I'm about to replace the O rings and thermostat and want to know how much coolant i'd have to drain to carry out the job? I'm loathed to drain the lot as its fresh after SC install.

 

I just did this job (very small coolant leak from the o-ring) and used a pela pump to remove a few litres of fluid (from expansion tank and then removed t-stat and drained some from block).

It was a bit messy. If I'd had the car on ramps I would simply have drained the radiator coolant - with the nose pointing up in the air you can remove the coolant bridge without any spills. Last time I retensioned t-belt I did this so I could remove hoses for access and the hoses came off without spilling a drop after rad was drained. Would probably work if car was level as coolant from bridge would run through top hose into rad and out.

I wouldn't worry about the coolant being fresh as you can simply pop it back in when you're done.

Use a little silicone lube on the main o-ring and the two small red gaskets on either side of the bridge.

 

+1 on lubricating the o-rings. I recently replaced the water manifold o-rings as part of the intake R&R. When re-installing the water manifold, torque the four bolts in two stages (7 ft.lbs. & then 15 ft. lbs.) to arrive at the correct final bolt torque spec.
Adam

 

Just catch it & put it back?

Marton