Coolant Expansion Tank R&R

[spooltime]

My expansion tank is now on day-by-day status, with coolant periodically dripping to the floor, and the engine temperatures fluctuating erratically. Also had an earlier low coolant warning that caught me off guard, but I topped it up until I could get the parts in.  I've got the necessary parts to replace on order, and had a question regarding the factory shop manual procedure for replacing versus other methods I've seen described on the internet.

 

Specifically, my question relates to draining the expansion tank before removing.  The shop manual calls for the entire cooling system to be drained at the radiator, while other write-ups I've found suggest it's sufficient to siphon out the expansion tank to remove without draining out the coolant.  Obviously, the latter approach is less involved, but my question is if it's really necessary to go for the full drainage method described in the shop manual?

[RFM]

Technically it is possible to siphon out the expansion tank without draining the entire cooling system, but think about the age of your car, after 10 years of age i would replace the entire amount of coolant. 

[jagman1]

I just did the replacement last weekend.  I drained the tank by removing the hose at the bottom of the tank.  The only fluid that cam out was in the tank and a little in the hose.  Refilling required about 2.5 liters of fluid.

 

There are a few DIYs out there.  I followed this one.  

http://www.pelicanparts.com/techarticles/Porsche-Cayenne/54-WATER-Coolant_Expansion_Tank_Replacement/54-WATER-Coolant_Expansion_Tank_Replacement.htm 

 

I pulled the headlight.  Removed the cover to the passenger side air filter.  Removed the torque arm and it's bracket.  Loosened the mounting bolts for the brake boost vacuum pump.  Removed the washer fluid filler neck.  All the steps recommended in the DIY's.

 

It's a lot of work for a simple task.  Do be careful around the brake booster.  The plastic vacuum lines can be brittle and breaking one will cause you lots of headaches.  I'd say the whole job took me 2-3 hours.