Tapping noise?

[fasteddie]

Right, i got a bit of a shock when driving down the motorway today when the engine started a tapping/rattling noise, at first i thought it sounded like a flat tyre so i pulled onto the hard shoulder and the noise slowed down with the speed only thing was it never stopped.
It is definitely coming from the engine bay but it is difficult to locate any further than that, i have checked all round and nothing seems to be rubbing on the belts and there is nothing that jumps out at me, it starts and stops with the engine and the regularity increases with the engine speed. I have checked all the fluids and everything is to the correct level.
I only had the damn thing serviced(full service, fluids,timingbelt etc etc) on the 16th March and have already taken it back once(last week) to have a coolant leak fixed, so not going so well as i have only owned it since 6th march.
The noise is difficult to describe but it seems more of a tapping noise like a spinning disc out of true bashing/touching on another piece of metal, that sort of scraping noise.
Anyone with any ideas greatly appreciated before i have to try and find more cash.

[marky]

Firstly Check Your Oil Levels

[fasteddie]

done that with no joy, everything is spot on! Cheers!

[marky]

just prey its not at the bottom end mate BIG ENDS

[fasteddie]

I am really hoping its not the bottom end, any ideas what else it could be, and if not how expensive a job is the bottom end rebuild?

[fasteddie]

Is it engine replacement time if the big end goes?

[marky]

HILUX bob had a quote not sure how much though. i would get it checked out first mate it could be something or nothing. is the noise heard while stationary & in neutral???
Big ends are shell bearings that sit at your con rod end of the pistons the crankshaft runs inside these bearings possible crank regrind & new shell bearings big ends can be done with engine in situ

[fasteddie]

Yep its heard when moving and stationary also can be heard when in neutral!

[marky]

you need someone to diagnose the noise mate

[Gamedawn]

Just a thought but check the bottom pulley on the engine. They have a rubber centre which acts as a damper and they are known to disintegrate. This eventually leaves the middle (crankshaft) spinning and the pulley (water pump drive) standing still.

[fasteddie]

Are you talking about the one on the timing belt or external on the engine? Cheers Roger

[Gamedawn]

Sorry - missed the reply. The external one at the bottom of the engine.

[TonyN]

I'd have the garage take the timing belt cover off and make sure all the pulleys are on properly, and the belt is tight.

Make sure the fan belts are all OK

[Vagrant No2]

Possible timing belt tensioner . You say a new belt was fitted so may have been fitted to tight and the tensioner is giving up . Common prob on motors these days . Some manufactures even sell the tensioner with a new belt now so they cover their a*$e against failure .

May be a dry alternator/water pump bearing .

Or Crank pulley breaking up like Roger said .

Many possibilitys to quote .
Best get it looked at , diagnois via computer is never 100% .

Rick

[fasteddie]

I have checked the water pump as its easiest to do and there doesnt seem to be any play in it, also checked all the other pulleys on the external belts and again doesnt seem to be any play.
If i had to hazard a guess i am thinking more towards the timing belt/tensioner/pulleys as it seems to be that direction the noise is coming from, esecially as it only 1 month since that was all stripped + the tensoiner doesnt seem to have been replaced on the service or at least there isnt one on the invoice.
Also the noise doesnt get any louder when you pull away from standing which i would prolly have expected if it was the bottom end bearings? Also doesnt seem to have any loss of power.
How big a job am i looking at to remove the timing belt cover on the 2.4 as it doesnt look particularly straight forward. I am pretty good with most mechanical jobs i have done but lack experience dealing with cars(i have only ever really worked on my motorbike) other than odd jobs with my old spitfire, and is there a haynes manual availble for the 4runner? presuming thats the same?
If it does turn out to be the crank bearings, can the shells be replace if the sump is removed? as someone suggested to me today?
Thanks everyone for all your help so far!