1990 toyota pickup overheats. 22r. Dumps about a gallon out the rest. O leaks

Hello, if you are experiencing overheating - and it's not a hose or coolant pipe leaking under pressure, then yes - diagnostic testing will be needed to determine why. Is the thermostat sticking closed? Is a cooling fan not working? I do not believe a cap concern will cause overheating. Is the water pump circulating coolant? You may wish to enlist a shop near you for guidance and assistance. https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.