Chassis brace question before investigating a leak

During an oil change this last weekend, I saw a film of something slightly wet on the aluminum diamond plate, rear sway bar, and pdk oil pan. Assuming it is oil of some sort, either engine or transmission. I’d like to go in that area and do a nice thorough cleaning, but need to remove the chassis braces to do so (image not my car, just included for clarity). questions: 1) I just want to confirm - if jacked up with the suspension free hanging, will removing the diamond and diagonal braces then refitting potentially require an alignment? I think not, but just wanted to confirm. 2) Are the torque values for those fasteners published anywhere convenient? 3) Is there a preferred leak detecting compound if the source isn’t apparent in the cleaning phase? And I guess a bonus 4th - anything else I should be looking into while I’m in there? Thank you for any insight!

I’ve removed and replaced mine with seemingly no impact on alignment. It’s helpful to use something that keeps the car even when lifted like a Quickjack . If using individual jacks, make sure you have things at the same height on each side. But structurally speaking, that plate doesn’t have any adjustments so it shouldn’t impact alignment. One thing you might consider doing while you’ve got it apart is installing a Pedro’s Garage Technobrace. It’s inexpensive and helps brace the rear suspension. Very easy install.

Depending on your cars milaege and service history you might consider doing your transmission fluid too, dead easy job but requires the plate to be removed. I did this a couple of weeks ago using redline 75W90NS ( 987.1 Base Cayman 5spd) Cheers, Julian

I seem to recall someone stating that removing that plate without messing up alignment is possible if you don't place weight on the rear suspension while it is off. Basically, don't lower your car to the ground. I honestly can't figure what could move unless you're doing some serious driving with it off.

While I had my trans fluid draining I gave one of my wheels a jiggle to feel for wheel bearing play and was shocked at how much movement/play you can generate with just your hands when the underbody braces are removed, all just a matter of leverage and rubber bushes but OMG, I would NOT put my car on the ground with the braces removed.

I’m at 83k now, and will have to check my records, but think the clutch fluid was changed at 60ish k miles by the PO. So I think I’ll just clean and keep an eye on it for now. Good suggestion, though! Thanks.

Good suggestion on the Pedro’s brace. I actually have a machine shop at work, so I may just look at fabricating something. If I’m not draining fluids, and only cleaning up (for now), how important is it to be level? That wasn’t something I was really worried about for now, prioritizing working clearance in my work plan, so just want to check if I need to focus on levelness for some reason.

If you have a machine shop - while the pan is off - have them make a hole so you can get the transmission drain plug out without having to remove the pan.... requires a bit of measuring - but a 1" or 1.5" hole isn't going to affect the function of the support pan.

Only issue here is that this is my daily driver and how I get to work, so I’d have to do this at home. They might have a dimple I can use to punch a clean, flanged hole, though. Good suggestion!

The reason I was thinking it would be best to keep the car level is that loosening and tightening those components is easier and more even if the car isn’t in a “twisted” state. These components brace the car so having the car in a neutral state will not apply sideways pressure to the nuts and bolts which are removed.

Ah, good point! I think level left and right would still take care of that, but if the car was *** up, not a big deal. Thanks for sharing your thoughts 👍

Quick question that I’ll be surprised if anyone has an answer for. I’m looking to build my own brace bar (have 1” round stock, measured the holes to be 562mm apart, etc). Before I disassemble since I’ll be away from the machine shop, does anyone happen to have 😂 one of those studs that gets popped out from the cast bracket to fit the techno brace? mostly curious about the shoulder size that presses into the cast bracket for a nice tight fit. Anyone have that OD? long shot, I know!

Got under the car at lunch today and measured the distance between the relevant screws and came up with Then grabbed some bar stock and jumped on the Bridgeport Added a bit more support to the part and a few more features figured out the part that was easiest to screw up (counterbored bolt heads to act as anti-rotation for easier assembly) and cleaned it up a little tomorrow I should be able (hopefully) to get it powder coated, and then get it installed after cleaning things up down there. I sure hope it fits! 😂. I eyeball lined it up under the car before heading home and it looks pretty darn close.

Hmm. Maybe a distinction without a difference, especially considering the lip you added, but it seems to me that the direction of the bolt matters. If you put the nut on top, then the unthreaded portion of the bolt's shaft is misplaced and not bearing the shear loads as intended. The Pedro brace comes with replacement bolts that have such 'grips.' Anyway, does it really seem easier to you to put the nut on top, rather than dropping the bolt down from the top? Seems like a fiddle to get it threaded while pushing the bolt up. Maybe I'm not picturing it right, whereas you've been really studying it. In any case, bravo for making your own!!! Wish I could do the same, but I'll be satisfied enough just to install the one I buy. I want one because I have definitely experienced exactly the thing that it purports to remedy; and I believe it will.

Now with some gravity taken out and (not really) strategic air holes to better facilitate pdk cooling as well as respect the buckling force that this thing will probably never see. Off for black hard ano tomorrow morning.

Wow! This is the sexiest stress bar I have ever seen, impressive build quality, congratulations! PS: In regards to your original question, I never had any issue by removing the triangle and diagonal braces, as long as the weight of the car is off from the rear axle. I would put the rear axle on jackstands, remove the diagonal braces along with the triangle, clean everything with simple green, assemble everything back again and after a few days you should be able to see the cause of the leak, good luck! .

Apexhunter, just to clarify when I mentioned 'using jackstands on the rear axle' I meant installing them on the rear axle ' side ' jack supports, this is the Only place where you are supposed to put the jackstands.. Perhaps I need to put more attention the way I write my English sentences

FWIW, I also used the same Redline (as Apenxhunter) last year and put the car on 4 jack stands to be level. Also my notes says 48 ft lb for the torque. As for the clutch fluid, I would also do the brake fluid at the same time as it is from the same master cylinder . Just be careful with the valve as it is plastic.

Just closing the loop on this one. As best I can tell, the oil film under the back of the car was the result of a messy oil filter change (as I kind of suspected). No oily mess above that point or forward of that point. Cleaned up the whole area pretty well just to keep an eye on it for the future. Also got the diy techno brace installed - not quite like I planned as the way I machined it didn’t fit above the diamond brace while still clearing the plastic pdk pan, so I pivoted to hanging below. To be honest, having spent a fair bit of time under the car this weekend, I’m not really seeing the value of that techno brace. The diagonal arms are pretty well triangulated and connected to the chassis, and the added brace only connects the two sides together rather than additional triangulation to the chassis. If the concern is that the unbraced subframe can flex, all the technobrace does is make that “spring” twice as stiff (flexing both sides vs. just one), and not dramatically stiffer. Oh well, it was a fun exercise and imo it looks pretty cool.

Opening this back up. I was under the car again this last weekend swapping in an S tier rear sway bar and taking out my “basic” one. But while in there, definitely saw more oil film on the rear of the diamond brace. My now current guess is pdk fluid. Are there any best practices for tracing down a pdk fluid leak? unsurprisingly, the fluid film is heavier to the rear of that diamond brace, but I can’t say if that is just airflow pushing it back or being close to the source of the leak. thanks for any advice on this