[ch.1953]

OK, I promised I would post pics...

Well as some of you know I am trying to make sure my 1987 420SEL gets back on the road. We thought we had a major over heating problem, but reinstalling the thermostat has kept it at 100 or less.

Below is a pic after 20 minutes driving and 20 minute idling:-

So today I drove it again and on start up heard the rattle (420 - top left guide rail I know is weak), but I was not sure what that sounds actually sounds like...

But then the dreaded chain rattle happened and it turns out I may be the luckiest guy in the world, as it definitely blew (see the big hole below) but the car still drove fine all the way home - and when I turned it off I only then saw the smoke and leak and the big HOLE!!

Of course I AM NOT going to start it again, as I can only presume that must have been caused by the chain and so if I start it, it will turn what I am hope is a simple timing chain, guides and cover job into a top end rebuild...

Here's what it looks like now:-

 

[ch.1953]

As the car has been sitting for a long time and there are NO MB techs here (don't ask!), so here are some other pics of my engine bay in case you folks can see something else. Let me know guys & gals...

And of course these photos were taken before today which is when the engine's timing chain punched a hole through the (what is it called) valve cover...

OK, over to you guys - really appreciate your eagle eyes, as there are NO MB techs on this island...

If you want me to take more pics I can. Just tell me where what else might blow up... My understanding is the only real weak point on the 420 W126 is the top left guide rail / timing chain issue - but what else might you expect to be about to blow up given it has been sitting for a long time.

OK, over to you all...

 

[flosshilde]

I would start looking for a new engine now. She is a goner.

 

[ch.1953]

Engine ran fine, all the way through....

I know the W126 4.2L has a weak point right where this happened so I think we should be OK. We'll see...

My expectation is that timing chain is loose due to broken guide rail and slapped the cover and punched a hold in it...

So respectfully, I don't think she's a goner.

But let's see what experienced W126 posters say!!??

 

[w126Sam]

Haven't experienced the dreaded chain myself, but I've read of plenty who have... Seems like a lot of people do get away without catastrophic failure, and you may be one of them. Only one way to find out...

 

[ch.1953]

Haven't experienced the dreaded chain myself, but I've read of plenty who have... Seems like a lot of people do get away without catastrophic failure, and you may be one of them. Only one way to find out...

And that is...?

Would you agree that as the engine ran fine until I switched it off, that it looks like I am lucky?

BTW - what is the name of the part that I punched a hole in?

Thanks, :thumbsup:

 

[flosshilde]

You could just replace the head and any damaged pistons , but its cheaper to replace the engine. But yes , over to more 'experienced" posters.

 

[ch.1953]

That is the question I am posting to more experienced W126 techs and posters, as I actually don't think the head and pistons are damaged...

... particularly as the engine was running fine all the way through to when I turned it off and saw this. QED - no interference yet...

... and yes over to the 126 experts

 

[luckymike]

Okay, not an expert but I have replaced two timing chains.

If it was my car, I would get those valve covers off and check things out. Depending on what I found, I might just replace the broken rail, roll in a new chain and change the oil. (Might pull the secondary oil pan to check things out there). It would be worth it to me to spend a few bucks on a chain before assuming everything is shot.

But look inside first.

 

[Grumpy560]

Yes, it's called a valve cover and that's exactly what the chain punched through as the broken guide rail was drawn up and over the cam shaft sprocket by the timing chain, shit happens..............

So, disconnect the battery. You will need to remove the valve covers, yep both of them. Pull all eight spark plugs out and don't forget to mark each lead wire as to where it goes.

Use a socket on a long breaker bar to rotate the engine clockwise via the harmonic balancer pulley, do this very carefully. You need to line up all timing marks, left cam + right cam + harmonic balancer to see if anything jumped though at this point I doubt it did since the engine was still running.

Do consider yourself very lucky not to have any other internal damage.

BTW, your engine temp is way up there where it should not be. Just a tick above the 80 mark would be a more desirable place to see the needle remain at after just 20 minutes @ idle unless the temp sender or gauge is faulty but yeah, that's a tidbit too warm.

Mine stays just a tick above the 80 mark even after an hour of stationary idle shown in the first pic.

 

[ch.1953]

So I did get lucky then...

Phew - thanks...

Sounds like you agree if the engine was running fine when I turned it off valves and so forth must be fine still...

 

[Grumpy560]

So I did get lucky then...

Phew - thanks...

Sounds like you agree if the engine was running fine when I turned it off valves and so forth must be fine still...

Maybe you got lucky, there's a good chance that nothing else happened but only a visual inspection will tell the truth of the situation and you can go from there.

It would be a very good sign to see all of the rocker assemblies still in place when the valve covers are removed.

 

[ch.1953]

Maybe you got lucky, there's a good chance that nothing else happened but only a visual inspection will tell the truth of the situation and you can go from there.

It would be a very good sign to see all of the rocker assemblies still in place when the valve covers are removed.

All I can tell you is I am sure it happened well before (500 - 1000 yards of driving) I turned the engine off and noticed it, as when I turned around at the end of my road to drive back to the house after seeing if the car was no longer over heating as badly (after my tech reinstalled the thermostat, after some joke tech pulled it out when he did the water pump without asking me) - I could hear a loud metallic jangly noise coming form the left side of the engine bay - but no misfire, no missing; in fact the engine ran perfectly smooth all the way back to the house, and under quote reasonable acceleration too (as I was trying to heat the engine up to see if the thermostat had fixed the bad over heating).

Does that tend to indicate we were lucky? :bowdown:

 

[nhzruthless818]

Hello Richard, did your chain snap or stretch? If the timing gets screwed up you can lose a connecting rod, valves, and/or camshaft damage. On my friend's m3 the camshaft sprocket ripped the chain, which broke 2 connecting rods, and bent a lot of valves (e46 m3). I can find you a valve cover thats not an issue but your best bet might be this

Mercedes W126 Black Engine Valve Covers 380SL 380SEL 380SEC 380SE 420 Sel | eBay

shipping valve covers to Canada is going to be horrible because if there is any oil in it, it can be seized and fees might be horrible. The headlights were not available and the taillight was $40 if I remember correctly. Valve covers are $40-45 the last time I bought one for my m119 ($45 for aluminum and $40 for steel)

 

[ch.1953]

Hello Richard, did your chain snap or stretch? If the timing gets screwed up you can lose a connecting rod, valves, and/or camshaft damage. On my friend's m3 the camshaft sprocket ripped the chain, which broke 2 connecting rods, and bent a lot of valves (e46 m3). I can find you a valve cover thats not an issue but your best bet might be this

Mercedes W126 Black Engine Valve Covers 380SL 380SEL 380SEC 380SE 420 Sel | eBay

shipping valve covers to Canada is going to be horrible because if there is any oil in it, it can be seized and fees might be horrible. The headlights were not available and the taillight was $40 if I remember correctly. Valve covers are $40-45 the last time I bought one for my m119 ($45 for aluminum and $40 for steel)

Thanks NhZ - but I'm not in Canada, closer to Zimbabwe actually...

NhZ - do you think there would be engine damage given the engine was still running perfectly when I turned the car off?

 

[420SELTOM]

Yes, a very lucky man indeed, go buy a lottery ticket you guys have them over there, lol. Do as the previous folks have suggested, replace all 3 upper chain rails, timing chain, tensioner and tensioner rail + replace the camshaft oiler tube holders, cheap part, but they can pop off and starve the camshaft from oil. Also be sure to remove the lower oil pan and recover all the broken pieces, if this step is skipped, and I've seen it happen, the broken pieces can / will get stuck at the oil pump pick up screen and eventually starve the engine from oil, then you WILL need a new motor.

 

[nhzruthless818]

Thanks NhZ - but I'm not in Canada, closer to Zimbabwe actually...

NhZ - do you think there would be engine damage given the engine was still running perfectly when I turned the car off?

It all depends on your luck Richard. Take the cover off and inspect. When did you get to Zimbabwe lol last i remember you were going to Canada. I dont think shipping would be cheap there its farther from canada lol

 

[ch.1953]

Yes, a very lucky man indeed, go buy a lottery ticket you guys have them over there, lol. Do as the previous folks have suggested, replace all 3 upper chain rails, timing chain, tensioner and tensioner rail + replace the camshaft oiler tube holders, cheap part, but they can pop off and starve the camshaft from oil. Also be sure to remove the lower oil pan and recover all the broken pieces, if this step is skipped, and I've seen it happen, the broken pieces can / will get stuck at the oil pump pick up screen and eventually starve the engine from oil, then you WILL need a new motor.

thanks, very good advice... much appreciated.:thumbsup:

Do I probably need to do all chain / guide rails too, not just upper?

Is this the part number for the oiler tube holders - 1161800184

 

[liviu165]

A very, very expensive restauration project

As the car has been sitting for a long time and there are NO MB techs here (don't ask).

A place where are no MB techs, ... so far I noticed you may not be very used to fixing cars (I mean no disrespect, just speaking my mind), ... a 26 year old car that doesn't look like it had enough TLC but definetely needs some, ...issues that do not hesitate to show up (and probably new ones will continue to show up), and so on... I guess you realize this will not be a cheap road, may actually prove a very expensive restauration in your case because of your specific conditions...

It takes a financial toll on us here and constant work (the older the cars get, more TLC needed), but in your case ... I just wanted to make sure you realize this will not be a walk in the park before you started spending a lot of your money ...

 

[Merc-S600]

Hi Richard
I think that you caught that engine just in time before a complete sealed engine due to no operation of it for a long period of time .
When you started the engine ,I think that with the oil pressure etc all of a sudden firing up again that all the harden'd oil & engine deposits came loose in one hit causing the chain to slip or jump by 1 or a few teeth ,you should be ok once you see the timing is perfect ,as already mentioned ,Its your lucky day and you have my blessing as well ,Halelujah ,now of to buy that lottery ticket so you can buy a few conrods ,lol.
Good Luck . :thumbsup: