This, I'd be looking at replacing it with a newer PC parts equivalent water cooling setup. I'm sure with a little bit of fabrication you could keep the standard cooling blocks and it would just be a case of rerouting the piping and radiators.
I'm not sure why more Quad owners haven't done this already with the age of the cooling units in their Macs.
Sorry for thread necro but somewhere on the net there is a handy guide how to rebuild the LCS. The stock coolant is a polypropylene glycol solution and being a pc guy for years we know how that stuff tends to eat through whatever it can. For the LCS the coolant loves to attack the rubber seals that join the copper blocks to the LCS base. Once that goes and comes into contact with other metals causing a slow reaction (dissimilar metals) which is why everything pc grade is all copper or nickle plated with no aluminum in contact with the coolant. Replace the rubber seals then flush the whole loop out then use different type of coolant. Will have similar thermal performance but the risk of future leaks will be drastically less.
For modding dealing with 200w+ worth of heat is no easy task :s