My 17 year old nephew’s 1989 Jeep Cherokee overheats. At first it was leaking and a mechanic added some stop leak in the radiator. It didn’t stop the leak. He has had the engine and coolant system pressure tested and it passed. The thermostat was replaced with a new one. The pressurized plastic coolant reservior was replaced with a new one, because the old one was leaking. It still overheats after traveling 10 miles. The coolant still boils in the plastic coolant reservior. What could be the problem?
A partially restricted radiator will cause overheating.
Well it may be the coolent or antifreeze itself because the coolent (antifreeze) stops the water from boiling or frezzing even at extreame temptertures. You should try a long lasting coolent (and if the moter is made out of aluminum you should buy a coolent that is safe for aluminum moters). But it can also be the radiator pressiure cap have it pressiure tested. But it can also be a old water pump because it leaks and sends out a noise before it gives out or a faulty thermostat or the belt from the water pump that needs ajusting or that need to be changed. Any of these may be the problem.
Stop leak is also stop flow. Maybe you need a new radiator. Check it for missing fins due to corrosion. White or green color on the back of the radiator is a bad sign.
We replaced the radiator, thermostat, and pressurized coolant reservior ( All New) It’s still leaking around the coolant reservior cap and the engine is still overhesting. I wonder if the new coolant reservior is faulty?
We replaced the radiator, thermostat, and coolant reservior ( all new equipment) The engine still overheats and coolant leaks around the coolant reseervior cap.
The coolant leaks around the Coolant reservoir cap? Meaning the coolant reservoir is full.
Is the coolant boiling and/or foamy?
If so, you may have a blown head gasket.
It was mentioned the rad cap may need replacing. Maybe.