Strange gurgling like noise under acceleration

[aidtwo]

Hello. I recently purchased a used 2010 Mazda5 touring trim with an automatic transmission and just over 24,000 miles. Once the engine is warmed up (temperature gauge is at normal operating temperature) there is a strange engine (or transmission?) noise under acceleration when it is under 2,000 RPM. It sounds like a faint gurgling noise. After coasting and starting to accelerate or driving on an incline (slight or steep) the noise can be heard. I think the automatic transmission is in 5th gear when this occurs. I am working with the dealer to identify the source of noise and eliminate it. So far the dealership has not been able to reproduce it but I have no problems reproducing it. The car seems to drive well but the noise does not seem normal.

What might be causing this noise?

Thank you.

 

[flcruising]

The last vehicle I owned that made that sound was a Chevy Blazer, and it was indicative of the heater core being bad. But that also meant that a good amount of antifreeze/coolant had leaked out because of it.

Does it sound like it's coming from the cabin?

 

[aidtwo]

The last vehicle I owned that made that sound was a Chevy Blazer, and it was indicative of the heater core being bad. But that also meant that a good amount of antifreeze/coolant had leaked out because of it.

Does it sound like it's coming from the cabin?

Thank you for the reply. The noise is coming from the engine compartment area and it seems to be on the passenger's side. I drove it around and noticed the sound in 3rd, 4th, and 5th gears when accelerating at low RPMs. I will try listening for it when idle as I thought I heard it briefly the other day when parking.

 

[Silentnoise713]

Maybe it’s just me or my lack of imagination but I don’t quite understand how 1) folks are able to identify “noise” related questions with text description and 2) why the OP didn’t just upload an audio (or better yet video) clip along with more history on the car/event.


Can you reproduce the sound in triptronic-manual mode cycling through the gears in questions?

 

[Vasy]

If you can reproduce it and shop can't, ask for a one on one with a mechanic to go for a test drive with you.
I had to do it once, dealer was trying to wash hands away saying that we don't do it and some other crap but after a few minutes they found the time.

 

[thaxman]

I know what this is. I have heard it on my Sube Legacy 4AT and my Accord 4AT. I don't know what it is, and it appears to not hurt anything from my experience, but its caused by being in too high of a gear for the speed and engine load. Both the above were 2.2L 4bangers. IIRC, it may have happened to my Daytona 3AT as well. I don't remember ever getting that type of reaction from the powertrain in any vehicle I have driven w/a V8-AT combo, and I have only had V6-MT combos, so I suspect it may be a 4-banger issue, primarily b/c smaller 4cyl are known for being torque-deficient.
Basically, DON'T drive uphill under 2000 rpms.

 

[aidtwo]

Thank you for all the replies. Bottom line, I am told it is an annoyance and not a sign of a failing part(s). Read on for details.

I contacted the dealership and they arranged to have their master Mazda technician investigate the sound. The tech both drove and rode in the car with me. We heard the noise. He acknowledged it is a known issue with the car at 1700 RPM caused by exhaust or muffler resonance. He said other customers have reported the noise and in the past they (the dealership) got on the phone (to escalate the issue) with Mazda and worked to replace various parts in an effort to eliminate the noise but without success. I asked if there were aftermarket solutions, he was not aware of any. He suggested accelerating slightly quicker to get out of the RPM range that causes the noise, but I pointed out that the noise can occur at cruising speeds too. So unless you force the engine into another gear, its really not helping. Finally, he suggested that I can check in later to see if Mazda offers posts a TSB for the issue. I searched online and have not yet found an existing TSB for the issue (although I see similar TSB for other older Mazdas models).

For what it is worth I tried to capture a recording but was not able to get a clear recording. If I find a way to do so, Ill post for others to check out.

Thank you again.

 

[MarkVII88]

So the master Mazda technician says it's an issue with exhaust resonance at lower RPM. If you really want to solve the problem, you should look into putting on an aftermarket cat-back exhaust. I'm not saying this is going to be cheap but you could check out speed shops for a nice custom stainless (performance) system or you could go to a more run-of-the mill muffler shop where they can fab-up a more stock exhaust for you. You won't get nice mandrel-bent tubing at Meineke though.

Thank you for all the replies. Bottom line, I am told it is an annoyance and not a sign of a failing part(s). Read on for details.

I contacted the dealership and they arranged to have their master Mazda technician investigate the sound. The tech both drove and rode in the car with me. We heard the noise. He acknowledged it is a known issue with the car at 1700 RPM caused by exhaust or muffler resonance. He said other customers have reported the noise and in the past they (the dealership) got on the phone (to escalate the issue) with Mazda and worked to replace various parts in an effort to eliminate the noise but without success. I asked if there were aftermarket solutions, he was not aware of any. He suggested accelerating slightly quicker to get out of the RPM range that causes the noise, but I pointed out that the noise can occur at cruising speeds too. So unless you force the engine into another gear, its really not helping. Finally, he suggested that I can check in later to see if Mazda offers posts a TSB for the issue. I searched online and have not yet found an existing TSB for the issue (although I see similar TSB for other older Mazdas models).

For what it is worth I tried to capture a recording but was not able to get a clear recording. If I find a way to do so, Ill post for others to check out.

Thank you again.