Took out the radiator yesterday and sent to the radiator shop for cleaning as there were too much rust inside. However when I installed back the radiator, put in the water and coolant, the water spilled over when the engine is on (the cap is not installed). This would not happen on other cars. Would appreciate your opinion. Mine is a 1994 MPV V6 3.0L

 

How much coolant did it take to refill sytsem. . The MPV is VERY slow to refill. Should have taken about 1 3/4 gallons to refill system after a drain to replace radiator. If took a lot less than this to refill then system may have overheated and spilled out. If filled to normal then overspill is not abnormal. Water expands in volume as it is heated. That is why you have an overflow tank under the hood to accept the expanding fluid level and replenish the system as it cools. If there was "too much rust inside" then maybe there are some other problems that need to be addressed. Rust in the radiator usually says poor service to cooling system and additional repairs will be needed. What is the condition of the water pump and/or thermostat?? They are equally affected by rust problems and should be considered as well'.