Pull the thermostat out and pan test it on the stove with a thermometer to see when it opens, even new ones don't always operate correctly, I jack up the front of the car as far as I can when refilling the coolant or use one of those burbing funnels.
Also make sure the t stat is oriented correctly.
There is the possibility of a blown head gasket. Compression test it.
Also make sure the t stat is oriented correctly.
There is the possibility of a blown head gasket. Compression test it.
@GT4Lyfe just noting the 4.6 didn't appear until 1996.
They also have those combustion-gas tester things to check if you have a blown head-gasket, at least the kind of leak that's pushing exhaust into your cooling system which it kind of sounds like yours might be. The compression test or leakdown test would determine what's going on too. The bubbling typically isn't a great sign unfortunately, but the General has good suggestions for what to check first. Aside from the thermostat, I'd also suspect a clogged radiator or worn-out water pump if coolant isn't moving.
They also have those combustion-gas tester things to check if you have a blown head-gasket, at least the kind of leak that's pushing exhaust into your cooling system which it kind of sounds like yours might be. The compression test or leakdown test would determine what's going on too. The bubbling typically isn't a great sign unfortunately, but the General has good suggestions for what to check first. Aside from the thermostat, I'd also suspect a clogged radiator or worn-out water pump if coolant isn't moving.
In my old car I got major bubbling in the res with a bad thermostat. Just depends on how it is, also with water pumps.
Well shoot, that's not good. Still a small possibility it's something else - leaking lower intake manifold gasket. So I'd leakdown test that particular cylinder for a final confirmation. Basically rotate engine to where both of the valves on that cylinder are closed (TDC), and hit it with compressed air through the spark plug hole. If you get the radiator bubbling, the head gasket is confirmed. If you don't, then you might be lucky and have a lower intake problem.
Here's a link that describes the process (you probably know how, for anyone else not familiar with leakdown tests): https://www.mobil.com/en/lubricants...vehicle-maintenance/how-to-do-a-leakdown-test
Here's a link that describes the process (you probably know how, for anyone else not familiar with leakdown tests): https://www.mobil.com/en/lubricants...vehicle-maintenance/how-to-do-a-leakdown-test