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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8607
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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I heard some ‘fluid gushing thorough in a pipe under

Customer Question

I heard some ‘fluid gushing thorough in a pipe under pressure’ kind of sound, only happen randomly, not very often (form time to time), when I step on the gas paddle accelerating from low speed, like from 2 gears. I was wondering if it’s the coolant flushing
noise or if it’s ATF noise from the torque converter. Did anybody experience the same? What it’s? Is anything breaking down or failing?
Submitted: 1 year ago.
Category: Mitsubishi
Expert:  Doug replied 1 year ago.

This definitely will not be in the torque converter, it is most likely going to be either the coolant like you suspected or the refrigerant in the AC system. In either situation it is an indication of potentially being low and needing service. There is a third possibility as well I will address in a moment.
The first thing you should do is make sure the noise still happens when the AC is turned off. This is a very easy check that will verify if there is a refrigerant problem. If the noise goes away when the AC is turned off, then you know there is a likely a low refrigerant charge condition. It is worth noting that the refrigerant can make this noise under certain conditions while it is still pretty close to proper charge, but generally speaking when you hear this noise it is 10% or more discharged.

If the noise is still present with the AC off then we would know it is not refrigerant related. At that point it is most probable that there is air in the cooling system. When air is introduced to the cooling system (either via leak or evaporation) it will create a rushing sound heard through the front of the vehicle and/or dash as the air pockets push the coolant through the tubes to the heater core etc.

When this happens you will want to get it addressed as soon as possible; that would mean checking for external leaks in the cooling system, pressure testing the system, and if nothing is found refilling and purging the air from the system. Left unaddressed, you do risk potential cooling related issues.

The last thing to consider, and this is only typical on certain models, is if you have AC condensation trapped in the dash from a plugged drain. This is again only typical on certain models (Endeavors, earlier Galant/Eclipses, etc), but is luckily pretty easy to check. Driving at low speed in a parking lot or other open space, steer the car hard in one direction or the other and see if the noise is reproduced that way. This is using inertia to move the water around if you have a clog. Likewise if you steer real hard to the left and there is a good amount in there you will hear it hit the fan as well which will make a unique noise.

Based on your description with it being infrequent I would say it is less likely to be that (AC clog) and most likely refrigerant level or coolant. Both are very common complaints across most of our product line.

Customer: replied 1 year ago.
Driving at low speed in a parking lot or other open space, steer the car hard in one direction or the other and see if the noise is reproduced that way.Yes, this reproduce the water flow sound. So, how to fix it?
Expert:  Doug replied 1 year ago.

Thanks.... if you can influence the noise why turning hard at low speed, then there is water trapped inside the AC box.

To correct it you need to clear the AC drain of debris... the way to do this varies by vehicle, however in most cases it will amount to locating the drain tube on the firewall, driver side, about 2/3 of the way down, then using compressed air or a rigid pipe cleaner etc to clear the blockage. When you do, substantial water should exit immediately. Proper repair is to pull the dash and AC box for physical cleaning, but is labor intensive and not terribly cost effective. Most people will just clear the drain as above and hopefully whatever was in there (leaves usually) will deteriorate enough to fall through. If it blocks again though, you have to clear it out again etc until the debris exits.

In some cases this is more work than others to reach the drain... notable exceptions are the full size Montero, the Montero Sport, and the Endeavor. All of these are particularly difficult drains to reach and in most cases should be left to a professional even for clearing of the drain tube unless the person doing it is very comfortable with this sort of work as they are not an easy clear like some other models.