7MGTE knocking noise

[fatboy13]

Hey all,

Ive got an MA71 and theres a strange kind of knocking noise coming from the motor from about 2000rpm upto about 3000rpm. I have no idea what it would be. It seems to go away once your over 3000 rpm, buts its quite annoying.

It kind of sounds like loud tappet noise thats the only way i can describe it. I did the Screwdriver test and it seemed to be coming from the cam covers around cylinder 3 or so. Im hoping its nothing too bad and I may be wrong where its coming from.

Any help would be much appreciated.

Thanks alot.

[doobs]

Could be rod knock?

http://www.supramania.com/forums/sho...ight=rod+knock, have a search on here and there about it.

I hope for your sake its not...

[WeekendWarrior]

check ur oil level first if all is good then i think u have a sticky lifter, try using some tappet quietening oil wich is available in most stores. if that dont work make sure ur oil pump is working ok and check ur oil pressure if thats good do a compression test look for noticable variation. just try the simplest things first even check make sure evrything is tight and not rubbing where it shouldnt be cheers.

[fatboy13]

Thanks for the replies

Yeah i hope its not rod knock as well. Ill have a search on that site and see what i can find!

As for the oil level it was quite low but its fine now and the car doesnt seem to be burning any oil and its definately not leaking any. Ill try some of that tappet oil and see what happens. The oil pressure guage in the car doesnt work so how would i check the oil pressure?

Thanks for the replies though and ill have a look make sure everything is tight and do some other things and ill let you know what happens.

[1200det]

Doesnt sound good if the oil was low , the 7M is one engine that doesnt like to be run low on oil at anytime , The yanks run theres always a quart over full which is about 950mls to try to avoid the famous rod knock.

Rod knock will go away under higher revs usually also . We will cross our fingers for you

.

[fatboy13]

ok can someone please explain what rod knock actually is?? and maybe i should try running it a little over full of oil?

[1200det]

Running with extra oil will assist with preventing Rod Knock it wont repair the damage once its done.

.

[fatboy13]

ok so maybe its worth a try.... what is rod knock and what is the damage it causes... thanks

[Jasper]

Rod knock can be the result of a spun bearing. When you run low on oil, the bigend bearing contacts the crank journal and sticks momentarily. Then the bearing shells rotate in the big end of the conrod, and usually break into a few pieces.

I can confirm from experience that the 7M is prone to this if you let the oil get low. The more you drive with a spun bearing the greater the damage it will cause. If seen to early you MAY get away with polishing the crank journal and resizing the bigend of the rod. (and new bearings of course)

[Jasper]

Also, Weekend Warrior, 7Ms don't have lifters.

[fatboy13]

ok so thats definately bad news then.... still hoping its not that.... when i had a listen with the screwdriver it definately sounds like its coming from the top of the motor, as in i could hear it best when i had the end of the screwdriver on the cam covers.... now so much when on the block.... does that help narrow it down?

[Jasper]

Drain the engine oil and check for fine brassy looking particles. If you see them, you are looking at little bits of bearing. You may need to run the oil through and old sheet to filter it.

[Shifty]

Big end bearing my friend. Start shopping or saving!

[WeekendWarrior]

my bad, jasper is exactly right about the lifters i dont know much about the 7ms or any later tech egines im too old school and simple for that plus being a dumbass dont help to much

but if u have spun a bearing the noise would get faster and faster as ur revs pickup but from what u said earlier about it being from 2000-3000 is it only between this rev range its doing it or right through the rev range if it goes away after 3000 theres a good chance it wont be a spun bearing, but be prepared for it

[ed]

yup - i concur - rod knock
is it worse when at a 'neutral' load point, ie not powering, not accelerating?

PS - rod knock doesnt come from a spun bearing - by the time the bearing actually spins, the engine is fucked completely

rather its just starting to get bashed out of round - (ie on the way to spinning)

an extra quart of oil is BS, just make sure you dont run LOW oil. pick the right viscosity.

all moot points now though - damage is done

PPS - its almost impossible for a 7m to have sticky lifters. its a direct bucket system