Slushing liquid sound under the dash when I start the car

[Ultramaroon]

Originally Posted by ermax

Didn’t know that. I’m curious why the manual still says to set the heat and turn on the blower.

It is odd but there's no valve. It's either a procedural oversight, or there's something significant about shedding as much heat as possible to have control over the cooling circuit. As rznt4r said, the heater circuit controls the opening of the thermostat. Keep the thermostat cold in order to maintain all flow through the heater circuit? Flush the bubbles by racing the engine?


I'm pulling shit out of my ass but it's an iterative process to be performed while the engine is cold.

[RZNT4R]

It's probably not SIGNIFICANT, as while the heat is on, they say the fan should be on low, so not much much cooling will occur on that front.

if I had to take a guess, I'd say the water pump and thermostat being at the lowest points, they are not what's going to trap air, the heater is, so rejecting a bit of heat from the heater bypass while the throttle gets bumped a few times is probably to ensure the thermostat remains closed and maximise the flow through the heater circuit to carry out any air that might get trapped. Once air is out of the heater bypass and into the water jacket, it can freely go up into the coolant crossover and up the upper hose to the cap.

[Ultramaroon]

I think the blower is set to low so any remaining gurgle can still be heard.

[jamestemperante]

Originally Posted by RZNT4R

Just

Stop

For

A

Minute

Your car was [fine], someone changed your coolant, then your car was [not fine]. Did you severely overheat your engine while it had the slushing sound condition? If not, your head gasket is probably fine.

Who said it was the thermostat? The heater bypass is what operates the thermostat, low circulation in the heater will result in incorrect thermostat operation. That does not mean the thermostat needs to be replaced.

Now, we will suppose you eventually let the car cool down, filled it properly according to the shop manual procedure linked in this thread, has that resolved the slushing sound? And you are still getting bubbles out in the overflow tank? There is a very easy test to do: With the car cold, coolant full to the top of the filler and no bubbles coming out of the bleed port. Close everything, start the car, warm it up, turn off the car, squeeze the top radiator hose a few times. Is it hard like a mountain bike tire or soft? If soft, can you hear fluid slushing in the overflow tank when you squeeze?

-i think the radiator cap is bad. replaced the cap and bubbles went away, did the air bleeding procedure again when the car is cold, slushing sound went away abit, but when the car is in operating temp, the slushing sound comes back when i start the car, top hose is hard though when the car is warm

[jamestemperante]

-i think the radiator cap is bad. replaced the cap and bubbles went away, did the air bleeding procedure again when the car is cold, slushing sound went away abit, but when the car is in operating temp, the slushing sound comes back when i start the car, top hose is hard though when the car is warm

[jamestemperante]

by the way. oem rad cap is 1.1 i think, replaced it with an aftermarket one 1.3

[jamestemperante]

-i think the radiator cap is bad. replaced the cap and bubbles went away, did the air bleeding procedure again when the car is cold, slushing sound went away abit, but when the car is in operating temp, the slushing sound comes back when i start the car, top hose is hard though when the car is warm

[RZNT4R]

It will probably need a few rounds of bleeding.

Don't warm it up, do as the shop manual says and from cold, bleed it from the bleed port and add coolant as needed, run it momentarily, rev it a few times and shut her down. Let her sit a bit to any bubbles can rise to the top of the heater hose and filler neck, repeat bleeding and adding coolant.

Do this until it's properly filled.

And this my friends is why vacuum filling is preferred over the yellow funnel: it's a perfect fill every time even in system with the most ass backwards impossible to bleed bullshit designs.

[ermax]

Originally Posted by RZNT4R

even in system with the most ass backwards impossible to bleed bullshit designs.

Yeah my IS300 takes weeks of topping off to get all the air out. I have no problem with the Twin though.

[RZNT4R]

I use the Snap-On RADKITPLUSA on everything and it's an absolute joy. Perfect every time on every car, from a large cooling system like a powerstroke to a... large cooling system... like a 911. Shit's perfect.

[jamestemperante]

update. change the rad cap, and the slight bubbles is still there. I just didn't noticed it. haha its like.1 bubble per second. is that normal? should i just do another coolant flush?

[Ultramaroon]

Originally Posted by jamestemperante

should i just do another coolant flush?

Only if you want to start all over again.


No. Just keep going. Is your car perfectly level where you are working?

[RZNT4R]

Originally Posted by jamestemperante

update. change the rad cap, and the slight bubbles is still there. I just didn't noticed it. haha its like.1 bubble per second. is that normal? should i just do another coolant flush?

There is no point in adding air to it.

The only way that would be worth it is if you started from scratch with a vacuum filler, as it's hard to pull a vacuum in a system that's significantly full.

[Ultramaroon]

Do you mean bubbles to the reservoir hose? I would expect to see bubbles until it reaches peak temperature. That's when the existing air in the cooling system quits expanding. Unless you're running it until the fan engages, you'll see bubbles.

Then, when the engine cools, the air bubbles shrink, and coolant back-fills the system. The smaller air bubbles collect at high points, like the one at the bleeder valve.

When the cooling system is working properly, there are no bubbles, and the cold fluid level does not change.