Does this sound like a timing chain problem?

[jriewer]

I recently bought a 87 420 SEL with 142K miles on it. Service records were good and I saw that the timing chain was replaced at 110K. About two weeks ago on cold start up I heard a severe rattling when I started the engine. It seemed to be coming from the passenger side valve cover. I turned the car off and immediately restarted the car. This time the car started fine and the engine idled smooth like it always had in the past. No rattle so… problem fixed! For the last two weeks the car has started normally and running fine until this morning when the same rattle occurred on cold start, coming from the passenger side valve cover. This time I had to restart the car 4 times before the engine stopped rattling. On the fourth startup the engine started normally. Common sense told me the timing change is making that noise and not to drive the car, but unfortunately, I had committed to taking friends to the airport for a flight to Tokyo and they and their luggage were already in the car and there flight was leaving in two hours. So with great hesitation, I departed for the 30 mile round trip to the airport. On the expressway the car ran as normal with no performance degradation that I could sense. So I’m looking for reassurance: Was it possible to have driven the car 30 miles to the airport at 80mph if the timing chain was broken, jumped a few teeth or if some valves are damaged? Would a loose timing chain cause intermittent rattling like I am experiencing or should I be looking at something else? I plan on taking my car in to get the chain checked but its Friday afternoon and that won’t happen until Monday so I’ve got 72 hours to run the worst case scenarios through my head as to what is making that rattling noise and if I have or am destroying my engine. Thanks for your replies.

[porkface]

i'd be very disappointed if the chain was replaced and the tensioner wasn't. but, that's what it sounds like. good luck, chuck.

[MikeTangas]

No it wouldn't have been possible to drive the car anywhere if the chain broke or jumped teeth, basically the top end (most likely confined to the left bank) would be toast. Cam, valves and a host of other parts in need of replacement.

Most likely you need a new tensioner. Definitely have the upper rails checked because if the tensioner was letting the chain rattle as bad as you describe it is very possible that one or more of the rails could have broken. Sometimes they only break a small piece off which can easily lodge in a sprocket and you're screwed. If you have fair DIY skills you can check the condition of the rails yourself - a broken end near the sprocket will be easy to spot as the rails almost touch the cam sprockets - age is not too difficult to read either. White = new, yellow/amber = mid-life, brown =time to change and last is beer bottle brown/black = borrowed time. All you have to do is pull the valve covers, driver's side will require the two fuel lines between the fuel cooler and fuel distributor be removed.

Hope this helps.

[stevebfl]

it sounds like you have recognized the great timing chain rattle. No matter what you do to it, it will happen again. The problem occurs because the timing chain tentioner check valve loses the pressure trapped in the tentioner. A new tentioner won't do it til it does. It will happen eventually some time. If it happens often the risk of failure increases.

The problem that relates to this is that during the event the chain bangs against the rails put there for such purposes. Unfortunately they built the rails out of plastic that petrifies into something as brittle as glass. This can break the rails and the pieces cause the damage.

You should have the rails integrity verified and if they have turned amber or brown they should be replaced. You probably should replace the tentioner if the rattle happens often even with good rails. And when it happens you are probably are better off just letting the engine run as the return of oil pressure is when the noise go away. To restart the car three times and rattle each time without running long enough for pressure you just magnify the risk of something breaking.

Mostly I wouldn't worry about it, if your history is true.