Diagnostic help!

[Essentials]

The problem:
I noticed I had intermittent heat (climate control) and so I thought I might have low coolant or a bubble in the system. I did have low coolant so I topped it off and that helped at first. Then it happened again so I looked into more. After some of the initial repairs I still had the same problem with the heat but noticed a bigger problem, the coolant had constant bubbles coming up through the coolant bleeder funnel I was using.

Things I’ve done so far:
-changed water pump
-changed thermostat
-flushed radiator, block, and heater core
-head gasket leak tester

None of these things have fixed the issue and with the head gasket leak test coming back negative it has left me stumped. I did do some research on here before posting and I found a post to where the guy had bubbling coolant but also had coolant sitting on top of the block (I do not have that issue) and it ended up being a seal on the intake. Idk if that would fix my issue. I really don’t want to waste more time replacing things that aren’t the issue. Hopefully this issue is very obvious to someone else, any help would be greatly appreciated. If any more information is needed let me know.

[DarkPira7e]

You need to keep bleeding until it stops bubbling. How long did you bleed it for?

[Essentials]

I bled it for well over thirty minutes and numerous times. The problem is that with the bubbles the coolant level never drops, only gets higher as the fluid heats up

[jrhudson]

You put the heat on without the ac? Perhaps heater core maybe has some air in it?

[Ultramaroon]

Coolant bleeder funnel? Have you cracked the high-point bleed valve? It's that right-angled fitting near the firewall.

[Essentials]

Originally Posted by jrhudson

You put the heat on without the ac? Perhaps heater core maybe has some air in it?

I did. I had the heat on high every time I bled the coolant system. The bubbles are endless so I’m highly confident that some form of gas is getting into the system somehow.

[Essentials]

Originally Posted by Ultramaroon

Coolant bleeder funnel? Have you cracked the high-point bleed valve? It's that right-angled fitting near the firewall.

Yeah it’s like a high walled funnel that you can over fill and should, in theory, allow for all the air to come out. And yes I also cracked the bleeder valve up near the fire wall on the heater core line.

[Ultramaroon]

Originally Posted by Essentials

I did. I had the heat on high every time I bled the coolant system. The bubbles are endless so I’m highly confident that some form of gas is getting into the system somehow.

Bubbles even with a cold engine? A hot engine will simmer at atmospheric pressure (cap off)

[Essentials]

Originally Posted by Ultramaroon

Bubbles even with a cold engine? A hot engine will simmer at atmospheric pressure (cap off)

I’m pretty sure yes, even cold. But it’s been a couple weeks since I have done anything with the car. I’ll test it tomorrow and post results.

[RZNT4R]

Why do people insist on running engines with the rad cap off? The system needs to be pressurized or you will always be creating bubbles.

If you have no way of doing a proper vacuum fill, engine off, fill it up with your funnel and crack the bleeder valve. Once it's full and you've got no bubbles on either end, seal it back up and give it a steady 1000-1500 rpms to warm it up until the thermostat open (keeping an eye on the temp of course). Shut her down and let cool. Reinstall funnel, open bleeder and top off system.

[Essentials]

Originally Posted by Ultramaroon

Bubbles even with a cold engine? A hot engine will simmer at atmospheric pressure (cap off)

Yeah even when cold and with the cap on it was sending bubbles into the over flow tank. I also noticed a little bit of moisture dripping out at the slip joint for my headers to the over pipe.

[Ultramaroon]

Originally Posted by Essentials

Yeah even when cold and with the cap on it was sending bubbles into the over flow tank. I also noticed a little bit of moisture dripping out at the slip joint for my headers to the over pipe.

Uh oh. Does your exhaust have that characteristic sweet smell? Any sheen on top of the coolant?

[Ultramaroon]

Originally Posted by RZNT4R

Why do people insist on running engines with the rad cap off? The system needs to be pressurized or you will always be creating bubbles.

Most people don't have a real understanding of those details. Even if someone is experienced with pressure cookers, it can be quite a leap from those to engine cooling systems.

[RZNT4R]

Oh and since we're going on about that...

Even if the rad cap is installed, it means nothing if it's defective. A bad rad cap is a common issue that shows up as low coolant/no leaks. In my youngers days as a mechanic I had an experienced coworker who was adamant that my old and busted high KM 4Runner had a bad head gasket. It held pressure, had no leaks but was losing coolant long-term. I decided to test the rad cap, it failed, was replaced and the issue was resolved.