replacing just the expansion tank

[rojeho]

My already replaced expansion tank has developed a hairline crack. Since I don't need to do a full cooling system, is there a trick to draining the coolant to just replace the tank? 2001 3.0 with the tank up on the back of the fender.

[Randy Forbes]

If it was me doing it, I'd undo the mounts and prop the reservoir up as high as I could. Siphon out enough coolant to get the level down into the hoses, then do a quick swap. To minimize any spilling, you could pinch off the hoses (w/clamps made for the purpose) above the water line.

[coolguy147]

If it was me doing it, I'd undo the mounts and prop the reservoir up as high as I could. Siphon out enough coolant to get the level down into the hoses, then do a quick swap. To minimize any spilling, you could pinch off the hoses (w/clamps made for the purpose) above the water line.

Isn't there a drain on the radiator?

[Z3MROADY]

Isn't there a drain on the radiator?

Yes there is a drain plug at the bottom corner of the radiator. It is a plastic threaded plug. Mine was blue. But once you drain your system down you'll have to deal with the air in the system and bleed it all out. The procedure is very specific. For me it didn't quite go as described. The trapped air was stubborn but everything finally turned out OK. Randy's method may be the best tip to avoid having to bleed the system. A quick tank swap sounds good.

[rickwinger]

Yes there is at drain plug at the bottom corner of the radiator. It is a plastic threaded plug. Mine was blue. But once you drain your system down you'll have to deal with the air in the system and bleed it all out. The procedure is very specific. For me it didn't quite go as described. The trapped air was stubborn but everything finally turned out OK. Randy's method may be the best tip to avoid having to bleed the system. A quick tank swap sounds good.

Can you point me to a link for Randy's method?

Thanks in advance!

[Randy Forbes]

Can you point me to a link for Randy's method?

Thanks in advance!

That comment was relative only to the original poster, who wanted to replace just his coolant reservoir; in his case, mounted to the top of the LH strut tower.

If you ever plan on servicing the cooling system in any modern car more than once, I recommend that you look into a device called the AirLift. You'd have to have an air compressor, but what it does is pull a vacuum on the entire system (which is__bar none__the best way to determine if you have a leak) and then it siphons the coolant in filling up the system in the absence of air. All the hoses get sucked flat, which is a little alarming at first, but it's definitely a huge time saver in the process.

If you don't go that route, then "burping" the system by systematically squeezing the hose(s) and opening/closing the bleed screw will work out much of the air, again saving time. Ultimately, you still have to run the engine (@ 2000 RPM or so) to get the last of the air out, but this is still faster than by running the engine without burping it.

http://www.amazon.com/UView-550500-A...=pd_sbs_auto_3

[Mr Bingley]

Can you point me to a link for Randy's method?

Thanks in advance!

=-

Just what he writes earlier in this thread. For guaranteed trouble free system bleeding use this: http://www.amazon.com/UView-550500-A.../dp/B000O3IGI6 It works perfectly and leaves no air behind.

[Vintage42]

… For guaranteed trouble free system bleeding use this: http://www.amazon.com/UView-550500-A.../dp/B000O3IGI6 It works perfectly and leaves no air behind.

How much of an air compressor does it need? I have a little portable 2-gallon tank with a 100 psi compressor, and no CFM rating, that I use for inflating tires. Will that operate the AirLift bleeder?

[rf900rkw]

OP -- The M54 cooling system layout is drasticly different than the earlier cars. You should be able to siphon the coolant out of the tank and change it with no danger of getting any air in the system. I would be more concerned about why the tank cracked. Make sure you are not overfilling the system. Over filling will cause the system pressure to skyrocket. The air in the tank is a much needed expansion buffer.

As far as the airlift device, I picked one up due to the glowing reviews. It did work well on a M44 and a S52. It didn't work worth dingles on a M62 or a M54. I haven't really played with the "why" of it, but suspect it's the water path through the waterpump. I'm back to my old method as it's the only way I've found to be sure the system is full when I ship a car.

[daven]

How much of an air compressor does it need? I have a little portable 2-gallon tank with a 100 psi compressor, and no CFM rating, that I use for inflating tires. Will that operate the AirLift bleeder?

I've got an early 90's Craftsman 1 1/2 HP 12 gallon compressor that has a hard time cracking 100 psi. I successfully used it with the Airlift at the end of a 25 ' line. It worked like a charm but I wouldn't go any smaller. The manual recommends 90 psi as the minimum.

[Mr Bingley]

Re: the Air lift, I've used it on a couple of S52's, several Volvo 5 cylinders and a 4 cylinder, Toyota's, Honda's, and a Saab 4 cylinder--worked flawlessly on each. Given the vacuum principal, it is hard to understand how it wouldn't work on any system, unless the system wasn't really sealed (a great diagnostic side benefit of using it btw). It must be hooked up properly, and the system must be completely sealed (so if there is an overflow, you have to plug it, etc.). Once the system is sealed, it draws a vacuum down to -29 millibars or so. From there it draws coolant (after a line purge) into the vacuum--that's it, physics does the rest.

[rickwinger]

=-

Just what he writes earlier in this thread. For guaranteed trouble free system bleeding use this: http://www.amazon.com/UView-550500-A.../dp/B000O3IGI6 It works perfectly and leaves no air behind.

Huh. Note to self - next time wear glasses! LOL.

I saw it when I went back and reread it. Thanks!

[rf900rkw]

Yes, the device is very good at testing for leaks. It's useless for finding a leak if you have one, but it does show if you have the most minute one somewhere. And as I stated, it works fine on M44 and S52. It will be fine on M52 and S54, and most other cars. The device has proven to not fully fill M54 and M62 engines, and I would assume M52TU with the same unique cooling design will suffer the same fate. Your examples do not use the M54, they all have conventional cooling system designs

There are several things to keep in mind. The vacuum drawn by these orifice pieces is not absolute, not even close, especially on a home grade ~125 psi compressor. I see around 25 inches at home, where I can pull 27 at the shop on 175psi. Second, physics says that a void will want to be filled, not that it has to be.

I'm just pointing out that on a few of BMWs later designs, if you have a _totally_ dry system (block drains pulled etc), these vacuum devices may not fill the entire system. It will happily fill the radiator and hoses, but not the block. You can tell when this happens by the amount of coolant pulled in. I learned my lesson the hard way, the first time in a very embarassing moment in front of the client.

[Z3X2]

+1 it is a good tool I have the Brass professional model and while it works fine on my Daughters Z3 it will not do a full fill on my 2001 Camaro I tried several times. It just not for all cars But worked fine on her Z.