W124 300d

[3ps]

Hi,

My W124 300TD (touring n/a diesel) has 220k on her and is fine in general.
There is a bit of diesel "knock", plus it's a bit tappety at idle. The tapping used to disappear at relatively low revs/speeds.

Anyway, today the tapping didn't go away and I can hear it all the time!

Any ideas what this is and how bad my wallet will be affected?

Thanks!

 

[television]

Are you sure that it is coming from the top and not the front, is the oil pressure still good

 

[3ps]

Not sure where it's coming from at all.

Oil pressure is 3 when driving, dropping to 2 - 2.5 at idle even after long runs.

 

[brianbrian]

I think you will find its an injector for the knock,and cam follower for the tap at that mileage, do a screw driver test, or undo the top of each injector where the fuel goes in individually, this will tell you, but nothing to worry about at this mileage it is to be expected,other than that very hard to say unless I hear it myself. Hope this helps you

 

[3ps]

if I "undo the top of an injector" will fuel get spurted out all over the place or am I just undoing power to it or something?

where is the cam follower and is it something that can be fixed cheaply/DIY?

I'm at the stage where the bodywork needs some attention as well as the mechanics and I need to decided how much more to put into her.

Ideally I would like to keep on top of the mechanicals... and touch up bodywork issues until it gets to the point where she is old enough to warrant a respray (17yo now)

 

[Number_Cruncher]

Yes, fuel will come out - put a rag round the injector to catch it.

Pay particular attention to the rearmost 2 cylinders. These are prone to valve seat recession, and with the resulting lower compression, diesel knock is a common symptom.

Like a fool, when I bought my E300D, I heard the knock on No6, because I listened to the engine with my stethoscope, but, thought it was the injector that was spraying badly. It wasn't the injector!

Are you using a decent oil or thick nasty gloop? - I have found that on mine, using a 5W40 has reduced valve train noise significantly, especially when cold.

 

[3ps]

I think I'm using 10W40 semi synth.

 

[fullmeister]

Gentlemen, while we are on the subject .... is it a fairly involved job to replace the hydraulic lifters/tappets ? I assume the cam must be removed ?

Any advice would be welcome.

 

[Number_Cruncher]

Yes, it's involved - less so on an OM603 than on an OM605 or OM606.

What tests have you done to make yourself sure that it is a hydraulic tappet which is failing?

If you do go ahead, be sure to obtain the correct MB procedure, because it's very easy to undo the cam bearings in the wrong order, and snap the cam!

Also be sure to follw the correct procedure with the cam chain tensioner - it needs to be bled with new oil.

Other than that, it's very straight-forward work. I would be tempted to fit new bolts on the cam sprocket.

 

[fullmeister]

Tests .... well.... none to be honest

The ticking noise fades and dissappears at about 1800 revs which (rightly or wrongly) leads me to belive it is a hydraulic tappet.

My car is a "92 250D non turbo.

I was a mechanic for ten years but, that was ten years ago so I'm a bit rusty to tell the truth . Sounds like a garage job.

Thanks for the swift reply!

Andy.

 

[simon_wall69]

I'd start with checking the injectors, eliminate the easiest first! As Number cruncher says, the valve seats could have recessed leaving you with compression loss - if this is case, I would leave it as it would be a head off job.

 

[turbopete]

agreed. my e300td has a similar (it seems) rattle at1200rpm or less. this is caused by air getting into the fuel (in my case)

 

[Number_Cruncher]

>>Tests .... well.... none to be honest

As mentioned, it's probably worth slackening the injector pipes one at a time, to see if the noise is combustion related. If it is, getting the injectors tested for;

- opening pressure,
- spray pattern, and
- leakage under pressure

would be a good first step - especially if you also do a compression test while they're out.

The noise going away at speed would suggest to me that it is combustion related rather than a purely mechanical noise like a hydraulic tappet.

If you do find that the noise is mechanical, i.e., slackening injector pipes one at a time doesn't stop the noise, remover the cam cover, and, for the valves which are properly closed, try to depress the lifter with a soft ended prod. If you find some tappets are soft to the prod, these are the suspect ones. You'll probably need to turn the engine over to get each valve closed - just as if you were going to set the valve clearances!

 

[brianbrian]

The cheapest thing to do why not change engine oil &filter and try putting 5/40 oil like Number Cruncher suggested it might work as these engines do go on for 500000 even though they get abit noisy. Hope this helps

 

[fullmeister]

The cheapest thing to do why not change engine oil &filter and try putting 5/40 oil like Number Cruncher suggested it might work as these engines do go on for 500000 even though they get abit noisy. Hope this helps

Did a full change of all fluids yesterday .
Seems the Shell Helix diesel (mineral) had a dramatic effect, the noise has gone!

A temporary state of affairs maybe?
I resisted the use of an engine flush as there are conflicting views around the MB forums. Any feedback on this chaps?

 

[wireman]

I find that my 602 engine tends to be a little tappety for the first few mins of running clearing up as the engine warms, this rattle gets more prolonged as the oil service interval aproaches, a little sooner with cheap oil (morrisons 10-40) later with fuchs semi 10-40.

As regards flushing, use the cheap stuff (not the very cheap) for 50-200 miles without a filter change and then change oil and filter for the good stuff, it will only cost an extra tenner (7.49 for the morrisons). This makes no noticable difference on my 124 (2.5 indirect 170k mlies) but her majesties rover 25 (pug 2.0 DI 60k miles) seems to benifit from this in taking somewhere like 2000+ miles to start blackening its oil after the two for one oil change.

Keep an eye (ear?) on it but perhaps your oil change has cured the problem.