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Brogs70, ASE Certified Technician
Category: Car
Satisfied Customers: 536
Experience:  20+ years as a Technician, Service Manager and Proprietor
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Customer Question

My son owns a 2002 Mitsubishi Galant. Problem after starting his car, he heard a very loud womp, womp, womp sound coming from somewhere under the hood. parked it on the street and had it towed to a shop I’ve used for years. The mechanic told my son that the battery had a low voltage problem that was causing the car to misfire and produce the loud womp sound. FYI- almost $300 to diagnose and replace a faulty battery?!? After less than a week the car is once again inoperable. Before we go back to the shop (which until now has given me no reason to question integrity) I’d like to see if my reasoning is flawed. I believe that the main purpose of a car battery is to supply enough power to ignite the ignition. Once started the battery doesn’t really do much except recharge. The only sound I’ve ever associated with a faulty or weak battery is a hum or clicking. I don’t think batteries are responsible for really loud womping sounds. Surely a really loud womp would more likely be faulty bearings or a bad CV. Am I missing something? And how would recommend we approach the mechanic at this point?
Submitted: 6 years ago.
Category: Car
Expert:  Brogs70 replied 6 years ago.

Hi Im Scott

The Charge rate of the Alternator must be checked if the alternator isnt charging correctly this can cause battery drain and then failure, if the mechanic replaced the battery without doing this then the new battery will eventually die.

Customer: replied 6 years ago.
they did not mention of the alternator, starter, fuel injection, pistons.... or any other part of the car other than the battery. Sorry, I'm not really looking for the cause of the sound... I'm looking for advice/answers to these questions:
1) is it remotely possible a faulty battery be part of the reason a car produced this really loud womp sound?
2) do my assumptions about how batteries work and thinking the bearings and the CV are more likely to produce the sound seem reasonable?
3) How do I tell the mechanic I think he is full of crap in a nice reasonable manner?
4) I'm trying really hard to trust this shop - should I bother?
Sorry, I appreciate your attempt to help...but please let me know if the questions are too woman vs man

Expert:  Brogs70 replied 6 years ago.

Hi again

The Mechanic replaced your battery. The Alternator's duty is to charge the battery. If your son's car is running rough due to power drain then the alternator is not keeping up the charge to the battery, you mention that after 1 week the car has become inoperable it may take this long in some cases for the battery to become drained enough to show similar symptoms as before if the alternator is not charging or is only partially charging.

Without hearing the womp sound you describe i can only assume that it is as a result of the vehicle misfiring as systems begin to shut down due to lack of voltage (battery flat).

If the noise you are describing occurs while the car is sitting still and not whilst moving there is no chance that it could be caused by a CV joint or Wheel bearing. If however it does occur whilst moving then yes it is entirely possible that it is a bearing or CV issue, but I can only assume your Mechanic would know this because it would be very obvious. As far as your problem with politely telling the Mechanic he is full of crap I would take the car elsewhere for a 2nd opinion and a little peace of mind.

Please dont hesitate to contact me if I can be of any further help ... thats why we are here after all.


Brogs70 and 4 other Car Specialists are ready to help you
Customer: replied 6 years ago.
I appreciate your input. I'll let you know what happens.
Expert:  Brogs70 replied 6 years ago.
I appreciate that thanks