Sleuthing a knocking 300 tdi

[shack]

Hi all,

Just pulled the pistons out of my defender, it has had a knock since just after I bought it, maybe it had it before but has just got more noticeable over the journey.

Anyway due too a clutch failure I've pulled the motor, it was still running fine, just knocking.

Here are the pistons:

Is this from overheating?

There has been previous water ingression in the bores by the look of it,I guess before I owned it, as it doesn't use water or much oil really.

And would this be enough to knock?
I could have sworn it was a big end knock but did them a couple times with little change

Cheers
Jameshttps://uploads.tapatalk-cdn.com/20191017/dcdaf7ee4e0873278dc2a521d175f948.jpg

[donh54]

Hi all,

Just pulled the pistons out of my defender, it has had a knock since just after I bought it, maybe it had it before but has just got more noticeable over the journey.

Anyway due too a clutch failure I've pulled the motor, it was still running fine, just knocking.

Here are the pistons:

Is this from overheating?

There has been previous water ingression in the bores by the look of it,I guess before I owned it, as it doesn't use water or much oil really.

And would this be enough to knock?
I could have sworn it was a big end knock but did them a couple times with little change

Cheers
Jameshttps://uploads.tapatalk-cdn.com/20191017/dcdaf7ee4e0873278dc2a521d175f948.jpgWithout seeing them in the flesh, I would hazard a guess that the engine has overheated at some stage.
Assuming the pistons in the picture are from left to right, 1 to 4, number 1 has suffered the most, then progressively down from there.
That would tend to point to the knocking being piston slap, rather than bearing knock. Not so much from piston wear, as from the rings losing tension.
Seeing what, if any, scoring was evident in the bores would paint a better picture.
Also, measuring the bearing gap, against the factory specs, may help.
This doesn't necessarily mean overheating to the point of seizing, but probably not far off it.
Depending on your plans for future use of the vehicle, either a comprehensive rebuild, or a set of rings and maybe bearings would be the solution.
Hope that helps

[Robmacca]

Funny... I've just had something very similar happen to me.... clutch failure, followed by removing the engine to replace the clutch and then looking at what else was needed doing while the engine was out... Well, that turned out to be a expensive idea in the end but at least I now know that the bottom end of the engine is in good order...

What was done to the engine:
> Removed the piston and it looked like they had gotten hot or something (see pics) - Block needed boring and new pistons and bearings bought
> New Rear Main Seal
> New Oil Pump gears
> Ended up having to buy a new Camshaft and Cam bearings due to what looks like something causing damage to No.1 (see pics)
> All new seals, etc
> New Reconditioned Injectors

https://www.aulro.com/afvb/attachments/90-110-130-defender-county/155018d1571297157-sleuthing-knocking-300-tdi-img_8041.jpg

https://www.aulro.com/afvb/attachments/90-110-130-defender-county/155014d1571297157-sleuthing-knocking-300-tdi-img_5216.jpg

Engine was seemingly running fine before Clutch failure, so I don't know how long it would have lasted... may have kept going ?? Engine has 362k kms on the clock

[shack]

Without seeing them in the flesh, I would hazard a guess that the engine has overheated at some stage.
Assuming the pistons in the picture are from left to right, 1 to 4, number 1 has suffered the most, then progressively down from there.
That would tend to point to the knocking being piston slap, rather than bearing knock. Not so much from piston wear, as from the rings losing tension.
Seeing what, if any, scoring was evident in the bores would paint a better picture.
Also, measuring the bearing gap, against the factory specs, may help.
This doesn't necessarily mean overheating to the point of seizing, but probably not far off it.
Depending on your plans for future use of the vehicle, either a comprehensive rebuild, or a set of rings and maybe bearings would be the solution.
Hope that helps
I wasn't going to post these pics but they came out better than I thought:

I've got another motor, supposedly 120k, it needs the timing/front covers replacing, I'm seriously thinking of dropping that in.

And yes, it ran well with the bores looking like that!

And yeah number 4 looks fine, the knock always seemed to come from number 3, it always abated somewhat when no.3 injector was crackedhttps://uploads.tapatalk-cdn.com/20191017/8544df1c0cdcae4609f7cbc5ffea9df9.jpghttps://uploads.tapatalk-cdn.com/20191017/bb9b0d8a42b6e80ef21294ca7351fb57.jpghttps://uploads.tapatalk-cdn.com/20191017/5e8a1b52b209c965ea2d2183e4d0212a.jpghttps://uploads.tapatalk-cdn.com/20191017/0b06556417d001b9965ee852de62173d.jpg

[justinc]

100% that engine has been HOT.

[shack]

100% that engine has been HOT.Yeah that was my take, just wanted back up!

Amazing how well it went

[Blknight.aus]

thats been hot to the point of the ally coming off the pistons.

also known as the piston grabbing the bore.

You know it got really hot when the ally is still fused to the bore. And yes, they'll run like that. not well but they run.

[shack]

We've also have a hilux that many years ago ran out of oil, the oil light wiring broke and the intake pipe got a hole in it during harvest when it was very dusty.

End result was all nipped up, similar to this but much much worse, we ended up having to die grind the alloy off the bores at the bottom, and you would not believe how well it runs, still no power though.

[rover-56]

I have a knocking 300tdi too. I could never decide what was causing it. I sounds like a big end but it is there hot and cold but only under load. Nothing like bearing noise in other engines I have had. Thought it might be a loose piston so I did a compression test.
The pressures on cylinders 1,3 &4 were about 300psi which is expected with an engine which has done 300k km. Factory spec is 348psi. Surprisingly the pressure on cyl. 2 is 375psi. No idea why it is so high.
Anyway I am replacing the crank bearing shells - needed because oil pressure is down to 100kPa hot.
Don't think it will fix the knocking but you never know....
Pics of the shells attached. Interesting wear pattern on 4 and 5 mains.
Terry

[rover-56]

New std shells in. 0.05mm (.002") bigend journal wear, no measurable ovality.
Hot oil pressure only came up to 200kPa hot. Pressure relief valve ok.
Interestingly the knock is very much reduced, I can hear it probably because my ears are tuned to it. It would be lost in the general 300tdi clatter to anyone else I think.
My theory is that no.2 cylinder with the high compression is working harder than the others and that was knocking the worn bigend. Can't think what else it could be.
No.2 bigend shells were not any more worn than the others so I think I can live with it.
Still don't know why the compression is so high.
I might tighten the no. 2 exhaust valve clearance a bit for a short run and see if the compression leak changes anything.
Terry

[rover-56]

Well, did the valve test and though it ran horribly rough the knock was gone.
All down to the high cyl 2 compression it seems.
Terry

[shack]

Finally got mine all back together yesterday, the knock is gone!

New pistons, rings, big ends mains, the head looks almost brand new in the water galleries, so I'm guessing it got cooked, destroyed the head, and they took a punt on the rest being ok with a new head fitted.

I don't rebuild motors very often, and I always forget just how much work it all is in between, especially when you keep finding extra problems as you go!

Cheers
James

[rover-56]

Good to hear. Even more fun underneath getting oil dripped in your eyes.[happycry]
300tdi's can actually sound good with a bit of TLC.
Terry

[shack]

Good to hear. Even more fun underneath getting oil dripped in your eyes.[happycry]
300tdi's can actually sound good with a bit of TLC.
TerryAs in with good servicing ? Or as in with a few mods?
Cheers
James

[rover-56]

Oh, I was thinking good servicing, mine has had a bad start in life with no oil changes by the 1st owner for at least 50k km according to the 2nd owner. 300tdi's seem to be prone to knocking noises anyway and I don't think crappy servicing helps. I have heard some really sweet running tdi's so I know quiet running is possible. Mine isn't one of them.[bigsad]

Personally i think the 300tdi is at the engines design limit at ~85Kw. They can be made to go with pump tweaking but I think at the expense of service life.
Terry

[shack]

Oh, I was thinking good servicing, mine has had a bad start in life with no oil changes by the 1st owner for at least 50k km according to the 2nd owner. 300tdi's seem to be prone to knocking noises anyway and I don't think crappy servicing helps. I have heard some really sweet running tdi's so I know quiet running is possible. Mine isn't one of them.[bigsad]

Personally i think the 300tdi is at the engines design limit at ~85Kw. They can be made to go with pump tweaking but I think at the expense of service life.
TerryI've actually got another one, only done 31000 from new, it's also noisy, I think that's one of the trade offs of having a direct injection diesel, but before pilot injection became the norm, they are pretty noisy at idle, diesel knock I guess.

Cheers
James

[rover-56]

I think there is a difference between normal direct injection diesel noise and the knocking that comes out of some 300tdi's.
Probably to do with assembly clearances, I have known 2 300tdi's that were really sweet sounding, one was in a S1 Discovery, and the other was in my previous Defender before this one. I know that engine came out of a Discovery. It got me wondering if quieter engines were fitted to Discoveries, I don't know.
The noisy ones don't seem to die earlier, my current one is clattery, but had done 300k km and is easily capable of pushing the Defender up to more than a true 130kmh.
Terry

[shack]

Maybe, but you may also find that some of the higher km engines are actually quieter than the tighter low km ones.

[Phil B]

My experience is not related to a 300tdi but i have two Isuzu 4BD1's, both with aftermarket turbos. One (an older '85 version) makes a lot of engine noise but easily outperforms the '88 version in my Perentie which is extremely quiet from an engine noise POV.
I believe engine noise is directly related to injection timing along woith other things. The more advance, the more noise I am told.
The joys of diesel.

[rover-56]

Yes I guess there are a lot of variables acting in this equation.
Terry