water gurgling noise after coolant change

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Fire0nic3FX

Member
As some of you know I had to change the radiator cooling fans in my G35. I thought I had bled the coolant right but I guess not. Everytime I start the car now for the first few seconds I hear a water gushing or gurgling noise behind the dash. I know the sound is air pockets in the coolant flowing through the heater core.

I already opened the bleeder valve to get the air bubbles out and it still makes this noise. I even run the heat on high and rev it to 3000 rpm as per what the factory service manual states. The car isnt overheating it just has air bubbles in the coolant I can't seem to get out. This water gurgling noise is annoying! Someone please help.
 
Silly question, but have you tried leaving the radiator cap off and letting the system "burp"? I know some people just use the coolant tank to do this, but that requires the radiator cap to open. This way, it just vents to the atmosphere.
 
Gurgling noise is normal and you don't have to "burp" the system. The noise will go away after you drive around for a bit and you'll eventually have to refill the reservoir.

I should know... the entire coolant from my M35 was completely drained from 2 engine replacements (damn lemon...).
 
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Thanks for the reply guys.

I did leave the radiator cap open to try and burp it from there but that didnt work.

How long did the sound take to go away? I did notice since the coolant change the reservoir keeps going low every few days. Could this be because the air bubbles are working their way out? Should I drive with the heat on so it flows through the heater core?
 
If you're coolant is dropping, it's probably the air bubbles working out. I would try leaving the heat on for a couple of days, can't hurt to have the coolant going through the entire system. How much is your coolant dropping though? If you bled the system properly there shouldn't be that much air left. I could understand doing it twice to make sure all the air bubbles are gone.
 
Its dropping about half an inch every time I drive it. Its done it only twice though since.I havent driven it much since the coolant change.
 
Looking at the manual, it seems normal to hear noise if the level keeps dropping and not stable yet:

Quote "12.If sound is heard, bleed air from cooling system by repeating step 3 through 6 until engine coolant level no longer drops"

So it seems that the job is not complete yet, check out the manual for your specific car and repeat the equivalent mentioned steps 3 to 6.

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---------- Post added at 01:21 AM ---------- Previous post was at 01:18 AM ----------

One more thing, a rule of thump, always measure what you drain before refill to have a reference when needed, do you remember how much you drained? If so you could compare it to how much you filled so far to have an idea how far you are from done.

Anyway, my manual says my FX45 needs 10 liters to the max mark on the reservoir.


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I drained about gallon and a half. I already tried what you suggested but it never worked. I did the steps of revving it to 3000 rpm for 10 seconds a whole bunch of times with no luck.
 
At this point, I would say to keep repeating it as long as your level still dropping, there doesn't seem to be another choice, the manual does not mention how many times this might take.

Just make sure in every time to open the air relief, pour more coolant from the filler neck @ less than 2 liters per minute, till it overflows the air relief, then plug air relief off, rev to 3,000 rpm for 10 seconds, cool it down and so on.

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sounds like there is air in the system. Oh course like everyone said the who leave the cap off and let it run also try squezing the radiator hoses and push the air bubbles out. But be careful when your doing that cuz you can easy shoot coolant everywhere if u squeeze to hard lol.
 
Mongolian was right the water gurgling noise went away after driving it for a few weeks. No more noise and the coolant level has now stabilized so all the air is out!


Thanks again everyone!!
 
Fire0nic3FX said:
Mongolian was right the water gurgling noise went away after driving it for a few weeks. No more noise and the coolant level has now stabilized so all the air is out!


Thanks again everyone!!
Click to expand...

Great! Yeah it sounded like there was just a bit to much air in the system. It will help next time when you flush it completely to squeeze the hoses a little to help move the air out and run the car for about 10min i think (should be on the back of the bottle) with the radiator cap off. It will get a lot of the air out. I only flushed a radiator once......lol that was in my 91 240sx. (old owner put water in it -_-) so i squuezed the hoses and ran it for 10min with the heater on full blast and never heard the gushing sound. :) hope this helps.
 
No prob! yeah it always worked for me. HUGE bubbles usually form in the hoses. I was always taught to gently squeeze the hoses the help "burp" the system. I usually fill it about 3/4 the way up so when i squeeze the hose to push the air bubles up it doesnt spray coolant everywhere lol. Then after i think i got a good amount of air out i fill it the rest of the way up, leave the cap off, start the car, turn on the heat full blast and open all the windows. let it run for about 10min and ur good :) LMK how it goes next time! I hope i helped. Sorry i kinda rant lol. but thats just the way i do it. I should probably check my coolant. Even though i just bought mine and its been at the dealer for forever id rather have piece of mind knowing I did it myself.
 
Fire0nic, were you able to remove the two coolant drain plugs on each side of the cylinder block during this coolant change job?

I had a look from above the engine, the sides of the cylinder block are hard to see or reach, I guess they can be accessed from below the engine?


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Never mind that, I changed the coolant today and used compressed air to push out as much old coolant as possible via the air relief plug and the drain plug. I replaced the old coolant first with fresh water, gave it several revs, and then replaced it once more time with a fresh coolant. All went well.

The connection to the reservoir tank right at the filler neck was plugged off completely with stain and dried up coolant all around it, I had that cleaned up and fixed.

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No sure what u guys are doing. But I drain and filled about 5 g35s and a maxima. All with no issues or bubbles. No compressed air or anything. Just simple common sense running the car without the cap and watching the flow.

Careful bleeding and draining of the rad and plugs is required. Just don't take them off instantly.

The squeezing hose is a great idea. I do it to most cars when I'm under the hood.
 
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