Community Forums

carlsagan · 03-25-2025, 07:37 PM

I am trying to locate an affordable master cylinder for my 2000 38MDDS. All have found is one for about $1,500 online. I found some old posts on this subject but none that listed where to go to get one, just talk of an updated version that is smaller bore and may work better. Any advice is much appreciated.

justcheckn · 03-25-2025, 08:21 PM

Can u post a picture?

SafariBen · 03-25-2025, 08:28 PM

So probably a bendix 2.0" bore with hydroboost or hydromax, and the smaller one would be 1.75" bore? As far as I know, there's not much variety, the two sizes, reservoir fluid level sensor, or pressure differential switch. The remote reservoir adapter can be swapped to the new one. Worst case, have to swap some internal hard parts, and essentially use the new one as a rebuild kit. They use O rings, not traditional cup seals like every other cylinder I've seen. What's yours doing?

carlsagan · 03-25-2025, 08:57 PM

My Coach has never seemed to have very great brakes, and it seems like the o rings are leaking off if you hold the pedal down. From what your saying it sounds pretty simple. Do you know of any source or part numbers on these? I attached pictures.

SafariBen · 03-26-2025, 06:55 AM

I think I see the hex plug for the differential pressure sensor on the other side of the master cylinder, so you'll need one with that if you want to preserve that safety feature.

Mine started leaking down with pedal application, and it was the check valve, that is located between the master cylinder and the remote reservoir adapter. The adapter is aluminum and had corroded enough to distort and damage the check valve. I ordered a similar looking bendix cylinder and only used the check valves. I couldn't find them anywhere in any rebuild kit or separately. The cylinder was cheap enough off ebay. I think there's one up now for similar price, a little surface rust, but shouldn't hurt. It might even be 1.75" and you could try the swap to see how you like it.

I might be able to stage a photo of the check valves if you need it, but just take the reservoir adapter off the top of the master cylinder and examine them to see if they're distorted and torn. You can also see the o rings from the holes if you use a mirror, or take the cylinder off.

Alpine36 · 03-26-2025, 10:52 AM

Read this old post. The 2239045 master cylinder is available without a reservoir, and you swap over the old remote reservoir hardware. This may be one of those rare instances where Napa or Carquest may be the way to go. Anyhow, here it is…

https://www.irv2.com/forums/f258/bos...ps-456457.html

SafariBen · 03-26-2025, 11:11 AM

Excellent. The first pic in that thread shows the check valve seals that I had issues with, the double O ring with the three radial "connectors", so a funny looking seal, but very important. My remote adapter plate had filled the seal groove with corrosion, cleaned that out with an o ring pick and light brushing, then put it back together. So even replacing the master cylinder, reusing the remote adapter plate, you'll want to clean those grooves.

carlsagan · 03-28-2025, 12:04 PM

Thank you both for responding. I definitely want to replace it rather than rebuild myself, but I will clean those groves out. I am finding a lot of options with that number 2239045 all over the place. Napa does not have it anymore but I can find it many other places with a surprising range of prices. I have not found any with out the reservoir but I assume I can just replace it with the adapter with no issue.

SafariBen · 03-28-2025, 12:22 PM

yes, you won't find it without the reservoir, you'll have to re use the remote adapter plates, and clean the grooves that the check valve "double o ring" sits in.

Alpine36 · 03-28-2025, 03:25 PM

Quote:

Originally Posted by carlsagan

Thank you both for responding. I definitely want to replace it rather than rebuild myself, but I will clean those groves out. I am finding a lot of options with that number 2239045 all over the place. Napa does not have it anymore but I can find it many other places with a surprising range of prices. I have not found any with out the reservoir but I assume I can just replace it with the adapter with no issue.

If you have a decent commercial brake and clutch supply jobber nearby try them first. The Bosch hydraboost system was used by various medium duty trucks and passenger busses and is reasonably common. Probably best to bring the old master cylinder in with you for comparison. When I replaced all our Alpine brake components front and rear I brought one of everything in for comparison. To my surprise they had everything in stock and reasonably priced. Even less cost than what I found online.

Taxguy · 04-01-2025, 04:29 PM

(This is from a post I made in 2013 don't know it applies here. But might help those with the old 2" bore that have to stand on the brakes. One of my best mods.)

I bought the Wagner MC131759 Master Cylinder Assembly with the smaller bore on Amason for $190 and free shipping. Had it installed by David at Accu Tract in Tucson with full brake bleed (all wheels off) for 5 1/2 hour labor and a gallon of Dot 3.

I can't say the brake capacity increased but the leg effort to apply the brakes definitely decreased. I didn't think my wife would be able to fully engage the brake before. Now the brake petal stroke is a little longer taking advantage of more leverage. Even easier to hold the brake at a red light.

If your going to do a brake fluid flush anyway it's a cheap simple upgrade that I think was worth it.