[TurboWeasel]

Thought I'd bung the revised tensioner in today as a preventative maintenance as the old ones are known to have a weak piston which bleeds off oil pressure, causing chain slack.

Also did a few other bits of what I call 'Cheasy' (cheap and easy) maintenance whilst I was there.

Old tensioner - 11 31 8 576 201
New tensioner - 11 31 8 490 219

I wasn't expecting any change afterwards but the engine is now a lot smoother, quieter and a LOT more responsive off boost now.

I always was a bit underwhelmed by it's lack of response low down and slight coarseness when accelerating, but that is all gone now As the car was only on 38K when I got it, and my first BMW diesel, I just figured that's how they are, but clearly not!

Anyway, here is the tensioner. It's a bit of a mission getting to it and has to be done by feel and/or a mirror/phone camera.



You can get tools onto it, just! The tensioner is made of soft aluminium (probably why they don't last) so be careful not to round it off.





Whilst I was there, I replaced the oil cap housing and oil cap as the O ring had shrunk, causing a leak. You can replace just the O ring but I chose to just replace the whole lot.



Whilst under the back, I replaced all the rusted out heat shield nuts, ground the rust off the wishbone bolts and caked them in body wax. When I got the car 25K mile ago, it was all mint and bright metal under there, so it only took 2 winters to completely rust the wishbone bolts! They are adjustable, so well worth protecting them to make future adjustment easier.



And there you go. Easy things anyone can do to prolong the life of these old cars

[Allworth]

Thanks for a write up, I might actually do a tensioner as a chain on my old N47 sounds like is slapping against something at a cold starts when outside temperature is low.

[gac]

This is the top tensioner you mentioned in another thread, right? Is there access from above, or only from below?

[bishbosh]

My car's coming up for 10 years old and just passed 162k miles so might treat it to a new tensioner.

In the last 6 months I've done the pcv valve, oil cooler gaskets and cleaned the intake manifold so anything to keep it running well.

[dave550i]

Did you make sure that the cams were not ready to jump over? like when on top dead centre i remember changing the tensioner on my E30 M3 to the E36 one and the bastard jumped a tooth when i unscrewed the old one they were oil pressurised as well had to pump it up with a oil can finished up a real pain in arse

[TurboWeasel]

Originally Posted by gac

This is the top tensioner you mentioned in another thread, right? Is there access from above, or only from below?

Yeah I did it all from above. Didn't even need to put the bonnet in the service position.

It's very tight and fiddly, but doable.

There might be more access from underneath, not sure, but anything that involves a lift, I give it to someone else to do

[TurboWeasel]

Originally Posted by dave550i

Did you make sure that the cams were not ready to jump over? like when on top dead centre i remember changing the tensioner on my E30 M3 to the E36 one and the bastard jumped a tooth when i unscrewed the old one they were oil pressurised as well had to pump it up with a oil can finished up a real pain in arse

That is a very good point, but no, I just wound the old one out and stuck the new one in. It certainly doesn't sound or feel like it jumped time.

I know of the tensioners you mention as my old VWs had a similar one, but there was no residual oil pressure in the tensioner I took out. Either it only holds pressure whilst the engine is running, or the old tensioner was bad. The reason they changed it was for not holding pressure, so likely the second reason!

The tensioner is sprung loaded, and given the big chain wrap around the N57's single cam sprocket, it's more likely it would have been a gradual slackening of the chain whilst the old tensioner was unscrewed, which the new one would take up again.

Diesel timing is more critical than petrol, and the cams and fuel pump share the same chain, so any jump in timing would be immediately apparent. Diesels run like a badgers arse if the timing is off. In my experience, there is also considerably less cam whip on a straight 6 than there is a 4 cylinder.

I know where you're coming from though..... and I hope I got away with it

[Eddamoo]

Originally Posted by dave550i

Did you make sure that the cams were not ready to jump over? like when on top dead centre i remember changing the tensioner on my E30 M3 to the E36 one and the bastard jumped a tooth when i unscrewed the old one they were oil pressurised as well had to pump it up with a oil can finished up a real pain in arse

Yeah i remember reading a post or 2 about this... maybe if the engine was freshly switched off and one of the cylinders was under high compression, it would be exerting that force on the chain and it could slip when the tensioner is loosened.

I would have thought a mitigation against this would be to rotate the crank pulley until a 'loose' point in the cycle - where you can rock the pulley back/forward with relatively little force.

Unfortunately in a 6-cyl engine, there will always be 1 cylinder in a state of compression (therefore 1 will also have its Cam-Lobes down) so its a risk. To mitigate further, go for TDC and take out the Cyl-1 Injector perhaps.

EDIT: Dont you just love AI - These are the forces on the Cams/Crank for an N57 at Cyl1 TDC:

Cylinders:
1. TDC - Maximum 18:1 compression
2. 120 degrees before TDC (on intake stroke) - Moderate/rising compression 6-8:1
3. 240 degrees before TDC (on power stroke) - Low compression
4. 360 degrees before TDC (on exhaust stroke) - High residual combustion compression 12-15:1
5. 480 degrees before TDC (on intake stroke) - Low/No compression
6. 600 degrees before TDC (on compression stroke) - Low compression

Valves:
Two cylinders (5 and 2) are in valve overlap with both valves open
Three cylinders (6, 4, 3) have both valves momentarily closed

[bishbosh]

Newtis makes no mention of any special requirements when changing the tensioner. Just whip the old one out and pop the new one in.

I can't believe the N57 chain would skip teeth unless the crank/cams were excessively worn as the chain hugs over 3/4 of the sprockets.

[ushafiq]

Now, this has given me some motivation…I didn’t realise that tensioner spec were updated, and changing it might improve car’s response - my car is 64 plate 435d, covered 63k miles - recently noted exhaust tips were getting little sooty, and car was little low on power when cold - dpf variables all good, and EGR fairly new and cleaned too - always used premium fuel with frequent oil changes in between AD services - I am now settled on getting the manifold cleaned with intake ports walnut blasted - I can certainly add tensionor upgrade to the list - inbetween all this, I also had a local carbon cleaning specialist who performed H2 Clean for £140 - I wasn’t expecting a lot from it but interestingly, It has made a difference! I too foucs on prevention, and already coated suspension hardware underneath with wax & underbody paint.

X35ds are great cars but with aging it will be more and more challenging to keep them operating at optimum level - therefore, knowledge and experience sharing by fellow members will be a great asset to keep our x35d’s in good nick for long - all the best 👍

[ade555]

Sorry but how can a tensioner improve response. Don't belive that one bit to be honest. If you don't have problems with chain leave it alone, stretched chain, worn teeth with new longer tensioner you might be asking for problems.

[bishbosh]

I don't think the tensioner plunger is longer, just that it doesn't lose pressure as quickly.

[Eddamoo]

Originally Posted by ade555

Sorry but how can a tensioner improve response. Don't belive that one bit to be honest. If you don't have problems with chain leave it alone, stretched chain, worn teeth with new longer tensioner you might be asking for problems.

Slop in a tensioner could cause advance/retard on the crankshaft position relative to the cams so its believable to me.

Back in the day i had an old VW PD engine (which admittedly also had cam-driven injectors), but that engine was EXTREMELY sensitive to camshaft timing. 1-2mm on the cam pulley could make a significant difference to how it behaved at the top/bottom end.

They never ran properly if a garage changed the cambelt without the proper locking tools. The cars came from the factory with an optimised 'timing offset' which was written on the cam cover which often faded by the first service!

[ade555]

Originally Posted by bishbosh

I don't think the tensioner plunger is longer, just that it doesn't lose pressure as quickly.

I didn't compare my self but looked in to this about year ago. If someone compare them on their own car please do share. This image will show that is longer, this might well be where old one is worn out.

[TurboWeasel]

Those are completely different tensioners. Could be a really early N57 in that picture?

Looking into it a bit more, it seems the tensioner was updated multiple times.

My 30d is 09/2016 build date and had tensioner no. 11 31 8 576 201, which is not shown on RealOEM.

There is also a tensioner 11 31 8 586 699 which ended in May 2019.

The new tensioner 11 31 8 490 219 is May 2019 to present.

My old one and the new one are identical externally. Same piston length and spring strength. The only change is to the piston inside it.

I questioned myself how a tensioner could bring about so much improvement, but it did.

It always had a slightly wobbly idle when hot like it was running on 5.5 cylinders, which I could only feel if my leg was resting on the centre console, so it was very slight.

That is also gone now. The idle is rock steady and smooth.

It was always good from cold, so it stands to reason if the piston is bleeding off pressure when the oil heats up and thins out, it would cause a bit of chain slack.

You don't have to believe me. I am only reporting my findings. I have done 200 miles since fitting the new tensioner and it's still the same, so it wasn't a one off or placebo.

BMW updated the tensioner multiple times for a reason, and this post was merely a suggestion to change it regardless as it doesn't hurt to run the latest parts. If people get the same results as me, then great. If not, no harm done and it's peace of mind the chain is as taught as it can be.

Obviously proceed with caution at your own risk. I have also not seen any special mention of setting the crank to a specific angle before replacing it, so it would appear to be a safe swap.

[TurboWeasel]

Originally Posted by Eddamoo

Slop in a tensioner could cause advance/retard on the crankshaft position relative to the cams so its believable to me.

Back in the day i had an old VW PD engine (which admittedly also had cam-driven injectors), but that engine was EXTREMELY sensitive to camshaft timing. 1-2mm on the cam pulley could make a significant difference to how it behaved at the top/bottom end.

They never ran properly if a garage changed the cambelt without the proper locking tools. The cars came from the factory with an optimised 'timing offset' which was written on the cam cover which often faded by the first service!

Exactly. Diesels have a tiny injection window. Any slop in the timing results in sub optimal running.

[TurboWeasel]

Originally Posted by ushafiq

Now, this has given me some motivation…I didn’t realise that tensioner spec were updated, and changing it might improve car’s response - my car is 64 plate 435d, covered 63k miles - recently noted exhaust tips were getting little sooty, and car was little low on power when cold - dpf variables all good, and EGR fairly new and cleaned too - always used premium fuel with frequent oil changes in between AD services - I am now settled on getting the manifold cleaned with intake ports walnut blasted - I can certainly add tensionor upgrade to the list - inbetween all this, I also had a local carbon cleaning specialist who performed H2 Clean for £140 - I wasn’t expecting a lot from it but interestingly, It has made a difference! I too foucs on prevention, and already coated suspension hardware underneath with wax & underbody paint.

X35ds are great cars but with aging it will be more and more challenging to keep them operating at optimum level - therefore, knowledge and experience sharing by fellow members will be a great asset to keep our x35d’s in good nick for long - all the best 👍

Can't promise anything but give it a try Not many BMW fixes are cheap and DIY doable, so you have nothing to lose

Yeah these cars are getting on a bit now. BMW did a great job with the paint and most still look brilliant, but they're starting to age underneath now. The F3x N57 engined cars tick many boxes for me, so I plan on keeping it running for as long as possible

[bishbosh]

Mine's a 2014 car so even older, I've received the part today. Bought from BMW Ebay shop which had a coupon saving £9

I'll take a picture of both tensioners when I get round to fitting the new one 🙂

[danb1979]

Said tensioner is here; it's the latest one for the N47s too

https://www.ebay.co.uk/itm/196189084....c101465.m3507

As said above, there's a discount to be had, so it's £51 delivered

[Watsey]

Originally Posted by Eddamoo

Slop in a tensioner could cause advance/retard on the crankshaft position relative to the cams so its believable to me.

Back in the day i had an old VW PD engine (which admittedly also had cam-driven injectors), but that engine was EXTREMELY sensitive to camshaft timing. 1-2mm on the cam pulley could make a significant difference to how it behaved at the top/bottom end.

They never ran properly if a garage changed the cambelt without the proper locking tools. The cars came from the factory with an optimised 'timing offset' which was written on the cam cover which often faded by the first service!

I appreciate the tutorial in this thread but I also don’t agree that a new tensioner would make any difference in terms of timing.

The tensioner will act on the slack/return side of the chain loop. The ‘driven’ side of the chain loop will always have the chain in tension between the sprockets, and any effect on timing will only be a product of chain stretch rather than chain tension.

I’ll leave my tensioner as-is for now, because the chain isn’t making any of the telltale noises, but it’s good to know that it’s an easy-ish job if needs be.

[Allworth]

Originally Posted by Watsey

I appreciate the tutorial in this thread but I also don’t agree that a new tensioner would make any difference in terms of timing.

The tensioner will act on the slack/return side of the chain loop. The ‘driven’ side of the chain loop will always have the chain in tension between the sprockets, and any effect on timing will only be a product of chain stretch rather than chain tension.

I’ll leave my tensioner as-is for now, because the chain isn’t making any of the telltale noises, but it’s good to know that it’s an easy-ish job if needs be.

I understand what you on about. But is a bit more complicated if you add vibrations and oil into equation. Simple example would be a bicycle with a stretched chain. Put a bicycle on a stand with an endlessly stretched chain and turn pedals, it will work as long as it's on the stand and still. Then try to ride it with a stretched chain and it will surely misbehave.

For the sake of experiment I have ordered tensioner, I think it should be easy for me to see a difference on my N47 with 120k miles that is making slapping noise for a first 20 seconds on negative ambient temperatures, although it may take some time to figure it out.

[bishbosh]

Bmw do have a tool to measure chain stretch. It fits in place of the tensioner and has marks which show if the chain is within tolerance.

My engine is by no means noisy, I have had the n47 engine with knackered sprockets /guides so I'm attuned to the sound these engines make. I'll be interested to see if the new tensioner makes a difference.