Bubbling is usually a sign that the system is low on coolant or that you have a head gasket problem starting. I would first test for a bad gasket using one of these methods https://www.2carpros.com/articles/head-gasket-blown-test
If it passes those then it is a good time to flush the system. When you refill it be sure to allow it to burp out any excess air. The best way to fill that engine is to use a vacu-fill system but barring that you can fill the radiator, then fill the reservoir. Run the engine until it warms up and the thermostat opens. Now let it cool off and top up the system again.
Then drive it and watch the coolant temperature as well as listen for the cooling fans.
Saturday, May 21st, 2022 AT 1:53 PM