Air bubble in heater core

When I first turn on my car and start driving I can hear the coolant moving underneath my steering wheel. I’m pretty sure this means that there is an air bubble in my heater core. I have no overheating issues. What’s the best way to bleed it?

 

I use a “Spilll-Free” funnel.
Run the engine with the heat on High and fan speed on Med or High.
Squeeze both the upper and lower hoses while the truck is warming up.
Some guys like to park the truck with the FRONT END on an incline. (Up hill).
This helps get heater core down lower and the radiator up higher. (Air rises)
I personally haven’t had to do this with my truck. But it does help.

You don’t have to use the funnel. But it makes a lot less of mess if you do.

Lisle 24680 Spill-Free Funnel, Standard Adapters, 11 x 7 x 7"es

https://www.amazon.com/Lisle-24680-Spill-Free-Funnel/dp/B00A6AS6LY

 

Was the coolant system opened up recently?

 

One of the most common no-no's people do when refilling the radiator is pouring it in quickly. That will trap more air and take longer to purge. Always pour the coolant in very slowly and pause every few seconds. This will purge alot the air as you go. Be sure to do this BEFORE you start the engine. You want as much coolant and as little air in the system before the pump starts sloshing things around.

Also....be sure to have the radiator cap off and let it idle for a while. This will purge much of the remaining air. And as mentioned....make sure the heat is on.

You may need to adjust your reservoir a day or 2 later, as the system will pull from it as it cools

 

What purpose does that serve? Coolant always flows through the heater core, there is no coolant valve.

 

To ensure that coolant is flowing properly through the core. If you have heat you know it's flowing. The core is the most likely place for an air pocket to lodge in

 

I usually just feel the inlet and outlet pipes down by the accelerator pedal. Both should be hot.

 

Simple to roll down the driver's window with the heat on. While it's idling with the cap off you can reach in and feel the air

 

Park on an incline like a hill or some ramps, remove radiator cap, start up truck. I like to massage the coolant pipes as well it helps to move any pockets of air. Don’t be afraid to let it idle for a while, it takes some time to get all the air out.

 

Do you want an honest answer....

its a 2005, look on the door sticker, if the manufacturer date is before 12/2005 it shipped with defective head gaskets. the bubbles in the heater core are the first sign that the defective piece of the gasket between cyl 4 and 6 is getting weak. what is happening is the gasket has not failed enough to have a constant leak. when the engine is good and hot and the RPM's get high for a second exhaust gas is pushed through into the coolant which gets trapped in the heater core. then after you let it set over night when you start it you hear the bubbles get flushed out. you have between 3000 and 10000 miles before you have bubbles coming out your overflow and over heating starts. of course try all the other options first, bleeding, etc... after you do all of that the bubbles WILL stop. depending on how you drive and how much you drive, after you get the bubbles to stop i predict in about 10-14 days the bubbles come back. if so you need to make a decision. you can put some Barr's sealant in it (the expensive version and follow the directions to the letter) and drive the truck for about 12-18 months depending on how much you drive before you have to either replace the engine or pull your current engine, clean all the sealant out, replace the hoses and radiator, etc to make sure the sealant is out of the system and replace the head gaskets or bite the bullet and replace the head gaskets or just put Barr's in it and sell or trade in the truck.

sorry for the bad news

usually bubbles start around 135000 miles +/- 20000 miles, how many miles on the truck?

 

a tip.... if you need to maximize time before you do anything major, you can run it until you get a check engine light with error code cyl 6 misfire before you either fix it or put Barr's in it. once you get a misfire on 6 gasket is about to go.

 

Remember, on older vehicles, the amount of heat coming out of the heater / defroster ducts was controlled by a valve that regulated the coolant flow through the heater core. On almost all newer vehicles, it works differently. Coolant flows through the heater core constantly, but the amount of heat coming out of the heater / defroster ducts is controlled by a blend door that regulates the amount of air going past the heater core. So in newer vehicles, cranking the heat all the way up has no effect on the amount of coolant flowing through the heater core.

BTW, I'm surprised nobody has picked up on the fact that the OP says he's hearing gurgling "under the steering wheel." The Heater Core is on the passenger side last time I checked.

 

this is true. Perhaps that gurgling is an old girlfriend trying to win him back

 

Yep

 

@Jimmyh

You are correct. And I actually thought of that while writing my response.
The main reason is #3 below.

The reasons I mentioned it in my post above was for a few reason.

1. The factory FSM says;
Fan Speed = Anything except OFF
Heat = Towards Warm
AC = OFF

2. This method is pretty safe to use on MOST other vehicles as well.
(You can help your buddy who doesn’t have a Tacoma or new vehicle, and still be ok doing this)

3. If I didn’t mention it, I was quite sure someone would tell me I was incorrect.
(Since the FSM say to)

Like the old saying goes, If you want the correct answer to a problem.
Give the Wrong answer. You’ll soon be corrected.

Again, I do agree with you.
As you are correct, there’s really no need to have the heat or fan on while filling the cooling system.
The fan could actually make the process take longer.

The important thing to watch it the TEMPERATURE.

 

I believe it more centered on the Tacoma.
I haven’t actually pulled the dash apart to look though.
I hope I NEVER have to. I’ve done a total of 3 cores in my lifetime.
The 1st one was enough to do me.

 

Yes it is nearly exactly in the center and the inlet / outlet piping is on the drivers side which is probably the source of the sound.

 

I definitely drive my truck hard. It has 200k miles on it. I can 100% replace the head gasket but will that fix the problem?

 

Don't go changing head gaskets unless you know you have a problem. Do you have issues with your heat? Have you checked the coolant levels? If you have a head gasket issue, your heater core isn't likely to be your only problem. Start with the simpler stuff first and work on diagnosis.

 

I have no visible leaks. coolant level stays the same, heat works really well, oil has no froth in it.