Hi all, lately my '87 started overfilling my resivoir, and running me low on coolant, think thats the t-stat?
thanks you all!!!

 

Minor coolant system leak. Common issue, as when the system cools it can't draw the overflow fluid back into the system. Could be as simple as a bad radiator cap or a clamp that has loosened up.

Rent (free) a coolant pressure tester from your local auto parts store.

 

Bad caps are a big culprit, especially if it's not letting coolant back in on cool down.