Rust on rear subframe...clean and use rust prevent coats or new subframe?

[therandike]

I recently did my MOT and was told the rear subframe has rust but is not seriously weakened. Car is 2008 Reg. Given that it is close to 17 years I can understand some rust. Is it worth getting this cleaned and using rust-proofing coats and paint? Or replacing the subframe?

I looked online I have seen Honda sub frames selling from £150-300 other model likes civic.

My car has not given me any problems for 5 years. so would like to extend its life  130k miles on it now.

Any help and advice would be great.

Thank you

[jasonevans]

That picture does not look that bad. I personally would rub it down and then a couple of cans of stone chip should do the job. 

Hammerite Vehicle Underbody Aerosol is decent and available from screwfix.

[Lord Voltermore]

If you can safely do it yourself , or know someone who can do it at minimal  cost thats  great. I'd avoid using too thick a coat of undersealing as this can make MOT testers suspect you are trying to hide problems.

If you have to pay a professional   they may be able to put the car on a lift and sand blast the rust off quickly and treat at reasonable cost.    But this can be a pig of a job ,best done with specialist equipment, and there is always a risk that halfway through the job they will find the rust damage is worse than it appears. 

 You may find more choice of garages  ,able and willing to fit a new sub frame. It could even work out cheaper, in parts and labour ,or worth a bit of extra..  A new subframe might come with  decent paint, but it might just be basic primer and would benefit from extra paint before fitting.

[therandike]

I have been looking into getting a new subframe, but I can't find that many for 2008 honda jazz my version of the car.

[madasafish]

We have a 2--3 Toyota Yaris an 2012 Jazz both basically rust free.
Your sub frame is not (yet) terminal but the blisters need to be removed soon as they harbour damp and speed up rust.
If you decide to replace it, what are the chances of finding a better one ? With all associated parts in good condition? Nil I  would suggets.

I would wire brush it , then spray with Dinitrol 4941  (See ebay  and Amazon  who have deals for three off.)
Dinitrol prevents rust increasing and covers it all with a flexible waterproof layer.
Applied it to a friend's rusty VW Passat   six years ago - still going strong.

Estimated cost - 2-3 aerosols   under £40...Lot less hassle than replacement subframe .

[embee]

Just looking at the photo on my phone it doesn't look terminal.  As said by others,  try to clean off as much of the "scabs" as you can.
 I use Bilt Hamber Hydrate 80 as rust converter to at least slow the spread, it reacts with the rust and sets as a primer layer. Personally I only then paint parts if I can get them clean and dry, otherwise you can end up just trapping the problem and having the paint lift and water getting underneath. If painting the best stuff I've found is Johnstone quick dry zinc phosphate primer (Screwfix own brand stuff is nowhere near as good in my experience, not recommended for this application). Top off with Hammerite if desired,  though the Johnstone primer is remarkably durable on its own.
I then use Bilt Hamber UC over the top.  I have found UB tends to harden and gets moisture under it rather like paint,  but UC is softer and while not as tough as UB it works better in real world situations. Just my experience.
I get stuff directly from the Bilt Hamber website,  usually try to get several items to get the free p&p. No commercial connection,  satisfied customer.

[therandike]

Just looking at the photo on my phone it doesn't look terminal.  As said by others,  try to clean off as much of the "scabs" as you can.
 I use Bilt Hamber Hydrate 80 as rust converter to at least slow the spread, it reacts with the rust and sets as a primer layer. Personally I only then paint parts if I can get them clean and dry, otherwise you can end up just trapping the problem and having the paint lift and water getting underneath. If painting the best stuff I've found is Johnstone quick dry zinc phosphate primer (Screwfix own brand stuff is nowhere near as good in my experience, not recommended for this application). Top off with Hammerite if desired,  though the Johnstone primer is remarkably durable on its own.
I then use Bilt Hamber UC over the top.  I have found UB tends to harden and gets moisture under it rather like paint,  but UC is softer and while not as tough as UB it works better in real world situations. Just my experience.
I get stuff directly from the Bilt Hamber website,  usually try to get several items to get the free p&p. No commercial connection,  satisfied customer.

I will try to do this. Looking hire some car ramps to  get some good space under the car. Hopefully this help to keep the car for two more years.