nasty knock, any ideas?

ThomasLRNL · Wednesday at 08:49

All,

i rebuilt this engine and paired it up to my gearbox. however, im hearing a knock. All bearings in the engine are new and have maybe max 5 minutes of runtime on them. I did feel/seem to have a slight gearbox knock from before when i put this engine in. this leads me more towards it being a gearbox knock. but i would like to hear opinions of more knowledgable people.

saxavordian · Wednesday at 09:21

12:15 to Exeter train leaving Landy platform 2

ThomasLRNL · Wednesday at 09:53

saxavordian said:
12:15 to Exeter train leaving Landy platform 2

xD its a bit of a train rn yes

Wildefalcon · Wednesday at 09:54

If it's in neutral, then can't be gearbox? Check valves first. I'd look at the dizzy, then the cam gear. Couldn't see from the video, is there oil coming through the rocker shaft?

ThomasLRNL · Wednesday at 09:57

Wildefalcon said:
If it's in neutral, then can't be gearbox? Check valves first. I'd look at the dizzy, then the cam gear. Couldn't see from the video, is there oil coming through the rocker shaft?

input shaft of the gearbox is always turning no…? i thought maybe its something there.

dizzy and cam gear what should i look for when inspecting those exactly? valves should be set correctly. yes oil coming through the rocker shaft and ive always had excellent pressure as well.

Wildefalcon · Wednesday at 12:04

It's hard to tell from a video. Get a stick/rod mechanics stethoscope to isolate the knock.

Sounds cam shaft speed, not crank shaft speed.

kermit_rr · Wednesday at 12:09

I'm going to go with a dead big end just on one piston

ThomasLRNL · Wednesday at 12:19

Wildefalcon said:
It's hard to tell from a video. Get a stick/rod mechanics stethoscope to isolate the knock.

Sounds cam shaft speed, not crank shaft speed.

yep agree

ThomasLRNL · Wednesday at 12:20

kermit_rr said:
I'm going to go with a dead big end just on one piston

weird though, since i redid all of them

steve2286w · Wednesday at 16:44

I counted about 15 knocks in 5 seconds that’s 180 per minute
Assume tickover speed about 720rpm, so cam speed is 360rpm
Does it sound noiser with ear to air intake
After rebuilding my 200di I had a regular clonk like that , turned out I stuffed a rag into tdi intake manifold to stop filings going in , on running the engine it got sucked into an inlet port and stopped air getting into cylinder
Compression pressure was only 90psi on that cylinder with gases being forced back out of air filter leading to knock noise
May be worth a check, also feel the gbox if you think it’s that

Exhaust not banging on gb mount ?

kermit_rr · Wednesday at 17:28

It did seem to be in time with the valves opening

ThomasLRNL · Thursday at 11:13

kermit_rr said:
It did seem to be in time with the valves opening

yes, i suspect it might be exhaust manifold… since i saw im missing a bolt on the fourth cillinder. AND i dont get the knock when i turn it over on the starter. ruling out a collision between the valves and the pistons

more info tonight, when i can work on it

kermit_rr · Thursday at 12:18

ThomasLRNL said:
yes, i suspect it might be exhaust manifold… since i saw im missing a bolt on the fourth cillinder. AND i dont get the knock when i turn it over on the starter. ruling out a collision between the valves and the pistons

more info tonight, when i can work on it

When a big end knocks, it's the bang pushing down on the piston that makes the noise, you wouldn't hear it during cranking

Wildefalcon · Thursday at 12:45

ThomasLRNL said:
yes, i suspect it might be exhaust manifold… since i saw im missing a bolt on the fourth cillinder. AND i dont get the knock when i turn it over on the starter. ruling out a collision between the valves and the pistons

more info tonight, when i can work on it

Thanks for the updates....

kermit_rr · Thursday at 12:52

Also it's not an interference head so couldn't be valve noise

Wildefalcon · Thursday at 12:59

Probably not, unless there's something odd in the cam follower or push rod area.

ThomasLRNL · Thursday at 18:27

not the exhaust. dismantled it and listened to the engine with a sthetoscope. still a tick. indeed does seem to come from the camshaft side of things. also indeed does seem to allign with the valves opening/closing.

going to set the valve lash again now. after that im a little out of ideas.

edit: i can also hear it ticking when i crank it over with a stetoscope although a bit softer.

ThomasLRNL · Thursday at 18:54

no improvement when adjusting the valve lash. i guess all that remains is pulling it again and inspecting the crankshaft and its bearings.

ThomasLRNL · Thursday at 18:58

ok definately seems to be the camshaft, ticks are lining up with the exhaust rocker of cil 3

edit: typed crankshaft instead of camshaft.

Wildefalcon · Thursday at 20:34

Cam follower? The big roller, or the slider? A bore camera down the push rod hole might be helpful.

nasty knock, any ideas?

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