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Accessories and Parts > Trailer Coupler > Replacement Parts > Brake Actuator Parts > Master Cylinder Parts > Master Cylinder > Atwood


Replacement Master Cylinder for Atwood Trailer Brake Actuators - Drum

Atwood Accessories and Parts

ratingratingratingratingrating (39 reviews)


Code:   85841

Retail:$75.99

Price:$56.95


Shipping Special

Shipping Weight: 4 pounds

Quantity: 







Atwood Accessories and Parts - 85841

Replacement master cylinder fits Atwood hydraulic trailer brake actuators for drum brakes. Includes master cylinder and hardware. Boot not included.

Features:

  • Replaces master cylinder for Atwood hydraulic brake actuator for drum brakes
  • Includes master cylinder and hardware
    • Does not include boot


85841 Atwood Replacement Master Cylinder

Replaces 85736










Customer Reviews

Replacement Master Cylinder for Atwood Trailer Brake Actuators - Drum - 85841

Average Customer Rating:  ratingratingratingratingrating4.8 out of 5 stars   (39 Customer Reviews)

Replacement master cylinder fits Atwood hydraulic trailer brake actuators for drum brakes. Includes master cylinder and hardware. Boot not included.


- 85841

ratingratingratingratingrating by: Jeff C.08/21/2012


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

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 - 05/01/2013


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



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 - 09/10/2013


2055



- 85841

ratingratingratingratingrating by: Reno R07/05/2014


Product came in a few days. Fit perfectly. Worked great. One tip for everyone. I had some rust in my old Master Cylinder and thought I could soak it in parts cleaner but the small passages must have been too clogged. I had purchased all the new parts except for the shock which was in good shape. I should have purchased all the parts AND the Master Cylinder. After watching the great video on how to install all the parts from etrailer on Youtube it was a cinch. You save a lot of dough DIY so just buy all the parts and sleep easy. 139346






- 85841

ratingratingratingratingrating by: Randy G06/18/2012


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


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 - 06/03/2013


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


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... WW 18801






- 85841

ratingratingratingratingrating by: TJL11/10/2013


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: DMAC11/23/2012


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 great 59956






- 85841

ratingratingratingratingrating by: James C.08/18/2012


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: KG07/06/2011


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: Richard M07/18/2013


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: Dan03/16/2011


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: Rebecca Nevel07/07/2011


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 You 18836






- 85841

ratingratingratingratingrating by: Gary C.06/09/2013


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: eric04/15/2012


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: Fred L06/22/2012


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: John B07/22/2011


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






- 85841

ratingratingratingratingrating by: Steve C08/23/2011


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: Craig F12/16/2012


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: Steve02/04/2013


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: Marty06/14/2013


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: Randy R.05/19/2011


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: mikey07/22/2011


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






- 85841

ratingratingratingratingrating by: Jay09/24/2013


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






- 85841

ratingratingratingratingrating by: Ron S10/12/2012


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






- 85841

ratingratingratingratingrating by: STU NEW JERSEY10/22/2012


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






- 85841

ratingratingratingratingrating by: Michael W.07/11/2011


Parts got here fast. Videos were great. Had no problems. Thanks 19168






- 85841

ratingratingratingratingrating by: Tim M.04/18/2011


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






- 85841

ratingratingratingratingrating by: mfh11/04/2011


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






- 85841

ratingratingratingratingrating by: Mike L05/29/2013


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






- 85841

ratingratingratingratingrating by: Jim M06/23/2014


An exact replacement for my 15 year old surge brake. 137128






- 85841

ratingratingratingratingrating by: Joe D05/28/2014


Fast shipping, Good product, Fits perfe ct!! 133039






- 85841

ratingratingratingratingrating by: Alan R.06/01/2014


Product as advertised, prompt delivery 133582






- 85841

ratingratingratingratingrating by: Terry H.02/21/2012


delevery was very fast, great service 32099






- 85841

ratingratingratingratingrating by: Ryan S08/15/2014


Perfect on prestige boat trailer. 146952






- 85841

ratingratingratingratingrating by: Kenneth A07/19/2013


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






- 85841

ratingratingratingratingrating by: jason08/16/2014


Perfect fit... 146989






- 85841

ratingratingratingratingrating by: EG07/09/2011


Great products 19009






- 85841

ratingratingratingratingrating by: Fred02/21/2011


fast shipping 7603






- 85841

ratingratingratingratingrating by: Bobby Looper04/26/2013


Works great 77985




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


  • Will Atwood Master Cylinder 85841 Replace an Older Atwood Master Cylinder 85736
  • I spoke with my Atwood contact this afternoon. Master cylinder # 85841 has been used on most, if not all Atwood actuators since 1980. If in fact your actuator is pre-1980 there are not any parts available for those older actuators, and it would probably be best to replace the actuator. I have added a link below to all our actuator couplers, both bolt-on and weld-on.
    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...
    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...

  • 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...

  • 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...
    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...

  • 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...

  • Reoccuring Corrosion and Fluid Contamination in Master Cylinder
  • A hydraulic brake system is designed as a closed system. If a master cylinder is kept full of fluid, corrosion is not a problem. My guess is that somehow water is getting into the system through a leaky fitting or cap. If it is your cap that is leaking, if you can provide me with the manufacturer and model number of your master cylinder I would be happy to look for a replacement 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...

  • 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...

  • Key Differences Between Disc Brake and Drum Brake Trailer Coupler and Brake Actuators
  • Drum brake actuators and disc brake actuators use different master cylinders. A disc brake actuator producer a higher psi than a drum brake actuator so the fittings will be a little different as well. The drum brake master cylinder will have a check valve in it that reduces the amount of psi the system puts out. The disc brake models do not have this valve because more pressure is needed to actuate disc brakes The problem could be air in the lines and/or pistons in the calipers that...
    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...
    view full answer...

  • Replacement Parts for Atwood Trailer Brake Actuating Couplers
  • Usually on Atwood couplers, there is information on the top near the fill cap, and/or on the top in front of the latch. There could also be some on one of or both sides. Despite that, I can help you with the replacement parts you will need. If your actuator is drum brakes (6,000 or 8,000 pound), then you will use Replacement Master Cylinder, # 85841. For a fill cap, use # A87478. If the shock or push rod has gone bad, they are parts # 85830, and # 85852. For disc brake actuators the...
    view full answer...

  • Will the Atwood Master Cylinder # 82541 Replace the Atwood Master Cylinder with Casting # 85736
  • As long as your trailer has drum brakes, the Atwood Master Cylinder, # 85841, will be the correct part to replace your existing master cylinder. This master cylinder has been used on most Atwood Drum Brake Actuators since 1980. We have an installation video showing how to replace this master cylinder that should be helpful. If you need a new cap for the master cylinder, the Replacement Master Cylinder Cap and Gasket, # A87478, is the correct replacement for the # 82541 master cylinder. ...
    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...
    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...
    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...

  • 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...
    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...

  • 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...
    view full answer...

  • Replacement Master Cylinder for Atwood Drum Brake Surge Coupler in 1972 Ideal Car Trailer
  • The Titan Replacement Master Cylinder you referenced, part # T1027100, is intended specifically for use as a replacement for their Model 6 Drum Brake Actuator. We do offer replacement master cylinders for Atwood couplers for both drum and disc-brake systems. Part # 85840 is for disc brake actuators and fits 6,000-lb and 7,000-lb disc brakes; part # 85841 is for drum brake applications like the part you referenced. These two master cylinders each deliver the specific hydraulic pressure...
    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...
    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...
    view full answer...

  • Need Replacement Master Cylinder for Atwood Master Cylinder 885736 for Disc Brakes
  • The part that you referenced, Atwood # 85841, is a replacement master cylinder for the Atwood drum brake actuator. This is a correct replacement for the part number you referenced, 85736, but for drum brakes. (This may be the casting number rather than the master cylinder part number.) My contact at Atwood confirmed that for your disc brake application you should use their replacement master cylinder for disc brakes, part # 85840.
    view full answer...

  • Can You Use a Power Bleeder to Bleed Atwood Brake Actuators
  • You definitely can use a power bleeder to bleed Atwood actuators, in the installation instructions for their actuators they say to use a power bleeder or bleed them manually. Is your power bleeder building pressure but nothings coming out of the fitting when you loosen it? If so, I would verify that your no lockout device is being activated. If you have a manual lock out be sure it's not activated and preventing the pressure from getting past the actuator. If you choose to manually...
    view full answer...

  • Replacement Master Cylinder for 2006 Ranger Boat Trailer
  • We do offer a range of replacement master cylinders for both hydraulic drum and disc brake actuators for various manufacturers. However, I was not able to confirm the brand of actuator/coupler installed on your boat trailer nor whether it has drum or disc brakes. For example, we offer Titan Master Cylinder for Titan Drum Brake Actuators, part # T2374400, which fits their popular Model 10 and Model 20 actuators. We also offer a replacement for Atwood Drum Brake Actuators, part # 85841....
    view full answer...

  • Troubleshooting Surge Brakes that are Locked Up
  • The shock of your actuator is designed to dampen the movement of the actuator so that the brakes apply smoothly without jerking. The shock itself does not push the tongue of the coupler out to release the brakes. If your brakes are locked up that is because the tongue of the actuator is stuck in the pushed in position with the brakes being applied. Most likely this is not the shocks fault, although the correct shock for your Atwood coupler is part # 85830. You have an actuator similar...
    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...
    view full answer...

  • Should a Disc Brake Trailer Coupler Actuator be Used With Hydraulic Drum Brakes
  • The difference is that disc brakes require a higher psi level in order to engage the brakes. The drum brakes are not really designed to handle that level of pressure so it would be best to use the correct coupler or switch to disc brakes. Depending on the coupler you have, you may just need to change the master cylinder to a drum brake application and not replace the entire coupler. If you are using the Atwood Coupler, # 88730, you have referenced, you would need Master Cylinder # 85841....
    view full answer...


Info for this part was:


Expert Research:
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Photos by:
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Updated by:
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