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advice on engine knock 

 

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 Post subject: advice on engine knock
Posted: Fri Jun 19, 2009 12:55 am 
Getting Side Ways
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Im currently the lucky mechanic working on a 2000 land rover discovery v8. Engine was rebuilt recently (over 12 months by owner)

now posses a really bad knock. Isolated it to no 7 cylinder by unplugging the ign lead and knock goes away, which tells me its the big end bearing. I unplugged the opposite cyl. lead to see if it could be a main bearing but knock was still present. had a look underneath and ended up pulling off the sump and No 7 rod cap. Bearing looked ok but to me had too little contact area. To try describe- had a wear point on the bottom, and areas near the top where the two shells meet. I think it may have too much clearance but am waiting on some plastigage.

What do yous guys think?
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 Post subject: Re: advice on engine knock
Posted: Fri Jun 19, 2009 8:33 pm 
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anyone......
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 Post subject: Re: advice on engine knock
Posted: Sun Jun 28, 2009 11:18 am 
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Did some of my apprenticeship on Land Rover.

Not a fault that we came accross in the workshop.

Do you know what the owner has done to the engine? Machined parts does the guy know his stuff etc ...
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 Post subject: Re: advice on engine knock
Posted: Sun Jun 28, 2009 5:59 pm 
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yeah, the engine dropped a sleeve so it was re sleeved, to match piston sizes. But recently i found out the crank was not machined but just supplied with STD bearings. We checked the clearance. Had bout 0.0025 thou. Bit on the excessive side but im not sure if its enough to cause knock. But someone has told the owner it may be a piston?

ZCompression test showed ok buy still maybe..?

Yeah guy knows a bit bout engines.
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 Post subject: Re: advice on engine knock
Posted: Sun Jun 28, 2009 11:13 pm 
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0.0025 thou. Thats about equal to 0.6mm.

Sounds a bit on the big side to me. But compare it to another cylinder or better yet, or a generic manual.

Keep in mind for yourself, some of the earlier blocks had an issue with the sleeves of the middle cylinders have been known to move.
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 Post subject: Re: advice on engine knock
Posted: Sun Jun 28, 2009 11:56 pm 
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yeah, had all sleeves redone.

Yeah apparently the max clearance is 0.5mm?
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 Post subject: Re: advice on engine knock
Posted: Mon Jun 29, 2009 1:02 pm 
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I dont want to give you the wrong information, so Ill say grab a generic workshop manual or download one if you can find one.

0.5mm sounds like a big gap.
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 Post subject: Re: advice on engine knock
Posted: Mon Jun 29, 2009 1:47 pm 
Oompa Loompa
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Sorry just have to chime in here,
2 and a half thou(.0025") is equal to 0.06mm which to my way of thinking is probably not too bad. But 0.5mm or 0.6mm (approx 20 thou to 25 thou) I think would knock!!

Hope this helps
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 Post subject: Re: advice on engine knock
Posted: Mon Jun 29, 2009 6:57 pm 
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yes sorry, gap is 0.05mm. bfxr6 put me off by saying it was0.6mm.
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 Post subject: Re: advice on engine knock
Posted: Mon Jun 29, 2009 10:35 pm 
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Mic clearance .. Don't rely on plasti gauge !!

 

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 Post subject: Re: advice on engine knock
Posted: Mon Jun 29, 2009 11:22 pm 
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whats wrong with pastigauge???
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 Post subject: Re: advice on engine knock
Posted: Tue Jun 30, 2009 12:13 am 
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eboost wrote:
whats wrong with pastigauge???

if the crank was ground and fitting the correct bearings------dry fit plasti gauge to check the crush,running the crank may be worn with new bearings-so may not get all the clearance,gudeon pins ok,piston clearance.i think you may have to check and record all of them,to see where the crank is and to get a average of the clearances.can you get a snake camera into the spark hole?if you get any top end issues.

 

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 Post subject: Re: advice on engine knock
Posted: Tue Jun 30, 2009 12:29 am 
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owner has been told it may be piston slap. Not sure bout gettin snake camera down there, will that tell you much?
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 Post subject: Re: advice on engine knock
Posted: Tue Jun 30, 2009 12:35 am 
Getting Side Ways
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eboost wrote:
owner has been told it may be piston slap. Not sure bout gettin snake camera down there, will that tell you much?

can see top of pistons and any marks from valves,or any or thing that looks strange-different,with out lifting the heads off.what type of oil was used in the motor?

 

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 Post subject: Re: advice on engine knock
Posted: Tue Jun 30, 2009 12:40 am 
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15 w 40
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