I've got what sounds like a cow under the hood. My car has been making a sound like a moo especially noticeable at idle. Here's what I've tried:

1. Thought it was PS pump (even though the sound did NOT change with wheel turn). Replaced hoses (all high/low pressure) and cleaned solenoid filters, flushed system. No change.

2. Tranny pan dropped, filter replaced, fluid exchanged. No change.

3. Timing belt / water pump service was recently done, and idler pulleys and serpentine pulley were replaced. No change.

4. A separate noise is the AC compressor. The moo'ing noise is not the same, as the mooing noise is more noticeable and idle, and even when the AC is turned off.

5. Now someone said this could be a low TRAC nitrogen cylinder. I don't think this is the TRAC nitrogen cylinder because I am not getting a TRAC warning light. Can someone clarify if it were a low nitrogen cylinder, if I would expect to see the TRAC light?

6. At this point I'm thinking either fan pulley or alternator, leaning more toward fan pulley as noise doesn't seem to change with electrical load.

Any suggestions for further steps to diagnose? Has anyone else figured this out on their cars? To the OP who described this sound as a mooing at idle, that's EXACTLY how mine sounds.

 

things you need to include:
-The year of your mitsubishi montero
-The model vehicle you have
-if your problem varies with rpm.

 

PureDrifter- sorry, I figured since I posted this in the LS400 forums, that both the model, and the fact it's not a Mitsu or a Montero, were already covered. The year is in my profile, though I should probably add it to my sig: it's a 1994. I will check if it varies with RPM and post up. Any suggestions for me on the problem?

 

Try running it for a few seconds with the serpentine belt taken off. That will instantly rule out if it is one of the accessories or not.

 

we request model and year be posted in the first post of every thread because 1- many people have multiple cars and checking the profile is inconvenient. and 2- you may be in the wrong forum and not realize it.

 

Just an update in case anyone else reads this thread. Turns out the mooing sound was from my alternator, which was slowly going out (typical PS leak onto alternator). Replaced and moo is gone.

 

I'll bet Elsie is pleased !!!!!!