I installed a new water pump but neglected the thermostat. I have a new one with the housing now but I absolutely do not want to drain the system again.
Can't I just swap them out and deal with the fluid loss with a top off after?
Will it drain a massive amount?
It will try to make a mess, just work fast. Clamping the lower hose will help a lot. Remove then reinstall the surge tank cap, to relieve any pressure, but then creates a vacuum when the coolant tries to drain out. Work the lower hose loose, but push it back on just enough to not leak. Hold the thermostat on while you take out the bolts, pull the hose off, pull/drop the old thermostat, have the new one ready to hold in place, the new thermostat will dam up most of the coolant, and hopefully the clamp keeps the lower rad hose from dumping. So work quick getting the new thermostat bolt in and shove the lower hose on.
Have a pan under(sized for worst case scenario), it’ll make a mess, but if it goes well you won’t be refilling much
