Thread: 300Tdi engine knock

if on the way out the lash cap was getting stuck on its edge between the valve head and the rocker you will have had pistons touching valves.

check the rocker assemblies, pedestal bolts, the adjuster nuts and pushrods for damage/deformation.

I have had the adjusted back off and let the lash caps loose before today but its always evident that this has happened as the adjuster is usually wound all the way back down with the ball up close to the rocker.

Makes a hell of a noise when you get to the point where the lash adjuster has jumped up and is taking up all the clearance and then some when the valve is opening.

Yeah. Mine knocked when the pistons got too friendly with the valves. It survived, with the rockers and pushrods being sacrificial. The bronze cam followers can also be damaged, but mine were ok. Of course, if the thing was revving then all bets are off.

Moved it into the shed today.

While it sounds fine at idle, the knock is there as soon as it gets enough throttle to make it move.

Engine and gearbox mounts are good, can't see anything that's hitting something.

I'll check the valve clearance, then pull the rocker shaft, check the valve heights and push rods.

If that's OK I'll pull the sump and have a look at the big ends.

Unless someone points me in another direction.

Please keep the ideas coming.

Tony

Just to be sure, and may sound a bit noobish(on my part) ... but have you confirmed it's definitely not the exhaust manifold/gasket, split exhaust, loose flange ... or something really simple like that too.

In the short vid, sounded more exhaust gasket broke type racket to me ... but then again videos are always hard to track sounds with.
Noises can be one of the hardest things to track, and very recently, Mike at Britannica Restorations had a 300tdi come in with a squeak in it.

IIRC I think it ended up being an injector, but bets were that it was the serpentine tensioner ... sounded exactly the same noise. Took a lot of disassembly and a few vids he did, but in the end he got it.

My worst 'knock' noise came about 4 or 5 years ago. I've changed a few serpentine belts, tensioner a couple times ... etc. then one day a loud "bearing type" knock developed. very worrisome.
Sounded like it came from the dipstick area, and though maybe waterpump bearing, I pushed pulled prodded, inserted various sized fuel hose in my inner ear .. couldn't find any source .. it just seemed to be on the pass side near the dipstick.

Anyhow, but chance I leaned on something(can't recall what .. I think the alternator) and the noise briefly disappeared, but came back, so I leaned again and didn't go, did go .. became variable leaning on stuff.

Then found that any pressure on the serpentine belt made it go away. Ah!! I got it, I thought, another not so good quality tensioner. But my deducing skills were amateur hour this time .. and did what I think most folks would assume. tensioner making noise, tensioner faulty. Was actually the serp belt itself. stretched so much that tensioner bottomed out on it's end stop. Had a old raggety belt, fitted and knock gone. fitted less raggety, but stretched belt for a bit longer and got a few belts for replacing.

Originally Posted by TonyC

Moved it into the shed today.

While it sounds fine at idle, the knock is there as soon as it gets enough throttle to make it move.

Engine and gearbox mounts are good, can't see anything that's hitting something.

I'll check the valve clearance, then pull the rocker shaft, check the valve heights and push rods.

If that's OK I'll pull the sump and have a look at the big ends.

Unless someone points me in another direction.

Please keep the ideas coming.

Tony

Before you check the valve clearances, check the timing.

check the timi

Hi All,

The timing is spot on.
Valve clearances were a smige tight at around 0.15, not bad for done on the side of the road without feeler gauges.
Rockers all good, push rods straight.
No sign of any exhaust leak.

I'm now trying t I get the sump off, it's stuck on with half the world's silicone, anyone tried one of the silicone dissolvers?
Any other ideas, other than brut force.

Tony

Edit,
Also ran it without the fan and auxiliary belts.

Ok, that's my theory out the window. You check the oil pressure by any chance?

as some also rans,

check the bolts that hod the TC to the fly wheel,
check the vac pump (drop the vac line off and test it at full flow followed by no flow)
check the steering pump pully bolts
with the engine running at just enough revs to make it start to knock, crack the injectors one at a time.
with the rocker cover off, watch the valves return (Ive had a valve with a bent shaft catching until the piston kissed it back upwards again)

good luck