Coolant Bleeder screw leak

[BennSport]

I’ve noticed that my bleeder screw has been leakingeven after recently replacing the aluminum crush washer. Because of this it’s now introducing air into the system that I constantly have to bleed out. At first I was only tightening it down snug as to not excessively wear the washer, but after increasingly tightening torque to no avail I ordered another washer and a new screw. What else do I need to do so my efforts won’t be in vain like last time? I’ve heard about lapping the face of the water neck the washer seals against but I don’t know how I’d go about doing that

[dr bob]

Your thread title sorta threw me for a loop, since I spent the afternoon flushing brake systems on the fleet here. Obviously not brake or clutch slave bleeders sine you talk about the sealing washer.

I'll share my double-to-secret trick for for getting a good seal on drains and bleeders that depend on crush washer. Same applies to banjo bolts and their washers. It's some PTFE thread sealing paste. Goes on the threads even though they are all 'straight' threads, not the tapered threads we expect on pipe. Add some to each of the sealing faces on the washer, the bolt, and the in your particular case the water neck. Then about 75% of the recommended torque should get you the sealing you need.

Aluminum and copper "crush" washers don't actually "crush". They are soft and tend to gall, and actually smear the faces together as you tighten. The sealing paste may sound counterintuitive, as it actually prevents that galling. But it also fills the tiny variations in the metal surfaces, usually enough to prevent leakage.

The lubrication on the thread means you won't need quite as much torque to get the same pressure on the sealing faces. It also helps prevent galling/smearing on the threads themselves. The ones that usually happen as we keep adding 'just a tiny bit more' trying to get that $%#@!!! bolt to seal.

I have a rather vintage can of that thread sealing paste, some that I bought on a whim and a guess while shopping at Home Depot at least 20 years ago. Maybe better for us more casual DIY'ers is the little tube of the Permatex version at any good parts store. Card pack and a little squeeze tube, much less mess to apply and store.

But do keep this tidbit between us please. No telling the havoc that might result from a public leak. If it does leak and you are still following this thread, I have an idea how to stop it...

[Tom]

Can you actually see the coolant coming out the bolt? If so, I'd look at the mating face of the neck closely for any nicks, scratches, or other imperfections... You can use an oil stone (blade sharpening stone) to sand it smooth if needed.

I once changed the fuel pump on an old Mercedes and I could not get the copper sealing washer to seal. I tried lapping it, annealing it, sanding the surfaces, nothing worked. Turned out to be the cheap copper washers I was using. I ended up going to a dealer and getting the official washer and that was that. Just a thought if you are using Amazon seal washers...

[BennSport]

I’ll look into some ptfe paste, thank you Bob. I can see the coolant after driving as it has dried up all around the bolt. The first washer I used was from pelican parts, and the washer and screw I had coming in the mail today is from 944online.

[walfreyydo]

Another thing to check is to look at the bleeder screw threads themselves on the coolant neck and be sure they arent crossthreaded or damaged, as that could allow coolant or air to move past.

[PSU_Crash]

I had a seeping leak after replacing the crush washer. PTFE on the threads and it's been dry ever since.

[BennSport]

Is there any specific brand or type I should look out for? I.e. hardening vs non hardening? Also does the paste hinder the venting ability of the screw?

[Zirconocene]

I'm sure that @dr bob 's method will work. The other thing you can try is bonded rubber washers. I've been using them for other applications (engine and transmission oil) and they've been great.

Good luck

[chrischrischris]

I bought a kit of aluminum crush washers for less than $15. It's great to have these handy and also great not to pay porsche prices for a generic piece of metal.

[PSU_Crash]

I'm sure that @dr bob 's method will work. The other thing you can try is bonded rubber washers. I've been using them for other applications (engine and transmission oil) and they've been great.

Good luck

I forgot about those! I've used them with great success in the past (and future). I have a pack of random sizes in the shop. May swap out my crush washer soon