Knocking sound when starting and ending spin cycle

Question

Bosch Washing Machine

Guides and repair information for washing machines produced by Bosch, a German engineering and technology company.

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gumpo @gumpo

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crwdns2931729:0crwdne2931729:0: Sun 26, 2025

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Knocking sound when starting and ending spin cycle

Hi fixers,

I've got a Bosch VarioPerfect Serie 4 washing machine that has started knocking loudly when the machine is ratcheting up or down from the spin cycle. The spin still works and the machine doesn't excessively wobble or move around. It'll knock very loudly, very quickly (3 knocks per second maybe) for 20-40 seconds when working up to the spin cycle, then it'll stop, then start again when the spin cycle winds down. During the normal wash cycle, it works perfectly. Whisper quiet.

I found a manual online but it didn't have any useful info. And I haven't cracked the machine open yet, so I can't say what's going on inside at this point. This will be my first time dissecting something larger and more essential for living than a sewing machine, so any insights are appreciated.

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Hey @mikeb44808 , @jayeff

Thanks so much for the advice, y'all and sorry for the delayed response. I took a few days to look into it and the dampers seemed to be the likely candidate. I watched a tutorial on how to change them out, and located and priced replacements parts. The drum didn't knock when I manually pushed it with my hands like in the tutorial I found, but everything else seemed to be exactly as described. So far so good, right?

Then all of a sudden, after 4 months of knocking, the sound has just...stopped out of nowhere. It's like the washing machine knew I was talking about it. Which is good news, I reckon? But if it starts up again at least I know what to check first.

Jayeff, the model number is WAN28121 /23

crwdns2934271:0Yan 1, 2025crwdnd2934271:0 gumpo crwdne2934271:0

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jayeff @jayeff

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crwdns2931729:0crwdne2931729:0: Sun 26, 2025

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Hi @gumpo

What is the model number of the washer?

90% of the time a knocking sound during spinning it due to faulty suspension rods which are positioned to hold the tub in place.

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crwdns2934285:0crwdne2934285:0

Hey @mikeb44808 , @jayeff

Thanks so much for the advice, y'all and sorry for the delayed response. I took a few days to look into it and the dampers seemed to be the likely candidate. I watched a tutorial on how to change them out, and located and priced replacements parts. The drum didn't knock when I manually pushed it with my hands like in the tutorial I found, but everything else seemed to be exactly as described. So far so good, right?

Then all of a sudden, after 4 months of knocking, the sound has just...stopped out of nowhere. It's like the washing machine knew I was talking about it. Which is good news, I reckon? But if it starts up again at least I know what to check first.

Jayeff, the model number is WAN28121 /23 — gumpo

score 0 · Answer 1 · 2025-01-26T09:13:56-07:00

Mike B @mikeb44808

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crwdns2931729:0crwdne2931729:0: Sun 26, 2025

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Hi @gumpo

My guess is your main washing tub dampers are shot. The washing tubs are commonly held by springs supported by several dampers so if the washing load is unbalanced, it kind of moves around a little. If it turns fast or very slow, the tub does not have the time or force respectively to slam against a side. In my case, the symptoms were the same, and I did see some oil leaks below the machine. Mine were oil filled. They are relatively cheap and easy to replace in most cases.

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Hartmut @hartmut88094 crwdns2934065:0crwdne2934065:0: 1 · Answer 2 · 2025-11-05T03:55:41-07:00

Dear User, thank you for your short video - it's very helpful. The sound I hear is a bright metallic sound.

Possible reasons:

a) a loosen spring on the top left and right side of the tub. Open the door and try to move the tub by hand to the left and right. Do you feel suspicious movements? Repair is easy by opening the top cover (3 screws from the backside. Shifting the top cover with some force to the back). You should see the springs top left and right.

b) It could also be the heating coil which is located between drum and tub on the lower side in the tub. The heating coil is fixed in the tub with a metal bracket. If this bracket is broken, the heating coil is free moving and may hit the drum during spin by unbalanced laundry. ATTENTION: If the heating coil gets broken, you have a direct connection between life parts and grounded metal parts. your fuse should trip. This repair should be done by a professional! (danger of electric shock).

As always: Before you open the washing machine cabinet, unplug the washing machine from mains:-)

Bosch Washing Machine

Knocking sound when starting and ending spin cycle

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