Frame Rot (Page 1/3)
gregr75 AUG 16, 09:19 AM
Jacked up the Fiero for a brake job and found some awful corrosion in a bad area, about 6 inches forward of the rear sway bar on the driver side.
I think this is the engine cradle?
I'm wondering what the best thing to do is.

1) Drop the whole rear suspension + tranny out, remove control arms, struts, etc, and rebuild with a junkyard cradle. I do have the tool that spans the rear and allows the engine to remain installed.
2) Do the same thing but perform a weld repair on that section of the engine cradle and rebuild
3) Do some kind of weld repair on the cradle while everything is still installed.
4) Something else?

BTW, I have zero welding skill.
Raydar AUG 16, 10:03 AM
I would replace that cradle. I think it's pretty much done. Probably the easiest option.

But then, I live in the south, so I seldom see rust like that.
IMSA GT AUG 16, 10:19 AM
There may be a bigger hidden picture here to where the car is not worth saving.....or maybe just the engine cradle needs to be replaced. Remove the rear wheels and wheel well liner and see if the entire frame has rusted away like this:

[This message has been edited by IMSA GT (edited 08-16-2022).]

theogre AUG 16, 10:35 AM
Yes, is the cradle at minimum.

Replacing is your only option when rotted so bad like pic above.

Just there alone, Welding needs enough good metal to stick and you don't have enough after sanding/grinding. You likely have more places that are rotted that just don't tell as easy as above.

When I look to find "hidden" rot areas, use 2-3 lb hammer, and gently hit a lot of areas and listen and watch. "Gently" like hit small to normal nail w/ big hammer. you quickly hear, see or both hitting in big rot frame areas etc because have different sound or "metal" will bend easy.

Replacing the cradle can be done without dropping engine etc but need special tools etc to hold the engine up safely. Even w/ right equipment shown in Fiero and other FSM, no-one should be under the engine and rest of drivetrain. MORE SO w/ HF etc "universal" engine supports that are easy to slip or outright Fail. I would use the support and add extra chains etc to backup the support. Chains don't need to be pulled tight but not let engine to drop on you either.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

gregr75 AUG 16, 11:24 AM
Good idea on checking the other frame components.

I'm never gonna buy another 32 year old new england car at night. Should have looked underneath better. Hopefully its just this cradle.
zkhennings AUG 16, 11:47 AM
Replace that cradle, I have repaired rot in mine but that is excessive and there is probably way more hiding. Also since you have the setup to support the motor and trans it will be an easy job, I would drop cradle with the suspension attached and take it off once out of the car so you have super easy access to everything. I have a feeling you will be chopping the bolts out.

I like using a slag hammer for finding rust, has a very pointy end and you can really pin-point where the weak metal is hiding.

Oh and one more tip is you can remove the rear bumper and the crash beam underneath it for a straight shot to the cradle nuts that like to rust and then spin freely when trying to remove cradle. No need to cut holes in the frame to grab them which you so commonly see.

[This message has been edited by zkhennings (edited 08-16-2022).]

Patrick AUG 16, 04:00 PM

quote
Originally posted by IMSA GT:

There may be a bigger hidden picture here to where the car is not worth saving...



Exactly. It's hard to imagine that the frame rails aren't rotted away when the cradle is that far gone.
sanderson231 AUG 16, 05:18 PM
I can probably gets you a parts car with a good frame for next to nothing if you want to haul one back from Texas

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formerly known as sanderson
1984 Quad 4
1886 SE 2.8L
1988 4.9L Cadillac
1988 3800 Supercharged

gregr75 AUG 17, 09:29 PM
Thanks for the offer @ sanderson231, I am looking at some used cradles on ebay for $350,400.

I am looking at whats actually involved in getting the cradle out. It appears after I get a low profile dolly underneath the cradle, and disconnect everything, I can lift the rear of the car over the cradle/trans/engine using a floor jack and 4x4 spanning the width of the car. Instead of using a cherry picker (which I don't have) to lift up the car. And then take apart all the crap to get to the cradle. I am looking at the following picture from skitime in the FAQ thread. https://www.fiero.nl/forum/Forum9/HTML/000024.html

After reading the thread, my only question, is, wouldn't this method crush the metal coolant lines running down the length of either side of the car. There doesn't appear to be much structure here too, just the floorpan?

I took a picture of me holding where I think the 4x4 is supposed to go, right by the spare tire jacking points. Of course it would span the width of the car, but again, I dont see this as a good support point to jack up the car. What am I not understanding?
Patrick AUG 17, 09:49 PM

quote
Originally posted by gregr75:

I am looking at some used cradles...



Have you looked at the rear frame rails yet? All your preparation could unfortunately be for nothing.