I think I finally found the source of my bizarre handling issue. Now, how to fix it?

Hello all. Long story (semi) short here, I have been dealing with a mysterious handling issue for the past couple years, and despite a whole lot of tinkering, multiple trips to reputable shops on both sides of the Atlantic, and a lot of money spent on replacing bushings etc, it would never go away. The basic problem was that the car started feeling unstable at anything more than about 50 mph. It behaves as if it is being randomly pushed around by strong winds, knuckleballing down the road, and basically refusing to track straight and true. The problem surfaced in the middle of a long drive initially. One minute the car feels fine, next I'm thinking "man it got windy all of a sudden". Then I stopped for gas and realized there was no wind, at all. A few months back I thought I had finally found the culprit, as when I removed my tow hook license plate holder to switch to a European format plate, the problem immediately improved noticeably. For a couple days, I thought it was gone, but soon realized it was still there, just not noticeable until higher speeds. The start point had moved from about 50 mph to around 90 mph. The fact that I now live in Germany makes that more of an issue than it might have been back home in the states, as I regularly cruise at around 100 mph, and would drive faster if the car wasn't all over the place. So the license plate issue clued me in that it was aerodynamic. I had originally thought it was suspension or alignment related after finding nothing wrong with any of the bodywork, and the other day it finally revealed itself. In the front of the car, there is a black plastic indent directly under the front license plate area. This is an area I have inspected many times over the past couple years as I washed the car, and never saw anything out of the ordinary. I guess a particularly fast run on the Autobahn the other day finally pushed things far enough that the issue was visible. This black plastic section is now visibly separated from the surrounding painted bodywork on one side, and inspection reveals that at least one of the clips that hold it together has snapped, and another one has been popped open, but appears intact. So, basically this section has been opening up on one side only and randomly allowing air through the bodywork, throwing off the balance of the aerodynamics for moments at a time, and causing the erratic behavior. I suspect that the off-center tow hook plate holder might have been shunting air forcefully into that corner, and might have been responsible for the initial failure of the clips connecting the two pieces, as well as magnifying the affect while it was still on the car. Now the question becomes, how do I repair this? The clips that hold this piece on are molded into the front bumper, and they have failed completely. The factory's answer to how to fix this would be to replace the bumper, but with paintwork, clear bra replacement, etc, that is a rather cost ineffective method. I need to figure out how to lock these two pieces back together in a way that will not fail down the road due to the air pressure applied on an autobahn run. Things that have crossed my mind so far range from duct tape , to glue, to even taking the whole bumper off and fiber-glassing the parts together. So, anyone have any thoughts on how to best repair this? Pic below.

I don't have any great ideas, but if it were me I'd take the front bumper off and try to fabricate something to hold it. I took the bumper off my 07 Cayman a couple years ago to clean the radiator area. It was not that difficult. Here is a picture of the center insert from the back, if that helps.

Thanks for the picture, Sir. That's roughly how I thought it would look. One idea that occurred since I originally posted is to replace the plastic blank with a grill. The grill wouldn't need as solid of a mounting due to the fact that it does have to hold back all of that air pressure, so one broken clip out of the bunch probably wouldn't affect it much. Other grill assemblies also seem to mount differently. Does anyone have any recommendations on grills?

When the radiator is present the site is vented through the lower panel (unless it's a GT3 ). If I were you I'd start by removing the bumper cover and see what has failed. It will be far easier to repair from the inside. If you decide to open it up is definitely open the lower panel to allow the air out. You can also go with the GT3 Smile that vents upwards. Rennline has parts for the smile as well as nice quality mesh kits. Sent from my iPhone using Tapatalk

There are clips and slots that the black plastic cover fit into. The question is there damage? If so, the open round trim piece used with the third radiator may not hold. Then again, with the bumper cover off, the trim may just pop back into place. If there is damage, you have several options. The most expensive is a new bumper cover. The next best fix is to glue the cover in place, 3M 5200 Marine RTV will work or Wurth Bond and Seal. The final way is to get the smallest zip ties and drill very small holes and use the zip tie to hold the opening cover to the bumper or a combination of glue and ties. If done right, it will not be very visible. V6

I thought I made it clear in my first post, but apparently not from the looks of things. Yes, there is damage to at least one of the loops protruding from the front bumper that the blank clips into. The one on the passenger side edge of the blank is broken completely off. At least two others are currently separated, but I don't know if that is due to damage to the piece on the blank that protrudes and locks the clip in place, or if they simply got forced open and would close properly again if I could get pressure on the blank from the back. Won't know for sure until I can take it all apart. Would have done that this weekend, but unfortunately I came down with a pretty nasty cold, which feels totally wrong this time of year. In any case, at least one of the clips will never work properly again without replacing the entire bumper assembly, which is cost prohibitive for such a minor problem, so I need to find a way to reinforce that section or simply replace the blank with a grill. Not sure you really need to cut vents as mentioned above, as there isn't actually a real need to evacuate hot air from the area. If vents are needed, I would choose to cut them into the bottom, as the GT3 "Smile" seems like a bit of overkill.

Why not just get a 3rd radiator kit. Not too expensive (~$300) and includes the aero bits to redirect the air under the car.

That could be a possibility. Where do you find the kit for that price? Also, do you still need to order a grill or does it come with one?

Suncoast has them for $389. Any screens or grills are aftermarket. Here is the caption from the Suncoast website. Cool down your Porsche with 100% Factory Porsche Parts. Adds an additional radiator to your Boxster or Cayman for increased cooling. This is perfect for the street or track, and comes with all of the necessary hardware. Professional installation recommended, ports must be cut into the bottom of the bumper to allow air flow. Fitment (Manual Transmission Only): Cayman or Cayman S, 2006-08 Boxster S, 2005-08 Boxster 2005-08 - Center duct must be cut into bumper, painting of small trim opening required.

I recently installed the 3rd radiator kit (form Suncoast ) and the engine stays nice and cool on the track. BTW - my independent mechanic says that they can't get it any cheaper than the price Suncoast offers.

There are actually outlines of 2 center radiator vent holes embossed into the plastic pan under the front of the car. Or maybe the nose itself. Anyway, foolproof. If you open up the center area I'd definitely cut out those holes as that is how it was designed.

The third radiator kit does nothing to solve the OP's broken slots; these are moulded into the bumper cover itself. I have a hard time believing that this is the cause of his handling woes, however. I'd suspect something in the steering rack or tie rod ends, or even -- in a rare case -- worn or loose bolts or holes in the subframe that the steering rack bolts into. This seems much more likely to be a mechanical issue than an aerodynamic issue, IMO. Sent from my XT1650 using Tapatalk

The suggestion isn't that the radiator will help, it's that if he can't repair the part to avoid air ingress that he needs to vent that air. And if he's going to open it up and vent it, he might want to go ahead and add the radiator. Sent from my iPhone using Tapatalk

So the thought is that this small plastic piece not being seated right is causing a 3,000 pound car to sway all over the road?

Yeah, that doesn't seem right to me either. I would think something is loose/broken in the suspension or steering.

I have zero exposure to this person's car and I'm not claiming this is his problem. Just keep in mind that 1/2" piece of plastic attached to a wing (aka gurney flap) can dramatically change the stability of a car at high speeds. So is this possible, yes, I thinks it's possible. Is it definite? Certainly not. It's seems like it's pretty easy to test though. Pull the bumper cover, either fix the damage or remove it all together and vent the airflow. Quite some time ago I had a 996 that just never felt all that stable then I turned at anything above 60 mph or so. Suspension was fine, tires fine, alignment fine. I added the factory aerokit and the car was rock solid ever after. Aero can have quite an impact when it comes to higher speeds. Sent from my iPhone using Tapatalk

I was listening to Smoking Tire video live stream - he mentioned a car that got all squirrelly on him. Turns out it was the steering wheel hub flange. Never would have thought.

I completely understand the skepticism on this being the issue, but you will just have to take my word for it that there is virtually nothing left to replace in the suspension that could cause this kind of issue. Since the onset of the problem, the following items have been replaced. Complete coilover suspension and mounts, three times(read my Ohlins thread for a breakdown on that nightmare/saga). All four LCAs, fronts being replaced with GT3 arms. Entire steering assembly including a new rack and pinion, and tie rod ends. All other control arms in the rear suspension. The car is currently on KW V3s. None of those changes made even one iota of a difference to this problem. It remained entirely the same, to my incredibly great frustration. So far, no less than 4 highly regarded Porsche Specialists, in both the USA and Germany, have been completely unable to find anything wrong with the car's suspension or steering systems that could cause this problem, at least that hasn't already been addressed at this point. Now the issue has become one of logistics. I have decided to go the third radiator kit option, but unfortunately Sun Coast refuses to sell me one due to my location, as they will not ship to an APO address. FCP also has a kit, but it is $75 more expensive, and they want an additional $57 shipping, despite the item qualifying for free shipment, and the fact that APO shipping costs exactly the same as shipping to New York City, as the military takes care of it the rest of the way. The nice thing about the FCP kit is that they have a parts breakdown on the website, so I was able to send an inquiry to the local Porsche dealer tonight, as all of the parts are factory parts. Hopefully I should hear back from them tomorrow , then I can make a decision on how to proceed.

Sorry for the necro-reply (bringing a dead thread back to life..) but looking at your photo on a real computer where I can blow it up nice and big makes me think something is seriously wrong with your bumper: That really does appear as a crack. And that would explain your center panel coming loose. Perhaps try some duct tape and see if that stops the feeling of instability. Since I believe that's the side the tow hook fitting is on, could the toe-hook license plate mount have wanged the section somehow? Or directed way too much air in the area? Closer up: Sure looks like one to me. A new bumper cover might be in order.. Seems strange that all the experts who've looked it over - overlooked something this obvious.

I understand the thought, but that is actually the seam between two pieces of clear bra you are seeing, not a crack in the bumper. I've been busy collecting all of the pieces required for a third radiator install, so far not quite successfully as most retailers will not ship to my address here in Germany, which is an APO address. I found a parts list for the kit on FCP Euro, and ordered all of the parts from a local Porsche dealer, but still am missing one critical part that I can't find the correct part number for. It's the part that clips to the bumper and secures the radiator cowl to direct the air. Also have yet to find the part number for the two nuts required to secure the bottom of the radiator to existing posts coming out of the body. Any help in finding those two parts would be appreciated.

Finally collected all of the parts needed and did the third radiator installation last weekend. The broken tab on the far right side was the source of my problem. The car no longer wanders all over the road as it has done for the last couple years. Took a couple pics along the way, but mostly I had my hands full. It only took about 2 hours to do the job though. Pretty straight-forward overall. Now that the job is done, I think I need to go back to something more like factory camber settings for autobahn duty. It has GT3 front control arms and I think it's running around -1.5° of camber up front. It's pretty good up to around 100 mph, but beyond that it gets a little hairy, as the car tends to react a bit unpredictably over bumps. It's nice and stable as long as the road is flat, but once is starts to heave up and down a bit, the car is still not particularly stable or confidence inspiring. A part of me does wonder if the bottom air exit for the third radiator might add some lift to the front end, as it does feel a bit light in the front at high speeds. On a side note, there was a ton of crud in between the factory radiators and the air conditioning heat exchangers. my car even has finer mesh covers over them, but it was still packed. Might be worth checking that every few years.

It’s too bad our center radiator isn’t factory ducted topside, like the GT3 .