A140 Broken Timing Chain?

[mymercaclass]

My A140, registered March 2000 (petrol) recently cut out whilst on the motorway. A vacuum test shows no presure in all 4 cylinders; I'm thinking the timing chain may have snapped. The car has done 110K miles and has full service history.

Anyone had similar experience or any suggestions as to cause. If it's the timing chain is this worth repairing on an engine with this many miles or is the whole engine likley to need replacement? Any help/thoughts appreciate...Thanks

 

[grober]

Whole engine replacement probably required. You might get one from a breaker. Economics depend on condition of rest of car? Its an engine out job whatever you do.

 

[stats007]

If the timing chain had snapped I'd think you'd have heard it!

 

[television]

Does the starter spin the engine

 

[BlackC55]

If the timing chain had snapped I'd think you'd have heard it!

Not necessarily.

one of my customers just had one snap. It just made a phut noise thats all.

 

[BTB 500]

If the timing chain had snapped I'd think you'd have heard it!

Particulary as you're virtually sitting on it in an A Class

 

[mymercaclass]

Thanks to everyone for their help so far. The engine turns over on the starter but faster then normal (consistant with the lack of vacuum pressure)

What's got me puzzled is the lack of pressure in all 4 cylinders (i'd expect one to have pressue even if the chain had snapped). Someone suggested the oil pressure relief valve could be stuck which meant the pressure opened all of the hydraulic tappets.
Anyone know if this's possible?
Where the oil pum on an A class?
Is the oilt pressure relief valve accessable?

 

[mymercaclass]

Not necessarily.

one of my customers just had one snap. It just made a phut noise thats all.

As you've had a customer with similar experience any chance you could give me a rough guide as to the cost of repair? sounds like I need to work out whether the expense is worth it given the age of the vehicle. Thanks

 

[BlackC55]

I would put a second hand engine in.

Its about 11 hours to remove and install the engine. From memory. If you can find an engine it maybe worthwhile but the job wont be cheap.

The last customer had a completely different car then you so its a very different cost.

 

[recycled]

why dont you just take off the oil cover and use a mirror to see the chain.
if it turns over, how can the chain have snapped.
it could be the cam shaft like in my friends audi. i doubt if it is the chain.
i will make sure first. what ae the signs of a snapped chain?.
Cam shaft not turning. rattling around the front part of the engine even though his A-class engines are a bit different

 

[mikevernon]

On most modern engines, if the camshaft stops turning when the crank is still rotating then the pistons will hit the valves and bend them slightly, which explains why you no longer have compression in any of the cylinders. (I presume that you meant a compression test rather than a vacuum test). The fact that you have no compression on ANY of the cylinders suggests that this is what has happened, unfortunately. But there is another possibility - the tensioner could have come loose causing the chain to jump as few teeth which would prevent the engine from running. Unfortunately this would also be likely to cause the valves and pistons to collide, in which case the engine may not be worth repairing.
I'm not familiar with the A Class engine but it's usually very simple to check whether the camshaft is still turning. Why don't you remove the cam cover and have a look while spinning it over on the starter?

 

[recycled]

or just take off the oil cap and see if it still spins

 

[Dieselman]

The fact that you have no compression on ANY of the cylinders suggests that this is what has happened, unfortunately. ?

That suggests just the opposite has happened. If the camshaft stops only the valves on the cylinder with them open at that point will be damaged, all the others will be ok normally.

I'm surprised that if the chain has snapped the engine made no noise of contact, unless it's not an interference engine, in which case a new chain and it should live again.

 

[stats007]

The pistons will only hit the valves if the camshaft continues to rotate out of sync with the crankshaft - the valve springs will slow it down - and with no chain the valves are free to retract and move the camshaft directly.

 

[recycled]

with no chain he camshaft will stop rotating anyway so the cylinders that were on the way up will hit the valves for that cylinder. if you were at a tremendous speed, all four will go up and down quickly and cause some serious damage but you will definitely hear it except yours is a case of
My music so loud im swinging and ridin dirty

 

[recycled]

unless it's not an interference engine, in which case a new chain and it should live again.

i am sure only americans do these type. not sure MB does them

 

[BTB 500]

Doubt it's going to be easy to check anything visually on an A Class, with the engine under the floorpan.

 

[skemball]

The fact the engine appears to turn over faster than usual, and you have no pressures implies that all valves are remaining partially open?

Do these engines have variable cam' timing?

 

[Dieselman]

The fact the engine appears to turn over faster than usual, and you have no pressures implies that all valves are remaining partially open?

All the valves cannot be open at once and the engine turning faster doesn't imply that.
It implies that the cylinders are failing to build compression which will happen if the valves remain closed even as no charge of air will be drawn in to compress.

 

[mymercaclass]

Problem Conclusion

Thanks to all those that provided suggestions.

I took the rocker cover off to investigate the cause, sure enough the timing chain had snapped. It seems in doing so the chain had rubbed against the casing and left metal filings in the oil ways and bent some valves.

If it helps anyone out there I can say:-
* Timing chain snapped despite full service history and running the car from new with Mobil 1 fully synthetic oil (at 110,000 miles);
* There was no warning and when it snapped there wasn't any lound bang or any noise at all;
* Only way to tell for certain what was wrong was to take off the rocker cover;
* My car was a March 2000, A140. having investigate the cost is beyond economic repair.