Stumped - Knocking 300tdi

[Greg B]

Hi Guys,

I'm stumped...my 1998 Defender 300tdi (422 000km clocked) is making a loud knocking sound.

I have listened with a DIY stethoscope and can't seem to pin point it's origin. From inside the cab it sounds like drivers side.

I have checked the vacuum pump...not that. Lift pump fine...pumping fuel. Head gasket was changed about to years ago. Checked for leak behind block ...cylinder no4...nothing. All clean.

Not using water but is using oil...burning a little blue when idling at robots and slow traffic. Been meaning to replace stem seals.  Leaking oil around sump area

Recently did oil change, fuel/air filter, tappets and timing...was running smoothly and quietly.  ( as Landy's go) for a couple of days. Then back to square one. The Annoying knock seems to occur when accelerating. Not all the time but mostly. There's no power loss at all.

Done all the basic checks..so where do I go from here... Before you say engine overhaul (im cash strapped and cannot afford that now) but what can I check to narrow it down and get to the bottom of this.

Thanks Guys

[Tal]

I would like more than one confirmation of this but knocks like that are most often worn big or little end bearings. loading the engine also suggests bearing wear, though decellerating can show the same thing, a more experienced mechanic could probably tell you which is worn if accelerating or decellerating,

It's a high mileage engine so it seems like the most likely place to start to me.

Removing the oil pan may well give you some basic insight

[Greg B]

Thanks Talk. That was something I had thought about but been procrastinating. I dropped the sump about a year ago to inspect and they looks good still. Guess I'll start there.Anythingg else I must check or change while I have the sump off ?

[Yostumpy]

you say checked the vacum pump, but have you swapped it for a known good one.maybe you could remove and try it,  if thats possible without spraying oil everwhere.  mine was loud. 

cambelt not slipped a tooth has it?

[GW8IZR]

does the noise change if you rest your foot lightly on the clutch pedal?

[Mo Murphy]

You say it was quiet after you did a service, what did you do with the timing ?

Mo

[Greg B]

Thanks for replies guys.

Yostampy...that's quite possible. I had a second hand one...not sure if it was totally fine. pulled mine last night and rebuilt one from the old one. Noise still there but now my breaks are hard its not pulling vacuum....ah the joys will have to put old one back this weekend.

GW8IR...no change in noise when clutch depressed. I replaced clutch and all gearbox bearings 4 months ago. That's 100%

Going to listen again tonight with stethoscope and see if I can hear which part of the engine its coming from.

Will report back

[Greg B]

Also checked timing again tonight....it's spot on.

[Greg B]

Update.... Tried listening last night...injectors 1&2 sound different than 3 & 4...much higher pitch. Not sure if old or blocked injectors would cause a knocking.

What's your thoughts