PontiacBonnevilleClub.com

That looks a lot like the kind of damage you get when you hit a curb while sliding sideways, except that there's no warping or distortion evident. That is unbelievable, and I will definitely be checking that point of the frame on my car.

BTW, PeterG, I don't believe the subframe carried over from the 99 to the 2000. In fact, because the 2000+ was actually on an entirely different platform, based on the G-body, it actually was a tweaked version of the Park Avenue subframe, which it self got a few tweaks for 2000, so it's actually a totally new piece.

Whoa, that definitely could have gone much worse. Glad nothing did though.

So just a replacement frame and you'll be good to go or did this bend or stress anything else?

Also adding to the stress is the force transmitting thru the front sway bar.

Rod, are you sure there has never been a curb hit that might have initiated a crack.

Something similar happened to my 70 Tempest. The steering idler arm tore a chunk right out of the frame. I had to get a new idler welded directly to the frame.
About two months prior to the failure, I had jumped the center meridian while attempting a U turn (didn't know it was there )

Peterg22000 wrote:also I believe the frame was a carry over from the 92-99 (possibly even from 87+) so it was in no way a new design, even if it got a few tweaks in 2000.

GonneVille wrote:BTW, PeterG, I don't believe the subframe carried over from the 99 to the 2000. In fact, because the 2000+ was actually on an entirely different platform, based on the G-body, it actually was a tweaked version of the Park Avenue subframe, which it self got a few tweaks for 2000, so it's actually a totally new piece.

You're right GonneVille, the H-Body in 2000 was a 100% completely new platform. It was based on the G-Body, which it shared with the Cadillac STS K-Body. The G, K, and H are virtually identical. Nothing should have even remotely been carried over from 92-99, especially from 1987.

The G/H/K-body featured an extremely resilient structure. It was one of the strongest unibody car frames in production at the time, at 25hz. This fact did not go untouted as GM literature made light of the need to use a 'frame crusher' designed to test heavy-duty truck frames to finally break the G-body structure in their crush-to-failure procedures. The new H-Body has a 27% increase in bending stiffness, and a 62% torsional stiffness increase over the previous Bonneville.

wow i have never seen anything like that. The only ones i have heard of issues with was the alumium ones i dont recall what they were used in.

2000Silverbullet wrote:
Rod, are you sure there has never been a curb hit that might have initiated a crack.

Not that I know of.
We have gotten very good mileage out of our tires and you would have to think that if we hit a curb hard enough to crack the frame the alignment would be off.
I think I will cut the crack part out of the frame and bring it to the WCBF '09.
We got the car back from the shop and I have the old frame and the crack is already starting to rust.

ROD

You said that the broken face when you saw it right after the failure was rusted partway. This was probably from the growing crack. The shiny part of the crack would have been the final brittle fracture. It would be interesting to know the % of each and also to confirm the actual point of origin. The starting point will most likely have fatigue striations in like a wave pattern on the face.

8 to 12% old, the rest new. It let go with a "POP" there is not much of the frame that is still together, I would say less than 1 1/2 in.

ROD

holy crap. that's insane. I know how much stronger those frames are than the 90-99s and even those frames are seriously stiff.

definitely a serious amount of torque placed on that area, when cornering, braking, and accelerating...all in one small area...kinda seems a bit demanding, but then again, if it was an issue, more people would have problems...and its especially odd since you're in California...not exactly a salt problem.

glad it was caught in time...had that broken fully...that coulda gotten ugly..real quick.

I would report it to the dealer the GM zone office and to the NTSB. That is completely unacceptable even if you lived in a rust prone state.

Paul is dead on the money in his diagnosis above. Although it SHOULDN'T have happened. This is a VERY high stress location as he stated, perhaps the most stress on the subframe compared to any other single point.

Here's what he's talking about (I can see it plain as day):


View from below. Red line indicates sway bar loads/forces. Green is torsional load exerted by the control arm.




Again, red is the swaybar load/force. Green is the control arm load. Yellow is the weight of the car, and is a big factor when you consider the other forces that may be exerting loads on the frame at the same time. You can have all three forces applied to that point at exactly the same time.



Taking it further, it looks like the spacing between the control arm bushings on the frame is not equal to each side of the center of the spindle. Can someone verify this for me? Here's what I'm talking about:


Control arm brackt #2 is going to bear the brunt of the torsional load when turning, torque-steering, hard accelleration (Go Cindy!) etc. More than double the load of #1. This isn't necessarily true for swaybar loads or the load of the weight of the vehicle though. Anyone who didn't fail geometry can see what I'm getting at here. If the frame were to fail, this would be the spot I would have bet on.

All these forces quite obviously should have been factored in, but there could have been a flaw in the steel during extrusion, a bad weld, or any other number of factors that played a role. In addition, that's ALOT more miles than the average for cars of your year. In fact, I can't think of another off the top of my head with more miles on it.

I'd be looking for a used subframe (or even new) from the lowest-mileage donor possible. Welding doubler plates isn't a bad idea, but beware the welds themselves can weaken the steel frame. Weld placement and the size of the plates (length along the frame) are critical.

it looks like the spacing between the control arm bushings on the frame is not equal to each side of the center of the spindle. Can someone verify this for me? Here's what I'm talking about:

Yes and bushing #2 is even closer to the wheel centerline.

Weak frame.....Poor design to have failed so catastrophically after suffering a small crack. Imagine if that was a rusty Ontario car.

I suspected it was weak the first time I jacked it up and saw it dent.

Crumple zones have ruined our lives. Designed failure points. Don't make the frame too strong, you might kill someone in another car.

Wow, incredible. But I would have to think that you were blessed with the one rare failure. This is unheard of, and certainly since that car has never seen rust, can you imagine how many failures would be happening up here in the rust belt if is was a common weak point? Makes you wonder if someone gouged the heck out of it with an air chisel or the like, whether it be at a repair facility or the factory. I'd think maybe someone got it way too hot with a torch, but then again you probably don't need such drastic measures where things don't get rusted together. It's got to be a freak, or others would be having issues.
I agree it should be reported to the NTSB, in case there is an issue, my Mom drives a 2000 SSEi, although she drives it like a baby carriage.

Mike

Very true.
If you look closely even at the frame, you can see crumple design.
Proof again that everything is a compromise......safety or longevity.

So now we know the life of the engine craddle frame in a highly loaded, strongly driven eight year old SSEi is about 180,000 miles or 288,000 kilometers. That's a very good life if you think about it.

Would be interesting to know how long it was cracked before it failed. There's an argument for annual safety inspections, of course no one would want to pay for a mandatory CORRECT annual safety inspection, so the minimal fee just buys you a sticker in states like New York. Ha, had a rusted-through frame on my old Chevy when I still lived in NY, I was a kid, didn't care, car looked brand new, the inspection facility would look at the car and then sell me the sticker. Here in Ohio, we have smog testing but no safety inspection, as long as you are not polluting the air, they don't care if you kill yourself.
Would rather have a crumple zone than have my family killed or mutilated, so I think I don't agree with Bill on this. Can't assume you will be able to avoid some other idiot's bad move - I had the misfortune of watching someone die in a head-on in front of my house when I was in high school, heard the crash, got there, professional help was on the way, could do nothing but talk to the poor girl as she slipped away, I think you could have saved the front clip of that car so her body took the energy of the impact, I'll never lose that picture in my mind...
But, if crumple zones are so good, why are school buses made like tanks? You would think they would be designed so they turned into dust except for the passenger areas? Mike

With a school bus the other vehicle is the crumple zone.

To add to Bill's analysis. (Referring to his drawing above.) The control arm bushing at point 1 is the "hockey puck" one; this style of control arm mounting is becoming common on the front of front drive cars. The bushing at point 1 is designed to flex in the axis parallel to the ground; this causes a dynamic toe change under hard acceleration and reduces the felt torque steer; unfortunately it also places a twisting load on the bushing at point 2.

Yeah, on a school bus, the other car is the crumple zone for sure. However, my Dad, who drives a school bus now, was rear-ended by a semi this fall. Neither have crumple zones, he had just dropped of his last elementary child, police report stated that if the bus was full, the jolt would have been disasterous on those kids. In that case, the children's bodies would have absorbed the energy. So, why no crumple zones on a bus?