knocking sound - Land Rovers Only

GreyGoose_01 Disco · 10-27-2009, 02:17 PM

My brother has a 01 Disco II, He was running mobil1 10W40 high millage and then he changed to Mobil1 15W50. with the Mobil1 M1-301 oil filter. and he changes it about every 3k to 3.5K miles
in the almost 4 years he has had the disco the head gaskets have been replace twice and all of the rockers have also been replaced. He has the QT HD motor Mounts installed, and change the transmission filter every 30k miles. My Local L/R mechanic we have some of the best maintained disco's he has seen.
Some time Last Spring he called me and told me that his disco was making a bad knocking sound, I flew out to help him drive back about a month later, and the sound that he said he heard wasn't there. Then in July or June the sound came back and this time I heard it. Then it went away after awhile, It a knocking sound like a bad rod bearing, I think. It makes the sound when the disco is cold or hot in all gears it gets faster when you increase the rmp's, and then seems to go away when you increase the rmp but It may be that I can't hear it over the exhaust note. But I don't know.
So he took it to the dealership and they said that it was a bad flex plate when we pulled in to the service drive. So upon removal of the transmission they found that one of the bolts securing the flex plate was broken, and three others were loose. but the flex plate was not broken at all. So they changed the flex plate put new bolts in and new rear main seal, and xyz switch, shuttle valve switched and left front abs overlay harness. It was in the shop for a full week. Brother got it and drove to school and the sound came back again. So he took it back, they had the disco over the weekend, and he picked his truck up again and the sound came back so he took it back again.
Please Any thoughts on Just what the sound could be as this sound that is coming from the disco has come and gone now for the past seven months.

p76rangie · 10-27-2009, 03:50 PM

Are you sure it is there when it is cold?

GreyGoose_01 Disco · 10-27-2009, 03:54 PM

It's there hot and cold

hafaday · 10-27-2009, 04:30 PM

if it was a diesel, i'd say an injector going bad. but gas motor

GreyGoose_01 Disco · 10-27-2009, 08:32 PM

But does anyone have any idea as to what it could be?

BruceK · 10-28-2009, 07:25 AM

My '03 DII had a similar knock that only happened after the engine warmed up. Got darned loud, too! After a long time at the dealer they traced it to a cylinder sleeve that had come loose. Got a new short block out of it.

Thank you, Extended Warranty!!

DiscoDream2 · 10-28-2009, 08:46 AM

Sounds like you are more patient with your disco than I. TWO hg replacements....UGH.

Ok, since you have the heads all redone etc...I lean towards the O'l Y-pipe connector gasket...It sounds just like a lifter noise and it's easy to check. Put a leather glove on and feel around the Y-pipe connection to the exhaust manifold you may feel pressure (air) on your hand. Easy check - easy fix.

If not then....on the short list of stuff it could be, Liner...as it goes away (lessens) after start up.

Love it when the dealer says "oh it's this" you replace "it" and low and behold the issue still exist...

k-rover1 · 10-28-2009, 09:54 AM

I had a bad flex plate.. only made noise when in park or neutral.. once in gear all noise stopped. Need to be more specific as to where the noise is coming from, does it do it under load?..

bonnettoboot · 10-28-2009, 09:07 PM

You say knocking so that usually means a heavier sound as opposed to a lifter or ex gasket. Have you done an oil pressure test, also, why two head gaskets, is it running hot, does the electric fan work? Look at my write up on the oil pressure problem on my site. If you go to www.bonnettoboot.com then click on technical issues.