|
Sponsored Links (Register now to hide all advertisements) |
|
|
Thread Tools | Display Modes |
08-06-2016, 04:36 PM | #1 |
Senior Member
Join Date: Jun 2014
Location: Salt Lake City, Utah
Posts: 756
|
Static Leak of Wheel Cylinders
I am looking for a solution to leaking wheel cylinders. They weep when the car is sitting. They are USA, NOS parts. They weep with new USA cups and the original USA cups which appear to be in remarkable shape. I cleaned the old packing fluid/ grease from the bores and seals and lubed everything with a light coat of new brake fluid.
I used the technique Dick Spadaro quoted in an old thread to clamp the pistons in place, all 4, and then bleed the system. I was also very careful to install the shoes in a balanced fashion so as not to displace the seals/pistons past the ports and induce a leak. It took several days but I find the new cylinders are leaking exactly like the old ones I replaced. The vehicle, 39 pu, has not moved since install. I am using Dot 3. Before I ruin another day of my life I'd like to know if there is some other trick to getting these to work. Thanks. |
08-06-2016, 05:07 PM | #2 |
Senior Member
Join Date: May 2010
Location: CLAYTON DE
Posts: 1,283
|
Re: Static Leak of Wheel Cylinders
Even without moving the PU I would (after bleeding) work the brakes with a bit of 'real time' vigor. This would allow the rubber cups, and the spring 'end cage? socket?' to marry-up under pressure and create a good square stance within the cylinder bore. If the job is a leaker you'll know right away. If the seal is tight today (and all was clean inside - surely it was - ) there ought to be no leak in three days. Good Luck.
__________________
Enjoy yer day. Tom Hate can't fix what it started. |
Sponsored Links (Register now to hide all advertisements) |
|
08-06-2016, 06:33 PM | #3 |
Member Emeritus
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
|
Re: Static Leak of Wheel Cylinders
What A bones said. If it is still leaking then you need to take them apart, hone them, clean them and put them back together. Something didn't get together correctly if they are leaking.
|
08-06-2016, 06:48 PM | #4 | |
Senior Member
Join Date: May 2010
Location: Wisconsin, USA
Posts: 9,016
|
Re: Static Leak of Wheel Cylinders
Quote:
I like the fact SofaKing is using USA parts. We've all heard horror stories in regard to the foreign made cylinders. Still, USA or not, defects happen and NOS does not necessarily mean the parts were properly manufactured. When I do a complete brake job, I power bleed the system and leave the pressure, set at 20#, on the system overnight. I expect to see 20# the next day. Only then am I satisfied the system is free of leaks. I would be 100% certain the new USA cups are the correct size. Seriously... I have experienced 1" cups that were not 1". If I were a betting man, I'd say the cups are the issue. The odds of all cylinders being defective has to be low.
__________________
"I can explain it for you. However, I can't understand it for you". |
|
08-06-2016, 07:05 PM | #5 |
Senior Member
Join Date: May 2010
Posts: 1,770
|
Re: Static Leak of Wheel Cylinders
if the check valve in the master cyl is not working they will leak.
|
08-06-2016, 10:05 PM | #6 |
Senior Member
Join Date: May 2010
Location: CLAYTON DE
Posts: 1,283
|
Re: Static Leak of Wheel Cylinders
Sponsored Links (Register now to hide all advertisements)
__________________
Enjoy yer day. Tom Hate can't fix what it started. |
08-07-2016, 03:04 AM | #7 |
Senior Member
|
Re: Static Leak of Wheel Cylinders
Original cylinders had a small bleed hole maybe 1/16 and the vent in some cases are 1/4 ,if you have thicker linings backed of and maybe new drums it will cause the cups to straddle the hole and leak , Ted
|
08-07-2016, 03:29 AM | #8 |
Senior Member
Join Date: Nov 2012
Location: Tauranga, New Zealand
Posts: 726
|
Re: Static Leak of Wheel Cylinders
My thoughts are like Richard.
Is there a line pressure valve in the master cylinder? This keeps a regulated low pressure in the lines. This residual pressure in the lines keeps the seal lips pushed against the bores. If you already have one, I understand they are available in 2 pressure levels. Lastly, what about expanders behind the cups? Last edited by Bluebell; 08-07-2016 at 03:38 AM. |
08-07-2016, 08:54 AM | #9 | ||||
Senior Member
Join Date: Jun 2014
Location: Salt Lake City, Utah
Posts: 756
|
Re: Static Leak of Wheel Cylinders
Quote:
Quote:
Quote:
Quote:
I am reluctant to hone them, they have a very smooth finish. When I honed the last set the finish was nothing close to being this smooth, almost polished, and I cannot duplicate what I have now. Thanks everyone for the suggestions. |
||||
08-07-2016, 08:56 AM | #10 |
Senior Member
Join Date: May 2010
Location: Wisconsin, USA
Posts: 9,016
|
Re: Static Leak of Wheel Cylinders
I think you guys have brought up a valid point in regard to the "check valve" in the master cylinder. Yes, if the rod is adjusted too tight, the pressure will not be allowed to release very well and will keep some pressure within the wheel cylinders.
I'd like to know if the pedal stays hard after a short drive. If not, the master is not the cause. As I'd noted previously, I place a constant 20# on the hydraulic system for at minimum a full 24 hours. No leaks... to me, that says there is an issue with the original posters cylinders.
__________________
"I can explain it for you. However, I can't understand it for you". Last edited by Kube; 08-07-2016 at 09:02 AM. |
08-07-2016, 09:01 AM | #11 |
Senior Member
Join Date: May 2010
Location: Wisconsin, USA
Posts: 9,016
|
Re: Static Leak of Wheel Cylinders
When you replaced the master, did you adjust the rod?
When you drive the car, does the pedal get harder after multiple uses? If so, does it stay hard for a bit? The "check valve" is located at the bottom of the master reservoir. If the rod is adjusted "too tight", the piston is not allowed to return far enough and as such will block the "check valve" and subsequently the fluid can't return to the master. This leaves a hard brake pedal and some pressure remaining on your hydraulic system. If you can pump the pedal and it gets hard but goes back to "normal" right away, the master is not the issue.
__________________
"I can explain it for you. However, I can't understand it for you". |
08-07-2016, 09:07 AM | #12 |
Senior Member
Join Date: May 2010
Location: Capital of Corruption , NY
Posts: 811
|
Re: Static Leak of Wheel Cylinders
I remember check valves were behind the brass seat where the brake line connects. When you rebuild, you pull the seat by threading a sheet metal screw in the hole and pry it out. Maybe old Fords are different. In your case, try putting a small drill bit in backwards or something in the hole and feel for a spring loaded device.
|
08-07-2016, 11:58 AM | #13 |
Senior Member
Join Date: May 2010
Location: Charlotte NC KiWi-L100 available here
Posts: 2,963
|
Re: Static Leak of Wheel Cylinders
The "check valve" is actually called a "residual valve" , it is the second piece you install in your clean master cylinder when assembling it. The first is a rubber washer that it seats on in the end of M/C. Third is the spring The purpose of the residual valve is to hold slight line pressure keeping the wheel cylinder seals seated against the W/Cylinder bores. Without the rubber washer or residual valve your wheel cylinders will probably leak just sitting & not being used .Good Luck !
Cheers Tony |
08-07-2016, 12:40 PM | #14 |
Member Emeritus
Join Date: Nov 2012
Location: Wichita KS
Posts: 16,132
|
Re: Static Leak of Wheel Cylinders
You can also add external residual valves.
Last edited by JSeery; 08-07-2016 at 12:47 PM. |
08-07-2016, 01:12 PM | #15 | |
Senior Member
Join Date: Jun 2014
Location: Salt Lake City, Utah
Posts: 756
|
Re: Static Leak of Wheel Cylinders
Quote:
The brake rod is adjusted so it has a small amount of freeplay in the linkage, a slight amount of pedal travel before any pressure build-up. To me the MC is working normally. When I get back to the brakes, I will hang a cinderblock from the pedal to simulate brake pressure to replicate your suggestion and seat the cups. |
|
08-07-2016, 01:52 PM | #16 |
Senior Member
Join Date: May 2010
Location: Charlotte NC KiWi-L100 available here
Posts: 2,963
|
Re: Static Leak of Wheel Cylinders
You will never be able to tell if it has it correct residual valve or rubber washer from pushing pedal , the master cyl. will operate perfect !
The sole purpose of the residual valve is as I explained above. |
08-07-2016, 03:30 PM | #17 |
Senior Member
|
Re: Static Leak of Wheel Cylinders
It will be the large end of the cylinder that has the hole in it (front ) .I had to grind 1/16 of the end of the shoe bit that enters the cylinder ,not ideal but after trying several . It could be the piston that's larger ,
As well as the residual valve the tension from the cups sealing against the wall should be enough on there own to seal ,If you do a carful inspection of the cylinders you may find that piston is fully retracted over the oblong hole ,Ted The feed and bleed holes were not 1/4" but I do recall on a couple cylinders one of the holes was oblong. How thick is too thick? Mine are all in the .220-230" range but I have nothing to compare that with, the drums are old, used. I am reluctant to hone them, they have a very smooth finish. When I honed the last set the finish was nothing close to being this smooth, almost polished, and I cannot duplicate what I have now. Thanks everyone for the suggestions. |
08-07-2016, 08:06 PM | #18 |
Senior Member
Join Date: May 2010
Location: Minnesota
Posts: 1,827
|
Re: Static Leak of Wheel Cylinders
We were having a similar problem with the large bore side leaking on the front wheel cylinders.
Discovered the same problem as described by Flathead Ted; after measuring everything we found the large piston was thicker than the original; so we milled the slot that contacts the shoe a little deeper as a correction. No more leaks. |
08-07-2016, 10:29 PM | #19 |
Senior Member
Join Date: Jun 2014
Location: Salt Lake City, Utah
Posts: 756
|
Re: Static Leak of Wheel Cylinders
[QUOTE=FlatheadTed;1335467]It will be the large end of the cylinder that has the hole in it (front ) .I had to grind 1/16 of the end of the shoe bit that enters the cylinder ,not ideal but after trying several . It could be the piston that's larger ,
[B][COLOR=#000000]As well as the residual valve the tension from the cups sealing against the wall should be enough on there own to seal ,If you do a carful inspection of the cylinders you may find that piston is fully retracted over the oblong hole ,Ted [COLOR="DarkSlateBlue"]Thanks, clearly I will have to start measuring and verifying the design, something I did not expect would be required, especially with NOS parts. |
08-08-2016, 02:44 PM | #20 |
Senior Member
|
Re: Static Leak of Wheel Cylinders
I recall that in my case the piston all measured up correctly ,it was all caused by the oval hole that intruded into the cup zone .On one we had to take more than 1/16 and there was not enough thickness on the piston to do this . Ted
|
|
|
Sponsored Links (Register now to hide all advertisements) |
|