Intermittent clacking sound

[Lawrence]

Hi fellows, there seems to be an intermittent loud clacking sound coming from my engine. It makes the sound once in a while. If i hear it today, i may not hear it for a couple weeks or longer. It makes the sound for about 5 seconds, during which time the engine also shakes, and then goes away. What could be the cause of this sound? Could it be bearings, or the fuel system?

[Robo]

Sound like sticking valve hitting piston.
turbo fins breaking up and being sucked back into cyl, and being crushed/hammered against head.
worst case scenario, not good.

[Lawrence]

Sound like sticking valve hitting piston.
turbo fins breaking up and being sucked back into cyl, and being crushed/hammered against head.
worst case scenario, not good.

Thanks Robo. No turbo (not yet). Would the sticking valves be sometimes or would it be constant?

[threedogs]

Could be staving for fuel every now and then,,, change the fuel filter and inspect, or,,,
Drop the oil and change it checking oil for metal contaminates,
That's all I have

[Lawrence]

Could be staving for fuel every now and then,,, change the fuel filter and inspect, or,,,
Drop the oil and change it checking oil for metal contaminates,
That's all I have

Thanks threedogs, will try both of those. Havent changed the fuel filter in quite a while.

[threedogs]

What motor and year is your Patrol ,helps with all the info.

[Col.T]

G'day Lawrie,
can only hope it's not Robo's prediction 'cause that would suck big time.
Are you absolutely certain the noise is coming from the engine rather than somewhere in/around/near the engine bay?
Does it happen at particular revs or speed? Under load or cruising easy? When it stops is there any noise/shudder and then all O.K.or does it just fade away? Could you stop when it happens and get your head under the bonnet, even with the dopey looking old trick of a long screwdriver on various parts of the donk and the other end in your ear to get a good idea of location? (By the way, it's best not to stick the sharp end in your ear).
Seems to me a bit unlikely that there's bits of metal banging around on pistons. Would have thought that sort of noise would stick around and have a very definite effect but I dunno as it's never happened to me.
Keep us informed
Col

[Lawrence]

Its a 1989 Y60 lwb wagon with the td42 engine. It comes suddenly and goes just as quickly as it came. I am not sure that it is coming from the engine, but it makes the vehicle shake a bit while it is there. And it doesnt seem to move with the revs. I wondered if it might be the vacuum pump on the alternator. I did have an mk that had that sound and I rebuilt the engine as it was the bearings, but that sound was constant and got louder with the revs.

[Robo]

Thanks Robo. No turbo (not yet). Would the sticking valves be sometimes or would it be constant?

Can be either.
I said worse case, ( hope it's not, fingers crossed Threedogs is on the money ).
otherwise you can take an pro-active approach and get someone qualified to take a look at it.
On the chance it's a valve you don't want that to continue to happen.
best of luck with it

[Col.T]

G'day again Lawrie.
guess by now it's either fixed or you're riding a push bike.
If neither, can you clarify the '...it doesn't seem to move with revs.'
There aren't many engine internals which don't change up/down with revs... Trans./drive train will vary with revs/gears... Suspension/wheels etc. with speed.
If it's ongoing, when it happens next, if manual, clutch in and rev it/idle it....... What do you do with auto? Maybe drop it a gear to get a rev change. Be useful to see if the noise varies with revs or not.
By the way, what do you do for 4X4 sport in the beautiful Carribean? Apart from drinking rum that is?
regards,
Col