Heater core bubble hissing noise

Hi,

More than likely you have an air pocket. Check out this guide and go to step 3.

Review and let me know what you find. Thanks

https://www.2carpros.com/articles/vehicle-bubbling-noise

Does it matter that it was an aftermarket? Once I jack the front end up do I need to do anything else like start the truck or take the cap off of the coolant box?

Good question. It should not matter because they operate the same it is just the quality is different.

When bleeding this system I would use a funnel called a spill free funnel because it allows you to keep pressure on the system with fluid so when air pockets open up or pop the air comes out and it immediately pulls coolant into the void. Then jack up the front of the vehicle and only the side of the radiator cap. Basically you want to raise the radiator cap as high as possible because the air will rise and you want it to rise towards the cap.

The process to do it is, hook up the funnel then fill the funnel about half way (not too much because if it pushes some out it will overfill the funnel). Then start the engine and turn the heat on as hot as possible and the fan on low. Run the engine so it warms up and you will see bubbles start to come out. Let it run for about 15 minutes then put the plunger in the funnel and remove it. Remove the radiator cap attachment and top off the radiator and put your cap back on. Take it for a drive to see if the noise is gone.

If you see small bubbling the entire time that is pretty consistent that is just the capitation of the water pump and not air pockets coming out.

Using this funnel I have never had an air pocket that I couldn't get out.

Let me know if you have questions. If you need to, there are a ton of videos online of people using this funnel.

How should I use the funnel if I have a coolant reservoir separate from the radiator? Because it has a fill line and in order for me to do so I'd have to over fill it to the top.

I am sorry. I forgot they used a de-gas bottle on that year. You are correct. You do not need that funnel for your system but I would jack up the corner of the truck that the bottle is closest too and run the engine.

It is possible that the heater core itself is the issue but most of the time this is due to trapped air so I would run the truck with it jacked up for about 20-30 minutes and then take it out for a drive. When you are running it to work out the air, just turn the heat on and fan on low. If the heater is not very hot then you have a large air pocket.