E300TD - Knocking noise at idle

[MPK]

I have noticed a slight knocking noise at idle on my E300TD.
Nothing major (at this stage ), you really have to listen to pick it up.
If I rev the car ever so slightly, the tickover smooths out and the knocking noise goes away.

From another MB board a contributor advised a possible cure : -

" I have been advised that this is caused by pressure pulses from fuel feed pump, and the remedy was to fit an expande fuel return hose on fuel return line,(merc service bullitin AF07-10-U-1800AG) "


For many months now, I have run with BP ultimate & Millers in every tank.
This does seem to make it a little quieter.( Jury still out on this )

Anyone had same problem and managed to resolve?
Could it be blocked tappets ? ( As also suggested on another MB board)
Can anyone shed any light on the MB tech bulletin ?

Or is this simply a characteristic of the E300TD engine ?

Many thanks in advance.

Mike.

E300TD 1999 150k

 

[230K]

hi

Might be a characteristic, i find they knock depending on the outside temp and with different fuels. Try a small amount of vegetable oil say 10-15% and see if it quietens down.

230K

 

[MPK]

Vegtable oil ? - Interesting. Any particular type or brand?

You mean, just fire a bottle of ASDA'a finest straight down in the tank !
Or should I mix up first with some diesel and then add ?

Any advice on exactly what to do here really appreciated.

( Dont want to go from a slight knock to a clogged fuel pump !)

Cheers Mike

 

[230K]

Hi

Trying Asda, tesco Lidl's finest will eliminate any diesel type knock if she is still knocking at idle after that it will be mechanical.

Another thing when she is idling press and hold the drive belt dampener with your thumb be careful of the fan, if the knock goes away then replace your drive belt damper.

The veg oil really makes them run quiet but is addictive Or so they say...


230K

 

[Dieselman]

Try revving the engine above the point where the knock stops then let it fall back to idle. If the noise only starts again once the fuel has come back on at idle then it must be fuel related.
My money goes on it being the MAF sensor wearing out.

 

[colin.dillon]

Had a slight knocking noise from my 300td on tickover which was pointed out when in for service. Mechanic lifted the bonnet & pressed down on the belt tensioner & the noise disappeared. New tensioner - job done! Hope yours is as easy to fix!

Col

 

[stuart1948]

I had a similar problem on my E300. It urned out to be the V belt tensioner. Sounded it bit like tappet noise.

Easy to test.(mind your fingers) Run the engine and put some tension on the tensioner.

 

[Vips]

I too think its the tensioner. I had a similar problem and initially thought it was tappets. But tried the finger pressure technique and the noise went. Simple job to do and took me about half an hour to replace this. Yours might be different as I'm not sure how difficult it is on the diesels.

 

[stuart1948]

E300

I too think its the tensioner. I had a similar problem and initially thought it was tappets. But tried the finger pressure technique and the noise went. Simple job to do and took me about half an hour to replace this. Yours might be different as I'm not sure how difficult it is on the diesels.

Actually had mine done today. E300 TD.
Charged for 2.6 hours = £45ph £117.00
Damper = £26.72. Lever = £51.82 + Maggie Thatcher tax.

Oh and an While it was there thought taht i might as well have an oil and filter change.
Mobil Oil £33.75.
Oil Filter £8.51
Fuel Filter £8.71
Air Filter £17.52.

Thought that it was going to be about £90. Felt like petrol had been poured over my nuts and set on fire.
Iv'e gone for a lie down


Total bill came to £310