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thehackmechanic

Front Strut Replacement Without Removing Strut Housings

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(edited)

Hey folks. Sorry I'm not posting here much these days (I'm always still reading, though :^). Here's a fun tidbit I'm posting here before I write it up for BimmerLife.

 

Years back, I was curious about whether you could remove a 2002's front strut cartridges while leaving the strut housing in the car—that is, undo the bushing at the top, but leave the housing connected to the steering knuckle at the bottom, tilt it out from under the fender, and compress the spring, remove the bushing, and swap out the cartridge in-place.
 

The answer turned out to be: Yes, you can, if you can find a spring compressor to slide under the fender and squeeze the spring in place, but a) it's difficult to find such a compressor, and b) if you do, you need to be very careful that the bushing's threaded studs and the end of the strut piston don't gouge the paint and the metal on the underside of the fender lip. Again, years back, I bought a hydraulic spring compressor that if you modified it, was able to do this, but not long after I used it, it began leaking horribly.

 

Fast-forward to this week. As part of planning a suspension upgrade in Louie, my '72tii that's the subject of Ran When Parked (and which I suspected was still wearing its original shocks and struts), I became aware of a recently-available spring compressor design with two curved plates squeezed together by a single thick threaded column, and was intrigued because a) it looked like you could fit it on the spring while the strut assembly was still in the car, and b) the bolt you need to tighten to squeeze the plates together is at the bottom where you can reach it.

https://www.amazon.com/YUAN-MacPherson-Interchangable-Compressor-Extractor/dp/B0788C9VFL/ref=sr_1_19?dchild=1&keywords=bmw+spring+compressor&qid=1589929281&sr=8-19

 

IMG_2726-1024.jpg

 

I saw one of these compressors on Facebook Marketplace for half of new, so I bought it, and figured that I'd try the in-situ strut removal again.

 

IMG_2727-1024.jpg

I first pulled off the caliper and undid the sway bar link, then maneuvered the compressor under the fender. I was thrilled that I could fit it onto the spring and access the tightening nut at the bottom, but I didn't seem to be getting enough squeeze on the spring. Remember, I was trying to not only compress the spring to take the tension off it to remove the bushing, but also to shorten the entire sprung length of the assembly so I could swing it out from underneath.

 

IMG_2728-1024.jpg

I re-positioned the compressor so that the bottom  plate was under the bottom cup rather than between two spring coils. This squeezed the spring downward quite a bit more. Placing a rag over the strut bushing so I wouldn't scratch up the fender, and using one foot to stand on the steering knuckle to force the bottom of the strut housing as low as possible, I WAS able to tilt the top of the assembly out from under the fender.

 

IMG_2730-1024.jpg

From there, the removal of the bushing and spring are the same as if the assembly is laying on the floor, though you do need to take care not to have the weight of the whole thing lean too much on the ball joint, which is at an unnatural angle.

 

IMG_2732-1024.jpg

Of course,  the real question was then whether the gland nut holding the strut cartridge in the housing would come out without a fight to the death, because if it wouldn't, I would've needed to remove the whole housing so I could lay it on the floor and apply maximum leverage. Fortunately, a little heat, a little wax, and two pipe wrenches pulled it off. The cartridge inside did indeed appear to be the original oil-filled damper.

 

IMG_2733-1024.jpg

 

So, it works. You CAN use this kind of compressor for an in-place strut housing replacement. But just to repeat:

  • You need to be REALLY careful not to have the strut bushing scratch the hell out of the fender lip, and beyond that, it is likely to put some gouges in the undercoating up underneath the tower and the inner fender. If you don't want to risk this, don't do it this way.
  • If the gland nut won't come off, you may still need to pull the housing out the old-fashioned way so you can lay it on the floor for maximum leverage.

 

I'm installing a used set of Bilstein HDs I've had laying around, and since they're pressurized gas shocks and not hydraulic ones, they naturally extend to their maximum length, which means that, to get things back in, even with the spring compressed, I'll probably need to wrap a ratchet strap around the top of the strut to compress and shorten it while I maneuver it under the fender.

 

Still, pretty cool, huh?

 

--Rob

 

 

 

Edited by thehackmechanic
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My memory may be a little hazy as it was a long time ago, but I seem to recall doing this replacement without removing the strut--as you did--with a pair of skinny spring compressors--sourced from JC Whitney, I think, back when McPherson strut spring compressors weren't easy to find.  They're not much more than a pair of heavy threaded rods with a hook on one end, & a sliding hook and nut on the other.  Not at all flimsy, just basic.  But they work, and positioned correctly, they'll clear the fender well handily.  But as Rob said, pad the top of the assembly well so as to prevent scratching the fender.   

 

Another suggestion:  loosen--but don't remove--the large nut atop the strut before compressing the spring and removing the strut assembly.  If it's stuck or reluctant, it's much easier to loosen while still attached to the car at both ends.  Just be really careful handling those compressed springs.  They have a lot of potential energy when compressed and can really hurt you if they get loose.

 

mike 

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If you have lowering springs you can usually skip the spring compressor to free the strut, you may need it on a few sport springs to remove the top bearing, but most are loose when removed. And yes pad the top to prevent fender damage a second person helps if one is handy but you can do it alone.

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