when you take off the thermostat, there is a hole beneath it. if that hole is left open, the pump will not circulate coolant thru the negine with any degree of effectiveness. In a 1st gen, you can use a big NPT plug available at the big boxes.

It doesn't need to be a perfect seal, but it needs to be secure.

(FYI) JB Weld will work for a while, but it breaks down eventually....

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]