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Loud clunking noises from 2005 Pontiac Montana minivan SV6

Hi there, I have a Pontiac Montana minivan SV6 that is making strange clunking noises from possibly the rear or middle of the van when I go over a bump, large or small. I have had it in to our local mechanic and the local tire/repair shop and transmission shop. They have not been able to locate a problem other than agreeing that there is a noise. Our mechanic replaced the front struts and strut mounts, the rear shocks and has gone over the entire suspension and transmission more than once. The noise is very loud, like something is broken but despite three separate shops checking it out nothing can be found. Any possibility is could be something with the automatic side doors, such as the motor being loose or something strange like that? If it didn’t have this clunking sound the ride would be very smooth and quiet. It doesn’t affect the ride at all. The other bit of info here is that we haven’t owned this van for very long, we bought it as is thinking that it needed shocks or struts. They’ve been replaced but the sound is still around! Any ideas?

Anything is possible. Do you have the ability, or a friend with the ability, to get safely under the vehicle and do some checking yourself? If you do, I can suggest a few common sources of clunks, but you’ll need to have the car safely and securely elevated and be able to shake a few items.

One common source is the bushings that hold the sway bars to the chassis. The bar twists in the bushing’s hole every time the wheel moves up or down, which is pretty much constantly, and the metal bar wears the hole too big.

Another common source of clunking is the links that connect the ends of the sway bars to the unsprung suspension parts.

Yet another very common source of clunking is any of the brackets and hangers that hold the exhaust system in place. The heat form the exhaust causes these to rust. Occasionally a clunk will even develop inside a muffler, baffle, or cat converter from the high heat and aggressive nature of the exhaust fumes.

But… and I say this emphatically… you must be able to be certain that the vehicle is secure and stable on whatever is holding it up. Never ever get under a vehicle unless you have the knowledge to be absolutely certain of this. You cannot breath with a 3000 pound vehicle fallen on your chest, and you will die of suffocation. People do.

Post back.

Any chance it could be a spare tire, lug wrench, etc loose and banging around?

Thank you! Now to ask some of the guys if they checked that. Fortunately our mechanic is not above suggestions! You are not the first person to suggest that, but I wasn’t sure of the source as the time. My only thought was “they surely must have checked that out” but one never knows…
ok4450 - I think the sound is much louder and “heavier” sounding than a jack, however I will check that out too as it seems like it must be something strange enough that three mechanics couldn’t figure it out!

Check the roof rack to see if the crossbars are tight. We have a Sihouette; very similar to your Montana. This happened to us. It sounded like it was in the side wall or maybe under the car, bu t it turned out to be a loose crossbar.

Well, here is what I know now. I checked the crossbars and they are tight. I also checked all the possible loose things like the jack and spare, etc, and nothing. So after checking with our mechanic again he told us that he did in fact check the sway bar bushings and had them apart a couple of times. He also said that he had his hands on everything he could reach, nothing is loose. My husband and I just took it for a ride and tried to pinpoint exactly where the noise is coming from. It surprised me to find that it seems to be coming from right along the passenger side automatic sliding door. My impression is that the door arm (bottom one) is rattling. It is louder if you are sitting nearer to the front than the back. You can heard it loudly from the outside too. I stood on the side of the road while my husband drove back and forth over bumps. I also looked under the van to see if was something loose, but other than the muffler (which isn’t really in the right place for this noise) there is nothing there. So I can only imagine the door OR possibly a heat shield. Ever heard of this?

Try pushing your fingers where the sliding door meets the frame while driving over bumps. Try several different places around the frame. You may feel relative movement coinciding with the noise. Also, try putting your ear to the inside of the same door.

Will do. Thinking about this more…the noise really does remind me of a door that isn’t fully closed. There are no “door ajar” indicators on though and the door looks closed. If this is the case how would I go about fixing it? How do you make an automatic door close more?

Door latches lock down on what is called a striker plate. Striker plates are adjustable.
To weed this potential problem out you might consider driving the car and having someone hold the door tightly or wedge it in some way to see if the noise will disappear. Maybe a rear seat rider could hone in on the exact area where the noise is coming from.

Does this model have the plastic cladding along the bottom? Loose cladding can cause different types of bumping or thumping.

Another possibility could be if the vehicle has been in an accident and during a repair someone inadvertently left a bolt or whatever inside a body panel. Yet another could be a seat belt issue.

Maybe some of the above is viable; maybe not. Hope it helps and good luck.

Yes I think we honed in on it and I am 95% sure it is coming from, ALMOST directly but not quite, under the (this could get complicated in the telling so bare with me) second row passenger side captains chair seat under the front right latch that secures the seat to the floor. I can actually feel the vibrating, clunking and it’s much louder there. There is no visible object directly under that spot as seen from under the van.
I’m beginning to think I should take it to a body shop… maybe they will know how to make it go away?

I’m not familiar with the Montana Mini Van, but are there any compartments for storage that might have something that bangs when you hit a bump. I’ve bought cars and never knew for months that there was a compartment somewhere.

I was on a road trip with my mom and kept hearing a clunking sound at some starts from stop lights and signs. I could have sworn that it was a suspension part that was broken and the stress of starting out from a stop made the noise.
I finally stopped and there was a heavy spray can under the passenger seat that would roll back and hit the seat frame if you took off fast enough. When you stopped it rolled back to the front.


I think you might want to check for a heat shield loose on the exhaust, or a broken exhaust system clamp or connector. A rubber mallet is often times helpful. I had one where a clamp was broken, and was doing the roller coaster ride up and down the exhaust pipe until a mechanic would look at it, and it would conveniently wedge itself in to a tight spot until after the analyses was done. The more conditions that you can associate to the noise the better. If you shift to neutral does it go away?

The noise never occurs unless I go over a bump. Just riding down the road is quiet.

Can you take that captain’s chair out and get down on the floor to listen?

Sorry for the long delay here. I’ve been trying everything I can think of to figure this noise out. So far every suggestion, every theory has not panned out. I thought I would run the latest one by you all. Here it is: how about a heat shield plate? Not the heat shield itself but the heavier plate above it. We had a friend tell us this happened on their Tahoe. Same story, mechanics couldn’t locate anything wrong but there was a loud clunking. Turns out it was aheavy plate above the heat shield that was loosened. Btw, we have driven, slowly, down a bumpy road with the side door open and our heads hanging down trying to locate anything specific. When you do that you do hear the heat shield rattle a bit but it’s not heavy enough to be this particular clunking noise. But plausible that something else may be bumping it as it slams itself against the bottom of our van. Also our mechanic says no way is the heat shield is loose. Any thoughts?

If you think there is something loose like this plate, just lay on your back, put your hands up, and start wiggling things. Wear gloves if you like, and you might make sure the exhaust system is cold so that you don’t burn yourself.

That said, I doubt it is a loose plate. Your Montana is a unibody car and the Tahoe is a body placed on a separate frame. They are not constructed the same way.

Food for thought . . .

A few days ago, I was working on a truck with a clunking noise. The truck was FAR too heavy to jounce the bumper and reproduce the noise in the shop

I hooked up my 6 chassis ear clips, and snaked the leads into the cab, to the selector box

While my colleague drove, I listened to the various channels, on the headphones. In less than 5 minutes, I had determined the front sway bar links were the culprit. Even though they seemed tight, when I was underneath the truck

It’s not a particularly expensive tool, and it’s a real time saver. It’s really come in handy a few times, over the years

Yeah, I can’t reproduce the sound anywhere either unless I’m going over a big bump/pothole/crack in road… I think the next thing I’m going to try is holding a mirror down there while driving to see if I can see anything banging in the area the noise is coming from. Strange thing is that you can feel, with your hand, something hitting the bottom of the van if you hold your hand to the floor where the noise is coming from. But there is NOTHING THERE but the frame! I’m gonna go bald…
Thank you so much for all the help. Please don’t stop!

I know this is an old thread but I was wondering if you had ever figured out what was wrong with your van, I have a 2006 Montana SV6 and I’m having the same problem

This may be too late to help @AnnieH , but may be helpful to @Annie_bueckert.

Way back when, GM issued Preliminary Information Bulletins PIT3323, the latest being PIT3323F (Nov.5, 2008):

Customers may report loud clunk or noise while driving in the rear suspension of their crossover sport van equipped with FE1, FE2 or FE3 rear suspension. The noise maybe described as the muffler hitting the floor pan or a loud slapping noise.

If no problems are found with the rear suspension components after thorough diagnosis, replace the rear trailing arm bushing and retest.

Notice that last note-that the bushing(s) make look fine but can still be a problem.