Water sloshing noise under dashboard

[Tree Ranger]

I have a 2019 Ford Ranger with approximately 51k miles on it. Around four months ago I heard intermittent water sloshing noises under the dashboard when having the AC on. Defrost setting, air blowing up, thermostat temperature set to half. A couple of weeks later in winter I also noticed it when only used in heater mode, no AC, same temperature setting defrost mode only. The noise is now constant when the engine is fully warmed up; it sounds like sloshing water and/or air bubbles.
Coolant levels are normal, no loss of coolant, no water in the oil. Since I have the truck I never saw any water puddles underneath the truck, even in the hot summers here in CA so my first thought was it might be a plugged AC drain. Four months ago I turned the truck into the Ford dealership and they said they could not verify anything noise never stopped.
Three weeks ago I got a deeper aluminum transmission pan installed on the truck and the mechanics shop stuck an air hose in the AC drain which is underneath the transmission and water came out but no improvement at all; noise was right back when I drove it home from the shop.
Since the noise is now almost constant, especially when truck is idling or in front of a traffic light, I again turned in the truck to the FORD Dealership since I have the extended Portfolio warranty, and they burped/purged the radiator and stuck an airhose in the AC drain as well. The noise is still there, not as loud anymore but still there; I still hear sloshing. There are still no water puddles underneath the truck; not sure if everything evaporates on the hot transmission. The noise only occurs in the defrost mode.
I also learned that the Ranger does not have a radiator cap anymore since I tried to purge it myself. I left the coolant cap off and parked it in uphill & downhill and level position and let it run each time for 20minutes after engine was hot with heater on high temperature setting. Not sure how the shop purged it or if there are any purge valves/screws.
The truck does not slosh when shaking the cab the Technician tried that as well.
I saw two posts in regards to this issue on this forum from a couple of years ago on this issue but there was no answer how it was resolved.
The constant noise is really annoying and I am ready to sell the Ranger because of that although it is the best truck I ever had and I really like it.
Should I replace the coolant level cap?
Any feedback how I could get rid of the noise or what the dealer can do in order to get that resolved would be greatly appreciated.

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[airline tech]

Being that you have touched some of the possible reasons for the noise.
Here are all of the possible sources that come to mind.

1. Dirty Cabin Filter
2. Air in the Coolant System, heard by the coolant passing through the Heater Core, can be viewed by the coolant temp (indication) jumping around as the air pockets flow past the Coolant Temp Sensor.
3. Faulty - Reservoir Cap not allowing the system to properly pressurize, this can be tested with a pressure tester. Should pressure test to 21 lbs. then blow off pressure but hold around 21 lbs.
4. Clogged Condensate Drain, blowing air with gun may be only temporally clearing the drain and then condensate flow (drain) moves debris back into the drain port.
5. Low Freon Charge - being that you only hear the noise when the AC is operating and in Defrost Mode.

Operational Notes:

1. The AC Compressor will activate in DEFROST mode if the outside temperature is above 32 deg
So, if Low on Freon, this can produce a hissing or bubbling sound in the EVAP Core.
2. A clogged Cabin Filter will cause improper airflow around the EVAP Core and cause excess condensate to build up in the drain system.

So, I think by all that has been done already.
1. Check the Cabin Filter
2. Check the Freon Charge (Most probable cause)
3. Test the Coolnt Tank - Cap or just replace it (Cheap Expense) and a good preventive maintenance item anyway.

 

[Conman50]

I hear these same noises too when parking sometimes. Sounds like water flowing through a pipe? I haven't noticed anything wrong so I thought it was normal. I had the dealer replace my coolant a few months ago and all seems fine. Just replaced because I felt it was time.

Is there an electric pump that pumps coolant when stopped at a light? I feel likevthat may be the sound we are hearing.

 

[Cmar]

1. The AC Compressor will activate in DEFROST mode if the outside temperature is above 32 deg
So, if Low on Freon, this can produce a hissing or bubbling sound in the EVAP Core.

I'm thinking this, I had it happen to me on a different car. Really does sound like water sloshing around. Well technically R134A these days but same thing.

 

[Tank20xl]

Do you notice any water or dampness on the passenger side floorboards?

 

[got3fords]

Here are all of the possible sources that come to mind.
2. Air in the Coolant System, heard by the coolant passing through the Heater Core, can be viewed by the coolant temp (indication) jumping around as the air pockets flow past the Coolant Temp Sensor.

Which could mean low coolant, right? The last time I heard a noise like that the coolant was low, meaning there was not a solid flow of fluid, air in it. I remember the cure was filling the cooland tank properly and the noise went away. But that was about 20 years ago.

 

[JohnsonEJ23]

I've only had my Ranger (2020 model year/30,000 mi.) for a couple of months, but I hear the same thing when I first start it up. I haven't noticed anything else wrong with it though, other than harsh shifting which a dealer is going to check out in a couple of weeks.

 

[Tree Ranger]

Being that you have touched some of the possible reasons for the noise.
Here are all of the possible sources that come to mind.

1. Dirty Cabin Filter
2. Air in the Coolant System, heard by the coolant passing through the Heater Core, can be viewed by the coolant temp (indication) jumping around as the air pockets flow past the Coolant Temp Sensor.
3. Faulty - Reservoir Cap not allowing the system to properly pressurize, this can be tested with a pressure tester. Should pressure test to 21 lbs. then blow off pressure but hold around 21 lbs.
4. Clogged Condensate Drain, blowing air with gun may be only temporally clearing the drain and then condensate flow (drain) moves debris back into the drain port.
5. Low Freon Charge - being that you only hear the noise when the AC is operating and in Defrost Mode.

Operational Notes:

1. The AC Compressor will activate in DEFROST mode if the outside temperature is above 32 deg
So, if Low on Freon, this can produce a hissing or bubbling sound in the EVAP Core.
2. A clogged Cabin Filter will cause improper airflow around the EVAP Core and cause excess condensate to build up in the drain system.

So, I think by all that has been done already.
1. Check the Cabin Filter
2. Check the Freon Charge (Most probable cause)
3. Test the Coolnt Tank - Cap or just replace it (Cheap Expense) and a good preventive maintenance item anyway.

Thank you for the detailed recommendations!!!
1.) Replaced the cabin air filter and the coolant cap so far no improvements.
2.) Waiting for an appointment with my Ford Dealer to get the Freon Charge tested. Does it need to be warmer weather for that or can it be done in winter temperatures? Mid 50 F.

 

[Tree Ranger]

Do you notice any water or dampness on the passenger side floorboards?

Do you notice any water or dampness on the passenger side floorboards?

No dampness or water at all in the truck!

 

[Tree Ranger]

Update on the sloshing noise:
I had my Ranger at a different Ford dealer for 10 days since I got all oils (diff, transfer) and break fluid changed; they could not verify the noise. They found a big air bubble in the coolant system but that did not solve the issue at all.
Drove it of the lot, same issue right from the get go. Came right back to the dealer and then service manager was test driving it with me and said it could be a thousand things, including a bad actuator but since they could not narrow it down there is nothing they could do to take my dashboard apart so that my extended warranty would cover that.
Dealer did not want to check my Freon Charge since the AC is blowing cold air and would only check it if it was blowing cold air otherwise they would charge me $300 to do a check. They also the AC compressor would not be on when the AC is off even in low setting.
I hear the sloshing noise now when the engine is warm, with AC and without AC on, blowing on defrost and also all other settings. I hear the noise especially when I drive it and then come to a stop at a light or on idle. Sometimes I hear the noise occuring for 15-20 seconds after I shut the engine off. I hear the noise sometimes for 10-20 seconds after the engine is shutt off.
I also heard when the engine was off this morning what sounded like an air bubble on the glove box compartment side, not sure if there is air going into the coolant reservoir but they pressure tested everything. I also had it run with the coolant cap off for a while but no improvement.
Frustrating.......
I ATTACHED AN AUDIO FILE Please turn up the Volume

 

[airline tech]

Ok, I hear what sounds like a faucet dripping (fast) into a sink full of water.

A few things that can be done in an attempt to isolate the noise.

Get a mechanics stethoscope and from under the passenger side footwell, place the scope on the heater core lines running into the heater core housing.

For the AC lines, this would have to be done from the engine bay.

I have a hunch that the noise is coming from the cooling system, but a stethoscope will help isolate it.

Get a scanner with Bi-Directional Control, and command the Cabin Heater Coolant Pump (ON)
With the engine at operating temp, this will circulate coolant through the system and heater core.
Note: This is the electric pump that runs when A/Stop is active, and engine is off
The purpose of this is to get circulation of the coolant without the engine running. (Troubleshoot and Isolate)

They pressure tested (Everything) Did this include the (CAP)?

I have a hunch since they found air in the system it is not circulating properly (lack of pressure and lack of proper flow) at idle, and the coolant is boiling creating air pockets.
Be it a bad cap, slow leak in the system (High) point sucking in air but not leaking coolant or a blockage in the system affecting flow to the heater core.

If you were to sit and let it idle, does the temp gauge climb out of the (Normal Middle) mark?
You can view this with a scan tool (digital number) or with the IPC Enginering Mode

My highly suspect items are the Cap (Releasing) pressure below 21 PSI or a small crack in the upper part of the reservoir.

Edit: I forgot you already replaced the cap, if you can isolate the noise to the cooling system then I would do another pressure test and focus on the reservoir

 

[airline tech]

The more I listen to the sound bite, I think I am hearing coolant (air pockets) in the heater core. It may be a good idea to do a combustion check of the coolant as well, as it may be a bad head gasket, pressurizing the cooling system creating air pockets.
This would be a worst-case scenario.

Either way, I am thinking the truck is overheating at idle, circulation issue.
Have you watched the Fan operation at idle? When Hot

 

[Jhbryaniv]

Ok, I hear what sounds like a faucet dripping (fast) into a sink full of water.

A few things that can be done in an attempt to isolate the noise.

Get a mechanics stethoscope and from under the passenger side footwell, place the scope on the heater core lines running into the heater core housing.

For the AC lines, this would have to be done from the engine bay.

I have a hunch that the noise is coming from the cooling system, but a stethoscope will help isolate it.

Get a scanner with Bi-Directional Control, and command the Cabin Heater Coolant Pump (ON)
With the engine at operating temp, this will circulate coolant through the system and heater core.
Note: This is the electric pump that runs when A/Stop is active, and engine is off
The purpose of this is to get circulation of the coolant without the engine running. (Troubleshoot and Isolate)

They pressure tested (Everything) Did this include the (CAP)?

I have a hunch since they found air in the system it is not circulating properly (lack of pressure and lack of proper flow) at idle, and the coolant is boiling creating air pockets.
Be it a bad cap, slow leak in the system (High) point sucking in air but not leaking coolant or a blockage in the system affecting flow to the heater core.

If you were to sit and let it idle, does the temp gauge climb out of the (Normal Middle) mark?
You can view this with a scan tool (digital number) or with the IPC Enginering Mode

My highly suspect items are the Cap (Releasing) pressure below 21 PSI or a small crack in the upper part of the reservoir.

Edit: I forgot you already replaced the cap, if you can isolate the noise to the cooling system then I would do another pressure test and focus on the reservoir

Without digging through your post history - what is the bi directional scanner you reccomend? I know you've mentioned the one you use in the past...

Thanks.

 

[airline tech]

I have an Autel MS906TS, any high-end scanner with Bi-Directional Control will work.

But your specific issue, this would only help in pinpointing (isolating) Coolant or AC Noise, I suggested it as it would allow you to command the pump on and circulate the coolant and the only noise would be the pump (humming) and coolant flowing.

A mechanics stethoscope or a long-handled screwdriver and place you ear to the plastic handle will most likely confirm my suspicion of coolant noise.

 

[Jhbryaniv]

I have an Autel MS906TS, any high-end scanner with Bi-Directional Control will work.

But your specific issue, this would only help in pinpointing (isolating) Coolant or AC Noise, I suggested it as it would allow you to command the pump on and circulate the coolant and the only noise would be the pump (humming) and coolant flowing.

A mechanics stethoscope or a long-handled screwdriver and place you ear to the plastic handle will most likely confirm my suspicion of coolant noise.

I have one of these - https://www.autoenginuity.com/scantool/ from my Subi days . . .

Guess it would be worth it to upgrade with this . . .

EDIT: Not that it matters here, but I am interested in seeing this. . .

Transmission Fluid Temperature
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