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I have been daily driving a 2001 BMW Z3 2.5i for 2 years now, and have had some issues with it that I was wondering if they are specific to mine or if more people share these same issues.
1. The car is extremely skittish in rainy or windy conditions. If the road is a little wet even if I accelerate in a straight line the car feels like it wants to slide. Taking turns in the rain requires me to slow down a lot and be very careful with my inputs. It's very unforgiving in turns. I let out the clutch too quickly or give too much gas and the back end comes right out. Also if I hit a bump mid corner even if I take it very slow the car looses its balance. Driving on the free way in the wind the car also feels very unstable.

2. Sometimes when I push in the clutch it makes a clunking sound. It sounds like something is loose. It only happens when the clutch is first pressed in and is more apparent between 1st and 2nd gear. I replaced the guibo and it still makes the same sound.

3. When I put the top down it doesn't fold correctly. It often pinches the plastic so I have to get out and push the window down evenly so it doesn't pinch on one side.

4. Driving 75-80 mph the rpms remain very high 3.5k-4.2k. I know that's probably normal because it has a fairly small engine, but it just seems weird to drive at 4K rpm for extended periods of time.

5. The top leaks a little when it rains hard from where the top meets the windows. I know this is common in old convertibles, but if there's a simple fix it would be nice to know.
 

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BMW CCA 1405
1997 BMW Z3 1.9
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Can you say how many miles and number of owners?
1. Perhaps the strut and shocks and tires are worn.
2. Need more info. What doe first press mean? Does it happen with engine off, or with engine running on the Neutral to 1st shift?
3. Does the window have a zipper (original top) or not (aftermarket top)? You could study the folding by doing it manually -- turn the little T-handle on the pump to disconnect the hydraulics. In any case, some put a foam noodle or rolled up towel across the window to prevent creasing. I just lay a towel over the window before lowering.
4. I have a 4-cyl and don't know what's normal for a 6, but that sounds high. Perhaps your differential was changed to raise the RPM for quicker acceleration
5. If the top does not come down over the windows, but is arched up, it sounds like a weathered and shrunk original top. The rubber gaskets that seal the top to the windows, 3 per side, can be rejuvenated with Gummi Phlege, or replaced.
This top is a little shrunk and exposes the gaskets:
 

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Discussion Starter #3
Can you say how many miles and number of owners?
1. Perhaps the strut and shocks and tires are worn.
2. Need more info. What doe first press mean? Does it happen with engine off, or with engine running on the Neutral to 1st shift?
3. Does the window have a zipper (original top) or not (aftermarket top)? You could study the folding by doing it manually -- turn the little T-handle on the pump to disconnect the hydraulics. In any case, some put a foam noodle or rolled up towel across the window to prevent creasing. I just lay a towel over the window before lowering.
4. I have a 4-cyl and don't know what's normal for a 6, but that sounds high. Perhaps your differential was changed to raise the RPM for quicker acceleration
5. If the top does not come down over the windows, but is arched up, it sounds like a weathered and shrunk original top. The rubber gaskets that seal the top to the windows, 3 per side, can be rejuvenated with Gummi Phlege, or replaced.
This top is a little shrunk and exposes the gaskets:
It has 55,000miles on it. And 8 owners but it spent the majority of its life as a garage queen in the north only being driven in the summer on nice weekends. Tires are new so I don't know why it feels like it had no traction in rain.

The clunking sound happens when shifting between first and second gear and sometimes 2nd to 3rd gear. Once I push in the clutch it change gears and makes the noise. Very strange. I took it to a BMW dealership and they couldn't figure out what the sound was.

The top is the original top with the zipper and the seals are in good condition. I use chemical guys VPR to condition the seals frequently, so I don't know why it still leaks.
 

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Tires are new so I don't know why it feels like it had no traction in rain.
What type of tires are they? Some high performance summer tires don't do well in the rain. Since they are designed for maximum traction on dry roads, they are not effective at moving water out of the way.
 

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BMW CCA 1405
1997 BMW Z3 1.9
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... 55,000miles... The clunking sound happens when shifting between first and second gear and sometimes 2nd to 3rd gear. Once I push in the clutch it change gears and makes the noise... original top... seals are in good condition. I use chemical guys VPR to condition the seals frequently, so I don't know why it still leaks.
Perhaps the sound is not related to the clutch since it occurs only when the clutch is released into the next gear. Since the giubo was bad and replaced, perhaps the center shaft bearing is also bad and knocking when the clutch gives it power after a gear change.
I assume you can see the leak between seal and glass, with water running down the inside of the glass.
If the top covers the window seals, and the seals are conditioned, perhaps they need to be tighter against the glass. The glass can be pressed tighter against the rubber using an adjustment under the door, or the seals can be moved out toward the glass with shim washers.
If you cannot see the water entering at the seal and running down the glass, there are other kinds of leaks to discuss.
 

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The handling issues you describe sound like Tramlining, which these cars are prone to. It can be caused by tires, shocks, front control arm bushings (FCABs) and/or bad rear subframe bushings.
You should consider replacing the rear subframe bushings in any case to prevent the expensive differential mount trunk floor tear-out.

The clutch actuation noise could be a failed bushing where the pedal pivots. They are just plastic, but aftermarket bronze ones are available.

The top leak could be the extremely common A Pillar leak: https://www.bimmerfest.com/forums/showthread.php?t=254611

Many more answers are available here by using the "Search This Forum" button near the top right of the forum page.
 

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Response to Q2...
I'm not a Z3 expert, as I've only had mine for a year. So I'm posting this "answer" as more of a question to the more knowledgeable folks here. I experience the clunk as well, and I found this video in my browsing. I'm planning on having the differential bushing replaced (as well as the subframe bushing) in the spring.

https://www.youtube.com/watch?v=FR--BoO-IGU

Any thoughts from the experts would be much appreciated!
 

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People have been debating and trying to figure out the 'clunk' when pushing in / letting out the clutch in low gear/speed issue for as long as these cars have been around. There are many possible causes, but I've replaced most bushings and even the clutch fluid line with a stainless steel braided one trying to help this issue in my car, but it still does it (I also have poly subframe bushings and the Randy Forbes subframe reinforcement).

Some people have done everything just to conclude that it's slop in the differential itself, and getting a new/rebuilt differential solved the problem. So in your particular case, who knows... You have to try to narrow it down, but all those bushings, giubo, etc are a good place to start.

The subframe issue is a big one, but the best thing you can do is understand what is actually happening and as soon as possible put in poly subframe bushings (NOT new BMW ones, the soft BMW ones are a big part of the problem). Understand that the differential is bolted to the subframe, which connects to the frame of the car at the subframe bushings. The mount at the rear of the diff (that you see from the rear of the car) is the 3rd connection point for the subrame+differential assembly, but it is all thin spot-welded sheetmetal that can't take a lot of abuse. The soft BMW subframe bushings allow all that movement to happen (which you see in the video), which hammers the thin sheetmetal mount at the rear of the differential until (in some cases) it starts falling apart.

So the best thing to do is lock down the 2 subframe connection points to the frame with firm subframe bushings (Ireland Engineering is a favorite). This will limit the movement of the subframe, and thus limit the hammering of the sheetmetal rear mounting system.

Also, as a bonus, it's one of the best handling improvements you can make to a Z3! With the sloppy BMW subframe bushings, the rear subframe (which includes the wheels) is able to move around independent of the rest of the car, so it really messes up handling. Imagine your rear wheels sort of jangling around back there, not necessarily pointing exactly where the car is pointing...

The ideal solution adds the Randy Forbes reinforcement, which adds sturdy steel beams from the diff mount itself all the way to the side frame rails.

As for the traction issue, tires are everything. Some models are grippy in wet, some are not. Also as they age the rubber cures and gets harder and harder, making the tire less grippy. What exact brand and model do you have, and when were they replaced? Also, the stiffer your suspension (springs and shocks), the quicker the tires will break loose from the road. Stock Z3 suspensions were soft, but if you have a really stiff aftermarket one then that could also cause you to lose grip quicker.

I have a 3.0 M54, and RPMs at 75mph are about 3500 if I remember right. Don't worry about it- these cars were designed to run at high speed/high RPM on the Autobahns of Germany. In fact, if you lug the engine at low RPMs too much, you can end up clogging up the CCV system with muck and cause all sorts of problems. Getting the engine up to temp for a good amount of time (longer trips, with some high RPMs) are great for keeping the system clean...
 

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Well, it's also possible that the letup of force/surge of force through the drivetrain when you apply or release the clutch pedal could cause a busted diff mount/trunkfloor to make a clunking noise. In other words, if the sheetmetal has started coming apart, it might make a noise when whacked by the subframe+diff movement.

Have you looked at the diff mount tabs (the part that the diff is bolted to at the rear) which can crack, also where they are welded to the crossmember can break loose, the spotwelds (visible in the trunk) can break loose. Basically the whole chain of thin sheetmetal and welds from the diff mount tabs->sheetmetal crossmember->trunkfloor->side frame rails are suspect.

IF there's no damage there, then I agree- put in the poly subframe bushings and new rubber BMW diff mount bushing (which by the way are apparently insanely expensive now... Some people are trying poly Rogue Engineering diff mount bushings due to cost apparently, but only along with poly subframe bushings and reinforced diff mount). Might even cure your clunking noise if you're lucky.

If there is diff mount/trunkfloor damage, on the other hand, well, then you'll probably want to put in the poly bushings after the surgery.

Long story short, first check your diff mount/trunkfloor sheetmetal and welds (you have to pull up the carpet in the trunk and probably remove the asphault sound deadening to check all the spotwelds). PS- I know I said first replace the bushings, but you need to check things out first.
 

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Thanks again! I will inspect the welds as soon as the car comes out of storage. The diff mount looks fine. I made a half-hearted attempt to check the welds last summer, but stopped at pulling up the sound deadening. How nasty of a job is getting the sound deadening up? Does it pull up as one piece? Or is it glued in and has to be scraped off?
 

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I think the best option is a heat gun, starting at one side and lifting/prying the asphault up as it warms so you can hopefully keep it in one piece (you'll want to put it back afterward). It's just sticky asphault... Maybe a hair dryer would work if you don't have a heat gun?

Ah, I just realized you have a coupe... The roadster just has a small strip of the asphault, but I think the coupe has the whole area covered in pieces. Check out this DIY reinforcement job, where they show the asphault part so you'll know which part to remove:

http://www.bimmerbrothers.com/z3-m-coupe-rear-subframe-reinforcement-part-1/
 
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