BMW 318i rear suspension the quest of the awfully designed dampers

[Just-another-joe]

I've been meaning to add to this forum for some years now, it's just that every time I've fixed something; car, bike, lawnmower, it only seems to be afterwards that it dawns on me that I should have taken some pictures instead of hyper fixating on what's in front of me. 

I've owned this car for the past three years (BMW 318i) and although I really enjoy driving it and it actually having been the first BMW I've owned, it would seem that it certainly hasn't been the most reliable car I've ever owned. Not that anything catastrophic has ever happened (until yesterday, but I'll get to that shortly) but it really does love to throw up an error code on the dash, I think I've pretty much collected most of them now. Engine management - from what I believe maybe the timing chain sensor, wheel speed sensor - which was on a really hot day and seemed to fix it's self and more recently the brake pad sensors - though all the pads seem to have plenty of meat on them? 

 

Anyway, 

Yesterday I was driving up a B road, up hill, when the back N/S wheel went over a slightly sunken drain cover. It gave me the sensation you get when one wheel slightly looses traction. This was followed be some squeaking and the back of the car suddenly felt like I was driving an old mattress down the road. I pulled over to have a quick check and there was oil leaking around the lower shock mount and around the dust boot. 

This all happened less than a mile from home (always seems to be the way) though I'm quite grateful i wasn't miles away. 

I've popped her on axle stands today and taken the shock out and well, mind the pun, have been pretty shocked myself on how these OEM shocks are put together. Absolutely FULL of oil. Clearly mine have had it but the dampening abilities are awful. 

 

Next step is to buy a couple of new dampers and shock mounts and a set of female torx sockets to remove the lower damper mount that I won't be re-using as it looks like it's been sat in the sea since 2011. 

Are there any dampers that anyone recommends? I've been saying it for some time now and although I enjoy driving this car it's probably time for me to get something a bit more practical, like a medium sized van. 

Been looking at the likes of bilstein and NAPA but considering 'eBay special' just to get it fixed and for sale. Anyone got any experience with the likes of 'drexler Gforce' or unbranded dampers?

Hope you've enjoyed my first contribution to the forum,

Joe

[twosmoke300]

Arent they meant to be full of oil? And gas obvs 🤣

 

KYB or Bilstein FTW

[Just-another-joe]

You'd think so wouldn't you? 

However, these seem to me to be a piston inside a cylinder that's full of oil. There must be an air (gas) gap there somewhere? 

Silver cylinder sits inside rusty AF cylinder 

In remaining oil 

Piston compresses oil, dampens rear of car. Alongside, spring which goes bouncy bouncy.

[Just-another-joe]

Somehow, the torque of the rear wheel under load (uphill at 40mph), with added sudden drop into the drain cover on the road must have been the perfect combination to separate the silver cylinder and the top housing for the piston. 

Since starting this post I've decided to buy a used rear shock off the same model car and fit it as a plug & play. Found one on eBay for £23 which:

a) will save me having to do the other side too

b) will save on having to buy additional parts

c) will mean I can get the car up for sale sooner

[Asimo]

1 hour ago, Just-another-joe said:

There must be an air (gas) gap there somewhere?

Many dampers are NOT gas-pressurised.

Just a cylinder with a piston that has spring loaded valves in it.  Cylinder completely full of oil. Sometimes the cylinder itself is the damper tube you can see, others have the cylinder within another tube that is also full of oil.

Dampers never seem to be a priority of German makes. (Those perfectly smooth roads)

 

[aotb]

I put Bilstein B4s on the back of mine, better than the shagged originals but it’s hardly a handling machine. Got Monroes to go on the front, which at 190k should see it out. 

[Just-another-joe]

@aotb it's impossible to know what to do. The perfectionist in me is well up for an upgrade along side polybush kit to stiffen things up a bit. The reality though is that it's not a fast car at all really and 'improving' the handling of this car that's probably going to need a fair whack spending on it soon probably isn't the greatest way of securing my finances.

In other news, I found out through using my friend chat gpt that the used damper I screenshot above won't actually fit my car as it's pre-LCI which apparently there were upgrades to the dampering so couldn't match the O/s and might make it feel uneven which I don't fancy passing onto a unaware buyer. 

So it's back to the drawing board and possibly back to buying a set and doing both sides.

[Crackers]

Shocks seem to fail on these quite regularly, I'd buy a new pair personally as a used one will probably just do the same again eventually. 

I implore you to change the top mounts while you're in there. They're £15 for a set and they absolutely will fail if you leave them alone. 

This is what happens when they let go and then you have no damping at all, plus will ruin the chroming on the shock ram if you drive any distance with it smacking against the body.

 

[Just-another-joe]

@Crackers ooft this looks like some head scratching! What was the fix? 

I've seen this kit but for less than £20 I'm questioning the quality.

https://ebay.io/m/YIUdPS

It looks like I'm going to go down the new damper route. Probably not quite as bad as Chinese dampers but probably not as good quality as bilstein b4's that were suggested above.

[Crackers]

Easy fix, by getting the shock off you've already done 90% of the work so it makes sense to replace them while you're in there. You'll just need to pull the bump stops out from your old mounts - they might fall apart so could be worth buy a new pair since they're cheap as well. 

I've no idea on the bottom mounts as mine were okay, I got my top mounts from BMW as I work for them but to be honest, any reputable brand should do.  IIRC it's a pretty universal part number across 1 series and 3 series, all powertrain variants. I was going to use these ones but the parts arrived through work quicker. 

https://www.partsinmotion.co.uk/car-parts/steering-suspension/mountings-bushes/kybtopstrutmountingrearsm5752-detail?srsltid=AfmBOoq0FDefTCHP3Eba2eua_sLuVIrczaKBz4D-J7l_tL22APbLYXkb

[Sunny Jim]

Just shout if you need a hand @Just-another-joe. I'll try and dig out that HG test kit this weekend.

[Just-another-joe]

To kick off from where I left off,

After deciding to go budget for now I bought some cheap dampers and a mounting kit which included bottom mount, top mount, and everything in-between.

Managed to get two rear dampers for the steal of £54.20. although I guess I'll see how well spent it was over the following year or soThey were easy enough to assemble and seemed quite decent quality (made in Germany on the box so 🤞)

Got the N/S off first, assembled the new damper, lay down on the floor on a large piece of cardboard and thought to myself "jesus the rear axle looks rust". So, yet again the need to change the rear damper turned into yet again another 'whilst I'm here job'. 

So I got back up the floor, popped a wire brush attachment on my grinder and set to work. Popped some rust converter on there, waited to dreaded waiting time, popped some underseal on top and lay back down on the floor with damper in hand.

Managed to compress the damper, pop it into place and 'tah dah!' she was set to torque into place. 

After getting advice by @Crackers to replace the top mounts I was glad that the kit came with two new top mounts. Popped them out the packaging, lined them up with the top strut of the damper and... Well, they didn't fit. I'd got my trolley jack to push the damper up but there wasn't enough thread to be able to use the new top mounts. The old mounts however, fit like a dream... I'm now however filled with anxiety after seeing the pictures I was sent in this thread. 

Time to do the N/S,

This is where I had to make a decision because after popping the wheel off, releasing the shock and holding it my hands, it was quickly apparent that the previous owners had already replaced the damper in the past and well... It was far better than the shock I was replacing it with.

That's right, I was replacing a Monroe shock for an eBay special that cost a third of the price. But I told myself that it's better to have matching shocks on both sides and that although it's a Monroe shock it looks a bit tired around the edges. 

So for now, they're on. BUT, I've ordered new top mounts so they'll be out again by next week haha! Oh ye and also the coil spring on the O/S needs replacing so that was a nice suprise too. 

I've been for a bit of a drive and I've decided that it definitely feels stiffer. But I've never driven another 3 series so I'm not too sure if I'd got used to it feeling like a saggy old sofa bumbling down the road. It feels a bit stiffer, a bit twitchy-er and not that I've really tried pushing the car (too old and sensible for that these days) it does feel as though it handles maybe a bit better. It doesn't have that awful crashing feeling when going over speed bumps or anything so overall I'm quite happy with it. 

So ye, done for now until I replace the top mounts, coil springs, inevitably change the dampers for a higher quality at some point and oh ye, all the bushes I looked at looked like old chewing gum so I guess they'll all need doing too... Great.