SaabCentral Forums banner
1 - 15 of 15 Posts

·
Registered
Joined
·
19,244 Posts
Discussion Starter · #1 ·
I was bleeding my rear brakes with a clear tube and watching the bubbles come out... after a while I think I was convinced that on one side, the air was coming in around the threads and heading out the bleeder with the fluid flow. If I moved the tubing around to make the screw move up and down in the threads, more air would definitely come out the tube. I think they're bled, but I'd be more comfortable if I could see it run clean. I only had the bleeder loosened about 1/8 turn, but there was still play at that point.

What can be used that resists brake fluid and will stay soft enough so I can bleed a few times, then break it free next time I need to flush the lines?
 

·
Registered
Joined
·
6,353 Posts
the bleed nipple relies on the tapered end to seal against the similarly tapered seat, therefore closing the flow of brake fluid through the nipple cross drilled orifice. Putting sealant on the threads is both unnessary and could be masking a problem you may be missing. Dont do it.

Whenever I have folks with this issue, I ask two questions: are the threads clean / is the caliper threaded port free of any corrorion or debris. The second question is what torque did you use on the brake nipple?

Clean and corrosion free you can check yourself easily enough.

Torque specs? 97 inch pounds. I use a torque wrench, its something that eliminates the usual questions "is that tight enough/what if I strip it and tighten it too much" and it also means using a socket that is better than an open end wrench. I use flare wrenches for bleeding and torque wrench for final tightening

and for those that wondered, the Brembo Cobalt caliper conversion, the bleed nipple torque is 124 inch pounds
 

·
Registered
Joined
·
1,483 Posts
I can relate with your experience..The threaded portion of each piece is slo
ppy/loose..Ive tried several OEM calipers and they all feel the same.. I just go with the "flow"...Your good on the 1/8 turn open. That works well for me...YOu can try to smear some "heavy" grease at the bleed nipple to caliper location.(threaded section) This will probably seal up the air that is bothering you.
 

·
Registered
Joined
·
2,176 Posts
Speed bleeders use a sealant on the threads. Pretty sure at least one of the makers of that type bleeder sells the sealant as well.
 

·
Registered
Joined
·
19,244 Posts
Discussion Starter · #5 ·
Qwik: The threads are vary clean, I can open and close this bleeder without a wrench. I know it will seal when I tighten it, I'd just like a better looking bleed.

I'll check out those speed bleeder folks. Good idea.
 

·
Registered
Joined
·
19,244 Posts
Discussion Starter · #7 ·
Yeah... just did some Googling. Options:

1 Permatex Hydraulic Thread Sealant ~$25
2 Loctite Hydraulic Thread Sealant ~$20
3 Speedbleeder sealant $15 shipped
4 Teflon Tape - MityVac recommended
5 Syl-glide
6 Grease

First three might be overkill for the size of the problem... there's a lot of arguments about TTape although MityVac suggests it and it seems unlikely to cause a problem. A little Syl-glide seems like it would solve the minor leak issue and is already in the system on seals so it's probably safe. Grease might have compatibility issue.

I think I'll just smear a little syl-glide on the upper threads and be done with it. I don't need a long term seal, just a little interference when doing the bleed.
 

·
Registered
Joined
·
6,353 Posts
Qwik: The threads are vary clean, I can open and close this bleeder without a wrench. I know it will seal when I tighten it, I'd just like a better looking bleed.

I'll check out those speed bleeder folks. Good idea.
torque them and be done. Cap the end with the rubber plugs they come with. Speedbleeders can go wrong. Not a fan. But the endless "my bleed nipples are leaking" deal I have gone through so many times. After bleeding a little brake clean and some compressed air takes care of residual brake fluid left behind in the cavity. Nice little rubber plug seals it and you are done. 97 inch lbs lol
 

·
Registered
Joined
·
16 Posts
I am bleeding for the first time and installing speed bleeders.

The speed bleeders have some sort of sealant on the threads, but I still see little tiny bubbles in the fluid as it goes through the tubing.

Both the speed bleeder guys and the mity vac instructiions say don't worry about the tiny bubbles, this is air coming through the bleeder threads, so I am not worrying.

Clean fluid through the tube and a firm pedal and I will be happy.
 

·
Registered
Joined
·
19,244 Posts
Discussion Starter · #10 ·
I am bleeding for the first time and installing speed bleeders.

The speed bleeders have some sort of sealant on the threads, but I still see little tiny bubbles in the fluid as it goes through the tubing.

Both the speed bleeder guys and the mity vac instructiions say don't worry about the tiny bubbles, this is air coming through the bleeder threads, so I am not worrying.

Clean fluid through the tube and a firm pedal and I will be happy.
The little bubbles bothered me as I like to see pure fluid coming through. I ended up putting some silicone grease on the bleeder threads (these were non speeder) and that stopped it. Probably has the side benefit of keeping the bleeder from rusting shut too, although that does not seem to be a common issue on Saabs IME.
 

·
Registered
Joined
·
2 Posts
I was bleeding my rear brakes with a clear tube and watching the bubbles come out... after a while I think I was convinced that on one side, the air was coming in around the threads and heading out the bleeder with the fluid flow. If I moved the tubing around to make the screw move up and down in the threads, more air would definitely come out the tube. I think they're bled, but I'd be more comfortable if I could see it run clean. I only had the bleeder loosened about 1/8 turn, but there was still play at that point.

What can be used that resists brake fluid and will stay soft enough so I can bleed a few times, then break it free next time I need to flush the lines?
A very long standing problem I feel, (air getting past the threads) this happens in my experience whatever method of bleeding you use, manual with tube in bottle, pressure and vacuum systems alike. Given that Speedbleed and some others do use sealant I think if done carefully this is pretty good. I do think that there is a fundamental problem with the quality of fit between male and female thread parts in nearly all callipers of all makes. They are pretty poor, sloppy in fact and if they were nuts and bolts the would all fail the standards of what constitutes a good fit. So, if the thread quality of fit was better and then with a small amount of thread sealant applied this would be a more assured outcome when bleeding brakes. On occasions when using the type of bleed screw that has a bigger hexagon than the thread diameter then I have placed a short section of rubber tube over the (exposed) thread between the calliper face and the hex head underside, it helps but is not perfect. The better the surfaces and the better the cut of the tube then the better the result. It can also serve a secondary purpose if you use a small amount of 'Coppaslip' or similar on the exposed thread and leave the tube in place it does protect from corrosion.
 

·
Registered
Joined
·
10,628 Posts
Permatex makes a decent thread sealant. I've used it to renew the sealant on the Speed Bleeders I have on a couple of my cars.
 

·
Registered
Joined
·
9,262 Posts
IMO, I think the reason these bleeders experience the issue is because they are not designed to bled in any manner other than pressure. If you pressure bleed the system from the reservoir, there's no opportunity for a problem. I use a syringe connected to the bleeder with clear tube - that way you can clearly see not only any remaining bubbles coming from the system, but also quite clearly when the old fluid is out.



If the bleeder to caliper has loose threads, the worst case is a little dribble down the caliper... but zero chance of a bad bleed.
 

·
Registered
Joined
·
2 Posts
IMO, I think the reason these bleeders experience the issue is because they are not designed to bled in any manner other than pressure. If you pressure bleed the system from the reservoir, there's no opportunity for a problem. I use a syringe connected to the bleeder with clear tube - that way you can clearly see not only any remaining bubbles coming from the system, but also quite clearly when the old fluid is out.



If the bleeder to caliper has loose threads, the worst case is a little dribble down the caliper... but zero chance of a bad bleed.
Hi there, get where you're coming from but essentially the passage of the fluid should be intact without leaks from the fluid inside the calliper to the fluid in the bottle. Seepage past the threads introduces the risk of not seeing the last of the bubbles especially as the bottle get more full the weight of the fluid may offer more resistance than the tread route. If you think I'm kidding I have seen it when doing a difficult to bleed system some years ago, just noticed the bubbles seeping past the bleed screw with nothing bubbling into the bottle. It was then that I used a piece of rubber tube on the exposed screw thread, this stopped it on that occasion. If we were designing the bleed screw form scratch we would probably put a small 'o' ring in the female thread to bear onto the unthreaded part of the screw perhaps?
 

·
Registered
Joined
·
9,262 Posts
That scenario only happens if you've unscrewed the bleeder too far or are using too much pressure. Half a turn, maybe a full turn is all it takes then only enough pressure in the system from the reservoir to force fluid out... 5-7psi is plenty. If anything would rather force its way past the threads rather than take the actual hole in the bleeder to get out, you're using too much pressure or you've backed out the bleeder too far, leaving not enough thread engaged. Brake bleeder screws haven't materially changed in almost 100 years... if there was a problem with them, someone would have changed something. Probably BMW - they love selling special tools.
 
1 - 15 of 15 Posts
Top