Thumping noise, clunking

Hi and thanks for using 2CarPros.

First, inspect the tires. Check for a bubble, uneven tread, or a shifted belt. If the tires are worn, they can cause this. If you suspect it may be a tire or even a bent wheel issue, rotate the tires to see if the noise changes location.

Here is a link that discusses clunking or popping noises in the front end. Take a look through it to see if it helps.

https://www.2carpros.com/articles/popping-noise

Now, if you are hearing a clunking noise, it is important to have the steering and suspension components checked. If you have a good jack and safety stands, lift one side of the front end off the ground at a time and grab the wheel at both 3 and 9 o-clock as well as 6 and 12 and wiggle the wheel to see if there is excessive play in any of the components.

I attached an exploded view of the steering and suspension components.

Check for bushings that are bad, excessive play in any of the components, and confirm the steering stabilizer bushings and bar are in good condition.

I hope this helps. Let me know if you have other questions.

Take care,
Joe

You should click on the link in the e-mail message you got so you can keep on replying to your original question. I can remember part of it from reading it earlier. If your van is all-heel-drive, the front suspension will use torsion bar springs. When that system was used on the smaller pickup trucks, the cross member those bars were anchored to was attached to the frame rails right under the front seat area, and they were mounted on rubber mounts, similar to engine and transmission mounts. When one of those would tear apart, that cross member would bounce up and down creating a very hard thumping feeling. That could transmit through the torsion bar to the lower control arm, and then into the steering linkage, so you could feel the thumping in multiple places. This does not cause a safety concern, but it will be very irritating. The fix is to replace the broken mount. Typically you will replace them on each side of the cross member because the one that is not broken yet is just as old as the one that is broken.

On Suburbans and large pickup trucks, that cross member is bolted right to the frame on both sides, with no rubber mounts in between. I am not sure if those mounts are used on Astro vans.

I cannot believe I gave you such a wondrous answer and forgot to include how to check this.

If you have this torsion bar system, use a pry bar to try to lift up on the cross member where it sits on the frame rails. If you can see that cross member is bolted tightly to the frame, this does not apply. If you can see rubber mounts between the frame and cross member, and one is broken, the cross member will lift up when you pry on it. That is what commonly bounces up and down while you are driving.

The additional clue is those rubber mounts are either fully-broken or not yet fully-broken. They will still be quiet as they break apart over time until they finally break completely. That is when they suddenly start to make noise. With these, they do not gradually get noisier and noisier over weeks or months. They are quiet one minute and noisy the next.