M52/S52 vs. S50 Euro Hydraulic Chain Tensioner

[JungleGus]

I have a bit of a rattle in my Alpina 3.3 M52 (basically a 3.3 S52 engine) and I wanted to replace the chain tensioner before I do the vanos. I ordered an S50 one (left hand side in the pic) - am I correct in assuming it will not fit?

I think I already have a hydraulic tensioner, but the movement feels "crunchy" and doesn't move smoothly. Am guessing it's likely that it's the original item on around 110K miles, so this being a wear item at this stage sounds about right?

So - what is the right part number for the M52/S52 hydraulic tensioner? Have been battling to find one that is confirmed to be hydraulic vs the spring.

Cheers,
Gus

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[HenryM3]

The b3 doesn’t have a tensioner mentioned in the Alpina parts for the b3 so therefore it’s a bmw part for the m52. The m52 tensioner isn’t listed as a whole part instead you can buy the parts that make it up individually

[HenryM3]

Looked a bit more The tensioner on the s52 is the same one as fitted to the e46 m3 and cls. P/N 11 31 7 838 675

[HenryM3]

Here’s a pic of the s52 tensioner

[DanThe]

Its an M52 tensioner Gus, same as any other M52 engine

The S50 one has the slot to fit into the chain guide which is different to the guide on an M52

[HenryM3]

So as I will have the same issue, what are you saying DanThe that the b3 is a standard M52 tensioner or it’s the S52. Which looks hydraulic in the pic.

[DanThe]

They are all hydraulic tensioners

[Brianmoooore]

Here’s a pic of the s52 tensioner

Nothing can be inferred from the pics. in the ETK, or its online versions. The pics. are of a generic part, and in many cases look nothing like the actual part.

[JungleGus]

Good old ETK...

OK - so I have a hydraulic tensioner....do they fail? There doesn't seem to be smooth movement of the piston. My old M52 had the spring tensioner and this one seems different (I can't get the piston out but looks hydraulic).

S50 EU engines are out, but the S54 tensioner isn't slotted? So that's the upgrade version? Or are all new M52 tensioners hydraulic? Unsure if I'm just overcomplicating this

[DanThe]

The M52 is hydraulic yes, they all have springs inside to push against the chain guide when the engine if off/starting/low oil pressure, this spring wears with age/heat and loses its pressure. The bore/piston of the tensioner can also become scored/worn and as such oil will pass reducing its effectiveness, therefore replacement of the tensioner is recommended

Good pic here showing new vs old from an E46 330i
This looks like your pictured tensioner to me, its the same as E36 singla vanos M52 tensioners

If you cant get the piston out then it may have a wire clip holding the two parts together, M52 (early single vanos) tensioners dont have this clip, or it may be very scored inside which is stopping it coming apart. Either way I would get it apart so you can inspect the parts to see exactly what you should be replacing it with

If you google the part number Henry posted above you can see the S52/S54 tensioner is different to what you have removed

I have a couple of Alpina engines at work so I will try and remove the tensioners over the weekend at some point

[JungleGus]

This is ultra helpful - thanks Dan!

[JungleGus]

Hmmm so - the difference between M52 new from BMW and what was in there....the old one definitely doesn't move smoothly so thinking I should replace?

[JungleGus]

Well, that seems to have sorted the rattling issue - will replace the upper tensioner and the VANOS unit when the recon'd VANOS unit arrives from the US. Still need to try track down which tensioner p/n that one actually is at some point.