Stuck Coolant Bleed Screw

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scanty

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My 3.0CS has been suffering from an engine that runs slightly hot. It seems to be alright while the vehicle is moving, but when at a standstill that needle slowly creeps up past the half way point getting closer and closer to the red zone. I came to the conclusion that the coolant system was probably not bled correctly. So I went to do that but came across a snag. The bleed screw is very rusted and wont budge! I've tried heating it, using greasers like WD-40 and the like but it wont budge! Any ideas on how I can get it out? I don't want to break that housing it's located in. Or, is there a way to bleed the system with the bleed screw still in place? Any ideas would be greatly appreciated!
 
Not a favorite subject for any of us. Some thoughts...

1. your favorite chemical such as Liquid Wrench, Aero-Kroil, Pb-Blaster or for the frugal, a 50-50 mix of acetone and auto trans fluid is liked by some. I tried it, and it smells nasty.

2. Heat, lots of it, on the aluminum surrounding the screw.

3. Impact to loosen the rust grip.

4. Try slowly tightening the screw. Counterintuitive, but sometimes it's what's needed to break the grip of the tinworm. Once freed, back and forth, back and forth, looser by just a bit each time.

5. Getting drastic, drill it out using a reverse bit. I recently had to drill out the 5mm socket head cap screw that tied the front brake rotor to the hub, in my daughter's E30. Start with a small bit as a pilot, then gradually larger; at some point tap in an Easy-Out but be VERY careful as these are hard but more to the point they are BRITTLE and will snap off if you don't apply balanced, even, on-axis torque. Worked for me in the end, though, I'm happy to say.

6. Ask yer pals on the list.

7. Prayer, foul language, inappropriate force. For the truly desparate, only, get your "mechanic" friend to have at it. When he breaks something, throw a fit and make him buy a new one. note that I've not trie this, and it's really not recommended... but once something is broken you have nothing to lose by really going at it. I remember a water pump once on my 533i, the cooling fan nut (yes I know it is reverse threaded) had me doing unseemly things to it. In the end, it yielded to superior force: a 3-pound sledge and massive 8" vise.
 
There are freezing methods available in spray can now made by Loctite and maybe others. I haven't tried them, so some research is needed.

My tool of last resort is hand held impact driver. It's gotten me out of a few jams. Make sure the bit has sharp edges and is held square and firm before you give it a rap. As mentioned, back and forth is recommended (with penetrating oil). If you keep turning in the same direction, sometimes the corrosion will jam things up further.
 
A couple more thoughts- If you have the original style bleed screw with the screwdriver slot, be sure to fit the correct size nut or two on the screw or you will surely break the slotted area. An impact screwdriver with the correct bit works very well. Use a small hammer and lots of sharp raps as opposed to heavy blows. If you have the later style bleed screw with the hex head, fit a six point socket to the impact screwdriver or you could use a six point box or combination wrench and a good size rubber mallet. Again, lots of sharp blows.
Once the bleed screw is loosened, be sure to remove it and clean out the bleed passage with the appropriate size drill bit.
 
Another method of bleeding is to (when engine is cool) disconnect the thin overflow hose at the overflow tank. Attach another hose about 2 feet long to the tank (no clamp). Hold the hose from the radiator up in the air and gently blow though the new hose until radiator fluid bubbles up the radiator hose, put your finger over the end when it does. Pull off the temporary hose and replace the original.

Also:

Drill a hole in the thermostat so when it is in the housing it is as close to 12 o'clock position as possible, this will help self-bleed the system.

Check that your fan clutch is operating, when engine warm it should be holding the fan tight and difficult to turn by hand. Living here in a tropical climate I have mine locked by longer screws (see the blue book for this). Your symptom sounds like this is your problem (or water pump).

You could do these without having to remove the screw.
 
I have the original type bleed screw. It's a flat head screw driver slot. So far my force has been causing the head on the screw to bend so I'm gonna take another go at it using some of these suggestions!
 
Simple math....

scanty said:
I have the original type bleed screw. It's a flat head screw driver slot. So far my force has been causing the head on the screw to bend so I'm gonna take another go at it using some of these suggestions!
Click to expand...

The same problem and tried all the tricks above, it ended like this for me :)
 

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So I think I've managed to bleed the coolant. No more bubbles. However, when in my garage at a standstill the engine still runs hot. But, when I take it out and drive it around the block the temperature drops off very quickly to a much lower and manageable temperature. This to me suggests that at idle with the car not moving, the fan is not effectively cooling the engine! Or, maybe it's the air not flowing through the rad that's my problem?

Anyone experienced similar situations?

As for the water pump. I just put a new replacement on a few weeks ago. The old one wouldn't even spin when I got it!
 
Did you test or lock the fan clutch? Remove and back flush the coolant from the radiator and engine block?
 
I had exact same condition. But now after bleeding I have erratic fluctuation. Before bleeding exactly the same condition as yours. My clutch seems to work OK. Your not the only one.
 
Infrared

heat gun pointed at several areas of the radiator is the way to check for flow on your radiator. It should be fairly consistant everywhere. If it's plugged in spots the temp will be lower there meaning there's little to no flow in parts. Not good.
 
Stevehose said:
Another method of bleeding is to (when engine is cool) disconnect the thin overflow hose at the overflow tank. Attach another hose about 2 feet long to the tank (no clamp). Hold the hose from the radiator up in the air and gently blow though the new hose until radiator fluid bubbles up the radiator hose, put your finger over the end when it does. Pull off the temporary hose and replace the original.
Click to expand...
Interesting method. I had never heard of it. Does it really work as well as the bleed screw method?
 
Thank you Chris.

So you're essentially blowing air into the overflow tank which then pushes fluid into the system from the back.
 
I recall the cover that houses the bleed screw can be removed with little coolant loss, have a new gasket on hand. Maybe attack the screw from inside with PB Blaster or equivalent?
 
Yup. Make sure everything else in the system is buttoned up. I basically have a duplicate section of hose just like the hose that goes from the expansion tank to the radiator that I try to keep clean so I don't get antifreeze in my mouth. Connect as Steve says, hold the hose from the radiator that is disconnected from the expansion tank up so that the end is higher than anything else in the cooling system. I use a rag on the end of that hose and then blow gently into the clean hose that is connected to the overflow tank until the antifreeze just starts to dampen the rag on the other hose. If you blow hard you will spray antifreeze all over yourself and your engine bay.
 
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