1 second engine rattle on cold start up (M271)

[190]

1.6 was only on clc 160 and very early w204 c class c180k

The c180k only became a 1.6 when the blue efficiency model was introduced in late 2008. It had the same power and torque as the 1.8 but with improved mpg and emissions. The 1.6 also did without a balance shaft to reduce frictional losses.

 

[markjay]

Yep bent valves being one of the consequences lol I thought I got lucky with just timing sprockets and chain until it turned over still without compression

My W203 with the M271 Kompressor engine was always properly maintained using 229.5 oil, and I sold it when it still had relatively low mileage (50+ K), so I wasn't worried about the timing gear issue myself. My W204 had the newer M274 Turbo engine so again no timing chain worries.

 

[Oleks1992]

My W203 with the M271 Kompressor engine was always properly maintained using 229.5 oil, and I sold it when it still had relatively low mileage (50+ K), so I wasn't worried about the timing gear issue myself. My W204 had the newer M274 Turbo engine so again no timing chain worries.

Yeah the r171 slk200k I bought also had full service history and only 70k miles on the clock. Sprockets still failed though

 

[TucksMirror]

Yes I see, no avoiding this check then. I’ll make some calls in the morning.

 

[TucksMirror]

Have spoken to a few independent specialists. MSL are going to have a listen to the clip and give me their opinion. I can take it into Hadens tomorrow afternoon and leave it there overnight. Andrew Gayle cannot see it until next week.

Both MSL and Haden believe it to be a timing chain issue just based on the description.

Andrew Gayle’s said they would need it in to listen before proceeding.

Bit stumped which way to go, but it’s small progress I guess.

 

[Oleks1992]

Have spoken to a few independent specialists. MSL are going to have a listen to the clip and give me their opinion. I can take it into Hadens tomorrow afternoon and leave it there overnight. Andrew Gayle cannot see it until next week.

Both MSL and Haden believe it to be a timing chain issue just based on the description.

Andrew Gayle’s said they would need it in to listen before proceeding.

Bit stumped which way to go, but it’s small progress I guess.

Was gonna say that if you was closer to me I'd be able to help

 

[TucksMirror]

Was gonna say that if you was closer to me I'd be able to help

Thanks, that’s kind of you. I have a car I can borrow for now, just to be on the safe side. It may well turn out fine and be nothing to worry about, but I’d rather not risk it unless I’m driving direct to a garage.

 

[Oleks1992]

Thanks, that’s kind of you. I have a car I can borrow for now, just to be on the safe side. It may well turn out fine and be nothing to worry about, but I’d rather not risk it unless I’m driving direct to a garage.

Yeah fore sure

 

[markjay]

Timing chain damage almost always occurs at engine startup (more so when the engine is cold). But timing chain damage rarely occurs while the car is being driven normally.

This is because of the additional stress on the chain when it starts moving from rest, coupled with the hydraulic timing chain tensioner not yet filled with oil thus leading to further slack in the chain, and the dreaded 'jumping one tooth' (or more).

If this happens, the main symptom will most likely be an engine sounding like a "bag of spanners" immediately after engine start up, which in effect is the engine not firing on all cylinders due to bent valves.

So while the car is under investigation due to a suspect timing gear issue... I would minimise the number of engine starts from cold until the situation is confirmed one way or the other.

 

[W1ghty]

Fellow M271 owner here as well with a C200 Komoressor 2009 , now got 92k with nothing to note on start up .
I have been wondering recently is it’s going to be worth just changing the tensioner and chain , not the sprockets which are the expensive bits . I’ve not got an answer to that yet though .

 

[markjay]

Fellow M271 owner here as well with a C200 Komoressor 2009 , now got 92k with nothing to note on start up .
I have been wondering recently is it’s going to be worth just changing the tensioner and chain , not the sprockets which are the expensive bits . I’ve not got an answer to that yet though .

I would say that the camshaft sprocket wheels need to be inspected. If they do show signs of premature wear, then a complete timing gear overhaul will be required, including two new sprockets, new chain, new hydraulic tensioner, and new guides.

But the timing chain itself is not more prone to failure in the M271 engine than in other single-chain engines. So as long as the sprockets are fine, the chain should just be inspected as you normally would, e.g. for slack, guides' wear, and leaking hydraulic tensioner. If there are no issues there, then there's no need to replace the chain pre-emptively.

 

[TucksMirror]

So I have borrowed a car, which gives me some breathing room. I think I’ll disassemble the necessary parts on the drive and get a look at these components before deciding the next step.

It’s a bit tedious that Mercedes have used reverse torx bolts on the engine, which is literally the first time I have come across these. Why can’t the big manufacturers standardise such things

Anyway, after a discussion with my neighbour, if it comes to it he may be able to dig out the cam locks for this vehicle, and he also has a chain crimper.

For now I’ll just focus on inspecting the parts. I’ll be back here with some updates once that is done.

Hints and tips are welcome at this stage.

 

[TucksMirror]

I would say that the camshaft sprocket wheels need to be inspected. If they do show signs of premature wear, then a complete timing gear overhaul will be required, including two new sprockets, new chain, new hydraulic tensioner, and new guides.

But the timing chain itself is not more prone to failure in the M271 engine than in other single-chain engines. So as long as the sprockets are fine, the chain should just be inspected as you normally would, e.g. for slack, guides' wear, and leaking hydraulic tensioner. If there are no issues there, then there's no need to replace the chain pre-emptively.

Any tips for checking the tensioner?

 

[TucksMirror]

One thing that was mentioned by one of the garages this morning, was that if the chain is worn (stretched?) then it is not generating the same oil pressure on startup, which is why the rattle occurs briefly, and then fades once the engine has ran for a few more seconds. This sounded quite plausible and I am no position to refute that, but I did wonder if the oil pump runs of the main chain or the secondary chain, the one that sits at the bottom of the engine?

 

[StMarks]

I don't suppose it could simply be the wrong grade of oil (too thin on startup).?

 

[TucksMirror]

I’ve had a few people ask about the oil. It was recently serviced before I bought it. I have also been told a spurious oil filter is not as good as the OE filter.

Quite a thing to get ones head around, as I have read many comments on YT videos suggesting this is normal and the same with their vehicles. Many of them concerned as I am.

Some have said this is normal until the oil pressure builds and the tensioner applies pressure to the chain. However i’d like to think the chain is always under tension, as if not that seems quite the design flaw.

I’m still of the mind that viewing the condition of the chain and cam gears will be useful given the known issues. If they are ok I will be somewhat relieved.

 

[TucksMirror]

Have began stripping down the various parts to get the camshaft cover off. Will continue tomorrow. Find the air filter housing a bit tricky due to a clamp that is very hard to reach. There is also a connector for the alternator that is difficult to get to, so will likely have to move the power steering pump and alternator.

I also found that one of the camshaft magnets is leaking oil into the electrical connector housing. So I’ll have to get a replacement.

 

[W1ghty]

Have began stripping down the various parts to get the camshaft cover off. Will continue tomorrow. Find the air filter housing a bit tricky due to a clamp that is very hard to reach. There is also a connector for the alternator that is difficult to get to, so will likely have to move the power steering pump and alternator.

I also found that one of the camshaft magnets is leaking oil into the electrical connector housing. So I’ll have to get a replacement.

Better check that the cam magnet oil hasn’t “wicked” along to the ECU , it’s a problem with this engine . The oil can also wick along to the lowest point , the O2 sensor

 

[TucksMirror]

Yes, was just reading one of your historic posts about this .

Well, now I have begun I may as well do things properly. I’m making a list and going through and checking it over thoroughly. It’s a really nice car so i’d rather get to know it mechanically than to seek out a refund.

I’ll add these two bits to the list, any tips on the best way to check this? I was going to start by making a small cut into the sheathing of the cable just by the connector, but I am thinking the wicking would be under the wire insulation and not over.

 

[markjay]

Yes, was just reading one of your historic posts about this .

Well, now I have begun I may as well do things properly. I’m making a list...

Add to your list a new crankcase breather, while you're there.... they get clogged over time.

Also check the vacuum hoses under the air filter box, they can get brittle and leak, and as you are finding out it's a pain to remove the air filter box so might as well check them now.

You could also consider replacing the thermostat, easy job and they're inexpensive, and they go after a while so will likely need replacing anyway in the not too distant future.