Hello!

Today I removed for the first time the battery on my C3 -74 and noticed that the glassfiber battery box has got a about 4 inch long crack on the right side...the box is besides to that in good shape. Should that crack be fixed ASP or can it wait?
Is the the intire box made of glassfiber or does it also have got a metalframe?

 

If you drive the car regularly I would fix it right away. You have a 40 pound plus battery bouncing around in there and the crack will only get worse. The box is all fiberglass and the repair is simple enough , just make sure all paint and undercoating is removed 3 to 4 inches away from the crack.and grind a bevel out in both directions from the crack. Also locate both ends of the crack and drill a small hole at each end. This will terminate the crack and help to keep it from spreading. Then use standard fiberglass repair methods and grind and glass both sides of the crack. Good luck

 

I wish you could post a photo of the exact location of this crack.. I know you stated it is on the right side...but knowing it exact location can aid in the options for the repair.

As for drilling a hole in it...that is up to you but is not needed due to this is not steel. Some of the fiberglass GM used does not crack straight through adn actually cracks laterally. So...drilling hole is pointless and does nothing to aid in the repair. because you will never drill and the correct angle and get to the actual end of the crack. But drill away if it makes you feel better.

Grinding it out 3-4 inches away from the center of the crack is also up to you and in some repairs I cannot be done. So as long as you have a good inch or more...that will suffice for a good strong repair.

Keep in mind once the exact lactation ahs been seen. So PLEASE try to provide us with the best clear photos you can. You can repair this quite easily but I would really like to see where it is at.. This repair MAY NOT require laminating to repair it....and can be all done form the inside of the battery box so NO undercoating is removed. The reason I am saying this...I have repaired my fair share of cracked battery boxes....many much worse than having a four inch crack in them.

REGARDLESS if you fix it from the inside or outside. IF you have a lot of battery acid contamination due to leaky batteries in the car over the years, THIS WILL effect the repair. SO...if you can see that this area has been effected by acid )which may be detected by a white residue and if you scrape on the fiberglass with a sharp object like a flat blade screwdriver and it is kind of soft and really wants to get 'fuzzy' rather easily adn quickly when scraping on it) ...and it seems to NOT show up well in the photo PLESAE let s us know about this. THIS IS IMPORTANT to know about.

DUB

 

Here are some photos of the crack.
When I push down close to the crack "the floor" moves a bit down and the crack gets larger...

 

Thanks for the GREAT PHOTOS!!!

This repair should be really no problem.. Seeing how the one battery cable is really close to where the crack ends. I would suggest getting out of the way so you grinder does not damage it.....because....all of the repair can be done on the inside.

You can clean of the underside where the crack is so your masking tape can seal up the crack so nothing you apply will drip though the crack. You will apply the tape AFTER you have prepped it on the inside first. Just get this area clean prior opt grinding. You may have to wipe off some dust after you have prepped it but at least you are not trying to get off stuff that will cause the tape not to stick.

Starting at the crack itself you can put your grinding discs outer edge in the crack and at a rather moderate to slow RPM ...slowly grind down and pull away form the crack like I said... about an inch or a bit more. Do this on both sides of the crack.

The idea her is to taper out the crack..SO IF you make the crack open just a little bit...such a millimeter or so. DO NOT worry. Because you can fill that back in. Bur what you are trying to do is to get down the bottom of the crack and leave a very thin amount of fiberglass...if possible. If you can't...don't worry about it. This is why I wrote to use grinder at a slow RPM so it does not get away from you adn you cut away too much body material and you do not have it create much wider gap.

The whole reason on trying to keep the crack from not widening too much is so form the outside...if you are worried about it.. The repair does not show that much and you can lightly apply some black paint of undercoating and the repair will not be easily detected if at a ..

When this has been completed. You can clean of the underside so your masking tape can seal up the crack so nothing you apply will drip though the crack.

You can use fire glass resin adn mat. (either epoxy or polyester are fine) Or you can use some of the two part adhesive that the guys who repair cars in Finland use in conjunction with some mesh or fiberglass and lay it in the area you prepped. AS long as it is designed to be applied on fiberglass. You can prep it out further if you choose to do so. But an inch or so should be ore than sufficient. No need for 3-4 inches. And the 'mesh' I was referring to is the type of mesh that can be used when doing sheetrock work. It is a plastic mesh looking much like a screen for window but larger squares in it. It will provides EXCELELNT strength has long as it is covered in the two adhesive you use adn use a few layers of it on top of one another. This make type of mesh is used when I repair urethane bumper covers and it is NO JOKE...it works.

SO if you choose to use the mesh...cut one section of it about one inch wide and the length you need and cover the crack....then the next layer of mesh can be 1-1/2" wide..then the next can be 2 inches wide. . Like I wrote..it all depends on how you want it to look when you are done.

So..it will depend on how good looking you want it when you are done to how well you apply any of these products.

Knowing that it is in the corner...you can apply quite a bit in this corner to further strengthen it....and YES...if you want to cover those two small holes near the crack. You can do so due to they were there for the vent hoses form the factory batteries back when the car was made.

DUB

 

Thank you DUB for your detailed instructions, I think I´ll get this crack fixed now! =)
I am sure that many other can also use your instructions...I think that everyone who has not yet taken out their battery from the box on a C3 should do that -It´s just a matter of time when these boxed can start to crack if they have not been fixed.

 

I agree...check your battery area out .

But what most commonly happens is that people do not secure the battery so it can move...and that slight movement up and down causes the 'beginning of the end' and crack to develop.

Not only that it is not good for the plates in the battery itself and cause it to go bad much faster.

So those of you who use bungee straps or 'Zip ties'. Bolt it down correctly and make sure it is solidly mounted. Or deal with what can happen.

DUB

 

Thank you for posting this question and to DUB for answering it in detail! I have the same issue in almost the same spot.
I'm sure that is due, like DUB said, to lack of battery hold down in my case at least.