Which leads back to the OP's question: "How do you seal the bleeder screw? I wouldn't consider that to be a valid method due to leaks. And I haven't seen any bleeder screws/wheel cylinders with o-ring seals, so they all leak when bleeding, in my long-term experience.
Reverse bleeding is the recommended way of bleeding most motorcycles, and is the only simple and effective way to bleed twin leading shoe brakes on many older british cars without standing them on end. As for leaking around the threads , the question is, what does it matter? You apply pressure to pump fluid in through the center of the bleeder screw. It is relatively low pressure (no more than 4.5PSI is required), so very little fluid will escape past the threads - and being under pressure there is NO chance of air (or any other foreign matter) entering via the threads.
Actually there is no commonly used method of bleeding brakes where leakage past the bleeder screw threads CAN cause a problem, and the bleeder screw seals with a tapered seat so has no need for a troublesome deterioration prone "O" ring. The only way I can see it being an issue is if you attempted to draw the fluid into the system through the bleeder screws by applying a vacuum to the top of the master - which would be a REALLY stupid way to attempt to bleed a brake system on so many counts.
I have actually repaired batteries in the past - back when you had tar-tops on rubber cases. I've repaired intercell connectors, and I've drained and flushed batteries and replaced acid to get more life out of them.(batteries shorted by all the active material flaked off the plates filling the reserve at the bottom of the case) In warm climate like central Africa you didn't need all the cranking power like you do in cold weather like a Canadian winter. I cut the negative post off a
12 volt truck battery with a bad second cell and screwed it to the center intercel link to make a 6 volt battery for my '53 VW Beetle because a new battery was a month's pay. No more back seat, but at least I didn't need to use the crank any more (I added the crank - using part of the gland nut from an old land-rover welded to the crank-bolt of the VW) I just about broke my wrist for the THIRD time several times forgetting to knock the timing back before cranking it.
When you are in a "third world" situation, you do what needs to be done!!!
On 3/17/2015 11:05 PM, firstname.lastname@example.org wrote: ...
Which is actually what started this: On 3/16/2015 8:54 PM, Jim Wilkins wrote:> Next question: > How do you seal the air leak along the bleeder threads when vacuum > bleeding? I didn't want to squirt on something incompatible that might > get back into the cylinder.
Hay , I distinctly remember my dad repairing a L/A battery ! IIRC the problem was an open between 2 cells . Dad dug the tar out , remelted the lead joint , and melted the removed tar and poured it back in . This had to be in the 50's , which would have me 7-8 yrs old . Do you feel old when you remember shit that happened over 50 years ago ? Then there was the time Dad used a set of jumper cables and two carbons from a pair of D cells to resolder a wire on Uncle Bill's starter/generator commutator (outboard motor) so us kids could ski . That was at Palisades Lake near Idaho Falls Idaho , and on Sunday morning we picked wild blueberries to make pancakes . Walk down memory lane ...
I've replaced brake lines and/or wheel cylinders on every vehicle I've owned, since I keep them in good condition a long time. The thread leakage had never been an issue for me until I had to diagnose and cure a spongy pedal, and couldn't distinguish leakage at the bleeder from air in the lines.
The advice I was hoping for was a recommendation of a compatible or insoluble heavy grease to put on the bleeder threads. The only "brake grease" I have is for the caliper slides and rear self-adjuster, and its strength is a high temperature tolerance to keep it off the friction surfaces rather than compatibility with the fluid and rubber cups.
I would and have used "SIL-GLYDE Lubricating Compound" for stuff like that. Been using it to protect/seal the reservoir/pumps area on my Magna motorcycle for many years now. The tube I have is very old, given to me by a professional mechanic. He was giving me advice on how to rebuild the front disc brakes on my truck. See:
Haven't noticed any thing odd/weird going on when I change the fluid in the reservoirs on the cycle yearly.
Most of which have disc brakes. That cuts way down on the mess left from a leak.
It's messy, and fluid can leak into the brake area beneath the cylinder on older cars and trucks. Not much (more of a seepage) and not on the shoes, but some. I prefer a cleaner job.
The low pressure used would make it seem less troublesome.
I have 53k miles on my '07 Tundra now, and need to check/replace pads. Do you have any specific suggestions or tips toward brake jobs for them? You've been in the loop considerably more recently than I. There is zero pedal undulation, so I doubt I need to turn the rotors, unless that's a recommended procedure. I haven't yet looked into it.
I know the brakes have been wearing because I've needed to adjust the emergency brake cable twice now. (step on/step off style) It's a
4-wheel disc setup, which I adore. It was the brake system alone which killed my enthusiasm for the Tacoma and sold me on the Tundra. The Tacoma took both feet and all I had to make it stand on its nose, and it still wouldn't. The Tundra danced to a stop quickly and easily, with little pedal pressure, nearly ripping up the macadam in the process. ;)
They make/sell it with several different names. I don't know if it is all the same or not. That article doesn't really say which version the original poster was using but I got the feeling it was the stuff for stopping squeals. Lots of other useful suggestions there though. For some info on the different "Glydes" see:
My shop manual is similar. The text says to "Coat the piston, piston seals and caliper bore with clean brake fluid", but doesn't mention the piston seal grease.
I suspect that a grease meant to go on the piston seals won't cause a problem if a bit of it leaks in from the bleeder screw, although they must have a reason for specifying a different grease on external parts.
Only thing I have done was to pull the bleeder and dab some silicone grease on the threads. I suppose you could crack the bleeder and coat the thread area with common RTV or even silly putty. It would stop the leak around the threads, but if you have drum brakes you might still get leaks past the cups.
I use a pressure bleeder for the vehicles that won't reliably gravity bleed.
For me it means connecting a Mityvac or HF bleeding kit to the wheel cylinder bleeder, pumping to 25", opening the bleeder and watching the fluid and maybe air flow out. Normally I stop when the fluid turns lighter, then torque the bleeder to spec, blow out the remaining water-absorbing fluid, replace the rubber cap and top off the master cylinder.
Now that I'm retired and not driving 50 miles in stop-and-go freeway traffic every day the fluid doesn't heat up enough to darken.