What issues can i cause by not having the cap on my coolant resivour?

Question

I got my oil changed the other day, waited a week before driving the car and it over heats and starts smoking a little bit. I thought mybe the shop forgot to put oil in the car and that wasn't it. I look toward the coolant resivour and the cap was not on and there was virtually no collant in the resivour. Now I have a blown freeze plug from overheating heating the car. Can not having the cap on result to me blowing the freeze plug. If so how?

Answer 1

There are two possible answers to your question depending on the vehicle...

1) If this is a closed loop system with a presure cap on the resevior, then running the car likely pushed the coolent out of the system and it overheated due to low fluid. This would be the same as driving around withour a radiator cap. Also the preasure raises the boiling point of the water so that it doesn't turn to steam as quickly.

2) If this is not a closed system car, then it is strictly a "burp jug" as they used to be called and it is used as an expansion tank, as the coolent gets hot some gets pushed out of the system into the tank and then as it cools it is pulled back in. If this is the case, then leaving the cap off isn't tat big of a deal as the cap is vented.

My thought is that they noticed that the coolent level was low, took the cap off to add fluid, got distracted and didn't put any additional fluid in or place the cap back on. You don't add fluid to a closed system when it is hot or you will get scalded. In either case, being low on fluid most likely did cause you to overheat.

Answer 2

the coolant resevoirs on todays cars are part of the pressurized radiator system. There is no radiator cap on the on the actual radiator itself,,,,the cap is on the coolant resevoir and it is supposed to be on tight to hold in the pressure.

Without that cap the water in the radiator had no pressure and the water literally boiled out of the engine causing it to overheat. the blame goes to the shop that serviced your car.

Answer 3

You don't get a blown freeze plug from overheating. There is also no correlation between having the cap off the reservoir and a bad freeze plug.