How bad are these weld spots in the trunk of this Z3M?

[erliban]

Hoping to get some help from folks here. I'm in the market for a Z3M Roadster and found one that I like. But it's not local and the seller sent me some pictures of the trunk floor.

I see at least 4 weld spots that seem to be cracked. My question is: how bad is this? Can I drive it as is or should I get it fixed soon?

Thanks!2019-03-21.jpg2019-03-21 (1).jpg2019-03-21 (2).jpg

[SteveG66]

Definitely make that part of the negotiation, at the very minimum I'd keep a very close eye on them keeping in mind it's only going to get worse. Personally I would purchase knowing it's going to need to be reinforced asap. BTW- I purchased a Z3M that had failed and repaired by a PO. I'm in the process of fixing the poor worksmanship and reinforcing the subframe and trunk floor pan. Good luck with your search and purchase, these cars are worth the hassle and extra work, this one would be as well!!!

[erliban]

Thanks for the feedback, usually how much would the repair cost? Is this something any BMW shop can do?

[Tigershark48]

Bad. All the welds in the first picture have failed and, at least one and more likely two welds in the second picture. The best fix out there Is Randy Forbes kit. Contact him for pricing. If you end up with this car, Randy’s kit is the best available fix.

[Mr Bingley]

Yes, those welds are popped and there are bound to be many more unseen. On the range of from "fine" to "catastrophic," they're "pretty bad." The car will need the RF reinforcement kit installed. The kit is around $500 for the steel, the install and additional parts should cost another 2-3K. Negotiate down $3,500 and you're golden. The repair will have to be done right away or it will move to catastrophic very quickly. I wouldn't let it stop me from buying, but I would insist on the $3,500 off, unless it's already under priced by that amount.

[pine1000]

If you swap in poly subframe bushings it may stop the progression of damage, but if you plan on driving it hard, you eventually need the reinforcement. I would keep a close eye on it and check from below the car as well. If the trunk floor is this bad there could significant damage to the differential mount.

The subframe reinforcement can be a DIY using Randy's kit. You would need to hire a welder or be willing to lear to weld yourself. These guys have an excellent blog post about doing the job themselves with no welding experience: http://www.bimmerbrothers.com/z3-m-c...cement-part-1/

[Tim95M3]

Not terrible enough that I wouldn't buy it. My welds in the roadster look very similar. Going on ~30k since I installed poly SF bushings, lots of abuse and they haven't gotten worse. I know I'm pushing my luck, but yeah...

[PhilPhil]

Randy's kit is (currently) around $700. Getting one put in is non-trivial. It doesn't bolt in. It requires removing the rear end and lots of cutting and welding. Expect labor to be somewhere between two and four kilobucks, depending on how careful your mechanic is, and whether or not they've done one before. My mechanic is an experienced welder and builds race cars. I'm a long-time customer, so he gave the car extra care and attention. It took him about four days and cost around $3600, including paint.

FYI: Hard launches are not what tears the subframe loose form the trunk floor. It's lateral loading, such as the forces generated under hard cornering. So, it's not a question of horsepower. Even the non-M versions can develop the trunk floor issue... especially since these cars are fun to go round a corner in. When I had mine done, my mechanic was initially skeptical about cutting into a "healthy patient", but once he got into it, he said "I get it now. This factory diff mount is chicken sh1t." After having the RF kit installed, he told me "This isn't going anywhere now. You could hang the car from the subframe now, and it wouldn't budge." A little hyperbole there, but he paints a picture.

[SteveG66]

Another member here and a friend of mine had a few failed welds as well, I helped him replace his subframe bushings with poly last summer. He is coming over to help me with the RF kit this weekend, he mentioned he lost more spot welds when with the poly bushings. YMMV, but I wouldn't take chances. Again, I'm living with a car that failed and was repaired and not reinforced, v it's something you don't want to experience, especially if you can avoid it. Prices I've seen for the installation is minimum $3500, which did not include new exhaust if switching to dual ear cover, etc.

[Adker]

Kit is $575 plus shipping ($35), well worth the cost. There are several threats on installing the kit..cutting and welding required. Randy instruction are very clear and contain lots of pictures, well withing the DYI skill set to prep it for the welding, welder can be hired.
https://www.bimmerforums.com/forum/s...0#post30224910

[timreldridge]

As SteveG66 said I replaced my bushes last summer with poly and had only one popped weld. While replacing the amp last week I found two more have let go. The poly bushes may prevent damage if you don't have any but once it starts the only fix is the RF kit. I drive my car like it was meant to be driven and put almost 20K on it last year so YMMV but I am not taking the chance of my diff hitting the pavement...

[erliban]

Thanks for all the great information. This car is in another state so I'll probably pass on it since it's already a lot of extra work to get it to California.

[catimann]

I saw only one weld like that and drove my car, like an old grandma, & still had four more 1.5 months later.

[ProductUser]

What you're not inspecting are the spot welds under the seam sealer. You may want to look for cracks under the car, where the spot welds pulled through.

I had four visible pulled-through spot welds and these lovely cracks.

subframecrack.jpg

[Trademark1]

What does the group think of the attached on the scale of 1 - likely OK for the foreseeable future when driven conservatively to 10 -certain impending doom? (‘98 z roadster)26638C60-E639-40BD-A82F-CEE24844B7B2.jpeg

[khammack]

You should be looking into getting Randy's kit installed. While it isn't going to fail tomorrow, the sooner you fix it, the less it will cost. It would be hard to put a 1-10 number on it because it all depends on your driving conditions (including road conditions).

[magnetchief]

This is mine. Progressed over a couple of years.
This past week myself and a friend (or two) installed the RF set up.
Also replaced the trailing arm, sub frame and differential bushings.
Went with a reinforcement of the single diff mount.
Took us 5 days work 9-4 with an hour for lunch.
I think next time we could knock this out in half the time.
Learnt a lot along the way.
The actual welding is not too involved.
It’s the disassembly and prep that takes the time.

Would be possible to do the prep and call in a mobile welder to knock it all out in a day.




Sent from my iPhone using Tapatalk

[Kram71]

Hoping to get some help from folks here. I'm in the market for a Z3M Roadster and found one that I like. But it's not local and the seller sent me some pictures of the trunk floor.

I see at least 4 weld spots that seem to be cracked. My question is: how bad is this? Can I drive it as is or should I get it fixed soon?

Thanks!2019-03-21.jpg2019-03-21 (1).jpg2019-03-21 (2).jpg

My friends looks very similar although better. The 3 on the far left look similar while all of his rest look new. He has never had an issue. Do you guys think I should tell him that he needs to reinforce? He barely drives his car. It has around 100k.

[khammack]

The thing you need to remember is that the trunk floor is where the differential is attached. Check under the car to see what is going on there. But if the spot welds are coming apart, then the differential is moving and things will get worse. BUT if the car is not being driven, then things will get worse at a much slower pace.

[ProductUser]

What you can visibly see is a small indication of a potentially much larger problem. There are many spot welds under the seam sealer that cannot be inspected. As I've said and noted by others, an inspection under the car should also be done to better assess the problem.

[TommyMaddox]

I had many popped and damaged spotwelds in my 2.3. Took one 3 day weekend to fabricate an RF style system and install it, along with a diff I rebuilt and new half shafts.

Highly recommend doing this. The car feels a lot more solid and you can upgrade or hoon around without any worries about tearing your trunk out.

[Kram71]

The thing you need to remember is that the trunk floor is where the differential is attached. Check under the car to see what is going on there. But if the spot welds are coming apart, then the differential is moving and things will get worse. BUT if the car is not being driven, then things will get worse at a much slower pace.

Seems like such a huge job. Don't think he will want to do it. Maybe he can fly Randy in to do it for him

[magnetchief]

Maybe he can fly Randy in to do it for him

He retired

[Kram71]

He retired

Good for him. Bad for us ☺

[Randy Forbes]

Seems like such a huge job. Don't think he will want to do it. Maybe he can fly Randy in to do it for him

That's been suggested before, for a number of different jobs. Won't happen.

He retired

Well, semi-retired...

Good for him. Bad for us ☺

I'm still doing the occasional car, but even if I (can ever) stop doing the installations, I do plan to continue to offer the reinforcement kit as long as possible.