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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 02-15-2011, 08:35 PM
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bluebee bluebee is offline
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How not to bleed your cooling system (i.e., how to break the bleed screw in half)

Just for the record, since I'm constantly referring others to this post:
- Post #124 in the alternator thread where the bleed screw broke

Here is a picture of the bleed screw (on right) showing the channel where air is allowed to bleed out of the cooling system:

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  #2  
Old 02-15-2011, 08:38 PM
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Here is what happens to the bleed screw if you twist it much more than one turn:

Note: This broken bleed screw happens to be on the upper radiator hose; there is a similar bleed screw on the top of the expansion tank.


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  #3  
Old 02-15-2011, 08:40 PM
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Worse yet, if you try to use a screw extractor to remove the broken bleed screw, you'll just make matters worse and ruin the plastic around the bleed screw (by expanding it - and it WILL crack!).

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  #4  
Old 02-15-2011, 08:42 PM
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The best solution, if you broke your bleed screw, is to find a non destructive method of removal, i.e., one that does NOT entail expansion in any manner of the plastic threads surrounding the broken half of the bleed screw shaft.

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  #5  
Old 02-15-2011, 08:43 PM
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lild lild is offline
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some times you may need to completely remove the retaining clip. and then twist to losein and then twist and pull, and you have to be carefull not to break it. some come off easy some are a lil harder than others.
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  #6  
Old 02-15-2011, 08:51 PM
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Some people resort to brass bleed screws.

Nothing wrong with that; but the "real" problem is not to twist the bleed screw more than one turn.

One way to ensure only one turn is to MARK a white line on your bleed screw so that you can count the single turn when you bleed your cooling system.

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  #7  
Old 02-15-2011, 08:54 PM
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Quote:
Originally Posted by lild View Post
you have to be carefull not to break it
I should have noted the picture was re-used from this thread:
- How do you safely remove the upper radiator hose with u-pins?

We came upon a "successively larger screwdriver teasing method" of removing the radiator hoses that seems to work perfectly to remove without undue strain.

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  #8  
Old 02-15-2011, 09:13 PM
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BTW, when you buy a new Behr/Hella expansion tank, it does NOT come with a new bleed screw ... (nor does it come with the pressure cap, nor the two-foot-long overflow hose, nor the electrical coolant level sensor found at the bottom of the expansion tank).



Yet, when you buy a new BMW OEM upper radiator hose, it DOES come with the expansion screw!

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  #9  
Old 02-15-2011, 09:18 PM
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So, in summary, the purpose of this thread, is merely to refer others to who happen to break their bleed screws.

If you know of a good method of REMOVING a broken bleed screw, or of PREVENTING a broken bleed screw, please append for others to stand on your shoulders.

As for "proper" bleeding methods, there are plenty of ways to do that (most revolve around elevating the engine a few inches).

Here are the three best threads that I've found for correct bleeding of the E39:

- Bleeding the cooling system (1) (2) (3)
- How to refill M52/M54 coolant DIY by cn90 (1)

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  #10  
Old 02-15-2011, 09:19 PM
kpex76 kpex76 is offline
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Thanks for the info Blue. This is the reason why I bought a pair of brass bleeder screws.
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  #11  
Old 02-15-2011, 09:55 PM
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Quote:
Originally Posted by kpex76 View Post
I bought a pair of brass bleeder screws.
I have no problem with brass screws; but I still think the real problem is twisting and not the material.

Of course, if you overtwist with the brass screws (actually bolts), they won't break; but who knows how the soft threads will handle that twisting force on the upper radiator hose or thermostat housing or expansion tank (depending on which E39 you have).

It would be nice for someone to do an experiment on an OLD hose or expansion tank, to see what happens to the female threads when the brass screws are overtightened ...

Here, for others to benefit, are pictures of the $5 brass bleeder screws:
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  #12  
Old 02-15-2011, 09:58 PM
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This thread shows evidence of BOTH the bleeder screws leaking on an E39:
- E39 OVERHEAT... again!

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  #13  
Old 02-16-2011, 10:53 PM
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Quote:
Originally Posted by kpex76 View Post
This is the reason why I bought a pair of brass bleeder screws.
Nyclad just installed his $4 brass bleed screws today, snapping these nice pictures for us to learn from.

Here's the OEM plastic bleed screw leaking somehow from an internal crack:

Here's the OEM plastic bleed screw sans, somehow, it's o-ring:

And, here's the blass bleeder screw in situ:



PS: Note the thermostat wiring loom in these pictures is missing the tie wrap:
- How bad is this mistake in putting my cooling system back together?
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  #14  
Old 02-19-2011, 04:36 AM
gumbi4u gumbi4u is offline
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The plastic bleeder screws break not because of "Twisting" too much, but due to the fact they are brittle after time and will break even with the slightest twist. I have seen tps of them fly off without even touching them. Please do not scare people where they will get over cautious and "screw" something else up.
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  #15  
Old 02-19-2011, 04:46 AM
helpmyfive helpmyfive is offline
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Who has time to grab the camera when water is sprouting from the car?
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  #16  
Old 02-19-2011, 10:13 AM
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Quote:
Originally Posted by gumbi4u View Post
The plastic bleeder screws break ... due to the fact they are brittle
Good point. I've read about the screws "turning to mush" a lot, but, I never believed it (if only because mine was broken because I was styupid and twisted too much).

So, it's good to confirm they actually do disintegrate (I shouldn't be surprised but mine were in fine shape at 8 years old).

Quote:
Originally Posted by helpmyfive View Post
Who has time to grab the camera when water is sprouting from the car?
I always keep a camera with me at all times.

I only wish when my alternator went south that I could have snapped a photo of the instrument cluster going haywire with the engine dying in the center of the highway!
- One users' example of total electrical failure (AAA towed away) alternator repair (1) (2)

Also, bear in mind, the engine was off when this happened. That water spout is from the pressure created with the auxiliary water pump only (as per the coolant bleeding procedures).
- Bleeding the cooling system (1) (2) (3)
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  #17  
Old 03-11-2011, 12:06 AM
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There is a very good discussion of the heads popping off the plastic bleeder screws in part 1 of this video referenced today by bobdmac:

BMW Cooling System Failure Points, Part 1 (e36, e46, e34, e39):


BMW Cooling System Failure Points, Part 2 (e36, e46, e34, e39):
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  #18  
Old 03-11-2011, 01:17 AM
reb78 reb78 is offline
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I just had this problem when i tightened the bleed screw on the expansion tank on my 528. Too much brute force, twisted it too hard and the top sheared off. Those screws are 4 over here in the UK, which is more than the cost of the nice brass replacements you guys have out up pics of!!

Now, for removal of the rest of the screw after i had sheared the top off, it was quite simple without damaging the thread on the pipe/housing. I just used a small sharp(ish) screwdriver and gently forced it onto the remains of the bleed screw, turned it and wound out the remnants. The screw wasnt in there all that tight (even though i'd wound it down with enough force to twist the end off!), so no need for a stud extractor.

It currently has a bolt with the same thread in the hole to seal it whilst i decide if the head gasket has gone or not!
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Old 03-11-2011, 04:47 AM
Spike Holmes Spike Holmes is offline
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The brass bleeder screw is $ 10.00 at the stealership but, worth every penny when you need it immediately. Ask me how I know.
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  #20  
Old 03-11-2011, 02:11 PM
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For the record, in this thread today, the bleeder screw broke:
- Bleed Screw Busted..

To remove the broken half, you DO NOT want to EXPAND anything; expansion will break the brittle plastic in the hose or expansion tank (which means it's toast).

You need to apply twisting force without expanding the broken bleeder screw itself; so a screw extractor is a bad idea (ask me how I know).

The best idea seems to be:
  • Heat a screwdriver on a flame and melt a notch into the screw
    • Then, simply twist it out
    • Replace with brass
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  #21  
Old 03-13-2011, 11:23 AM
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For the record, here was the solution to that prior thread:
Quote:
Originally Posted by WaveSurfin3100 View Post
I thought about using a Dremel tool to make a deep slot on the top side of the broken-off bleed screw. Then I would use a flat blade screwdriver to remove it. Since I lent my Dremel to my neighbor and he wasn't home, I went with the idea that "energizedmortal" put forth.

I heated up a small-tipped flat blade screwdriver with my propane torch and made sure to stab the broken bleed screw right down the center. Careful of not veering off to either side and melting the threads of the expansion tank; if I had, I would've been screwed...and not in a good way!!

I pressed the heated tip down the center, deeply enough to where it would have had a good grip. I removed it just as quickly as I drove it in because the propane torch heated the tip pretty well and it was melting at a very fast pace.

After a minute cool down, I inserted a flat blade screwdriver in the newly made slot and out it came...Sweet!

I placed a new plastic bleed screw in place, started the engine, and let it run for some time, increasing revs up every so often. No leak at bleed screw, success! Thanks again to all that came in with ideas!
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  #22  
Old 05-13-2011, 09:11 AM
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For the record, it was asked today what the difference is between brass & plastic bleed screws:
- E39 (1997 - 2003) > Cooling system Bleed screw locations 540i?

My response was:

Quote:
  1. It really won't matter all that much either way
  2. The brass screws don't cost (in the scheme of things) much
  3. The brass screws won't 'turn to mush' over time
  4. However, the main problem is we torque the screws down too much
  5. The secondary problem is the mush
  6. So ... if you turn the screw (either kind) only a single turn ... you won't have the main problem
  7. And, if you replace your cooling system every few years, you won't have the secondary problem
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  #23  
Old 05-22-2011, 10:05 PM
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For the cross-linked convenience of all who follow, an old resurrected thread today ...
- E39 (1997 - 2003) > Broken bleed screw culprit

... provided a very nice picture of a crack in the upper radiator hose bleeder screw housing ...


... causing extensive BMW white spray ...


.. necessitating a cooling system overhaul.
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  #24  
Old 01-29-2012, 10:18 PM
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For the cross-linked record, today, yet another broken screw occurred:
- E39 (1997 - 2003) > Broke the radiator bleeder screw, can I just JB weld it?
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Please read the suggested threads, where the best always add value to those threads, either by pictures or by descriptions, so the next person with the same problem stands on your shoulders.
See also: E39 Bestlinks & How to easily find what you need
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  #25  
Old 02-19-2012, 08:39 AM
EconoBox EconoBox is offline
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Stupid question, but when you turn the bleed screw, are you TIGHTENING it?
Is that why they can get overtorqued?
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