A few questions regarding radiator cap and coolant expansion tank.

1. Can a faulty radiator cap that visually looks ok actually cause coolant loss?

2. If expansion tank has coolant then is there still a chance that coolant inside the radiator cap could be low? I am under the impression that if radiator runs low it will draw coolant from the expansion bottle so hence the coolant bottle will have to be completely empty before levels inside radiator start to go low

3. If expansion tank goes below minimum then is there a chance of getting air in the system?

Thanks

 

Rad cap allows heating/expanding coolant to be pushed into the reservoir, when hot it then seals and the system pressurizes. When the engine cools the cap allows coolant to be drawn back into the radiator as the coolant reduces in volume. If the cap is not working properly you can have loss of coolant, air in the system, both, over heating and other issues.

If in doubt buy an OEM cap, never ever buy aftermarket they are all crap. All of them. End of story.

 

I made a thread about this awhile ago, change your cap and buy a coolant bleeding funnel and see if any air comes out then. Drive it and see if you continue to loose coolant, I did and my upper rad hose clamp was weak and that caused it to loose coolant, so those clamps can fail or maybe the water pump.

 

Agreed. Buy an OEM radiator cap, they are like $18. I changed mine at 55K