Knocking m42 valvetrain

[Ryann]

Don't panic, hold it at 3K for a while every now n then and after a week of driving it will go away. I started with a thin oil and worked my way up to 20w40

This is true. If your lifters are dry you need to run THIN oil to get them pumped up. Definitely shouldn't take a week though, just a few times of good hard 6k and they should quiet down.

We had an ls2 GTO in the shop that had this problem. The kid's machine shop sold him this thick "break in" oil shit that kept his lifters from pumping up. We drained and filled it with 5w-30 and lifter noise disappeared after like 30 seconds.

[Simon S]

any chance it could be off time?

there's always a chance - but I'm pretty sure it's on time.
Crank arrow? - dead on
Cam sprockets? - up like I found them
Several rotations by hand - and after these runs - always checks out.

[///digitalme]

damn that sucks i just saw your thread....
it doesnt sound like the chain tensioner to me...
it sounds like when i busted my engine and had some bent valves..
but its one of those things you wont know until you take it apart.

any chance it could be off time?

[Simon S]

Holy cow - look how many little chambers are in there..



"The self-adjusting hydraulic tappets function with the use of engine oil pressure, internal chambers and orifice control.

1. Engine oil pressure
2. Large oil chamber
3. Small oil chamber
4. High pressure chamber "

[Vtec?lol]

Just like everone else is saying I can also vouch for one loud ass M42. Once you take the head off and such it's a bitch for a minute until all the lifters seal and the tensioner gets settled. Mine was louder upon install of a new tensioner.

Don't panic, hold it at 3K for a while every now n then and after a week of driving it will go away. I started with a thin oil and worked my way up to 20w40

[Simon S]

Hick and Ken - thanks so much!
Imput is valuable to me.

10-4 on pre-fill. I have some small seringues saved from when giving meds to cat - they'll work perfect.

and 10-4 on wait time. Also noted from manual.

[Hick]

Do you have a source for that? That seems totally counterintuitive. The slap is usually when they're gunked up.

The lifters take 30-60min to compress after install too.

They also dont work if there is zero fluid inside. There is only one port in/out and if they are full of air its hard to 'bleed' new oil into the lifters without displacing the air.

[KenC]

I remember reading somewhere that you MUST fill the lifters with a heavy oil before reinstalling if they have sat for a while/been cleaned. I have had the heads off several M42s and each one had a noise similar to this before building oil pressure, but not as bad. Since you said you drained all the oil from the head i would suggest pumping some heavy oil, or even a grease into the hole pictured above.

And speaking of oil pressure, if that does not fix the noise; check that the oil pickup is torqued down and that the gasket is fully seated. The M42 will make a noise like this if the pressure drops, but there tend to be other (more serious) problems with low oil pressure

Do you have a source for that? That seems totally counterintuitive. The slap is usually when they're gunked up.

The lifters take 30-60min to compress after install too.

[Hick]

I remember reading somewhere that you MUST fill the lifters with a heavy oil before reinstalling if they have sat for a while/been cleaned. I have had the heads off several M42s and each one had a noise similar to this before building oil pressure, but not as bad. Since you said you drained all the oil from the head i would suggest pumping some heavy oil, or even a grease into the hole pictured above.

And speaking of oil pressure, if that does not fix the noise; check that the oil pickup is torqued down and that the gasket is fully seated. The M42 will make a noise like this if the pressure drops, but there tend to be other (more serious) problems with low oil pressure

[trackjunkie21]

That sounds a lot like my engine did before I replaced all 16 lifters. See if you can narrow down to the cylinder, on my engine it turned out to be cylinder 3 and 4 exhaust lifters causing the majority of the knocking. Just letting you know what the case was for me.

FYI those fuckers ain't cheap $17.25 a piece times 16 = a good chunk of change but the loss of the noise was well worth it.

This, if you are going to replace the lifters, buy the 16v VW ones, they are cheaper and they are lighter, better for teh revving yo!

[Ryann]

still think your chain tensioner isn't working properly. Mine sounded the same way after i rebuilt the engine. Extended a new tensioner prior to install, prob solved.

+1! Sounds like t-chain slap.

[Simon S]

I suppose that's worth a shot before taking cams out..

I've tried the old and new tensioner - both were extended. Had to push in pretty hard to get threads to catch on both. When I put the new one in - there was 3-6 seconds of really loud - and really scary noise - then that noise went completely away.

[KenC]

Still think your chain tensioner isn't working properly. Mine sounded the same way after I rebuilt the engine. Extended a new tensioner prior to install, prob solved.

[Simon S]

After 20 minutes at idle:



After 12 minutes at 1.5K rpm:



After 12 minutes at 2.5K rpm:



no change

[McGyver]

dude, i really wish i could help, but i know nothing of m42/4 engines. i am intrigued and hope it all turns out to be something simple, good luck!