Tappets or Timing Chain?

[Zagato]

As of late, money is a problem. This means my beautiful Merc is in a tough position, facing parts car land or a heroic rescue.

The engine has developed the sort of 'tick-tack' metallic noise that would make anyone worry about their wallet.

On these cold days, there's noisy tick-tacks during warm up, noisy tick-tacks during acceleration, faint tick-tacks during idle.
As the car is D-jet with non-hydraulic tappets, I would LIKE to assume they just need adjusting. Trouble is, I have no history of the timing chain. At 333,000 kms now ( 207,000 miles ), I worry that it might be the one causing the noise. Strangely, engine performance seems to have not changed compared to the months before the tick-tacks. I should also note that it's starting to burn oil now, but not a lot.

Is there a distinct difference between the noises of the timing chain and tappets? If it's the tappets, I can easily get that adjusted and work on my leaky injector. Then deal with the excess transmission fluid. Then the sticking auxiliary air valve.
If it's the timing chain, then I'm afraid I'll have to wave goodbye to the ol' panzer tank. Not something I can afford, especially if the cam sprockets need changing as well.

[s class]

A constant tick-tick, that is the same on start-up as when warm is most likely tapets.  THe chain will make a more hollow rattling, (bit of a death sound), and will be most pronounced in the seconds immediately after starting. 

On the 4.5, it only takes about 5 minutes to remove the air cleaner, remove the right valve cover and inspect.  The right valve cover is the one on the right as seen from inside the car, and the one on the left as seen from in front of the car.

Once the valve cover is off, you can check for chain stretch (its easy - we can talk you though it), and see if the chain tensioner rail is in tact.  You can also get some idea of the tensioners extension. 

Once you have opened up, inspected, and closed, it won't take more than an hour (most likely half that) and you will be in a much better position to assess your situation.

If a chain is required, they can be bought on-line at Autohaus.  Sprockets are only $25 each there.  A tensioner too is reasonable.  You can change the chain yourself with some care and basic tools. 

[TJ 450]

Small exhaust leaks can also make annoying ticking sounds too.

It also doesn't cost anything to remove the rocker cover and check the timing chain... the gaskets are reusable most of the time.

I would be checking the timing chain ASAP, as my 450SEL was at 333,000km when a guide broke. It was the car's second timing chain which was replaced in 1995. Fortunately no damage was done.

Tim

[CraigS]

Irrespective of the cause, whether tappets, timing chain, chain rails or tensioner, all of these are jobs that can be done by the average home mechanic, and at very little cost. It would certainly help to have the relevant page from the manual around if you haven't tackled any of these jobs before, which you can get from the library here, and if you have to buy a new chain, guides, and/or tensioner, it is not going to be more than $200 or so. The biggest job in terms of time is a toss up between the chain and the tappets, but irrespective, no more than half a day for each - and that is taking it very slowly and carefully.

[WGB]

If it is the chain (less likely in my opinion unless the chain has jumped a tooth or two) it is imperative that it is checked PBQ.

More likely just a tappet adjustment but with the 450 motor plastic cam oilers can let go leaving a camshaft running dry.

450 motors have re-usable rubber cam cover gaskets - just take off the air cleaner and the cam covers and have a look.

Bill

[Zagato]

Thanks for the helpful advice guys. I'll pull the cam covers off this weekend and check for excessive timing chain stretch and the condition of the plastic guides.

About the cam sprockets, do they usually last more than two timing chain changes, or after the first change they definately need replacing on the second?

[WGB]

The cam sprockets on a 450 motor are not particularly expensive and the there will be a loss of 3 to 4 degrees of timing if you don't replace them which will need to be corrected by offset keyways.

Bill

[Zagato]

Argh, too late gentlemen.

Was too busy this weekend, driving the folks around, to pull the valve covers off. When starting the car tonight, the driver's side cylinder head immediately starting making a serious racket. I'm guessing the plastic guides finally broke and the chain skipped a tooth, causing the valves on that side to strike the cylinders. Unfortunately the car was in the way of traffic when I started it, so I was forced to drive it about 50 metres to get it out of harms way (Which I know is a BIG NO-NO with this chain crisis). It's now sitting in a parking stall at a gasoline station, and I'll be leaving it there overnight.

There's no way I can afford to deal with the size of this problem, so it looks like this is the end of my 1974 450SE.

[WGB]

The chain slops around on startup and then either jumps a few teeth or a plastic guide breaks and goes around the system.

Minimal fix is usually two (Bent) exhaust valves in the left hand bank and a head gasket but obviously valve guides, chain and tensioner will also usually be required.

It's unusual that you had some warning.

Bill

[Zagato]

Took the car to the European car specialist and they found that the exhaust manifold on the driver's side has cracked badly. They say this explains the terrible noise coming from my engine. Unfortunately, I'm told it will be a big job to get the headers off, as the bolts are very rusted. They say they'll be lucky to get them off without needing to pull the engine out to do it. On top of that, the exhaust manifolds sound very expensive to get replacements for.

Either way, I can't afford these repairs.

[s class]

huh?

Second hand manifolds come up on ebay in the US all the time. Just make sure it is the correct version for your car.  Ask the seller for the part number. 

Access to the manifolds on the 4.5 is comparatively easy.  I accept you may have a lot of trouble, but its still doable.  Just soak the studs generously in decent penetrating oil for a couple of days before you try to loosen them.  The risk is, you might break a stud, then you have problems like this :

Link

[WGB]

Manifolds are not that difficult to remove - as S-class says - lots of penetrating oil - and a 3/8 socket set with a universal drive from memory.

Bill

[TJ 450]

Indeed, as long as you don't beak off any studs or round off nuts, it should be quite straightforward. A broken exhaust manifold seems like an unusual problem though, how broken is it?

Tim

[CraigS]

I would also suggest the liberal use of a gas torch to try and break them free -  soak with plenty of penetrating oil first as suggested, then heat them up as you are about the loosen them. The manifold is already damaged, so I wouldn't be too concerned about damaging it further. If you do break a stud, the biggest problem is removing the old one as there is not a lot of space for a drill.