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Comparisob Between E36 & E46
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<blockquote data-quote="E46Fanatic" data-source="post: 59871" data-attributes="member: 81"><p>There is quite an extensive amt of owner experiences with this issue. You can google it to find out more... I just googled it and found more links..as well. Quite an interesting read below..</p><p></p><p></p><p></p><p>------</p><p>Sub Frame Failure - E36</p><p>Date: Mon, 15 Feb 1999 </p><p>From: KC </p><p>Subject: </p><p></p><p>Can anyone who has done the following repair/preventive measure please</p><p>shed some light on this subject. As I understand it, from D. Finch's</p><p>explanation, the problem is that the right (and eventually the left)</p><p>rear sub frame where the control arm is mounted to the body may be</p><p>susceptible to fatigue (especially on cars with modified suspensions</p><p>and/or race tires). Apparently the "hat" that is spot welded to the</p><p>unibody and the three bolts that are welded through it can pull out.</p><p>This eventually leads to a total failure of the surrounding sheet metal</p><p>and/or hat resulting in costly repairs. The questions are:</p><p></p><p>1.) Is it strictly the three spot welds that are susceptible to failure,</p><p>or can the three studs pull through the hat as well?</p><p></p><p>2.) Would the following be sufficient to prevent the problem from</p><p>occurring? Welding completely (360 deg) around the hat, and welding a</p><p>(what size) piece of (material) aluminum/steel on top/underside of the</p><p>hat so that the bolts go through both</p><p>(reinforcement and original) pieces?</p><p></p><p>3.) How difficult is it to gain access to this area and effect repairs,</p><p>and is it worth doing if the the car is going to be taken to the track?</p><p>What special precautions need to be taken, i.e., is the fuel tank in the</p><p>vicinity of where the welding needs to be done?</p><p></p><p>If anyone has done this repair/preventive procedure would you please</p><p>write up a very detailed "how to" so that I may make the necessary</p><p>improvements and not worry about this happening. I have looked in the</p><p>FAQ's but did not see any posts on how to prevent this from occurring.</p><p></p><p>Any suggestions are greatly appreciated. Thanks</p><p></p><p>Cornelis (KC) Kome</p><p></p><p></p><p>--------------------------------------------------------------------------------</p><p></p><p>Date: Mon, 15 Feb 1999</p><p>From: "Duane Collie" </p><p>Subject: E36 Stuff</p><p></p><p>>Subject: </p><p>></p><p>>Can anyone who has done the following repair/preventive measure please</p><p>>shed some light on this subject. As I understand it, from D. Finch's</p><p>>explanation, the problem is that the right (and eventually the left)</p><p>>rear sub frame where the control arm is mounted to the body may be</p><p>>susceptible to fatigue (especially on cars with modified suspensions</p><p>>and/or race tires).</p><p></p><p>While this can and does happen, my understanding from the pros on the race</p><p>teams is that this is only caused by excessive bottoming out of the</p><p>suspension. When the suspension hits full travel in the rear, the</p><p>subsequent forces rack the bushing area and tear/fatigue it, causing flex</p><p>which in turn rips out the sheet metal. If you don't bottom your suspension</p><p>out, you should not have an issue. Keep an eye on it and watch your driving</p><p>habits. I inspect mine every time the wheels are changed - so far all is</p><p>good. But I don't launch over railroad tracks with the car, either. If you</p><p>really want to weld them up - get a pro to do it.</p><p></p><p>>can someone tell me what that wire is for that comes out of the left</p><p>>(driver side) front caliper? i noticed that the other side doesn't have</p><p>>one..</p><p></p><p>Brake wear sensor. Wrap 'em up and tie em off to the strut. Things are a</p><p>PITA and when they grind down, they short out as designed and the "BRAKE</p><p>PAD" warning stays on until you go to the dealer and buy a new sensor lead.</p><p>So if you use the feature, you haveta replace 'em $$$. Superior German</p><p>Engineering INDEED!</p><p></p><p>- - Duane Collie</p><p></p><p></p><p>--------------------------------------------------------------------------------</p><p></p><p>Date: Tue, 16 Feb 1999 </p><p>From: Jason Lile </p><p>Subject: Re: E36 Stuff</p><p></p><p>Duane Collie wrote:</p><p>> </p><p>> >Subject: </p><p>> ></p><p>> >Can anyone who has done the following repair/preventive measure please</p><p>> >shed some light on this subject. As I understand it, from D. Finch's</p><p>> >explanation, the problem is that the right (and eventually the left)</p><p>> >rear sub frame where the control arm is mounted to the body may be</p><p>> >susceptible to fatigue (especially on cars with modified suspensions</p><p>> >and/or race tires).</p><p>> </p><p>> While this can and does happen, my understanding from the pros on the race</p><p>> teams is that this is only caused by excessive bottoming out of the suspension. </p><p></p><p>Well, I wouldn't go that far <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink ;)" loading="lazy" data-shortname=";)" /> We sold a 94 325i AT car with 20k miles</p><p>to a 5' 2" female school teacher a couple years ago. In those two years</p><p>she has put about 10k miles on the car (I doubt she bottomed it out</p><p>racing over too many railroad tracks <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite2" alt=";)" title="Wink ;)" loading="lazy" data-shortname=";)" />). She just had this very</p><p>expensive repair done a few months ago. I think this problem will</p><p>become more and more common as these cars get older... regardless of how</p><p>they've been driven. FWIW, IMHO, IME, etc...</p><p></p><p>___________________________________________________________</p><p>Jason Lile Administrator </p><p>Parts Manager BMW Parts Digest </p><p>Zionsville Autosport </p><p><a href="http://www.zionsvilleautosport.com" target="_blank">http://www.zionsvilleautosport.com</a></p><p></p><p></p><p>--------------------------------------------------------------------------------</p><p></p><p>Date: Tue, 23 Nov 1999 </p><p>From: Marco Romani </p><p>Subject: Re: [uuc] E36 M3 Sub Frame Cracks</p><p></p><p>Some one today mentioned to look for subframe cracks on E30 M3 as part of a</p><p>used car inspection. Well all you E36 M3 types guess what? We too are</p><p>blessed with the cracked subframe problem. I replaced mine last week due to</p><p>both motor mounts practically not being mounted to the subframe. Big cracks</p><p>and actually some missing metal. The replacement subframe was of a</p><p>different design of the original one, fewer holes and thicker metal where</p><p>the engine mounts are bolted. The new subframe has a redesign date of Jun</p><p>98 I believe.</p><p></p><p>Symptoms where a squeaking metal on metal noise when going from lock to lock</p><p>on the steering wheel and a general feeling that the front end of the car</p><p>wasn't attached correctly.</p><p></p><p>Yes the car visits the track at least 8 days a year, but with only 60k miles</p><p>I was surprised to see cracks that bad. I suspect the stiffer suspension</p><p>has something to do with it, HR and Konis.</p><p></p><p>Watch out and becareful out there.</p><p></p><p>Marco</p><p>95 M3</p><p></p><p></p><p>--------------------------------------------------------------------------------</p><p></p><p>Date: Tue, 16 Feb 1999 </p><p>From: Steve Walsh </p><p>Subject: RE: </p><p></p><p>Cornelis (KC) Kome asks about rear sub frame failure. I have experienced</p><p>both to one degree or another.</p><p>There are 2 distinct failure modes. The first are the 4 mounting points</p><p>for the rear sub frame or differential carrier. On non-M3 (like my</p><p>325is)</p><p>the mounting points are not reinforced, as they are on the M3's. They</p><p>tend to fail in the following order: Rear passenger side, forward</p><p>passenger side, forward driver side, rear driver side. In my case the</p><p>rear passenger mount had completely torn around it's circumference, and</p><p>the forward passenger side had torn 270 degrees around the mount. The</p><p>forward drivers side mount had also cracked tangentially from the mount.</p><p>The repair requires removal of the rear suspension, differential, fuel</p><p>tank, rear seats rear carpet, exhaust, battery, yadda yadda... In case</p><p>the forward differential carrier cross member was also replaced. In</p><p>short,</p><p>many hours, big $$$. Despite being out of warranty (88K miles), in did</p><p>manage to get BMWNA to pick up the tab. For non-M owners the M3</p><p>reinforcement plates are available, and these are the part numbers:</p><p>41 00 2 256 495</p><p>41 00 2 256 496</p><p>41 11 2 256 497</p><p>41 11 2 256 498. They each cost $25.73.</p><p>Note: they require the aforementioned rear sub chassis disassembly to</p><p>install them !</p><p></p><p>The second mode of failure is the rear trailing arm bushings and mounts.</p><p>This is the failure mode that David Finch has reported in detail in the</p><p>past. In short, the rear trailing arms mount to the chassis under the</p><p>rear toe adjustment plates. These plates are held to the chassis through</p><p>3 bolts. The threaded receptacles for these bolts are prone to fail</p><p>(circumferential cracks), and under extreme situations will tear the</p><p>'hat' from the chassis.</p><p>In my case I was lucky that there was no cracking of these points when I</p><p>replaced the rear bushings. </p><p></p><p>In my experience the best thing to do, if you suspect damage (mysterious</p><p>clunks), is to check it early. Even though replacing the rear bushings</p><p>cost me about $750, it is certainly cheaper that repairs David Finch</p><p>described. The health of the bushings is directly related to the stress</p><p>placed upon them, and visual inspection is difficult, at best. If they</p><p>are worn, then they are not anchoring the trailing arms correctly. This</p><p>movement, and the stress of cornering will transfer additional torque</p><p>(stress) to these 3 mounting points.</p><p>I have read a possible method for 'beefing up' these mounting points,</p><p>but don't remember where I read it. Check at the NJ chapters web page</p></blockquote><p></p>
[QUOTE="E46Fanatic, post: 59871, member: 81"] There is quite an extensive amt of owner experiences with this issue. You can google it to find out more... I just googled it and found more links..as well. Quite an interesting read below.. ------ Sub Frame Failure - E36 Date: Mon, 15 Feb 1999 From: KC Subject: Can anyone who has done the following repair/preventive measure please shed some light on this subject. As I understand it, from D. Finch's explanation, the problem is that the right (and eventually the left) rear sub frame where the control arm is mounted to the body may be susceptible to fatigue (especially on cars with modified suspensions and/or race tires). Apparently the "hat" that is spot welded to the unibody and the three bolts that are welded through it can pull out. This eventually leads to a total failure of the surrounding sheet metal and/or hat resulting in costly repairs. The questions are: 1.) Is it strictly the three spot welds that are susceptible to failure, or can the three studs pull through the hat as well? 2.) Would the following be sufficient to prevent the problem from occurring? Welding completely (360 deg) around the hat, and welding a (what size) piece of (material) aluminum/steel on top/underside of the hat so that the bolts go through both (reinforcement and original) pieces? 3.) How difficult is it to gain access to this area and effect repairs, and is it worth doing if the the car is going to be taken to the track? What special precautions need to be taken, i.e., is the fuel tank in the vicinity of where the welding needs to be done? If anyone has done this repair/preventive procedure would you please write up a very detailed "how to" so that I may make the necessary improvements and not worry about this happening. I have looked in the FAQ's but did not see any posts on how to prevent this from occurring. Any suggestions are greatly appreciated. Thanks Cornelis (KC) Kome -------------------------------------------------------------------------------- Date: Mon, 15 Feb 1999 From: "Duane Collie" Subject: E36 Stuff >Subject: > >Can anyone who has done the following repair/preventive measure please >shed some light on this subject. As I understand it, from D. Finch's >explanation, the problem is that the right (and eventually the left) >rear sub frame where the control arm is mounted to the body may be >susceptible to fatigue (especially on cars with modified suspensions >and/or race tires). While this can and does happen, my understanding from the pros on the race teams is that this is only caused by excessive bottoming out of the suspension. When the suspension hits full travel in the rear, the subsequent forces rack the bushing area and tear/fatigue it, causing flex which in turn rips out the sheet metal. If you don't bottom your suspension out, you should not have an issue. Keep an eye on it and watch your driving habits. I inspect mine every time the wheels are changed - so far all is good. But I don't launch over railroad tracks with the car, either. If you really want to weld them up - get a pro to do it. >can someone tell me what that wire is for that comes out of the left >(driver side) front caliper? i noticed that the other side doesn't have >one.. Brake wear sensor. Wrap 'em up and tie em off to the strut. Things are a PITA and when they grind down, they short out as designed and the "BRAKE PAD" warning stays on until you go to the dealer and buy a new sensor lead. So if you use the feature, you haveta replace 'em $$$. Superior German Engineering INDEED! - - Duane Collie -------------------------------------------------------------------------------- Date: Tue, 16 Feb 1999 From: Jason Lile Subject: Re: E36 Stuff Duane Collie wrote: > > >Subject: > > > >Can anyone who has done the following repair/preventive measure please > >shed some light on this subject. As I understand it, from D. Finch's > >explanation, the problem is that the right (and eventually the left) > >rear sub frame where the control arm is mounted to the body may be > >susceptible to fatigue (especially on cars with modified suspensions > >and/or race tires). > > While this can and does happen, my understanding from the pros on the race > teams is that this is only caused by excessive bottoming out of the suspension. Well, I wouldn't go that far ;) We sold a 94 325i AT car with 20k miles to a 5' 2" female school teacher a couple years ago. In those two years she has put about 10k miles on the car (I doubt she bottomed it out racing over too many railroad tracks ;)). She just had this very expensive repair done a few months ago. I think this problem will become more and more common as these cars get older... regardless of how they've been driven. FWIW, IMHO, IME, etc... ___________________________________________________________ Jason Lile Administrator Parts Manager BMW Parts Digest Zionsville Autosport [url=http://www.zionsvilleautosport.com]http://www.zionsvilleautosport.com[/url] -------------------------------------------------------------------------------- Date: Tue, 23 Nov 1999 From: Marco Romani Subject: Re: [uuc] E36 M3 Sub Frame Cracks Some one today mentioned to look for subframe cracks on E30 M3 as part of a used car inspection. Well all you E36 M3 types guess what? We too are blessed with the cracked subframe problem. I replaced mine last week due to both motor mounts practically not being mounted to the subframe. Big cracks and actually some missing metal. The replacement subframe was of a different design of the original one, fewer holes and thicker metal where the engine mounts are bolted. The new subframe has a redesign date of Jun 98 I believe. Symptoms where a squeaking metal on metal noise when going from lock to lock on the steering wheel and a general feeling that the front end of the car wasn't attached correctly. Yes the car visits the track at least 8 days a year, but with only 60k miles I was surprised to see cracks that bad. I suspect the stiffer suspension has something to do with it, HR and Konis. Watch out and becareful out there. Marco 95 M3 -------------------------------------------------------------------------------- Date: Tue, 16 Feb 1999 From: Steve Walsh Subject: RE: Cornelis (KC) Kome asks about rear sub frame failure. I have experienced both to one degree or another. There are 2 distinct failure modes. The first are the 4 mounting points for the rear sub frame or differential carrier. On non-M3 (like my 325is) the mounting points are not reinforced, as they are on the M3's. They tend to fail in the following order: Rear passenger side, forward passenger side, forward driver side, rear driver side. In my case the rear passenger mount had completely torn around it's circumference, and the forward passenger side had torn 270 degrees around the mount. The forward drivers side mount had also cracked tangentially from the mount. The repair requires removal of the rear suspension, differential, fuel tank, rear seats rear carpet, exhaust, battery, yadda yadda... In case the forward differential carrier cross member was also replaced. In short, many hours, big $$$. Despite being out of warranty (88K miles), in did manage to get BMWNA to pick up the tab. For non-M owners the M3 reinforcement plates are available, and these are the part numbers: 41 00 2 256 495 41 00 2 256 496 41 11 2 256 497 41 11 2 256 498. They each cost $25.73. Note: they require the aforementioned rear sub chassis disassembly to install them ! The second mode of failure is the rear trailing arm bushings and mounts. This is the failure mode that David Finch has reported in detail in the past. In short, the rear trailing arms mount to the chassis under the rear toe adjustment plates. These plates are held to the chassis through 3 bolts. The threaded receptacles for these bolts are prone to fail (circumferential cracks), and under extreme situations will tear the 'hat' from the chassis. In my case I was lucky that there was no cracking of these points when I replaced the rear bushings. In my experience the best thing to do, if you suspect damage (mysterious clunks), is to check it early. Even though replacing the rear bushings cost me about $750, it is certainly cheaper that repairs David Finch described. The health of the bushings is directly related to the stress placed upon them, and visual inspection is difficult, at best. If they are worn, then they are not anchoring the trailing arms correctly. This movement, and the stress of cornering will transfer additional torque (stress) to these 3 mounting points. I have read a possible method for 'beefing up' these mounting points, but don't remember where I read it. Check at the NJ chapters web page [/QUOTE]
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