I was recently passed down a 2005 Honda Pilot EX-L with around 250,000 miles. While driving around, we’ve noticed that after a while a gurgling like noise comes from the passenger dash. Shutting off the AC and heat does not stop it. My mom thinks it might be the heater core or radiator fluid. Any suggestions or helpful threads?
I'd guess heater core. See if theres an air bleeder screw to release any air in the system. If not, I'm guessing heater core has a small hole causing pressure release. Check the passenger footwell area to see if its wet
Blend door motor. You can find an aftermarket brand on Amazon for like $30. Do a search on youtube for "Honda blend door motor noise" and you'll see some great examples of what it sounds like plus where to find it. It's directly above where a front passenger's left foot is. It makes noise anytime the AC system is on, even if the key is just in the ACC position because the motor is twitching back and forth and ends up making a gurgling sound, but it's actually just the motor spazzing out.
To do a quick test, you can disconnect the cable going to the motor to see if the noise stops. If everything is quiet when the cable is unplugged, then that's the source of the noise. Mine sounded exactly like water gurgling and I'm glad I didn't go chasing air bubbles in the coolant system when it was actually a bad motor.
Coolant level low. Buy either Honda or matching spec branded coolant.
When engine is cold, refill expansion tank to max mark. Drive a weeks worth of normal miles.
When engine cold, recheck coolant level, add to max. Level drops as air bubbles are expelled from heater core.
The heater is the high point of the system where air will go. Try burping the system by filling with 50/50 coolant the same color as what is in there now. Run the engine until the thermostat opens and squeeze the radiator and heater hoses. There are also vacuum devices that will draw out the air that attach where the radiator cap goes. Just make sure you don't have a leak somewhere that caused the system to pull in air. Sometimes just letting the overflow tank run dry will do it.
Most likely air in the heater core as previously mentioned. Funnels like the below tend to be great and allow you to warm the car up with the radiator cap open but have some coolant in the funnel. This is the process I'd follow:
1) Start with a cold engine
2) Install funnel on the radiator where the cap goes
3) Fill the funnel 1/3 of the way up
4) Start the car and turn the heater on the hottest setting, but lowest fan setting and A/C compressor OFF.
5) Allow the engine to warm up while idling - making sure funnel never drops too low
6) Occasionally while warming up (carefully) squeeze radiator hoses to help burp air out of the system
7) Also occasionally while warming up, rev the engine up a bit. This will also help burp air out of the system
8) When the radiator fans kick on and the hoses are all HOT, you'll know that it's completely warmed up. Additionally you'll be able to tell that coolant is now moving THROUGH the radiator indicating the thermostat is open.
9) Go ahead and squeeze hoses / rev the engine a bit with the thermostat open and warmed up. Don't go too crazy or quickly or you may make a mess.
10) Use the plunger to seal up the funnel and quickly replace the radiator cap. It helps to squeeze a radiator hose a little to keep the fluid from wanting to over flow during this.
11) Top off the coolant overflow bottle to the max line using the coolant left in the funnel.
12) Over the next few drives monitor the coolant overflow bottle to make sure it stays at least 1/2 way to the MAX fill mark when cold. You'll likely need to top it up once since you filled it to the max when it was already warm.
Your dangling hose for your front A/C is up a little behind the front passenger tire. Your center nipple is pictured below.
Once located, try sticking a pen or a barbecue skewer up the hose, and just pinching the nipple.
Adding to the coolant system burping process:
1) Park on an incline so the radiator fill port is the high point.
2) Be sure the rear heater is also turned on in case there is air trapped in that section of the system.
UPDATE:
Today I finally got around to bleeding my cooling system. I figured out that the reason it had bubbles in the system was because my sister had the radiator replaced in July of 2020. Now I no longer have that “gurgling” noise behind my dash, but there is still a different noise when I turn my A/C on. I’ve now figured out that there were two different sounds happening at the same time, and I thought they were the same. I’ll get around to fixing it now that it’s finally getting nice outside, but I suspect that it’s the motor like many have said. Turns out all of the different answers were right. Thank you all for your help .
2ND UPDATE: I took out the blend motor and took it apart, cleaned it, put in some dielectric grease, and put it back in (turns out my mom’s 2007 odyssey has the same noise, so now I know how to fix that for her). That solved another noise, but there was still that last noise that came on every once in a while when the A/C was on. I checked the A/C drains and they were fine. Turns out, my refrigerant was running low, and the next week my A/C stopped working, on the hottest day of the week of course. I took it into Honda and they put more Freon in and some dye and said come back soon so they can check for leaks. Now I have no noises in my dash, which makes driving a much more enjoyable experience. Thanks for all the advice!
Not if you don't mind the blend door actuator not working and therefore the cabin temperature not being controllable much, if that's what causing your gurgling sound.
Keep and eye on the coolant level since I recall one of the symptoms of the gurgling being low coolant level in the heater core . . . which could be caused by low overall coolant level and that has potential to damage the engine.
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