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I installed the R.F. subframe kit in my car this winter and had a welder do the serious stuff. In the process the thought to paint it was forgotten. Like so many other things at the age of 59!
So I started to look for solutions to this brain fart. The old rust proofing methods came to mind when cars used to rust. They don't offer that now, at least not here. I tried a spray can of stuff that is designed to do do rocker panels. But the spray tube that east wo od supplies is curved and has a nozzle that sprays forward more than to the sides. Even plugging the end and buying tiny tiny drills to drill extra side holes didn't help. A coat hanger does get it straight but does not get it around corners and there are lots of problems to getting into this space.
So I came up with the idea to drill two ~~ ⅜" holes in the top plates of the R.F. kit on the passenger side and fill it up with paint. I then wondered if that space went further into other areas, meaning the paint to escape to other body cavities. I tested this with a smoke generator and a shop vac. The space is not sealed and paint can get past and go other places. (Those other places are not going to show so who cares.) The volume of the enclosed space is, very roughly, 2L. That is one L per hole and way more than needed as I have a L that dripped out. I plugged the two holes on the underside and a couple of other holes near by, bought a plastic funnel to get into the holes and poured in direct to metal marine enamel that I slightly diluted with mineral spirits (about a fluid oz) The paint was still thick but could flow.
I then double blocked the front wheels and put two jacks under each side. This allowed me to "tilt" the car down on the drivers side so a builders level showed it would be enough to fill to the holes. Then I tilted back a bit so the paint came out of the holes.
You might ask where the paint came out. About half way down under the drivers door button in the rocker area. More inside of that. Nothing anyone but a mechanic might see. I also do not care about it. I plan to keep the car till it is almost worthless. And if someone does not like my fix or my paint job or anything, well that's nice, keep your opinion to yourself becuase I don't care. Why do I say that? Because the purpose of this and all forums is to communicate solutions and ideas. Not to do all the other stuff that I see over and over. Yup, stupid move but I found a solution that worked so I shared it.
Last edited by catimann; 03-15-2019 at 03:24 PM.
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I'm watching your thread with great interest, I'm in the process of installing the kit myself, I had planned on treating the xmbr and parts with weld thru primer. Thanks for the heads up!!
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I used that stuff or equivalent over 40 years ago in my 2002 and it is paraffin based. I don't think it helps to spray paint on top of it.Originally Posted by catimann
BMW MOA 696, BMW CCA 1405
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As this repair in a couple of my own cars are going on fifteen (<15) years now, I've wondered myself. I always paint the inside of the xmbr before putting on the top plates, but have never painted the underside of those plates (!) At .120" (nearly 1/8") thick, I believe it will take many decades before anyone has to worry about them rusting through (and with the holes now sealed in the bottom, there won't be any direct contact with water).
I don't think it was a dumb idea, but for the ease and sake of anyone else, might I suggest a product called Waxoyl (you can find it in the US easy enough, just used this picture for an example). There are DIY kits that include nozzle, tubing & a pump-up container.
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Randy, how are the holes sealed in the bottom? Is that with the bottom plate or are you plugging it?
I'm still unsure about the order of surface coatings: Etching Primer then do I use an epoxy primer or go straight to seam sealing? Do you recommend using a weld-thru primer?
As this repair in a couple of my own cars are going on fifteen (<15) years now, I've wondered myself. I always paint the inside of the xmbr before putting on the top plates, but have never painted the underside of those plates (!) At .120" (nearly 1/8") thick, I believe it will take many decades before anyone has to worry about them rusting through (and with the holes now sealed in the bottom, there won't be any direct contact with water).
I don't think it was a dumb idea, but for the ease and sake of anyone else, might I suggest a product called Waxoyl (you can find it in the US easy enough, just used this picture for an example). There are DIY kits that include nozzle, tubing & a pump-up container.
Member
On a related note, has anyone heard of filling structures like this with some kind of resin? Reason I ask is, I was thinking about something like this myself (my idea was some kind of asphault, more for sound deadening/vibration absorption purposes due to the differential connecting to this crossmember) when I happened to find this awesome writeup of a guy who bought a beat-up E46 M3 and completely refurbished it into a gorgeous better-than-new state:
https://www.pistonheads.com/gassing/topic.asp?t=1715557
This is an inspiring (and well-documented with photos) project and outcome, but the part that caught my attention is about 3/4 of the way through (do a search for 'resin' and it will bring you to it):
"Then final procedure is to inject the rear end just as BMW would do with Resin to further strengthen the chassis, this stuff literally has no weight but is unbelievable strong."
Ok, so if you ever had to do something inside this crossmember (don't know why, but who knows) this would be an issue, but anyone (especially Randy) have any thoughts on what could be used and why it would/wouldn't be a good idea? And also, this is normal for BMW? Maybe newer ones? I've never heard of it, but it would be an interesting way to strengthen the chassis.
Also, another interesting thing is how this problem is different on E46s--- in their case, the subframe bolts to sheetmetal that tears apart. He first tries gluing on reinforcement plates, but those eventually fail, so he then welds in reinforcements.
Anyway it's a good read...
Member BMW CCA, PCA
Eastwood has aerosol product for coating internal structures like rocker panels, should work for this application.
https://www.eastwood.com/eastwood-in...z-aerosol.html
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Randy, how can I purchase your reinforcement kit for my 98 M Roadster?
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Send $575.00 + $35.00 shipping (lower 48) to my PayPal account: SPORTSCARSPLUS@AOL.COM
Make sure I have your email (for tracking updates) and your ship to address
For future reference, and so as to not get sideways with our forum hosts, please contact me via PM, FB or email. Thanks though!
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I was just looking over this tread again and noticed this. I bought this and tried it. I tried the supplied extension with other spray paint and tested it in a replica cardboard test pc. The cardboard was taped together to be able to see what the result was. In short it was an utter failure. No mater what I did (used coat hanger wire to keep the plastic extension straight and other ideas) it would always spray one section very well and others (mostly oposite sides) not at all. In the end I drilled two holes and poured in some amount of paint that I calculated would over fill the space by like two cups or so. I used direct to metal marine enamel. I tilted the car way over (like the passenger side was a foot off the ground) and filled it up. After that I let it drain and it did for well over a week! Am I anal? Yes! As Randy pointed out, because of the metal thickness it will take decades to rust. The rest of the car will be long gone.
Moral of the story is install the RF fix and paint it outside and in the trunk where you can see it. Drive the heck out of the car and have fun.
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I tried to PM you and never got a response. I figured it was somewhere obvious and you were tired of the question. I killed facebook three years ago and never looked back. Thanks for the info.
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