metallic marble type noise

bournemouthken · Post by **bournemouthken** » Thu Oct 11, 2007 10:26 pm

When in neutral, I can rev the engine (diesel) and it is sweet as anything, quiet, just like new, yet when in drive, I accelerate and under load there appears to be a noise like a couple of metal ball bearings clanking / vibrating on to each other at high speed, , it’s as if something is loose and knocking against something, could it be something like the cam belt tensioner or am I way off the mark, as I say, in neutral I can rev hard and the engine is very quiet – any suggestions please, the engine has done about 35000 miles and the oil changed regularly, there is no loss of power and the exhaust is very clear.

Baldeagle · Post by **Baldeagle** » Fri Oct 12, 2007 8:14 am

Hi Ken, after buying my Bongo (still a newbie) I heard a similar noise. After studying everything I could find on this wonderful forum, I decided to block the EGR.
On a trip to the UK I drove to Allens, I was staying in Devon so no big deal. Got back here fitted the blanking plugs and wow, noise was gone.
Not saying this is the definitive answer but for £12 worth a try.hope you soon find it. Brian

bournemouthken · Post by **bournemouthken** » Fri Oct 12, 2007 8:21 am

Cheers Baldeagle, but my EGR is allready blocked off, I will check again in case the plug has come away.
Happy Bongoin

Post by **Simon Jones** » Fri Oct 12, 2007 11:17 pm

Ken, I can't help with your ball problems, but it looks like your avatar has swollen somewhat in size.

See here for details on the permitted size (100 x 75):
http://www.igmaynard.co.uk/bongo/forum/ ... ght=avatar

bigdaddycain · Post by **bigdaddycain** » Sat Oct 13, 2007 2:40 pm

It sounds like your engine is suffering from "diesel knock" This can sometimes happen (under load) when the air/fuel ratio is running too lean,it may be worth getting a diesel specialist to check the settings on the pump.

bournemouthken · Post by **bournemouthken** » Sat Oct 13, 2007 3:58 pm

Thanks bigdaddycaine - I will indeed get the pump checked out just incase
Cheers-----------

scanner · Post by **scanner** » Sat Oct 13, 2007 4:06 pm

bigdaddycain wrote:It sounds like your engine is suffering from "diesel knock" This can sometimes happen (under load) when the air/fuel ratio is running too lean,it may be worth getting a diesel specialist to check the settings on the pump.

Sorry, but how does a diesel run "too lean"?
They only run lean, as the only thing the pump does is inject more fuel, the air inlet is unrestricted.

bigdaddycain · Post by **bigdaddycain** » Sun Oct 14, 2007 1:11 pm

scanner wrote:
bigdaddycain wrote:It sounds like your engine is suffering from "diesel knock" This can sometimes happen (under load) when the air/fuel ratio is running too lean,it may be worth getting a diesel specialist to check the settings on the pump.
Sorry, but how does a diesel run "too lean"?
They only run lean, as the only thing the pump does is inject more fuel, the air inlet is unrestricted.

Diesel knock occurs more than likely due to incorrect settings at the fuel pump,which then can give insufficient fuel to the injectors,a poor spray pattern from the injectors can lead to diesel knock when the engine is under load.

Most people can associate the term running "lean" via a petrol engine,as a comparison is possible with the term pinking (pre-ignition) and diesel knock in a diesel.

It made sense to me anyway

scanner · Post by **scanner** » Sun Oct 14, 2007 1:43 pm

If it supplies insufficient fuel to all the injectors it just runs slower as that is just the same as less accelerator. But less fuel to one injector would produce an effect similar to missing on a petrol engine. All I can think of that would produce a "knocking" would be wrong timing on one injector.

If it only occurs "in gear" my suspicion would be something in the gears.

bigdaddycain · Post by **bigdaddycain** » Sun Oct 14, 2007 2:02 pm

scanner wrote:But less fuel to one injector would produce an effect similar to missing on a petrol engine. All I can think of that would produce a "knocking" would be wrong timing on one injector.

Its all linked in my understanding of the fundamentals of diesel engine operation... (bear in mind that i'm not a mechanic, i deliver chinese meals for a living) Insufficient, or improper spray patterns of any, or all injectors,via a impropely set-up fuel pump, could in my opinion,lead to a compression loss,which in turn could cause ignition delay,and consequently diesel knock.

scanner · Post by **scanner** » Sun Oct 14, 2007 2:32 pm

Surely "knock" would result from pre-ignition BTDC (as with pinking or "dieseling" in a petrol engine) not from late ignition ATDC, which would happen as the piston was dropping and thus enlarging the combustion chamber.

If it only happens when revved up "in gear" I reckon that makes it in the gears.

bigdaddycain · Post by **bigdaddycain** » Sun Oct 14, 2007 3:00 pm

Well, if bournemouthken gets to the bottom of his problem, and posts the results, i guess we'll find out.

Good luck ken.

bournemouthken · Post by **bournemouthken** » Sun Oct 14, 2007 7:13 pm

Wow - now my overloaded head is knocking as well as my engine, I don't thnk the noise is to do with the gearbox, I will take the Freda into a diesal specialist in Poole and ask a few questions and will post the reults as soon as Iknow,
many thanks to all Bongonaughts who replied, it's nice to have people on line who are willing to help out -

Dave up north · Post by **Dave up north** » Sun Oct 14, 2007 7:18 pm

Have you had a good look for marbles?

harpo42 · Post by **harpo42** » Sun Oct 14, 2007 7:38 pm

I am absolutely no expert but it could also be the Universal joints in the propshaft. Apply the handbrake hard and select drive accelarate forward slightly, then select reverse and accelarate backwards slightly. If you hear a mettalic "clang" as drive is taken up then this could be play in the UJ bearings.

metallic marble type noise

metallic marble type noise

ball bearings

metallic noise

metallic noise