I need some feedback on frame rot please. I have been working on a door handle/latch/panel issue since Sunday. I finally figured it all out and while I wait for parts I was drawing on information from this forum to repair some badly damaged door panels. While I was at it, I also decided to change my oil last night since I can't drive her and needed a break from plastic repair. I went to jack the car up and heard a loud crunch, followed by the car slowly dropping about 3/4" while the jack was not moving at all. I dropped the car immediately and got underneath to find the problem. The frame had a small rust area that I had been treating until it could be looked at by a frame shop. When I jacked it up, part of the lower frame crushed on the drivers side just behind what looks/looked like a tow hook at the S bend of the frame. The passenger side looks like it may have been replaced/repaired in the past as it's shinny black and the spot welds are really clean, almost perfect. I didn't get to take pictures last night but will post some later this evening. When search the forum and via Google I can find very little info on C4 frame rot. Even to the point where I have read notes on this forum that these frames rarely rot and never all the way thru. Again, I appreciate any information available. If she's about to crack in half it would be a good time to stop pouring cash into her. Attached is a pic of the area of the rot, circled in red. I'll post actuals tonight.

 

Where did you jack from?

 

Actual pics would be good. I've never seen a C4 frame with rot. I've never even seen one with surface rust...out side of a car fire frame.

Are you sure you didn't punch through the floor?

 

Right under the battery.. Did your battery cause it?

 

I misspoke. I jacked it up right under the drivers side mirror. Then put a jack stand under it and that's where the frame disintegrated. The jack stand was about 3-4 inches behind the tow hook/eyelet in the frame.

 

I'll post pics tonight. It's not just surface rot, the one lower section just crumbled. They eyelet/tow hook actually broke right in the middle when the lower section gave way. The rest of the "box" is intact.


It's the frame, the floor pan is fine

 

I bought it May 1 last year. The battery was 2 years old when I got it. If the battery did it I would think the top of the frame would be gone, not the bottom. It does look like work had been done to the passenger side in the same section as it looks brand new.


Car was never in an accident other than a small fender bender with the previous owner in a parking lot. A truck pulled over the top of it and cracked the nose and hood. The ins company totaled it, so the owner bought it back and had the hood and nose fixed. Nothing that would even tweak the frame.

 

This is the exact spot the eyelet/tow hook just rear of the cross member split in 2

 

 

 

I took an ICAR structural welding and sectioning course a long, long time ago. What I know is, you can probably replace that section with a used one, making sleeves to go inside and using plug welds, and then a butt weld at the joint if you want. Use weld through primers for corrosion protection at the welds, following up with a wand and a good product inside the rail afterward..

The designation of "HSS" is worrying though, as some of those revert to mild steel if they are heated high enough. But I don't know enough about what type is used here? (Door crash bars, for example, are something you don't want to weld on. )

Assuming the steel isn't a problem and if you're good with a welder, it wouldn't cost much to do the repair. It would be a major hassle.

A good frame shop in the area could probably tackle it without a second thought, but most of them are pricey.

It's a shame you're not closer to Cincy, because there's a really good outfit in Harrison Ohio that could handle this, I'm sure. Their prices aren't out of line either.

 

This scared me. Corrosion protection is now on the list.

 

My thoughts are that this isn't worth repairing...but you CAN cut that section out, then plate it with sheet formed into the same shape...if you're ambitious.

 

There was a thread here on the forum in the last yearish that was detailing a build turning a C4 into a race car. The OP of that one showed how they welded up some frame rot. Maybe you can find that thread and then see if the OP is still on the forum and ask for some details.

 

It looks like it rotted from the inside out. I'm pretty sure the PO of my 84' drove it in the winter because she has her share of surface rust. Also on that EXACT same spot on my frame rail I welded a plate on where it had a few rusty/starting to rot spots. Maybe it's time to dig in a little bit more to see if the rail is rotting from the inside out. Even with the bad fix job I did when I was 20/21 I have had her teetering on 2 wheels in a steep driveway with the top out AND I was able to open the door fine. That would make me think the rails are certainly still strong. A few years later I went back under and did a more thorough repair of the rail. I don't remember checking more of the rail going forward or back though.

Considering how hard it is to see the inside of the frame rail I wonder how many other C4's are getting this same rot and the owner has no idea. Especially if it's rotting from the inside out. I wonder if the frame flexing a bit can cause the galvanized coating to flake off? Is that even possible? If it's a stiff coating I would think it can crack like paint and it wouldn't take much to make it crack.

 

..... Your screen name a "tipoff" ? ... Ohio is the state shaped like heart ... its gonna have a heart attack with all the salt it consumes every winter ! ... Thanks to International Salt Co. Mine under Lake Erie in Cleveland ! ... Dump your rust bucket ! ... and head South and get yourself a solid 'vette to play with forever ... just don't drive it from November to April .....

 

...

 

Lots of kali C4s for sale cheap that won't pass smog.

 

These answers are based on your profile saying you are local to me here in Ohio.

I went back and saw your car is an 85. If it turns out it is really bad and not repairable, there is a guy out in the Randolph area that strips/parts out early C4's for the suspension. I know it would be a LOT of work, but depending on how much money you have invested in that car, you could get a rust free shell and swap parts. If this is becomes an option, he advertises on Craigslist.

Alternatively, and probably the first thing I would do, is take the car to a shop that is experienced in welding up frames. I know that Condor welding on St Rt 261/Wadsworth Rd, in Norton, Ohio does decent work, at a reasonable price. They are the ones that I had do some welding on my harness bar so I could get it to fit.

If it is repairable there is the possibility of th getting a chunk of frame rail from the guy in Randolph.

 

Thanks for the info. I have an appointment Thursday morning with a reputable frame shop in Akron. I'll see what they have to say and go from there. It does look like the passenger side from the firewall forward was replaced at one time. It looks like it's right out of the factory.