getting air in the lines or have a wheel cylinder that needs to be replaced. It is also possible that you have the wrong side brake assembly on that right side but since it is only an issue after braking this is probably not the case. There could be something in the brake assembly itself that is getting stuck. I recommend pulling the wheel and drum off to inspect the operation of the brakes, check for any foreign objects that might be causing the malfunction. If the wheel cylinder
    view full answer...

  • Repairing or Replacing Hydraulic Drum Brake Components on 14 Year Old Boat Trailer
  • Although it would be a bit more expensive, I would recommend replacing the entire brake assembly on each side, not just the wheel cylinders. This will provide all new parts, and you will know that it will be quite some time before the brake shoes, adjusters or springs will need replacement. The Demco # 40715 and 40716 you referenced would be an acceptable replacement. In my experience, there is not perceptible difference in quality between Demco and Dexter brake assemblies. This being said, I
    view full answer...

  • Replacement Master Cylinder for Atwood Actuator
  • We have 2 Atwood master cylinders and # 85841 should be the correct one as long as the trailer has drum brakes. The only other option is # 85840 which is not even close to your picture. i have linked a video showing a typical installation of the master cylinder for you.
    view full answer...

  • How to Reassemble a Trailer Brake Master Cylinder
  • It looks like you have it lined up correctly based on the picture you sent for the most part. The only thing you might need to do is flip the spring around. If you have drum brakes and there is a check valve on the end of the spring that is partly covered by the black cover in the photo then you will need to flip it around so that it goes in first. It is hard to see in the picture but it looks like there is a brass check valve at the end of the spring. Basically the spring goes in first with
    view full answer...

  • Resetting and Releasing a Break-Away Cable on an Atwood Hydraulic Brake Actuator
  • To reset the break-away cable on a hydraulic brake actuator, you will need to feed the cable back through the opening in the top of the housing so the push rod can be properly released into the master cylinder. Once this is done, pressure from the master cylinder is released and the brakes will disengage. The break-away cable is attached to a clip on the push rod. The break away cable activates the breaking mechanism by pulling on the clip that pushes the push rod into the master cylinder whi
    view full answer...

  • Putting a Titan Model 6 Brake Actuator Master Cylinder Back Together
  • I have included a picture that will help some but it does not show the internal components. The thick rubber washer you mentioned should go on one end of the spring and acts as a cushion and seal. It should go on the back of the spring. The multi-hole disk goes against the end of the metal cylinder. You can see on the back of that cylinder where the holes line up. The black cap goes between the metal cylinder and spring. The spring clip holds everything inside the master cylinder. Place the boot
    view full answer...


Info for this part was:


Expert Research:
Michael L

Expert Research:
Robert G

Expert Research:
Patrick B

Expert Research:
Michael H

Expert Research:
Jameson C

Expert Research:
John H

Expert Research:
Brandon M

Expert Research:
Adam R

Expert Research:
Rachael H

Photos by:
Sam P

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