Knock Knock!

[lowbro]

Recently my 25det neo engine in the 34 has decided to make a very healthy knock noise!

In the attached video clip I have 1st put a pool noodle to the timing cover which has enhanced the sound, then 2nd onto the exhaust side rocker cover which sounds like normal tappet noise, so the knocking is either coming from the belt area or worse it is resonating up through the block.

Any ideas? Big-end bearing/timing belt bearing/worse?

Cheers All.

timing cover then rocker cover.wmv

[Jaymie]

Sounds like a bearing issue to me man doesnt sound healthy

[toffy]

Hard to say by that vid, sounds a lot like a big end knock though

[Akshunhiro]

RUH ROH

What oil are you running?

[vorse]

+1 on bearing

[lowbro]

Last change penrite 10's racing 10w-40 full synthetic + 1/2 qrt of lucas, before that it was motul 300v

145,000kms btw on the clock, compression is very healthy/engine is still very strong and responsive.

Hoping it is timing belt, loose/slapping/timing bearing that needs replacement, but after listening to a load of youtube vids I am thinking rod knock

[Hadouken]

shouldve stuck with motul

[toffy]

You could just replace the bearings , i mean , it won't last forever and is by no means a permanent fix , but it would get you out of trouble for Atleast 6 months (providing there is no crank or con rod damage ) . ~$50 and a good day of work for someone mechanically minded

[lowbro]

Yep Motul all the way from now on!

I am lucky enough to have another nice 34 to drive atm, will be looking to pull down my 26/30 proj engine that has been sitting for almost a year now and try and do all the work myself/save coin, bottom end needs a rebuild, does not look to be too hard a job once the machining has been done, and there is so much info round here I am sure I can do it with patience and learn along the way.

[DVS JEZ]

Did u give it a hard time the day that it started knocking?

[lowbro]

Nah not at all eh JEZ, that engine is stock and so healthy across all cycls that is why I was not worried about the high kms, was looking to just put a bolton package in there as it is the weekend/cruiser, just bad luck I guess or previous history has now caught up.

Still deciding if a RIPs 30 bottom end delivered would work out better than rebuilding the current patrol 3ltr bottom end, would just need a better oil pump and be machined/bored/honed to accept forgies. RIPs stay with stock internals and do some crank work, but they are good for 600 ponies.

[B-Boi34]

Wow that does sound a fair bit worst than mine.

Still a bit worried that mine isnt just an exhaust gasket/manifold leak.

Think i should have a listen again with one of those pool noodles

[lowbro]

Hey Brody,

Feel free to pop round and have a listen to your car through the pool noodle, it will locate the problem straight away if it is the same as mine

You know where to find me!!

[lowbro]

Right O!

I have finally located the the source of the issue, the knocking sound is the CAS arm that enters into the exhaust cam shaft area, it appears to have too much play/wobble in there and the effect is a vibration/knock sound inside the chamber, this has resulted in what so sounded like rod knock resonating from the block up!

So on to resolve the issue - replace the CAS unit (expensive as all hell from Nissan) or further diagnosis and pull off the rockers and inspect the cam shaft and barrell area? I wouldn't expect this part to be the issue/worn out as it is forged steel.

Anyone out there know if this is a common worn out part issue for a CAS unit or has come across?

Cheers All.

[iplen]

Mine did the same, the damage with mine was mainly the nose of the cam, and the CAS to a lesser degree. The damage to cam is pretty obvious, if you look in the front of it the teeth should be square, and 1+mm across the top. Just Jap had the CAS second hand in good condition, the cam I just bought second hand off here

[lowbro]

I had to strip some parts from the 26/30 today and use the aluminium bracket from the 26 head gear that the CAS is mounted to , on the 34 it was fractured and only being held in place by the CAS bolts to the timing cover, now the CAS has no play whatsoever all fixed, but the knocking is now very clear and coming from the front of the exhaust cam shaft, so perhaps the same issue you had IPLEN and it has been worn away, I guess it is a pretty inexpesive exercise to swap a factory exhaust cam in there and see if the problem goes away, it should not cause any dramas if I leave it as is, but I want rid of that knock noise that is only there on idle, when on accelaration it goes away and then comes back on decel to idle, very noticeable at idle.

Check out the fractured bracket, it is just cast aluminium not very strong, and I am not sure what caused it to break just recently either!