Slushing liquid sound under the dash when I start the car

[jamestemperante]

Hi everyone, I just had my coolant flushed and replaced, and I noticed that everytime I start the car, I hear a slush sound, kinda like a sudden flow of liquid under the dash. I tried bleeding it by filling the radiator with more coolant and opening the bleeder cap and reving the engine 5x @3,000 rpm. everytime I do this, when I open again the radiator cap and bleeder cap hose, bubbles come out. I did it about 10x already. lol. Hope you can enlighten me. Thanks!

here is the video. hope you guys can hear it.

[Ultramaroon]

I didn't even have to listen. You just had your coolant flushed. Immediately goes to air in the heater core circuit. There is a bleed valve on a right angle hose nipple, (connector, whatever) and a procedure.


https://gt86stuff.onrender.com/t3Por...0419K00HX.html

[jamestemperante]

Ive done this steps today and also did a burping with a funnel ontop of a radiator. 40 mins in and bubbles still rising in the funnel. closed everything and found that air bubbles rising in the reserve tank.

https://www.youtube.com/shorts/_AMZdJIm7fs

[ermax]

Are you bleeding while the heat is on? If not you can’t get all to air out of the heater core.

[RZNT4R]

The old school yellow funnel is really bad for modern cooling systems.

Bubbles keep rising in the funnel because the system is open. The radiator cap holds pressure because the pressure raises the boiling point. If you're running the engine for 40 minutes without a radiator cap you're very likely creating those bubbles.

Let it cool down, fill it only as described (by opening the bleed valve) and don't start the engine until you've reinstalled the radiator cap.

[RZNT4R]

Originally Posted by ermax

Are you bleeding while the heat is on? If not you can’t get all to air out of the heater core.

These cars don't have a heater valve like an older honda. Coolant will flow in the heater core regardless of the heater settings because the heater circuit is what opens the thermostat.

[jamestemperante]

yep. heater is on and blower fan at 1.

[jamestemperante]

thank you for this info. but why are bubbles still rising in the reservoir?

[Ultramaroon]

Originally Posted by jamestemperante

thank you for this info. but why are bubbles still rising in the reservoir?

Will have to go through a few heat-cool cycles to eliminate all the trapped air. Keep going. It will work.

[Sportsguy83]

Originally Posted by RZNT4R

The old school yellow funnel is really bad for modern cooling systems.

Bubbles keep rising in the funnel because the system is open. The radiator cap holds pressure because the pressure raises the boiling point. If you're running the engine for 40 minutes without a radiator cap you're very likely creating those bubbles.

Let it cool down, fill it only as described (by opening the bleed valve) and don't start the engine until you've reinstalled the radiator cap.

I've seen literally hundreds of 86s bled with the old school yellow funnel and they are all fine and work as intended. Nothing wrong with it.

[Ultramaroon]

Originally Posted by Sportsguy83

literally hundreds

so many flushes

[jamestemperante]

Went to the dealership and said it might be a faulty head gasket -_-

also noticed something, when pressing the gas and holding it to 2.5k rpm, bubbles in the reserve tank (radiator cap closed, bleed cap closed) seems to go slightly faster. Any idea what might be causing this? some say its a thermostat.

[RZNT4R]

Originally Posted by jamestemperante

Went to the dealership and said it might be a faulty head gasket -_-

also noticed something, when pressing the gas and holding it to 2.5k rpm, bubbles in the reserve tank (radiator cap closed, bleed cap closed) seems to go slightly faster. Any idea what might be causing this? some say its a thermostat.

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?

[ermax]

Originally Posted by RZNT4R

These cars don't have a heater valve like an older honda. Coolant will flow in the heater core regardless of the heater settings because the heater circuit is what opens the thermostat.

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