Noisey W202 250td

[brynton]

Hi all,

I have a 97 c250td with 85000 miles, and I know its a diesel but is there any way of reducing the dreaded clank(apart from buying a petrol version). Inside the car you cant really hear the engine that much, but it is definatly noticable from out side.

It has just had the oil, fuel and air filter changed and is running on 10-40 oil.

Does this engine have tappets or hyrdrolic lifters that could be replaced??

Also at what mileage would you advisefor the timing chain to be changed??

Many thanks

 

[jaymanek]

=(apart from buying a petrol version).

These are fairly noisy old engines, if you cant hear much inside then id be inclined to say theres nothing wrong!!

Timing chain is best replaced at around 150-200K and the tensioner too as this could be the cause of some of the noise...

 

[Dieselman]

What do you mean by "clank"?

These engines are generally pretty quiet as far as combustion noise goes due to be in indirect engine.

Is the noise when under load or when idleing.
I would suggest a strong dose of injector cleaner with cetane improver. If this works then just do it regularly.

 

[PeterE320Cdi]

Mine seems quieter when starting after dosing it with millers diesel power plus.

 

[brynton]

cheers for all of the advice so far.

I am probably just being picky

The noise sound like the top end of the engine, and I know diesels do produce some noise, thats part and parcel, but when it is idleing it is more promenent. a few revs and it sounds alot smoother.

As for the treatment, is it a diesel/fuel attitave or the oil flush??

Once again, thanks for the info.

 

[Dieselman]

Fuel additive.

I suspect you mean there is some cackling when the engine is idling. This could be down to a poorly spraying injector but is also normal, especially when cold.
Diesels often cackle at idle due to the VERY lean mixture causing a rapid rise in temperature during combustion. A cetane improver will reduce this.

This is where people get the impression that diesels are noisy, however under load they are usually quieter than petrol engines as shown by the drive by noise levels and was demonstrated at our rolling road day. The diesels were significantly quieter than the petrols then.

 

[brynton]

Spot on,

would the millers be any good, or is there a specific treatment with a cetane improver??

Is it worth pulling the injectors out and getting them cleaned??

I will be replacing the rocker gasket in the next weeks so I could whip them out then??

Cheers dieselman

 

[GazCaff]

Mine tends to "nail" a little bit when idling. At the end of the day though, it is a stone age engine in terms of diesel technology inspite of having engine management and 20 valves. Still love it though

 

[racall]

Have you checked the fan belt shock absorber on the front of the engine ?.
Lean a screwdriver on it when the engines running and see if it quietens down (watch yor fingers)
They have a tendency to rattle.
A replacement on mine worked wonders

 

[Dieselman]

At the end of the day though, it is a stone age engine in terms of diesel technology

Hmm. You obviously believe all the marketing hype surrounding "new" direct injection engines.

Original diesel engines were direct injection and have always been used for heavy engines and plant etc. Indirect engines were developed to enable their use in passenger cars as they as quieter and smoother due to using a pre chamber.
Mercedes stuck with the "old" indirect engine longer than most because refinement was more of an issue for them.
At low speed an in line CDI can't be said to be as smooth as the old OM606, however the new V6 engines are good due to the multi firing of the injectors and the lowering of the compression ratio. Both have the effect of reducing the rapid expansion of gas but in return are not as efficient as an I6.

 

[Dieselman]

Spot on,

would the millers be any good, or is there a specific treatment with a cetane improver??

Is it worth pulling the injectors out and getting them cleaned??

I will be replacing the rocker gasket in the next weeks so I could whip them out then??

Cheers dieselman

Millers will do nicely. I wouldn't bother pulling the injectors out unless you have excessive smoke.

 

[GazCaff]

Hmm. You obviously believe all the marketing hype surrounding "new" direct injection engines.

Original diesel engines were direct injection and have always been used for heavy engines and plant etc. Indirect engines were developed to enable their use in passenger cars as they as quieter and smoother due to using a pre chamber.
Mercedes stuck with the "old" indirect engine longer than most because refinement was more of an issue for them.
At low speed an in line CDI can't be said to be as smooth as the old OM606, however the new V6 engines are good due to the multi firing of the injectors and the lowering of the compression ratio. Both have the effect of reducing the rapid expansion of gas but in return are not as efficient as an I6.

Actually, I'm not as gullible as you appear to believe I am. I was thinking more along the lines of the five cylinder engine in the 250 TD being able to trace its roots back a fairly long way, albeit in 10 valve form. While I bow to you superior general diesel knowledge, I do already know the different principles for indirect injection, Direct injection and common direct injection and unit injection but thanks for the lesson.....

 

[Wezzel]

Definately sounds like diesel knock. Mine was quite bad until I started using injector cleaner (Redex) in every fill up.

Now it's a quiet as a mouse (well nearly).

 

[brynton]

I filled up and emptied a bottle of STP diesel treatment and that has reduced things quite a bit:bannana: , but it has unearthed a squeak/rattle from the fan belt tensioner. A quick dose woth WD and this was gone for a few minutes then came back so I will order a new one.

As for the fanbelt shock absorber, do I wedge the driver in any where just to see if it takes the play off???

Cheers