w124 estate e320 1994 knocking from rear/ replacing rear sub frame advise sought

robbieesprit

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OK, so my trusty old w124 estate (1994 s124), has always had a bit of a whine coming from the rear, some times it would go when i turned left so thought it was a rear bearing. Then one trip I stated to get this knocking, it came and went, but was quite bad, so i limped the car home. I suspect cv on drive shaft...
Car has done 240k miles, I bought it with 185k, and i suspect its original running gear...
I managed to get hold of a second hand rear sub frame, complete with hubs shafts and diff etc, chap said it came from a car with no issues/ no noise , so i thought i would drop the old and replace with this unit. This would give me time to inspect the old units bearings etc..
I have never done this before so this is a shout out for any tips? ill be working on my drive.
id like to keep job as short as possible, my car is not a show car, but much loved family/ work hack, with pretty much everything else working ok (apart from sun roof), so it just needs to work. Im not into up grades as i love the softy wofty ride of the original set up.
should i replace any rubber mounts at the same time, which are the good ones to go for?
Can i keep my shocks in place without depressurising the self levelling system?
I did look in the haynes manual but doesnt really cover this topic.
any advise greatfully received, many thanks Rob.
 

GP801

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This will quite a challenge on the drive but your post suggests you know what you are doing and can handle it. The main issue will be corrosion on the subframe mounts. Unless you are very lucky these are likely to need some remedial work/welding. Ours had been Dinitrolled but still had some rust when refurbished earlier this year. Luckily it did not need major repairs. Replace all the mounts/bushes whilst you are there. Still available from MB and not too pricey. Replace the diff seals if you can and also check the brake pipes. I think the subframe has to come off to replace the brake and SLS pipes so n=might be worth doing at the same time. Good luck!
 
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robbieesprit

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Just starting to line things up now, tools and materials, probably start in the new year....
I hadnt considered the condition of the mounts as not mentioned in MOT...but yes could be an issue ill check...
I use different rust killer, one called Fertan, only recently started to use after i read about it in practical classics mag. I put it on some rusty bits on the kids bikes as a test and its worked remarkably well.
I have a heat source, (plumbers torch), and also a half an old hot tub lid to lie on...
And yes, good call to check the brake lines....
The good bit is that I already have the replacement subframe here so i can see what im dealing with, my first task will be to wire brush replacement subframe, Fertan it, then paint...
Could be a challenge on the drive, agreed, but i have two spare trolly jacks, and might make up a ply jig to help with lowering and raising the frame....
Ill up date this post with how I get on...
 

millo777

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Just a thought, but my 320te had similar symptoms when the prop shaft centre bearing failed. Horrible whining noise, then it started knocking when it ripped the bearing mounting off. Either way, its worth checking the prop shaft bearing and flex discs while you're under the car.
 
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robbieesprit

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Hi Milo777, thanks for the post, yes thats a good call, do you know how test to prop bearing? disconnect from diff and give a good shake? in not sure of the location of this bearing, would it be at the end way from the diff? also, not aware of the flex discs, are these worth replacing as part of the job? cheers
 
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robbieesprit

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OK Quick update:
Once I had removed the rear n/s wheel, the cause of the noise became apparent. The brake disc had play in it...so wheel bearing.
My plan, having bought a second hand "good no noise" subframe assembly (with everything attached inc hubs, shocks etc) was to replace one frame for the other, as i do not have equipment to press out the large estate bearings. I could then refurbish my subframe assembly at my leisure , while the second hand subframe would keep me on the road, and buy me some time.

So plan was to remove excess weight in the replacement and sub frame to make it easier to install. So I removed the self levelling shocks, then the brake callipers...and then at this point I find that having removed the callipers, I found the wheel bearing is shot on the n/s. :rolleyes:

So im now thinking, ill have to remove, and get bearing pressed out at a local garage. Use of car now not an issue was we are in lockdown.

Odd thing is that my car has vented discs at the rear, while the second hand subframe has solid disc, which is correct?
 

Doodle

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They both are, for their respective fitments. Disc size varies with age and specification of vehicle.
 
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robbieesprit

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Hmmm thats interesting...

Mines a 1994 e320 petrol estate, replacement subframe from a1995 E300D estate, i thought they would be simular...clearly not.
I wonder if they are different if car is 7 seat or 5 seat? mines a 7 seater...?
Might have to check with MB via my vin number....
 

Doodle

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No, it's mostly determined by engine size and destination market. An E300D has a little over half the power of the E320, hence the smaller brakes.
 

grober

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The DIFF may also be different [ratio wise] and half shaft couplings design changed at least once. BEWARE mixing and matching components from different ages of the same model. Mercedes back then had a continuous program of component improvement over the lifetime of any model- so compare carefully for fit/design before swapping.
 

d w124

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Diff and driveshaft will be different on the one you bought,not sure about the bearings.Another thing is that once you drop yours,there's a 99% chance that you gonna need welding on the mounting points
 
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robbieesprit

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To be honest, when i bought my car in 2013 with 185k miles on it, and with no service paperwork, so i have no idea what been changed in the past...im only assuming what is on my car is original...
Underside, and subframe all look in very good condition. So will leave in subframe place, and tackle the bearing.
I will look for some ID numbers on the diff, and compare to mine in the car....
Might be in the future i will have to do full rear strip out and do arches, jacking points, inner arches, rear windows, subframe mounts......
i'll need somewhere dry and out of the wind and rain for that project! and plenty of time!
Thanks for comments, very useful....
I will update with progress....
 

GP801

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Those wheel bearings can be a pig to do. Both rears on ours have been replaced in the past few years. One came out easily. I think the advised time to do the job according to the manuals is 3.5 hours per side. The other more recent one would not budge despite the best efforts of the crew at PCS. Ended up fitting a complete new hub.
 
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robbieesprit

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Yes, from what I can make out the estate bearings can be a mission.
Im going to have a go with what I have (10 ton press) and see what the car gods deal me.
 

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