Subframe Rust Options?

[Bli]

Hello,

Just bought a e87 130i few months back. I know all the shocks were pretty much dead, so have a budget for full suspension refresh. Had a look underneath while it is on a lift while swapping out all tyres, and noticed the rear subframe is super rusted...

A mechanic told me it's ok, he sees the same for 15 yr old BMWs, but it bugs me how crusty it is. The options are to swap out the rear subframe for a refurbed unit. Was quoted for 6 hrs labour. I don't have a drive / garage unfortunately - so doing my own isn't an option.

Wondering if there is alternative options besides a full swap. Anyone used one of those gel type rust removers. If any had any success, i will give it a try.

Attaching some nightmare photos. Any views appreciated!

[NorthernDancer]

Do not get it replaced; far too much money for something most will never see. If you have spray on rust proofing service in the UK, then get that done. If you can rent hoist time from the garage, use a paint brush to coat it with oil [NOT the rubber bushings] or paint it black with anti-rust paint. POR 15 used to be the gold standard for this work-not sure if it's available in the UK.
You'll be spending important money on the car: tyres, shocks/struts, rubber brake lines, plastic cooling system parts, brakes, oil pan gasket [$$$], valve cover gasket, water pump & thermostat.
The car is 15 years old and will need most of the above if not done already. The 130 is a great car that needs little maintenance but at 15 yrs, it is time for some, if not done already. I have a 128 E82.

[Thunderguts]

Holy Toledo Batman! I've never seen rust like that on an E82. I wonder if some markets didn't get the same rustproofing as others. BMW is generally pretty good about rustproofing.

[asbrr]

It almost looks like it's coated with mud - I've never seen rust that bad either and my car lives in a harsh Canadian climate with lots of road salt/salt spray.

I do agree that you tyupically dont need to replace subframes at this age, but I would just get it checked for structural sound-ness and then do some rust treatment/prevention as suggested by another poster.

It is pretty horrendous to look at though...

[Bli]

I've not seen one that bad, hence bugging me. About to refresh suspension - would hate to find out 6 months later subframe needs replacing... good shout - will get another mechanic to give a view on structural integrity.

Ref POR 15 - been reading about it - think that needs the subframe sanded before applying right?

Thanks for your thoughts, will start exploring different rust remover products. Will report success if any!

[Dieselboy]

Yikes. I've swapped subframes. You can find a used one for ~$400 in the US. 6 hours sounds about right. If you're planning long time ownership, I'd replace it, the bushings are probably even worse.

[Thunderguts]

Yeah, I don't know what to recommend. If the subframe is that bad, I'm thinking it's not worth the effort. The diff case looks just as bad so there are probably many parts in equally bad shape. This is one of those rare cases where I would just say drive it until it dies. I don't think it's a safety issue yet, but it might become one in maybe 5 years at that rate. If you're not careful that car will quickly become a money pit. Get what enjoyment you can out of it and send it on its way.

[Bli]

Was hoping to turn this to a little beast that flies under the radar. I'd be tempted for a swap if chasis is good shape and rust limited only to the subframe. See your point - the diff looks flaky, then the drive shafts.... money pit

Putting up on a lift and poking around is a good suggestion.

Thanks all for your views

[tsk94]

Replace or remove, sand blast and repaint.

There is NO good option to fix this so it won't come back while leaving it in the car or using some type of chemical while it's installed. It needs to be completely removed and worked on or replaced.