325iX Preventive Maintenance

[pozzello]

Hi everyone. I inherited my mother's 1990 325iX and it's in fantastic condition :-))) I have to replace one of the front fenders for the typical rust near the rocker panel but once I repair it what is the best preventive maintenance to avoid it from rusting again ? Should I re-undercoat the whole car ? The sunroof is also rust free and the surrounding area are spotless - would spraying fluid film prevent it from rusting ?

[roguetoaster]

Remove undercoating around any rusty areas until you see clean metal. Remove undercoating from pinch welds, jack pints, places with scrapes, joined seams, and near any drain hole. If needed, cut out and repair sections, treat the raw metal, undercoat with quality material, being mindful to not block drains or pool around the insides of the holes.

Do it once, do it right, save headache down the road, and don't just cover it with more undercoating as the rust will spread.

Fluid Film is great for crevices of course, but I'm not sure I'd use it near the sunroof, and instead would just be vigilant about drainage and mpisture buildup in that area. Also remember, areas under ix body cladding are also prone to rust.

[packratbimmer]

Use PPG epoxy primer and good quality seam sealer, preferably 2-part.

[packratbimmer]

The paint looks great on the car. Could the fender be repaired to retain the original paint match along the top? It will be very difficult to match the paint perfectly on a replacement fender.

[pozzello]

Remove undercoating around any rusty areas until you see clean metal. Remove undercoating from pinch welds, jack pints, places with scrapes, joined seams, and near any drain hole. If needed, cut out and repair sections, treat the raw metal, undercoat with quality material, being mindful to not block drains or pool around the insides of the holes.

Do it once, do it right, save headache down the road, and don't just cover it with more undercoating as the rust will spread.

Fluid Film is great for crevices of course, but I'm not sure I'd use it near the sunroof, and instead would just be vigilant about drainage and mpisture buildup in that area. Also remember, areas under ix body cladding are also prone to rust.

Thanks for those tips. What should the metal be treated with ? Do you recommend a particular brand of undercoating ? So as long as I make sure the roof drains are clean I don't have to worry about them rusting ?

[pozzello]

The paint looks great on the car. Could the fender be repaired to retain the original paint match along the top? It will be very difficult to match the paint perfectly on a replacement fender.

The paint is really good. 15 years ago she had the right fender replaced and blended - you still can't tell. my body shop (a custom hot rod builder) suggested replacing it, matching the paint and blending the whole front (both fenders and hood) into the doors. The lower part of the fender is rotted through - wouldn't it be better to replace with an original ?

[roguetoaster]

Thanks for those tips. What should the metal be treated with ? Do you recommend a particular brand of undercoating ? So as long as I make sure the roof drains are clean I don't have to worry about them rusting ?

POR15 or another epoxy primer/coating. Rocker schutz is pretty good. The roof drains don't rust, they're plastic, the things around them rust, and no, worry about all metal rusting.

[packratbimmer]

The paint is really good. 15 years ago she had the right fender replaced and blended - you still can't tell. my body shop (a custom hot rod builder) suggested replacing it, matching the paint and blending the whole front (both fenders and hood) into the doors. The lower part of the fender is rotted through - wouldn't it be better to replace with an original ?

If a fender has already been done, yes I would replace and blend again.