Component parts and Assembly
Timing chain

This picture shows the Poly V belt and the timing chain and its location,
It should always be born in mind that the timing chain drives the camshaft and the oil pump sprocket, that in turn drives the oil pump.
The crank shaft pulley wheel in turn drives the poly V belt which drives the water pump, alternator and air conditioning compressor where fitted. If while driving the water temperature light, or ignition light comes on in the instrument cluster, there is every chance that the poly V belt has broken, and that the alternator is no longer producing power and the water pump has stopped circulating the coolant around the cooling system.

DO NOT continue to run the engine(drive the car)or it will over heat ant and the engine will cease causing massive damage to the engine.

Timing chain auto adjuster components

This information has been forwarded to me by:-Alin of Romania, who rightly feels it will inform and assist other owners, For the Record The car has done 181734 kilometers (113584 Miles) and the approx cost of the replacement of parts was €130 (115.00)
Thank you Alin for your input and photo's.

Recently I bought an A160 for quite low price but it had a strange engine noise that got worse as the engine revolutions increased.
It sounded just like this one. Copy and past this link into your browser to hear the engine

First I thought was the poly belt but after searching the WWW it ended being the timing chain.
The work involved to undertake an overhaul of this problem took two days as the engine had to come out and the front end stripped.

How we did it:

First we wanted to inspect all the parts for damage including the chain guids and chain as well as the chain tensioner.

Air filter, Ecu and the Inlet exhaust manifold was removed leaving the engine as it is looking in photo

Then we removed the rocker box cover which will revealed the camshaft and upper part of the timing chain and the sprung loaded portion of the chain tensioner.

there were no signs of a failure of parts at this point.

The chain appeared to properly tensioned but as the noise was loud, so obviously something was either worn or slack. I therefore made the decision to replace all the parts.

The oil was drained as the sump had to be removed to allow access the bottom end of the engine as well as oil pump and drive chain.

There is a plate over the oil pump drive pulley that prevents the tensioner for the oil pump chain being replaced.
That can be seen in Photo 2

The pulley/gears seen are the crankshaft and oil pump drive, the plate shown at the bottom can be seen better in photo 3 below

In photo's 4 and 5 you can see the engine with the new timing chain and new chain guides installed.

However we faced a big problem when old chain was removed as the camshaft rotated and the timing positions were lost.

It was at that point that we discovered that there were no timing marks on either the crank or cam shaft pullies, we therefore had to ensure that piston number one (1)(situated at the timing chain side of the engine was at TDC ( Top dead centre ) and with all valves closed.
We were then able to fit the new timing chain.

It turned out that the old timeing chain was 1-0 1,5 cm longer than the new one.(obviously stretched over time)
The upper plastic chain guide was badly worn where the chain had been running against it.
I am of the opinion that it was these two items that were causing the car to be noisy and also prevented the timing chain tensioner from taking up more slack in the chain even though the plastic is very hard.

I'm shocked that plastic parts are used for something that is as important as the timing chain, even though the plastic is very hard.

Also as a warning, there is a tube used for the oil/gases recirculation from the inlet manifold to the oil sump.
Shown in picture 1 next to the oil filter cap.

We unfortunately managed to break it when replacing the engine.

The tube is hard to replace so take care and try to avoid damaging it.
it is also quite difficult to fit.
If you do need to replace this tube ensure that an MB spare part is used as the tube is carrying oil at low pressure and need to fit correctly.

This mail was received from an owner who had problems with a noisy timing chain .Please read details Question No 99 on page.3

Hello Lofty. Just to give you an update on the problem I had regarding the timing chain. After rigorously searching the net for a solution, I found that a few of the A140 owners worldwide had ended up with snapped timing chains due to malfunctioning timing chain tensioner. I decided to change the tensioner and hey presto! problem solved! When I took the tensioner apart, I noticed the rubber seal on the piston had hardened which meant that it was not holding the oil pressure. I will try and send you a picture of the offending article as soon as I have downloaded it to my PC. Once more thank you for all your suggestions and your excellent website.

More often than not the cause of chain failure will be the chain tensioner, 'C' ( in the cut-away above), where this jams it allows the chain to flop about instead of being under steady tension, this photo was kindly supplied by 'Specer' whose car had suffered a timing chain breakage.
He is currently undertaking a rebuild of the engine as the garage costs are astronomical and would easily have exceeded the value of the car.
If it needs replacing then the air filter housing has to be removed to allow access, the tensioner is only held by two bolts and is easily replaced, the unit will need to be pushed down and held while the bolts are replaced and tightened.

Many owners will be aware that the 'A' Class does not have a timing belt, sometimes known as a cam belt like a lot of other modern cars and vehicles, but still has a metal link 'timing chain' A which unlike the belt is housed within the off side engine casing.
The engine oil pump drive is also an orthodox metal chain
B These are examples of 'A' Class timing chains One is new the other well used, the arrow pointing to the severe wear of the used chain.

Mercedes Benz would have owners believe that the chain will outlast the life of the engine!
Sad to say this is not always the case
There are many cases of timing chains having broken, yes invariably lasted the life of the engine, But only because the damage caused by the breaking chain is usually so great that the engine is written off. It is not always a high mileage engine that suffers this dramatic failure. In fact in one case reported on the Benz-world .org by the owner of the car ( W168 forum) The car had only clocked 40,000 and Mercedes_ Benz were not co-operating in respect of a repair.

In older models it is more often than not the cause of the car being scrapped, so the car outlasted the chain!

If you are unable to tackle this job yourself and it is a massive and expensive job costing several hundreds of pounds just for parts then the repair becomes unviable.
With Mercedes-Benz garages charging in the region of 100 an hour and the engine having to be removed from the car, the bill could amount to several thousands of pounds

That doesn't mean the engine cannot be repaired it can with time, money as well as patience.
But its certainly not a job for the weak hearted as the engine has to be removed if the job is going to be done well one such repair is being undertaken by the owner at present with all entails.
We do when making the decision also have to remember that there are two chains, one timing and one oil pump drive chain, if one has broken there is every chance the other will be at least badly worn.

Inlet and exhaust valves may well be bent and you may, unless the gods are with you find at least one badly damaged piston in some severe cases they can be holed. In this instance the impact of the piston head can be seen in the metal of the piston.
In this case I would not expect it to need replacing.

Because these items cannot be seen until the engine is removed and stripped, Mercedes will almost certainly quote for a replacement engine
Having said that it doesn't then make sense to not replace the clutch which is normally part of the gearbox and not the engine, so again extra parts and labour would be charged, all of these things and more need to be taken into account before making a decision to repair.
Where as the poly 'V' belt is inspected on the 'B' Service and replaced at a specified mileage I'm not aware of any set time or mileage for the replacement of the timing chain.
So why is so much damage caused when the timing chain/devise breaks.
The timing chain as it is name implies maintains the timing for the various components .It ensure that when the piston reached (TDC top dead centre)that the all valves are closed this is done by the timing chain which drives both being driven by the crankshaft pulley turns the chain which turns the cam shaft which in turn being fitted with cams opens the valves at the correct time. When the chain breaks there is nothing to turn the cam shaft and the valves can be left open where upon the piston comes into contact with the open valve, the degree of damage would depend on the position of the valve s when the chain breaks.

Golden rule Never attempt or allow others AA, RAC,INTERNATIONAL BREAKDOWN, MERCEDS BREAKDOWN (Mobilife)to attempt to turn an engine over (try to start)using the starter where the timing devise, Chain in the case of the 'A' Class is believed to have broken.

More damage than previously the case can be caused.
One theory put forward is that the timing chain tensioner sticks allowing the chain to float/flop about which then allows the chain to jump a sprocket on the cam shaft this obviously throws the whole of the timing out of sync and multiple valves are bent even though the chain has not actually broken. vehicles that have done a very high mileage may also have badly worn timing chain sprockets

Owners of early A140 would be well advised to replace the chain tensioner it is a relatively simple job and the cost is minimal.

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