E300TD top end rattle

[popben]

I have just bought an E300TD and it has a top end rattle which seems to disapear at normal running speeds. It is quite noisy at tickover and it does sound to me like its a metalic noise. I bought and replaced 2 tappets which showed signs of softness but the noise remains. It also seems to be down on power especially when towing. I dont have anything to judge it against as I've never driven one before. Any advice/help would be greatly appreciated.
Stan.

 

[simon_wall69]

The rattling at idle could be the tensioner on the auxillary belt or worn engine mounts, quite common problems.

What's the mileage?

 

[AMC]

I have just bought an E300TD and it has a top end rattle which seems to disapear at normal running speeds. It is quite noisy at tickover and it does sound to me like its a metalic noise. I bought and replaced 2 tappets which showed signs of softness but the noise remains. It also seems to be down on power especially when towing. I dont have anything to judge it against as I've never driven one before. Any advice/help would be greatly appreciated.
Stan.

Hi i have also just bought an 1998 e300 td auto and it has a top end rattle, i took it to my mate who has been a mercedes mechanic for nearly 20 years who said he thought it was an injector causing diesel knock. He said by replacing the injector this would solve the problem, he said roughly injector might be around £100. Thanks hope this helps you.

 

[popben]

Hi sorry I forgot to say its 1997 and done 120,000 miles.

 

[Number_Cruncher]

>>injector might be around £100.

You can have all 6 overhauled for about £200. Find a local well established Bosch diesel workshop.

When you disconnect any of the high pressure pipework, be sure to cap off the ends of the pipes straight away - dirt and contamination is the enemy of injection equipment.

However, I would begin by checking carefully with a mechanic's stethoscope to find the source of the noise before spending any more money.

If you do decide to overhaul your injectors, I would recommend you also do a compression test while the injectors are out. There is also a good list of work you should do while the inlet manifold is off, but, more of that later perhaps.

 

[teddycatkin]

Hi popben --welcome to the forum --I would go with the mechanic advice if he has seen the car --but source a used injector 1st to see if it cures the problem (circ-£20)
--a top end rattle is usually the hydraulic tappets ? cant see an injector causing it to"rattle" myself??

 

[popben]

Hi Folks |Yes it is definately a rattle(does a dad injector cause a rattle or is it more a knock) and I have used a stethascope and its coming from no 3 cylinder. Any ideas where I could get a second hand injector to try.
Thanks for all the help
Stan.

 

[Number_Cruncher]

>>cant see an injector causing it to"rattle" myself??

They can, very easily.

If the injector isn't spraying well, the ignition of the fuel can become more sudden and causing loud knocking, which can easily be confused for mechanical noise.

You sometimes briefly hear a similar effect if someone starts a diesel before the glow plugs have done their job, the engine will knock loudly for a short while.

Another, more sinister cause is poor compression, which leads to a cylinder not quite being able to begin the combustion of the fuel soon enough, and, by the time the combustion begins, there's so much fuel in there that it goes with a bang, and you hear a similar knocking. (Hence my suggestion of checking the compressions)

This knocking during combustion can also be responsible for ruining glow plugs in short time - which just makes the problem worse.

The rattle from No 3 - does it go away if you temporarily slacken the pipe to that injector? (You'll need some rag to soak up the small amount of fuel which will leak out)

 

[popben]

Hi There, That sounds like a great idea I'll try slackening the injectors one at a time and see what happens. Is there a special tool required to remove the injectors and do you know what the compression rate should be.
Again thanks very much for taking the time and all the advice.
Stan.

 

[Number_Cruncher]

The injectors need a deep 22mm socket with cut outs in the sides to clear the leak off barbs (don't damage these whatever you do!). The MB special tool number is 606589000900, (other makes of sockets are also available) and the injectors need to be installed with new heat shield washers and torqued to 40Nm.

When new, the spec for the (HOT) compressions of these engines was 29 to 35 Bar. The wear limit is 18 Bar, with a maximum of 3 Bar pressure difference between cylinders.

Be sure to blow out the cylinder with an airline before pressure testing it. If there's any residual fuel in there which fires, it will blow your compression tester to bits!

 

[brianbrian]

Hi Sorry to dispute the socket size & torque but I think socket is 27mm, injectors should be 75nm=55lb ft make sure you put new heat shield washer right way up. Robparker123 is a member he will sell you a good injector and post it to you at a reasonable price, Hope this helps

 

[Number_Cruncher]

>>Hi Sorry to dispute the socket size & torque but I think socket is 27mm

As this is a later car, it's an OM606 engine - these have slimmer injectors placed centrally in the head. There isn't room for a traditional injector, they're much slimmer, and use a 22mm socket rather than the 27mm socket which are used on earlier engines.

So, yes, on earlier engines, like OM603, a 27mm socket and a higher torque is correct, but, not on this engine.

 

[popben]

Once again thanks for that.
Stan.

 

[brianbrian]

sorry about that number cruncher - you are perfectly right

 

[television]

I think that the car is normal for one of those, I had one 2 weeks back, noisy as hell on tick over, load it and rev it it all goes quiet

 

[Number_Cruncher]

>>noisy as hell on tick over

Being a fairly old tech diesel, they're never going to be absolutely quiet, but, "noisy as hell" means there's something wrong.

Many times, it's just the drive belt damper rattling, but, clearly not in this particular case.

 

[television]

>>noisy as hell on tick over

Being a fairly old tech diesel, they're never going to be absolutely quiet, but, "noisy as hell" means there's something wrong.

Many times, it's just the drive belt damper rattling, but, clearly not in this particular case.

Sorry a bad post from me, the knock was loud and nothing else, it quietened right down once loaded.

So sorry

 

[Number_Cruncher]

>>the knock was loud and nothing else

Sometimes, that can be a cylinder with marginal compression - when running at speed, the race between the air being compressed and the air leaking away is more readily won by the compression, and so, combustion is good. At low speeds, the leakage has more time, and tends to reduce the compression pressure, hence gas temperature, leading to late uncontrolled combustion, and hence knock.

 

[television]

>>the knock was loud and nothing else

Sometimes, that can be a cylinder with marginal compression - when running at speed, the race between the air being compressed and the air leaking away is more readily won by the compression, and so, combustion is good. At low speeds, the leakage has more time, and tends to reduce the compression pressure, hence gas temperature, leading to late uncontrolled combustion, and hence knock.

Thank you and I would be lost now without you

 

[popben]

Hi Number Cruncher, I believe your right in that I would say that the rattle is in time with the engine revs and not just loose. I havent had a chance to do the check on the injectors yet but if it is not that and it is down on compression would you say it is more likely to be the valves or could it be needing a rebore. I know I'm asking the impossible without you hearing it but you seem to have a vast knowledge of this model and I would imagine you would have a good idea.
Thanks Stan.