It's more like the oil bypass filter.
The coolant doesn't all flow through the filter, only a very small portion regulated by the orifice in the outlet.
Btw: The hose into the heater should have a shut-off valve for the summer, otherwise it will always bypass a portion of hot coolant back into the block uncooled.
The heater passages slow down the flow, but everything counts in the summer.
When the filter gets more clogged it will gradually flow less. - You can feel the temp difference between the two filter hoses to check for flow...
The first filter is supposed to be replaced after 500 miles, then replacement every 1000 miles.
Yes, the original filters were soaked in a corrosion inhibitor.
You have to drill to mount the filter. I put mine on the firewall.
It's great for cleaning out a used block from fine sediment, that flushing alone doesn't get.
On a new block, I would only use waterless coolants. An expensive one-time investment, but good for the life of the engine.
And you get so many more benefits, that is pays for itself, the more you drive.
