Thread: 300TDi knock noise

Hey folks,
I'm going to pull the sump off tomorrow for an inspection.
How can i test for piston slap with the sump off from underneath the Disco? Just put my hand up the cylinder and see if the piston can move horizontally a fair amount?
Thanks!

Righteo

Well if your doing that!

Once sump is off and you’ve cleaned the black off your nose

Pop off the Conrod caps and pop out a shell or four.
Honesty not much effort and you’ll see in the cap shell any significant wear. Actual slap will be hard to establish as there is always a bit of play in the system
If you take high resolution photos of the Conrod big end shells people like Rick130 will be able to ID significant wear patterns.

I wish I was closer - I have a set of 300tdi big end shells rotting in my shed - for the effort your are showing id offer them up gratis!!!!


S

piston slap will be most noticeable around 2000-2500 rpm only when coasting , it doesn't happen at idle .

Originally Posted by roverrescue

Righteo

Well if your doing that!

Once sump is off and you’ve cleaned the black off your nose

Pop off the Conrod caps and pop out a shell or four.
Honesty not much effort and you’ll see in the cap shell any significant wear. Actual slap will be hard to establish as there is always a bit of play in the system
If you take high resolution photos of the Conrod big end shells people like Rick130 will be able to ID significant wear patterns.

I wish I was closer - I have a set of 300tdi big end shells rotting in my shed - for the effort your are showing id offer them up gratis!!!!


S

So i pulled the sump and all the big end shells, and.... as i expected they are all perfect! I slipped in a new set of Kings STD anyway just for maintenance. Also, checked conrod end float on the crank and they are within spec.
That's good news and bad news!!
Now, i will pull the head this weekend (if i get time) and check out all the lifters. I'm hoping i find one of the brass lifters visibly damaged from a snag in the guide/maybe a roller with a visible flat spot etc...

Any specific ways to check for wear on the lifters? How to tell how much 'play' is too much and would cause a knock sound?

Thanks!

Originally Posted by Finnius

So i pulled the sump and all the big end shells, and.... as i expected they are all perfect! I slipped in a new set of Kings STD anyway just for maintenance. Also, checked conrod end float on the crank and they are within spec.
That's good news and bad news!!
Now, i will pull the head this weekend (if i get time) and check out all the lifters. I'm hoping i find one of the brass lifters visibly damaged from a snag in the guide/maybe a roller with a visible flat spot etc...

Any specific ways to check for wear on the lifters? How to tell how much 'play' is too much and would cause a knock sound?

Thanks!

That's all the things I did! I even re checked the big ends...no joy, decided the crank was out of round so I plasti gauged it, came back fine so I decided the plasti gauge was lying, nope, then thought the wrong head gasket was fitted, and the piston was tapping the valve's, wrong...it had simply been over heated and caught the pistons....piston slap, I hope yours is less traumatic though!

Originally Posted by shack

That's all the things I did! I even re checked the big ends...no joy, decided the crank was out of round so I plasti gauged it, came back fine so I decided the plasti gauge was lying, nope, then thought the wrong head gasket was fitted, and the piston was tapping the valve's, wrong...it had simply been over heated and caught the pistons....piston slap, I hope yours is less traumatic though!

How did you find out it was piston slap? Marks on the cylinders?
Was the knock there all the time even at idle - or only at certain revs?

Originally Posted by Finnius

How did you find out it was piston slap? Marks on the cylinders?
Was the knock there all the time even at idle - or only at certain revs?

Mainly at idle for some reason, probably harmonics, it was better when I cracked injectors off, oil pressure was spot on at all revs/temperature, it definitely knocks more when cold though.

And yeah, the bores and pistons were pretty scruffy , don't know how hot they got it, but when I pulled the head off I realised it looked brand new, so I'm guessing whoever heated it up had to put a new head on and took a punt on the bores and pistons...lucky me,

although I'll happily take the new head!

Originally Posted by shack

Mainly at idle for some reason, probably harmonics, it was better when I cracked injectors off, oil pressure was spot on at all revs/temperature, it definitely knocks more when cold though.

And yeah, the bores and pistons were pretty scruffy , don't know how hot they got it, but when I pulled the head off I realised it looked brand new, so I'm guessing whoever heated it up had to put a new head on and took a punt on the bores and pistons...lucky me,

although I'll happily take the new head!

Thanks for the info. How did you end up fixing it? Re-bore with new piston? Or re-hone and new piston?