Hi I have a 3.0 v6 problem. Been searching but cant find relevant info. It is a loud knock/ tap. Thought it was a lash adjuster so replaced them but to no avail. It used to start when teh engine was cold and go away, then it stayed around longer and longer. loudest at idle and goes away after 1500 rpm. it is quite a regular tap coinciding with RPM increase, rather than a rattle. Interestingly I think sometimes when the car is started there is no noise, then after a few moments, almost like after a switch or value has been activated, the sound begins. using a piece of curtain rod I listened to the noise over the engine, It is loudest and most distinct,ie sharp tap, when placed over the water pump housing or from the oil sump, so not coming from the rocker cover area. Any ideas welcome please!

Cheers,

Tim

If it is a manual gearbox, the input shaft can rattle at idle. My understanding is that you leave it alone. Possibly someone else can advise although my TF has had it for years without any problem.

Unfortunately its not a rattle but quite a loud knock/tap, very loud at idle, scaring pedestrians! never used to be so loud but progressively worse.

if it is loudest from the sump area, as you have said, then more then likely it could be big end bearing. best way to find out is drain the oil, and check for any bronze looking materials in the bottom of the oil.

yep will agree with ziek!
my GTO did the same!
out of the blue it started doing what you have stated then bang it went!
now im up for more then a crank grind and need to replace!
if i was you i would drain theoil and pull the sump and check for play on any of the con rods!

cheers
baker

Big end bearing or crankshaft bearing if it is a deep metallic sound like a blacksmith hitting his anvil with a big hammer. Valve lifters are a wimpy little metallic tingle in comparison.

Hi, just to add a bit of confusion, I pull a plug lead and the noise went away, put it back and it slowly reappeared, pulled a different plug, same thing, and again on the other bank of cylinders. though I didnt start the engine again after plugging the last one back in.
Drove it to work this morning, no noise. I know it will be back and suspect you are right about being a main bearing, but very strange.
Can I get the sump off while the engine is in the car? does that mean I can change the bearings with the engine in the car? (I have a challenger)

Sound I would describe as a clack!
can hear a a more destinct tap, metallic sound when listening with a screw driver or rod.

need to find out first if it os bearing, best and easiest way is to drain the oil, and see what comes out other then oil, if its bearing then you will find little fragments of it on the bottom of what ever you drained the oil in to, it will look like someone put a hand full of little 1mm pebbles in your oil. this would be what i would do first. yes the sump can come off without removing the engine, you can even give the engine a quick rebuild while its still in the car even (not saying to do this though) like i said drain the oil and see what comes out, its the quickest, easiest, and less painful way to check.

Drove it to work this morning, no noise. I know it will be back and suspect you are right about being a main bearing, but very strange.
Normally once they start bearings don't suddenly stop making noise.....other than when the motor finally grinds to a halt of course!!
Check your belts incase there is a large crack in one......known to have fooled many a mechanic also check your waterpump bearing and all other moving parts off the end there also the belt tensioners as one might be loose and snapping back and forth.
Check one of the hydraulic lifters is not getting stuck occasionally as that can happen. Vee

Exactly right, big end bearing do not just stop making noise. i'd be look at things as suggested above.

From the above, I would suspect excessive clearance on a crank shaft bearing or bearings rather than a single big end. Could be an endfloat problem too. Open it up and have a look, piccys please!

Well, I am curious as to where people think I should start first, the front of the engine? or the Sump. I am struggling to work out how a cylinder not firing would effect the water pump or belt etc. Perhaps less load on a cam may allow the hydraulic tensioner to load up properly if that was failing? would there be much difference in load?
Will get started following opinions. Cheers.

at the moment its just a guessing game, seems strange that when ever you pull a spark plug lead the noise stops, dosent matter what lead you pull. we probably need more info, like does the car idle rough, or miss while this is happening, is there smoke comming out of the exhaust. if you can make a small video of the noise would be helpful. a single lifter can clack, but wont go away if you pull a lead, not saying it isnt a lifter thats the cause either, same thing goes with big end/main bearings. a valve maybe, but this would cause idle issues. a timing belt tensioner is more of a rattle, it could knock i suppose, but ive never heard of it before. piston pinging maybe, usually happens under load. could even be piston slap, once again dumping the oil and seeing whats at the bottom will tell you about this, shiny metal like shavings usually bits coming off the pistons, little round copper like balls is bearings (but this is worst case senario)

will make a video when it starts again. No smoke, no change in noise under load just goes away at higher revs ie 1500+, no miss, no rough idle, just a clack. Changed the all the lifters on one side where I though it was coming from. have change the oil twice but not noticed anything. Video soon...

do check your drive belts as well, i know the power steering belt can deleminate and smack up against the power steering pipe (thats metal) and will give out a distinct clack every revolution. think it was mentioned here before

Just an update, all monday nothing, Tuesday morning starts again, but not as loud as before, drop in at a mechanic and asked what he though "broken rocker arm" told him I just had it out and it was fine... little more bullshit about the death of the engine being imminent and $3000 quote to take the head off and I was away, stopped in at another mechanic "slapping piston" new engine required and $6000 plus 10 hours at 99 bucks. Drove of and as I got closer to work the sound slowly dropped away. Drove home from work, no noise. Next day noise on start up quieter again and slowly dissapearing to nothing, etc, in short the process of the noise appearing, getting louder, staying longer, appears to be reversing itself. the only thing I did other than the lash adjusters was take the egv value (I think thats the letters!) so wonder if crap is getting knocked out of that to improve it. either that or one lash is taking its time to fully prime, perhaps I should have had a look at the oil galleries in the rockers while I had them of.

now things start to make sense, "you had the lash adjusters/lifters out" and yes they do take a while to prime, OR, you can put the car in park/neutral and take the revs of the engine to 3000 rpm for i think 30 secs and that should prime them.

If you had the rockers off and the lash adjusters out I would say your issue are the bleed holes in 1 or more rocker arms are blocked. This is common issue and you will not resolve your issue until these are all clear and pumping oil

If you had the rockers off and the lash adjusters out I would say your issue are the bleed holes in 1 or more rocker arms are blocked. This is common issue and you will not resolve your issue until these are all clear and pumping oil

Crap.

I mean to say, what a pain in the arse.. my fault for being hasty, mind I started on friday arvo after work and was keen to get it all back together by midnight.

I mean to say, what a pain in the arse.. my fault for being hasty, mind I started on friday arvo after work and was keen to get it all back together by midnight.

Still, if that is all it is, no biggie - better than the "doom and gloom" scenario in above posts. lol Give them some time to settle in.

Yes, thats the third mechanic to think Im an idiot, sorry to the mechanics out there but its hard to find one thats not full of sh!t. The first guy I spoke to said I needed a new engine too, when I suggested that maybe it was the lifters/lash adjusters, he told me they didnt have any in this engine, I nod slowly, listen to some more rubbish and make my retreat. At least when you do it yourself you know whats been done and can only blame yourself when things go wrong.
Will take it for a longer drive and see if it settles completely.

.....

Update. Pulled the rockers off again, cleaned the oil galleries in the rocker arms and shaft. No sign of a blockage really. Interestingly though I did notice a bit of wear on one of the cam lobes, it is possible that a lifter is struggling to fill the gap if the cam is worn and / or the roller. Still going. Though again the noise has disappeared today. Sorry no noise video yet. I should mention having looked at other posts on the net the price of lifter seems to be slightly exaggerated, whilst they may be expensive factory, I got some after market for $3.50 each, not as people have written, $50 each.
If it doesnt improve with some running I will start with pulling all the auxiliary belts off to isolate externals. If still there, I will replace rockers and cam shaft, perhaps inspect the cam shaft bearing first as that could be effecting the lobe hight too. whilst Im there I will have to have the cam belt off so replace the belt and water pump at the same time. Time consuming but not too expensive. Will see...

The 3.50 lifters will generally last about 3 months and collapse, the ones we sell are about $11 each BUT are Japanese made and have been used by us for years, again is a matter of getting what you pay for

Doing the belts is a good idea as often the sound can be lower down but echo up

Where do you get your $11 lifters?
So far these 3.50 ones are holding up.
I am yet to get to doing all that is decribed above but should have some time soon. Any comments on the Ebay timing belt kits while Im in there?

The OP said that he had replaced the lifters and the noise was still there, so unless he replaced a dud lifter with another dud, you can almost rule out lifters. Further, he said that the noise seemed to be coming from down low, not up near the lifters, so maybe it is something else. Oil pressure relief valve?