M42 Radiator Expansion Tank

[KenC]

Is it possible to remove and reseal the side mounted expansion tank?  Mine has developed a small leak at the bottom, but it's fairly new so I don't want to replace it.

[hoevesruperd]

i tried to remove it for the same reason. i couldn't find how and was sick of wasting coolant so the airline is still there 3 months after. going to buy an aluminum radiator soon anyways.

although i heard there was a product that you can put in your coolant and it sticks inside the tank and seals it. dont know if its any good tho

[D. Clay]

realoem shows the tank and the upper and lower sealing rings available as separate parts. I don't know anyone that has actually done it, though. I put an old radiator in the bin at my friends salvage yard last week. If it's still there, I'll take it apart tomorrow and see what it looks like as far as repairing goes.

[tjts1]

Is it possible to remove and reseal the side mounted expansion tank?  Mine has developed a small leak at the bottom, but it's fairly new so I don't want to replace it.

Yes!
http://www.m42club.com/forums/showpost.php?p=25156&postcount=23

[Jak318]

^^ Damn thats the thread I was looking for too! I couldn't remember which BMW site I saw it on, lol.

[D. Clay]

I pulled the one apart that I took off my car. It was hard to get the tank out but it wasn't leaking either. I had to pry up with a screwdriver at the top. Best place was where the metal inserts are for the top plate screws. RTV and/or new seals should work.

[jscribble]

Just did this today, as I had a leak at the bottom of the expansion tank. Still letting it cure, but I wondered if I could tackle my thermostat now while the coolant is drained.

I have rtv gasket maker says it will hold to 700F. Can I use this on the thermostat housing, or should I wait and order a gasket?

EDIT: Decided to hold out for a gasket. Still curious where rtv can be used if anyone has an answer.

[locknload]

I did this repair several years ago with the old ex. tank and new 0rings.  Needed a bit of lube to get it to seat easily, but it has held up well.  

RTV can be used just about anywhere on these cars that needs a gasket, but it is almost always preferable to use the correct gasket if one is available.  I have used the orange "high temp" RTV to coat exhaust flange gaskets without issue.  Rule of thumb for me is, RTV can be used to replace paper gaskets and seal metal ones, but I avoid using it on cork or neoprene, such as valve/cam cover gaskets as the thickness of these materials is generally there for a reason.  The only thing to be aware of is 02 sensors and MAFs, which you may or may not have, as the wrong RTV can damage them if used in excess.  There is a "sensor safe" RTV out there that supposedly will not damage them.

[jscribble]

Thank you very much. I do have "sensor safe" Copper RTV. Figure I'll keep it around. (quotations for skepticism lol)

[Cobra Jet]

You can also use "The Right Stuff" sealant, which cures SUPER FAST - so there's really no wait time and it's impermeable to liquids, such as fuel, oil and coolant.  It works excellent and can be purchased at NAPA, Pep Boys, Auto Zone, Advance Auto, etc...  it can be used on nearly every engine component without any effects to any sensors.  Been using this stuff for years without ANY issues whatsoever... and it's better than any current automotive silicone/sealant product on the market.

http://www.permatex.com/products/Automotive/automotive_gasketing/gasket_makers/auto_Permatex_the_Right_Stuff_Gasket_Maker.htm

[jscribble]

Well, it looks like I have other damage on mine. New rad it is.