Engine Bay Body Rips - Page 248

JData · 04-17-2008, 08:24 AM

I've driven Corvettes before. They have a low-hanging front spoiler. Their drivers creep over speed bumps. They don't fly. There's a time to fly, and it's not over speed bumps. Maybe the FJC deserves the same respect.

I don't know about that logic, the truck sits higher and more clearance, you should be able to take a bump with no problem. You aren't on the ground like a Corvette. There's a big difference in design.

**k44** · 04-17-2008, 07:52 PM

Quote:

07Tonka previously said:

how would cracks without bulges fit in your theory? ... even now at 25 k or so there is absolutely no deformation in my inner fenders and the cracks are all the way through the inner fender member

any insight?

The cracks are fatigue cracks. They're not happening like glass cracks, due to a stone hitting it at high speed. These cracks in the FJC's inner fenders are happening because of work hardening, and subsequent flexing (after the work hardening has saturated the lattice of iron atoms in the crack area).

Imagine a 3-d grid of atoms, all aligned uniformly on the 3-d grid. If you bend a piece of steel made of these atoms, it's necessary for some of the bonds between planes of atoms to slip--to shift to the next atom in the underlying pane--so that the steel can maintain its integrity despite being bent. It's kind of like how a pad of paper shifts when you bend the pad, the sheets at the top slide relative to the sheets below.

When a plane of atoms slips relative to the next adjacent plane, it leaves a distortion where the slip begins. Atoms are sort of hodge-podged in this area. When viewed microscopically, metallurgists call these odball arrangements of atoms "dislocations."

When another bending of this same area of the FJC steel metal is attempted, this dislocation is now a "pinned" area. It resists the orderly slipping of one plane of atoms relative to the next. So instead, the slipping occurrs elsewhere in the lattice, and it's likely that this second slipping of atom planes is more severe and results in even more dislocations (pinned sections). Eventually, when the lattice is filled with these distortions (pinned sections), the steel becomes harder, stiffer, and more brittle. This is called "work hardening."

Further attempts to bend these fully work-hardened areas will result in cracking. This is undeniably the condition of the FJC inner fenders which have cracks, regardless of whether there has also been buckling (bulging) of the adjacent sheet metal.

The buckling may indicate that along with small overloads which work harden the cracked area, some FJC's may also be experiencing higher overloads (less often) which are buckling the fender sheet metal in a substantially independent process relative to the fatigue cracking of unbuckled sheet metal.

In other words, it could be that:
1. small overloads repeated 1000 times could cause the cracks, and
2. larger overloads, repeated 10 times, could cause the buckling.

**cruiserlarry** · 04-17-2008, 08:42 PM

Quote:

07Tonka previously said:

I never have flexed the truck, it does spent a lot of time on forest service roads however.

at 20k I had cracks on both sides - no bulge (I posted pictures)

I have always suspected the mounts ... slam the hood and notice how much the whole front end deflects

hit a pot hole at 80 (yes highway 5 to Sacramento is where the cracks appeared) see how much it deflects - hit a series and the front end (body) starts to "dance"

or drive on washboard roads ....... more dancing

do any of this for a while (20k in my case) I will just about guarantee the inner fenders will deform or crack

I think you guys are on to something - are you with us Toyota?

As I've hypothesized previously, I believe the cracks and bulges to be separate issues that are interacting. The cracks appear to be generated from some vibrational stress-related issue - occurring in mostly earlier production vehicles, mostly after 15-25k miles, and most w/o off-road usage. The bulges, on the other hand, appear from the front suspension bottoming out and the tires contacting the inner fender well, pushing up on the inner fender 'til it bulges, affecting even the newer FJCs. Once cracked, off-road use exacerbates the bulging problem, and vice-versa. So, while the revised inner fender may (and I'm being generous with may ) resolve the cracking issue, it will have no effect, IMO, on the bulging problem...

**Chatsworth 818 FJ** · 04-17-2008, 08:53 PM

Quote:

cruiserlarry previously said:

As I've hypothesized previously, I believe the cracks and bulges to be separate issues that are interacting. The cracks appear to be generated from some vibrational stress-related issue - occurring in mostly earlier production vehicles, mostly after 15-25k miles, and most w/o off-road usage. The bulges, on the other hand, appear from the front suspension bottoming out and the tires contacting the inner fender well, pushing up on the inner fender 'til it bulges, affecting even the newer FJCs. Once cracked, off-road use exacerbates the bulging problem, and vice-versa. So, while the revised inner fender may (and I'm being generous with may ) resolve the cracking issue, it will have no effect, IMO, on the bulging problem...

My bulge/s got worse over the last few months, and I didnt off-road at all. Also I had my coil overs adjusted for more height , my upper control arms are down much further then normal. So I know for 100% sure my tire hasnt even got close to the inner fender.
Mines in the body-shop now, and the body-shop guy said the same its from impact. But the other techs, service mgr, and area rep. all agreed theres no way the tire could articulate that high. At least with out other damage.

**cruiserlarry** · 04-17-2008, 09:18 PM

Quote:

Chatsworth 818 FJ previously said:

My bulge/s got worse over the last few months, and I didnt off-road at all. Also I had my coil overs adjusted for more height , my upper control arms are down much further then normal. So I know for 100% sure my tire hasnt even got close to the inner fender.
Mines in the body-shop now, and the body-shop guy said the same its from impact. But the other techs, service mgr, and area rep. all agreed theres no way the tire could articulate that high. At least with out other damage.

Does the tire hit the back of the fenderwell ? If so, it could transfer impact to the weakest point w/o making direct contact. Also, if the bulges were already started from prior contact, it would get worse from normal vibration/ flex, like a crack in a glass pane.

And, of course there's a third possibility - my theory is just plain wrong...

**puulboy** · 04-17-2008, 10:54 PM

Update on my contact with the dealer
I talked with the service manager about the new aprons. He contacted Toyota and they have not revised the aprons to fix this issue. He advised me not to have them fixed untill the the fix is made by Toyota. He told me not to worry my truck is covered without a doubt. I would advise anyone that has apron issues to contact their dealer again to allow Toyota to hear it from many angles.

thanks
Don

**bernd** · 04-18-2008, 12:00 AM

Don
Thanks for the update.

thubub · 04-18-2008, 01:08 AM

As I type this my FJ is being repaired under warranty at Crown Toyota. The Head service tech said mine is the first one they have seen, but have been waiting for one to come in. They were forewarned by the area Toyota service rep. I was told that there is a new part #'d inner apron. I will update as soon as I see the results. Should be back wheeling by the first of May.

FlyNdrive · 04-18-2008, 06:22 AM

Quote:

thubub previously said:

I was told that there is a new part #'d inner apron.

I still can't get a TSB number, but have several questions for those who are getting "the fix".

I checked this morning and there is no new (third) fender apron part number. The original fender apron (PN, 35702-35A01) was the original fender apron form 1-06 through 12-06. It has been replaced by the new one (PN, 53701-35A11) 1-2007 through 6-2008.

There is no part number for a third apron. If there is reports of the newer designed (second) apron cracking will this still be considered a fix? Those getting "the fix" I assume you are getting the second apron installed. I have read every post and I hear of complaints that the second aprons are cracking as well. Is there any pictures or proof?

Sorry if I'm opening up a new can of worms.

-Ben

Bodegas · 04-18-2008, 06:57 AM

Quote:

cruiserlarry previously said:

As I've hypothesized previously, I believe the cracks and bulges to be separate issues that are interacting. The cracks appear to be generated from some vibrational stress-related issue - occurring in mostly earlier production vehicles, mostly after 15-25k miles, and most w/o off-road usage. The bulges, on the other hand, appear from the front suspension bottoming out and the tires contacting the inner fender well, pushing up on the inner fender 'til it bulges, affecting even the newer FJCs. Once cracked, off-road use exacerbates the bulging problem, and vice-versa. So, while the revised inner fender may (and I'm being generous with may ) resolve the cracking issue, it will have no effect, IMO, on the bulging problem...

Ummm.... My bulges also started in January and definitely not wheeled anywhere near that time period. I also have stock size tires, Im not sure if they make contact or not.