Radiator Reservoir Bottle Cap -- how to test?

1995 Tacoma (2.7L) had to recently replace the radiator and it appears that the reservoir may not be flowing properly. Was running a bit hot so checked the radiator level and appeared to be low (took a bit to fill), however reservoir bottle level has not changed at all (still full). I'm wondering if the reservoir bottle cap is not working properly to draw/discharge.

Is there a simple way to test it?

 

It works off of suction as the radiator cools. Just make sure the ports are free of any debris in the reservoir cap and the nipple coming off the radiator and of course the attached hoses. Otherwise, I would guess the radiator cap is not the correct one and is not allowing the coolant to be drawn out of the reservoir.

 

Check that the hoses are not clogged.

The hose coming from the radiator should be attached to the reservoir cap port that attaches to the hose going to the bottom of the reservoir. This allows the radiator to suck coolant in after driving when the engine cools down. The other port allows coolant to run out of the reservoir from the top if it overflows. Check that these are not reversed.

It will also take a few hot/cold cycles to expel air from the radiator and suck coolant back in. That's if you have the correct radiator cap, no leaks, etc.

 

I will take a look. Radiator cap was replaced with the new radiator: AZ Spectra Premium #B1755, radiator cap AZ Duralast 7913.

 

I was thinking this might be an issue so I pulled both hoses off and checked them / ran water through them, clear with no restrictions.

 

Radiator definitely builds up some pressure when running. When I opened the radiator cap the other day to take a look inside (after it was cooled down) big pressure relief to the system to the point that I could head the plastic caps settle. This kind of pressure normal on these?

 

Radiator caps usually keep in around 10-15 psi. It should say on the cap, maybe in atmosphere units. 0.9 atmospheres of pressure is 13 psi. It's kind of hard to judge the pressure just based on the sound.

Make sure the cap is matched to the radiator. If the cap is too tall for the radiator, the spring on the relief valve will be compressed too much. With all the different radiators available for different Tacoma engines, it might be possible you have the wrong type of cap.