New noise - 300Tdi

[Leo109]

Hi All,

Our '97 300Tdi Discovery has developed a 'new' noise in the last couple of months, as 250,000km rolled around. I know it's hard to describe noises in writing but here goes...

Sort of a deep, slightly 'hollow' sounding, regular: thoongk, thoongk, thoongk at idle. I'd guestimate about 12 beats per second or 720 per minute, so that'd be about once per revolution at idle. Quite distinct from the 'normal' injection/ignition rattle (that happens twice per rev).

Haven't been able to pin it down to a specific location but I think front of engine somewhere. The noise is more distinct when you are about 10m from the car, rather than with your head under the bonnet.

Have checked the the turbo outlet flange and the flex-joint in the exhaust pipe, suspecting leaks, but it appears this is not it.

Just about due for another timing belt - does it sound like anything in that department? (If so, please let it stay together another month until I have time to change it!)

So, any clues, Gurus??

Thanks,

[isuzu110]

Lift pump ?

I had a similar noise and found out that my lift pump had failed. When I replaced it the noise disappeared. The noise was resonating along the fuel lines and drumming against the chassis in places.

Just a thought.

[Bush65]

From time to time mine gets a noise that resembles your description. A little like a slight miss. Haven't noticed it lately.

Might be time for me to check the lift pump.

[jimbo110]

I've just been through the "oh crap, whats that knocking noise" saga this weekend. A loud knock that would some times be there, some times not, but when it was there would go away when the engine was rev'ed then return again at idle. It turned out to be the front pulley bolt was loose (could be turned with my fingers) and the pulley was knocking, I would have swarn it was comming from the center of the engine when I was tracing it! I think it may have been loose for some time, as now the engine is the quietest it has ever been since I have owned it! I hope yours is as easy a fix as mine was. :D

[rick130]

camshaft only spins at half crank speed so if it was the lift pump it would be around 360 cycles at idle ?

[justinc]

Hi Ian!!

That noise you are hearing is a loose and/ or out of adjustment tappet. Please adjust to factory specs, and call me in the morning.:)

JC

(.208mm, 008", inlet and exhaust, cold or hot, not running.)

[Leo109]

Hi Guys,

Thanks to all the respondents.

Isuzu: No the lift pump sems to be fine. Thanks,

Bush: My noise is not at all like a 'miss', it's a very regular beat.

Jimbo: Your suggestion sounded promising and would have had the advantage that, if it had been the crank pulley bolt, I could have been confident of getting it loose when I do the timing belt shortly.

Justin: What as that? Adjust to factory specs, and respect you in the morning? :eek: No worries. :angel:

But seriously: Hail, oh great Guru and Grand Master of all knowledge on matters LR! Don't you ever get sick of being right? :D

Yes, it was the tappets! I would have sworn they would be OK but no, 'twas them indeed. A few months ago, I replaced the valve stem caps, as I've heard they can be worn right through by about 250K km. About 1500 kms later I readjusted them them and thought I'd be right for another 20,000 or so.

It seems the new caps must have been 'hammered out' in the few thousands of kms since. All were out to at least 10 -12 thou. And a couple, 4 and 6 as I recall, had huge clearances! The "thoongks" are gone - just a nice 'normal' cacophony of diesel rattles again!

Thanks again to all, especially THE GURU.

[rick130]

<snip> All were out to at least 10 -12 thou. And a couple, 4 and 6 as I recall, had huge clearances! The "thoongks" are gone - just a nice 'normal' cacophony of diesel rattles again!

Thanks again to all, especially THE GURU.

Bloody hell ! :eek:
What oil are you running Ian ? almost sounds like the adjusters have loosened off.
FWIW, mine had blown out a tight 3 thou on every rocker after 70,000km.

[Leo109]

Hi Rick,

Thanks for the kind words you said about my EGT gauges, that I read only recently.

I suppose the tappets could have loosened off. Because the adjuster screws are small, with fine threads, I'm wary of being heavy-handed in tightening the locknuts. Maybe I've been too gentle?

Funny you should ask about oil. I've been meaning to post a question about that too. Generally I've used Castrol oils, GTX Diesel/GTD for some time and, more recently, RX Super as I can now get 20L drums for a good price. However, the last two fills have been Shell Rimula-X as Supercheap had 20L drums quite cheap a few months back.

Strange thing is, the Rimula-X smells like EP diff oil when you are handling it and the car stinks like hell for the first couple of days after a change whenever you pull-up and idle. Does Rimula-X always smell like this? Or could I have got an incorrectly blended batch? If it does mistakenly have EP additive in it, do you think it would be detrimental to the engine?

Should I have samples of the clean oil and my sump oil tested? Can you recommend a good oil testing mob? I'm due for another oil change so I'll be swapping back to RX Super. Might use up the remaining Rimula-X in the SIII/Holden and or the Grey Fergie.

Thanks in advance for your help.

[dmdigital]

...

[Leo109]

Dear dm_td5,

Que??

[rick130]

Either oil should be fine.
Never used Rimula X, but it has an excellent reputation, it sounds like the adjusters have backed off.

I probably wouldn't bother oil testing, unless you start getting anal like me :D
If you really, really want to get the oil tested, Australian Laboratory Services have offices in most states. Their cheapest test kit is 'E-monitor', but I prefer their 'Wear Check' test as you get extras like TBN (Total Base Number) that are important when determining oil change intervals.
Just remember things can slip past the lab, too. When I had the stem caps fail, it didn't raise a flag at the lab as the Fe levels were still under their threshold, but the PQ Index (Total Fe in sample ) was through the roof but they don't have a threshold for that ...... :rolleyes:
The measured Fe is usually under 5 micron and the chunks were bigger than that :mad:
I noticed it and started to question it, and the lab shrugged it's shoulders. When the 'tick' became noticeable a week or so later, I pulled the rocker cover to find a cap laying in bits. When I removed the rest, half the others had started to fail, too.
Anyway, thankfully they list the PQ Index on most Oz oil tests as it isn't a usual listing from overseas Labs.