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RV-4 master cylinders

G

Gerald Loyd

Active Member
I built my RV-4 back in the 80s and have the Cleveland break master cylinders that are mounted upside down. The upside down position makes it real hard to bleed the breaks. After 20 years they have started leaking and need to be replaced or overhauled. An RV-4 owner told me at Oshkosh that he mounted his rightside up when it came time to replace his. I have lost his name & number. Can anyone tell me if this can be done and what changes have to made to the mounting brackets if any.
 
Gerald,
I also had mine mounted upside down but never had any leaks over a 16 year period. It was always a pain to bleed the brakes though. For that reason I decided to mount them the other way on my rocket. I couldnt quite get enough room to use the cleavland master cylinders but the Matco cylinders are quite a bit narrower and fit nicely with a little longer bolts and spacers in the right places. I believe the new kits come with the matco master cylinders so I am sure vans carries them.
Ryan
 
Will try Matcos

Thanks for the responses. I think I'll get a set of Matco cylinders from Vans and try mounting them up right.
 
Don't spend money yet

I'm pretty sure my MCs are Cleveland and all I had to do was flip them over. The fit is tight but it worked fine in my -4. I think I took the pedals out to do the work but my airplane was in a significant state of disassembly when I did this. I'm not sure how easy this mod is going to be on a completely assembled aircraft. I guess it depends on how much room you have behind your panel. I found another way to bleed the brakes with the upside down MCs but it is a workaround at best. Let me know if you want that technique. It does require a mod to the plumbing. Good luck.
 
Cleveland to Matco

I explored the option of rebuilding my leaky cleveland cylinders, but discovered that the return spring had worn the surface of the shaft beyond serviceability. Converting to Matco cylinders was simply a matter of bolting them in place.

I also installed the little aluminum fluid reservoirs from aircraft spruce for a tidy setup.
 
Ordered Matcos

I ordered new Marcos because several guys told me that overhauling the master cylinders dose not always stop the leaks the 1st try. I'm too old and fat to get to those MCs many times. Vans teck advisor said the Matcos are a little slimmer than the old Clevelands, but they still won't fit up right. I hope he's wrong and you guys are right.

Thanks for the infomation.
 
I Flipped..

Hi Gerald,

Believe it or not, the early RV-4 plans showed the MC's mounted inverted, like me, you just followed instructions! I too flipped the MC's on my RV4 way back in the 90's when my teflon lines began leaking after 5 years. I replaced all my lines with braided steel from NAPA, all the way to the wheels. Excellent fix, I definitely mounted them "up-side right" in my HR2. Later a friend asked me to "flip" his RV4's MC's. It was actually fairly easy, but get some plastic line plugs or rags ready.

1. Remove bonnet/forward glare shield.
2. Place old towel in floorboard below pedals.
3. Remove brake lines from MC's, remember which line went where, it matters.
4. Take MC's to vice, clamp and hold. Turn fittings to face "north", take care not to strip them. You can remove them, place pipe seal around them and re-install. Slightly offset them in either direction for clearance. Repairing leaky MC's is no big deal, the key is getting the proper O-rings. Get them from Aircraft Spruce or an aircraft parts store, they won't leak. Take them apart by first removing the upper "u" keeper with pliers, carefully so the spring doesn't shoot across room! Then using small snap ring pliers remove snap ring from upper MC. Pull out plunger, clean inside with mineral spirits, feel for burrs. R&R O-rings Upper is Part#ms28775-110, lower is 28775-113. Re-assemble MC.
5. Take MC's back to RV4, re-install in proper direction. Note, clearance on lower rudder pedal will be close, but OK. Use washers as necessary. If lines don't quite reach, you may have to replace with newer/longer.
6. Service brakes from wheel brake cyllinder. I use a hardware store oil can with clear plastic line attached to lower fitting with 1/4 in box end over fitting. I have a fitting attached to the top of my reservoir with a line going into a pill bottle. I can then pump until it overflows into the pill bottle. I then tighten the lower fitting, remove the upper fitting, remove 1/2 straw-full of fluid from the top of reservoir and re-install cover plug.
7. Check for leaks, firm pedal. :)

Smokey
HR2
 
Last edited:
I got Matco cylinders with my kit and replaced them with Grove. The Grove stuff is far superior in quality. I went with remote reservoirs to give more room for big feet. While I believe strongly in high-grade aircraft hardware and have teflon/braided stainless lines in my Rocket; my certified Super Decathlon uses plain polyethelene lines on the pressure side (transitioning to rigid stainless before it leaves the cockpit) and tygon tubing on the remote reservoir side of each master cylinder. Sounds and looks cheap and chincy but it works and I'm not supposed to change it given it's "certified".
 
You guys convinced me, I flipped mines too !

smokyray said:
Hi Gerald,

Believe it or not, the early RV-4 plans showed the MC's mounted inverted, like me, you just followed instructions! I too flipped the MC's on my RV4 way back in the 90's when my teflon lines began leaking after 5 years. I replaced all my lines with braided steel from NAPA, all the way to the wheels. Excellent fix, I definitely mounted them "up-side right" in my HR2. Later a friend asked me to "flip" his RV4's MC's. It was actually fairly easy, but get some plastic line plugs or rags ready.

1. Remove bonnet/forward glare shield.
2. Place old towel in floorboard below pedals.
3. Remove brake lines from MC's, remember which line went where, it matters.
4. Take MC's to vice, clamp and hold. Turn fittings to face "north", take care not to strip them. You can remove them, place pipe seal around them and re-install. Slightly offset them in either direction for clearance. Repairing leaky MC's is no big deal, the key is getting the proper O-rings. Get them from Aircraft Spruce or an aircraft parts store, they won't leak. Take them apart by first removing the upper "u" keeper with pliers, carefully so the spring doesn't shoot across room! Then using small snap ring pliers remove snap ring from upper MC. Pull out plunger, clean inside with mineral spirits, feel for burrs. R&R O-rings Upper is Part#ms28775-110, lower is 28775-113. Re-assemble MC.
5. Take MC's back to RV4, re-install in proper direction. Note, clearance on lower rudder pedal will be close, but OK. Use washers as necessary. If lines don't quite reach, you may have to replace with newer/longer.
6. Service brakes from wheel brake cyllinder. I use a hardware store oil can with clear plastic line attached to lower fitting with 1/4 in box end over fitting. I have a fitting attached to the top of my reservoir with a line going into a pill bottle. I can then pump until it overflows into the pill bottle. I then tighten the lower fitting, remove the upper fitting, remove 1/2 straw-full of fluid from the top of reservoir and re-install cover plug.
7. Check for leaks, firm pedal. :)

Smokey
HR2
Click to expand...

Since I had everything removed from my cockpit, I've decided to flipped my MC's. Job completed, went easy.

Great info Smokey
Thanks
 
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