What's causing a thumping noise from my van's front end?
Recently I started noticing a soft thumping noise coming from the front end of my 2002 Ford Windstar LX van. Around the same time my transmission started slipping, so I assumed the thumping noise was related to it. Well, after I had my transmissions checked, and subsequently rebuilt, the noise hasn't gone away. The transmission is fine, shifts fine, the fluid level is good, etc. Therefore, my attention shifted towards the thumping noise having something to do with the wheels, steering, etc.
Before I had the transmission rebuilt, I did notice that both of my front sway bar end links were shot and needed to be replaced, so they were. I was also told about a year ago that my wheel bearings were going bad on the front wheels, but I haven't replaced them yet. I've heard a light whirring noise at lower speeds and I think that's from the bearings.
The thumping noise started out only being audible at higher speeds, but recently it's gotten louder and I can now hear it at lower speeds. It's not always consistently audible. Sometimes I don't hear it at all. I've recently noticed a couple of curious things that will hopefully help you have an idea of what is going on. For one, the thumping noise seems to be present normally when I'm accelerating. If I let off the gas, or if I brake, it seems to stop. Also, I've noticed that if I turn the steering wheel slightly to the right, the noise stops, even while I'm continuously accelerating. When I return the steering wheel to its former position, the noise instantly appears again. I've tried that several times, and it does the same thing every time.
I'd start by checking the tires for a broken belt.
March, 17, 2011 AT 3:47 AM
I thought a broken belt would cause more of a vibration or shaking rather than a loud, repetitive thumping noise. Of course you're the expert, and I'm not, so I'll certainly keep that in mind. Thanks.
March, 17, 2011 AT 5:30 AM
You're right on both counts. I AM the expert and don't you forget it! Well, at least that's what I kept telling my students. I figured they would believe it eventually if I reminded them often enough. Most commonly a broken belt will form a hump that you will see and feel. If it's bad enough it can just about knock your dentures out. But it can also be very subtle. When the break occurs slowly over a long period of time, the hump wears down as quickly as it grows. You won't see that right away but it will let the tread squirm sideways when it contacts the road. It will make a squishing sound. To find that you have to jack it up and spin it, then watch the carcass in the grooves rather than the outer tread that hits the road. You will see the tiny bumps of the wear bars but a broken belt will be much larger. This seems to happen more often to tires that had a nail hole patched. The patch keeps the air from falling out but water and road salt can get into the hole from the outside and corrode the steel belts. Related to belts is a tire pull. You won't feel anything but the vehicle will drift to one side when you let go of the steering wheel. Most of the time you can identify that on front-wheel-drive vehicles by braking a little harder than normal. If the van pulls to the right when accelerating, there's an 80 percent chance it will pull left when braking. If it continues to pull right, possibly even harder, it is more likely to be an alignment problem. By the way, have you noticed that you do not hear the sound when standing still with the engine running? If you do, suspect the serpentine drive belt for the generator and power steering pump. The noise will change if you dribble a little water on it while the engine is running. Other things to look at include rust on the back of the brake rotors, dry axle seals, either where the half shafts leave the transmission or around the outer cv joint by the wheel. Fords use plastic brake splash shields that can crack and rub on the brake rotor but you usually won't hear that. Another odd one is a warped brake rotor. That can happen two ways. The rotor is made of two plates of metal that must be perfectly parallel. When they are not, we call that "thickness variation". You will feel that as a pulsing brake pedal. But, if the two plates are nice and parallel to each other but not to the center part that it mounts by, the brake pedal will feel normal but the brake caliper will walk back and forth sideways twice per wheel revolution. Depending on the mounting system, that caliper might be sliding on dry, rusty, or dirty metal brackets and you may be able to hear that. When it's real severe you may get a shimmy in the steering wheel during braking. All of these things so far will appear in step with wheel rotational speed and of course will increase as your speed increases. You might be able to hear the noise with the front end raised up and running it in gear unless it's tire-related. If all else fails, there is a tool called the "Chassis Ear" that you might be able to rent or borrow from an auto parts store that borrows tools, but be aware that many mechanics have never heard of it or seen one. It is a set of six microphones, headphones, and a switch box. By switching between them you can listen for which microphone is closest to the source of the noise.
March, 17, 2011 AT 6:37 AM
WOW! That's a lot to take in, but certainly VERY thorough. I appreciate the time you've taken to try and help me figure out the cause. I believe I'll just print out what you said and take it to my local shop to help them along in trying to diagnose the problem.
By the way, the guy I go to for work on my vehicles does in fact have a "chassis ear." He mentioned that to me just recently.
Thanks again. I'll let you know what I find out, if anything!
March, 18, 2011 AT 12:41 AM
Just want to update you on what I had done today. I took the van to the shop, and they determined that I needed two inner tie rods replaced and a wheel hub. They got it ready by this evening, so I picked it up and test drove it around for about 10 minutes at different speeds on various roads, inclines, etc, and I didn't hear the noise that I'd been hearing. The steering was also much tighter(in a good way) than it was before. So far so good. Knowing my luck though, the noise will reappear as soon I drive it tomorrow!
I hope that sounds about right to you, at least as far as the possibilities of what was causing the noise!
March, 18, 2011 AT 2:26 AM
Usually a wheel bearing will make a buzzing noise like an airplane engine, but there's no arguing with success. Hope that takes care of it.