Tips for inspecting a used 330i for subframe cracks

[ANGST]

Is there a way when looking at a used e46 with unknown history to know if it has cracks , or had reinforcement done either by BMW or aftermarket ?

Assume you are just responding to to a CL add and can't get the car up on a lift reasonably easily .

[legoman67]

You wont be able to see anything without fetting the car up in the air. I highly recommend having a pre purchase inspection done before you buy one of these.

[Hellmet]

Would a third party actually go to the trouble to clean the area and check for subframe cracks? (I don't live in the US and don't know how the pre purchase inspections work).

Barring any major and devastating damage which would make itself apparent on a test drive (unlikely), without getting the car in the air you can't check for subframe cracks, and even then there's only 1 place that you could really see any signs of a typical hairline crack and you would have to scrub and clean the area first. This would be the area next to the diff where a very fine crack will usually lie.
The 330's are generally OK, I think the majority of them may have a couple of hairlines cracks in the usual areas but nothing that would produce any noise or affect handling. If you don't plan on tracking the car and if you hadn't read about the issue on the forums, you would never know the problem existed, as for the majority of owners, it is not a problem.

[ANGST]

Would a third party actually go to the trouble to clean the area and check for subframe cracks? (I don't live in the US and don't know how the pre purchase inspections work).

If you don't plan on tracking the car

Yes the place I would do a PPI would most certainly check for cracks . The sole purpose of the car would be to put on the track (and driving it to the track) , so I would be adding a reinforcement anyways.

[legoman67]

Would a third party actually go to the trouble to clean the area and check for subframe cracks? (I don't live in the US and don't know how the pre purchase inspections work).

This would vary depending on who you took the car to. A specialized shop that knows the ins and outs of these would likely at the very least shine a flashlight at each mounting point and do a quick visual check as part of their normal routine. If you took the car to a general repair shop its likely they would be unfamiliar with the potential issue and would only do a general undercarriage scan, likely missing hairline cracks.

Most PPI's also involve a brief road test by the mechanic. When i road test a customer car i have one corner that i always put the car into a bit hard(without crossing the 'abusing the car' line). It usually brings any weird suspension issues or noises to light. There is also a set of railroad tracks on my usual test loop that are great for finding suspension issues.