Oil Canning Roof

Machspeed

Machspeed

Member
Was not aware of this little problem until yesterday while doing a little sanding on the roof. I'm a noob to autobody stuff but pretty sure this is not normal??? I suspect this happened when the car was media blasted too.

I see no issues in the roof.... looks good, actually. Thinking about taking buying a 9"shrinking disc to see if I can draw out the oil canning. Thoughts?
 
Every roof I’ve ever worked on will oil can to some extent but that seems pretty excessive. I have never had any success with a shrinking disc and I think the consensus on this forum is they’re a bit gimmicky?

Either way, definitely wait to get some solid advice from here before you start attempting to shrink anything because you can make that roof go south really quickly.
 
Oil canning can happen from too much (stretched) or too little metal (shrunk) on a panel. Panel can also oil can simply from the metal being displaced. Trick is to figuring out what is happening. Many cases a dent displaces the surronding metal and causes oil canning. Dolly out the dent the oil canning goes away. It's fairly rare to encounter a dent that requires much if any shrinking after being worked out (correctly).
Lizer said:
I have never had any success with a shrinking disc and I think the consensus on this forum is they’re a bit gimmicky?
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They work but they need to be used in a situation that requires it. Too many guys would just start randomly shrinking on that roof above. That won't fix anything and will actually make things worse. You have to identify where shrinking is needed and apply it only where it's needed. Figuring where that is the hard part oftentimes. And with a roof, you shrink too much it starts oil canning because of the shrinking. So it's a fine line.
 
chevman said:
What is going on at the side of the roof, is that filler? That could be a likely area to cause this.
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Actually, that's the front. Had a couple of very shallow dents but do not believe they are the cause of the oil canning. I really think it was done during media blasting. But, you could be right.

No roof bracing in that area.

There are people that swear by those shrinking discs. Not going to jack with it until I know exactly how to best address it though.
 
chevman said:
What is going on at the side of the roof, is that filler? That could be a likely area to cause this.
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I haven't watched the video as the old computer I'm on now I can't view it.

My post above wasn't specificlly addressing the video. More just in general.
 
Machspeed said:
There are people that swear by those shrinking discs. Not going to jack with it until I know exactly how to best address it though.
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I bought one for exactly that reason. It’s one of the only tools I have that I never use.
 
JimKueneman said:
Have @MP&C explain a donut dolly. I use a PVC fitting that I took a hammer to the store to find one that the hole was just a bit bigger the hammer head. It works like voodoo. I have removed oil canning in panels with just a handful of easy taps of the hammer over the fitting.
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I'm interested! MP@C has incredible knowledge and does amazing work with metal. Hope he pipes in!
 
The problem is not where you think it is IMO, and shrinking there will only cause more problems. The center looks like it is the right shape, but pictures can be deceiving. What kind of car is it?
 
Interesting? Where do you think the problem is and why do you think that? Thanks for the input, as I'm learning that bad techniques can take one down a real rocky road. Begging for input and advise here. Car is a 69 Mustang fastback.

Thanks!
 
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As Chris pointed out earlier, damage somewhere else can quite often cause the oil can effect. I doubt that the blasting was done so evenly that it shrunk the whole roof evenly, and there doesn't seem to be any damage on that area. You also need to think about how flat the roof is on the fastbacks, seems like it would have some kind of support under it.
 

This gives you 90% of it... you then position the "dolly" and tap it with the hammer... Go very slow... just love taps until it is clear nothing is moving then hit a little harder if needed. It won't take much.
 
JimKueneman said:

This gives you 90% of it... you then position the "dolly" and tap it with the hammer... Go very slow... just love taps until it is clear nothing is moving then hit a little harder if needed. It won't take much.
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That's a pretty slick idea using a PVC coupler, and a magnetic to find the spot.

Another tech tip.......
For metal panels that have some natural flex in them such as hoods and roofs, another helpful tool are paint sticks hot glued to the underside of the roof while block sanding. The sticks will help stiffen up the metal so you can block the panel flat. Use the hot glue sticks Paintless Dent Repair uses, along with the releasing agent so you can remove the paint stick (s) after sanding is completed. I did this on the roof of the Barracuda due to some flex in the panel so it would block out flat without waves.

You're asking good questions, keep it up. There is so much to learn which makes it fun, at least for me it does.
 
JimKueneman said:

This gives you 90% of it... you then position the "dolly" and tap it with the hammer... Go very slow... just love taps until it is clear nothing is moving then hit a little harder if needed. It won't take much.
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That would have saved me on several that are not under a brace.
Good stuff
 
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