More heat now - how? rad cap!

[Vinnie6]

I wanted to make sure of something before I created this thread because I run the risk of being soundly ridiculed. However, after a week of testing, I am confident to declare something that sounds absurd. I replaced my radiator cap. I took off the aftermarket stopsign shaped metal 16 lb cap and put on a new original equipment ACDelco round black plastic 15 lb. radiator cap. My cabin heat has increased (quite a bit, actually) as a result! I cannot explain the correlation. I'll leave that to the experts. I would be very curious to know myself. But now I find myself sliding the heat blend knob a click or two off full hot even with the fan on low with it 20 degrees f outside. I invite others with heat problems to also try this $13 experiment and see if you have similar results.

[chevymaher]

I wanted to make sure of something before I created this thread because I run the risk of being soundly ridiculed. However, after a week of testing, I am confident to declare something that sounds absurd. I replaced my radiator cap. I took off the aftermarket stopsign shaped metal 16 lb cap and put on a new original equipment ACDelco round black plastic 15 lb. radiator cap. My cabin heat has increased (quite a bit, actually) as a result! I cannot explain the correlation. I'll leave that to the experts. I would be very curious to know myself. But now I find myself sliding the heat blend knob a click or two off full hot even with the fan on low with it 20 degrees f outside. I invite others with heat problems to also try this $13 experiment and see if you have similar results.

Mine had a similar cap and radiator was always low.Put on stock cap now it not puking into overflow tank radiator stays full.Maybe it was air bubbles in heater core.Just a thought.

[fast68]

the rad cap function is very important


you gotta have that 15 or 16 psi pressure in the system

it will help cool the engine as well

water under pressure cools better



replace the cap every couple years and use a good one not a cheapo one


if you can squeeze rad hose when engine is hot then the cap is failed or you have a leak somewhere