[vcu_ece2324]

Hi,

When doing a front suspension refresh this summer i noticed that my front subframe is rusting pretty badly (car was previously owned in the Northeast US so the salty roads definitely took a toll). Since i intend on keeping this car for the rest of its life, a subframe replacement is definitely in the cards. Is a subframe replacement/swap a possible DIY job or should i take it to an indie dealer?

Also what other areas should i check rn to see if any rust is building up anywhere else. Rn i haven't looked at the rear subframe (blissful ignorance)...

[cfm56d7b]

Originally Posted by vcu_ece2324

Hi,

When doing a front suspension refresh this summer i noticed that my front subframe is rusting pretty badly (car was previously owned in the Northeast US so the salty roads definitely took a toll). Since i intend on keeping this car for the rest of its life, a subframe replacement is definitely in the cards. Is a subframe replacement/swap a possible DIY job or should i take it to an indie dealer?

Also what other areas should i check rn to see if any rust is building up anywhere else. Rn i haven't looked at the rear subframe (blissful ignorance)...

I owned the same vehicle in the past. Loved it.

How many miles does your vehicle have?

Depending on the mileage, a thorough inspection of all suspension parts would be recommended, especially parts with rubber bushings.

[vcu_ece2324]

Originally Posted by cfm56d7b

I owned the same vehicle in the past. Loved it.

How many miles does your vehicle have?

Depending on the mileage, a thorough inspection of all suspension parts would be recommended, especially parts with rubber bushings.

Ive had the car for 7-8 months now (3rd owner) and it handles like a dream. Currently pushing 89K miles right now. As mentioned before i've refreshed the suspension with OEM Bilstein B4's. The front subframe is what im mostly worried right now since that is pretty rusty.

[Ennoch]

Originally Posted by vcu_ece2324

Ive had the car for 7-8 months now (3rd owner) and it handles like a dream. Currently pushing 89K miles right now. As mentioned before i've refreshed the suspension with OEM Bilstein B4's. The front subframe is what im mostly worried right now since that is pretty rusty.

Do you have any photos of what it looks like so we have an indication? The BMW steel seems pretty good quality so if it's just surface corrosion rather than anything more sinister (the 22yr old subframe on my Impreza looked crusty but cleaned up fine) then you could always wire brush and then paint, or douse heavily in an underbody wax like BH Dynax or similar (depending on what's available in NA vs EU) to prolong it. I think Surface Shield is similar from videos I've seen from Repair Geek on YT. I'd be hesitant to start pulling it all apart unless it was genuine structural rust. It may be, but I've also seen lots of garages comment that rust 'looks bad' when in reality it's just scale.

[vcu_ece2324]

Originally Posted by Ennoch

Do you have any photos of what it looks like so we have an indication? The BMW steel seems pretty good quality so if it's just surface corrosion rather than anything more sinister (the 22yr old subframe on my Impreza looked crusty but cleaned up fine) then you could always wire brush and then paint, or douse heavily in an underbody wax like BH Dynax or similar (depending on what's available in NA vs EU) to prolong it. I think Surface Shield is similar from videos I've seen from Repair Geek on YT. I'd be hesitant to start pulling it all apart unless it was genuine structural rust. It may be, but I've also seen lots of garages comment that rust 'looks bad' when in reality it's just scale.

I don't have pics on me right now but when i saw the corrosion there were some parts of the subframe that (at a glance) seemed thoroughly rusted.

I plan to grab pics in the upcoming weeks when i get the car on the quickjacks to replace the tie rods, do my cooling system refresh and change the oil. Was also going to see if i can do some kind of anti corrosion measure like you mentioned since i funnily enough now live near where the previous owners of my car lived. So salty roads is definitely a thing (again).

[casualDIYer]

Originally Posted by vcu_ece2324

Hi,

When doing a front suspension refresh this summer i noticed that my front subframe is rusting pretty badly (car was previously owned in the Northeast US so the salty roads definitely took a toll). Since i intend on keeping this car for the rest of its life, a subframe replacement is definitely in the cards. Is a subframe replacement/swap a possible DIY job or should i take it to an indie dealer?

Also what other areas should i check rn to see if any rust is building up anywhere else. Rn i haven't looked at the rear subframe (blissful ignorance)...

Without a photo, I'd guess the rust is probably 'sacrificial' rust which is a fancy way of saying the steel is thick enough to resist rusting for years. I'd get a little wire brush, start brushing away some of the rust to see how pitted the steel is. Post brushing, be sure to apply some rust resisting paint, like Tremclad or POR-15. Put on a few coats as it wears off over time. You can use some undercoat on top of the paint if you have the patience to let the paint dry a day. Alternatively you could scrub off most of the rust and correct with paint but like any painting project, the surface has to be clean, clean, clean. No need for spray. Brush, while not pretty, is fine.

Front swap of the subframe? That's not a small job. I'd get some help with it. The electronic steering rack is extremely heavy if that is coming out as well (as it is mounted to the subframe). I guess you could leave it in but be sure to support it. Damage it and you'll have an expensive mess on your hands. The biggest problem is space. On jack stands it's going to be a quite tight getting it out so I'd get it done at a shop that's done that kind of work before.

If you want to change the handling of your car, consider a front sway bar replacement. It's going to be pretty easy with the sub frame out. As for bolts? Replace 'em all.

[vcu_ece2324]

Originally Posted by casualDIYer

Front swap of the subframe? That's not a small job. I'd get some help with it. The electronic steering rack is extremely heavy if that is coming out as well (as it is mounted to the subframe). I guess you could leave it in but be sure to support it. Damage it and you'll have an expensive mess on your hands. The biggest problem is space. On jack stands it's going to be a quite tight getting it out so I'd get it done at a shop that's done that kind of work before.

If you want to change the handling of your car, consider a front sway bar replacement. It's going to be pretty easy with the sub frame out. As for bolts? Replace 'em all.

Yeah I was guessing that dropping the subframe would probably be beyond a diy in my garage, but i wanted to get some 2nd opinions first. I have been putting out feelers to some indie dealers as well. Also im thinking since the front subframe will be going out, i might as well have said indie shop also do the oil pan gasket and rod bearings since they're already in that area...

[casualDIYer]

Originally Posted by vcu_ece2324

Yeah I was guessing that dropping the subframe would probably be beyond a diy in my garage, but i wanted to get some 2nd opinions first. I have been putting out feelers to some indie dealers as well. Also im thinking since the front subframe will be going out, i might as well have said indie shop also do the oil pan gasket and rod bearings since they're already in that area...

If you have an N55, 100% get those bearings done. I bet 5 will be perfectly fine and one worn. As for replacement bearings, if not BMW, take a look at King's sputter bearings, part#: CR222GPC. These have a coating similar to the bearings used in the B58 (BMW calls the coating IROX). IROX coated bearings are used to overcome the problem created by the start-stop engine killing mechanism. The obvious problem being that once the engine stops, how does the oil pump keep oil flowing over the journal? The IROX coating helps cut down on wear.

The stop-start feature is one I stopped using the minute I got the car. It doesn't save much gas, wears out the starter, shortens the life of the rod bearings, and is a annoying to listen to. It's a bad idea that makes the tree huggers weak in the knees but is menace to car owners everywhere.

[vcu_ece2324]

Originally Posted by casualDIYer

The stop-start feature is one I stopped using the minute I got the car. It doesn't save much gas, wears out the starter, shortens the life of the rod bearings, and is a annoying to listen to. It's a bad idea that makes the tree huggers weak in the knees but is menace to car owners everywhere.

Yeah i disable the start stop feature every time i get in and start the car up. I plan on coding it out in the upcoming weeks.

[vcu_ece2324]

Hi all, went underneath the car today and snapped some pics of the subframe rust. IKD how the images will be formatted (previewing the post showed them really large so i was forced to zoom out to see the whole thing) so i apologize in advance if the images get posted wonky.

[Ennoch]

That looks absolutely fine IMO, although I'll caveat that and say there's always a chance of something not being visible in a pic. I'd just spray it in a good layer of lanolin based anti-corrosive wax and leave be. Check out Repair Geek on Youtube for some suggestions as he's closer to you geographically so will be reviewing products you can likely get hold of a lot more easily than anything I can suggest. I think Wool Wax and Fluid Film are his two favourites. Usually aerosols will go on thinner than anything you apply with a Schultz gun as it needs the additional solvent for it to spray effectively. This makes it easier to DIY but won't last as long as if the thicker paste is applied with a compressor. But both will be significantly better than doing nothing - all I'd say is that with the aerosol you will likely need to apply it onto the leading edges and higher impact edges more regularly. It really is great stuff though. In the UK there's one getting lots of attention on social media called Lanoguard but it's watery piss and just useless (all the influencer 'reviews' are from people who don't have a clue and are giving feedback having literally just sprayed it on, which is meaningless). Bill Hamber Dynax is what I use, the S50 for cavities as it's thin and creeps into seems really well, and then the harder wearing UB which goes on the external chassis surfaces and dries harder but still 'self repairs' to a degree. The UB is a dark brown but UC is also available in a clear-ish coating which is ideal for show/restored cars and such where you don't want to hide your fresh paint. The downside is that it doesn't last as long as the UB.

[vcu_ece2324]

Originally Posted by Ennoch

That looks absolutely fine IMO, although I'll caveat that and say there's always a chance of something not being visible in a pic. I'd just spray it in a good layer of lanolin based anti-corrosive wax and leave be. Check out Repair Geek on Youtube for some suggestions as he's closer to you geographically so will be reviewing products you can likely get hold of a lot more easily than anything I can suggest. I think Wool Wax and Fluid Film are his two favourites. Usually aerosols will go on thinner than anything you apply with a Schultz gun as it needs the additional solvent for it to spray effectively. This makes it easier to DIY but won't last as long as if the thicker paste is applied with a compressor. But both will be significantly better than doing nothing - all I'd say is that with the aerosol you will likely need to apply it onto the leading edges and higher impact edges more regularly. It really is great stuff though. In the UK there's one getting lots of attention on social media called Lanoguard but it's watery piss and just useless (all the influencer 'reviews' are from people who don't have a clue and are giving feedback having literally just sprayed it on, which is meaningless). Bill Hamber Dynax is what I use, the S50 for cavities as it's thin and creeps into seems really well, and then the harder wearing UB which goes on the external chassis surfaces and dries harder but still 'self repairs' to a degree. The UB is a dark brown but UC is also available in a clear-ish coating which is ideal for show/restored cars and such where you don't want to hide your fresh paint. The downside is that it doesn't last as long as the UB.

Yep, i've already started scraping off the rust w. a wire brush in preparation for anti corrosion measures. I appreciate hearing a 2nd opinion that my subframe is most likely not a lost cause though.

[Ennoch]

You can also put a rust convertor on that's phosphoric acid based (i.e goes black), and they're usually blue/purple-ish in liquid form. Over here we have Bilt Hamber Hydrate 80 which is amazing, and Hammerite Kurust which is less amazing, but there are others. They can be called rust encapsulators, but I'd avoid the ones which are paint based as they generally allow stuff to creep underneath the paint. That and then the wax is great, but if you've got rid of all the loose stuff then the wax will be fine as long as you don't mind keeping an eye on it and coating any worn off areas when needed (probably once a year if the aerosol and lots of bad weather driving). You'd be surprised at how crusty car parts can be and still be absolutely fine structurally.

[Ennoch]

I was curious vcu_ece2324 so I did a bit more digging; Woolwax appears to be the thicker, external coating, and a bit like our Bilt Hamber Dynax UC/UB while Fluid Film is thinner and designed for creeping into the seams of internal cavities, and therefore an equivalent of Dynax S50. What I don't know is how they hold up against each other for a comparative recommendation but I think in your shoes that's what I'd be using. If you can I'd get the car up in the air, soak in a strong degreaser and then jetwash, preferably hot. This will help get all the dirt and junk off as best as possible. Remove the plastic under trays, and then soak all cavities in the Fluid Film. Personally I'd apply a second coating but keep doing it until it's running out of every nook. Lay a tarp down before doing this as you'll never get it out of concrete! Then do the Wool Wax externally - if you can I'd even go as far as removing the bumpers to get all the front slam panels/radiator supports etc done too if you're planning to keep the car long term. Then re-install all the plastics after a day once it's set. The areas under the plastic won't need redoing for a long time as the stuff really does stick well, but as I mentioned previously the areas that are more heavily hit by water spray and grit will need more regular applications (annual etc), but luckily the very nature of their greater exposure to damage also makes re-application simple too.

I'd avoid anything that dries as a hard layer, or goes on as a paint/rubbery substance. The reason for this is that they only sit on the top layer and convert it but if it's in an area where it can still get hit or damaged it will still allow stuff to get under and the rust to propagate. The rust convertors I mentioned before are reasonably good but even then I'd still only use them if you can get it back to approximately clean metal and then use this as a final belt and braces measure, before overcoating. Where the lanolin style coatings really beat the alternatives is that they really soak into the rust that remains and prevents it propagating that way even when some rust remains; this is why an already rusty car is better done this way, or at least that's the approach I take. My Impreza on the other hand needed significantly more work, including cutting out bad metal, grinding back to good where good still existed, and was then coated with a thin layer of convertor where necessary, epoxy primed, stone chipped and then top coated. I really don't think any of that will be necessary for your car and as it's not a restoration, just added effort for little reward. Deal with any loose bits, soak it in the wax to arrest any spread and keep an eye on it. That's already going to be 99% better than any equivalent cars you'll see on the road!

[casualDIYer]

The last 2 photos look a little concerning. After wire brushing how pitted does the metal look?

[vcu_ece2324]

Originally Posted by casualDIYer

The last 2 photos look a little concerning. After wire brushing how pitted does the metal look?

I haven't gotten a chance to hit those spots. I spent this afternoon getting the fan out in preparation for the water pump/ T stat but then i discovered oil leaking from the OFHG so a new side quest has been started unfortunately...

[Ennoch]

Originally Posted by casualDIYer

The last 2 photos look a little concerning. After wire brushing how pitted does the metal look?

As someone who spends a lot of time working on rusty classics and modern classics, I can assure you it absolutely isn't. Pretty it is not, but it's nothing to worry about. If it was left then yes, the potential is that it could become concerning in years down the line, but right now it's a prime example of being easy to prevent it worsening by treating with the right tools and coatings to make it last a long time. Manufacturers build in a fair amount of redundancy for things like rust scale so unless it feels soft or you can see holes through it there's a lot of strength remaining.





I just removed all this from the back end of my Impreza. A bit of sandblasting, followed by epoxy and then black topcoat and it all looks mint again, albeit some of the pitting is still visible. Rust can make it look worse than it is, especially as iron oxide takes up more volume than simple iron does and therefore breaks away from the main surface so it bulges and leaves pits. Nothing major though usually, especially on some thick steel like that usually used on subframes.

[casualDIYer]

Originally Posted by Ennoch

As someone who spends a lot of time working on rusty classics and modern classics, I can assure you it absolutely isn't. Pretty it is not, but it's nothing to worry about. If it was left then yes, the potential is that it could become concerning in years down the line, but right now it's a prime example of being easy to prevent it worsening by treating with the right tools and coatings to make it last a long time. Manufacturers build in a fair amount of redundancy for things like rust scale so unless it feels soft or you can see holes through it there's a lot of strength remaining.

I guess the invention of steel can't be overstated enough. We couldn't have the modern world without it.

[casualDIYer]

Originally Posted by vcu_ece2324

I haven't gotten a chance to hit those spots. I spent this afternoon getting the fan out in preparation for the water pump/ T stat but then i discovered oil leaking from the OFHG so a new side quest has been started unfortunately...

Sounds like the jobs are piling up. Since you are diving in to do the OFHG, might want to check the valve cover gasket. I was surprised to find mine leaking discovering it during a spark plug change. Oil on the threads of cylinder 3. Damn it. A straight forward job made difficult by the removal of the injectors.