Thursday, December 12, 2013

Rear Subframe Strip Down - Part 3 (Ish) - Foam Filler!

Having spent what seems like a spare lifetime stripping down the rear subframe back to bare metal, it becomes obvious why they have a reputation of rotting to bits within a few years of fitting. Well, it seems obvious to me, there are so many nooks and crannies for muck and debris to hide and set the rotting process off. No matter how diligently you clean your car, there is no way you are going to be able to make sure that the unseen subframe pockets are clear.

So what to do. Mmmm, I thought, maybe if I fill all the cavities with expanding foam and all the smaller holes with a good thick layer of paint, this will get rid of all those little hideouts that the muck finds and hopefully as a result of that, will make the whole thing less lightly to corrode. I had a search around the internet to see if anyone else had done this, but all I could find was a reference to people filling the sills with foam for some reason. Nothing about the subframe.

Maybe this is a crazy idea, but I think that after all the hard work I have put in restoring the subframe it is a shame to paint it back up, stick it back on the car and let it rot away from the inside out. It's worth a shot... I think!

So, off I went to the hardware shop to get some fire retardant expanding foam to do the job. I thought that I had better get fire retardant stuff due to the close proximity of the exhaust. This is the stuff I went for...

Having worked with this stuff before with various DIY jobs around the house, I know from bitter experience not to get it on your skin. If you do, it turns black and there it will stay until to grows out. So overalls, gloves and even a face mask were used for this job.

Started by filling all the cavities I could find.

It truly is awful stuff to work with!!

Then, after leaving it to set for a few days, used a hacksaw blade to cut off the excess.

After that, I tried painting it, but it was a bit rough.

So decided to use a thin layer of car body filler to create a smoother finish.
Remember, this is complete experimentation!!

Filler applied
And here.
Sanded backThis method allowed me to make nice smooth contours.

Then painted...

There is still some way to go, but I think that the general principal is workable. I will just keep going with sanding and filler until I am happy with the shape and finish.

As I mentioned, this is complete experimentation and it may turn out to be a total disaster, but I think it is worth a try as hopefully I will be left with a subframe that will last an awful lot longer and will be easier to keep clean. Time will tell, come back in a few years!

Luckily, I am in no hurry to get the car back on the road so can take as long as I need to get this just right, so I'll post again when it is finished, but it may be a while yet.

If you are reading this and you have done the same, please let me know how it went.

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  1. Hi.

    How did this turn out in the end or is it still early days? I'm about to start stripping my subframe so I'd like to try anything that's going to prolong it's life

    1. Hi Huw. It still seems pretty intact. I was under there recently fitting a new exhaust and it all still looked pretty good.