97 VQ25 Cefiro motor 'tapping / ticking' ?

extrayda, Apr 2, 8:46am
Hi,
I have a 97 Cefiro with a VQ25, 170,000k's, Auto.
I've had it since 90,000ks without any significant issues, and basic servicing done.Car is not thrashed or nannied.
It has developed a ticking/tapping noise (seems to be from the top of the engine), more noticeable at lower rpms.Has done it for a little while, but seems to have got a bit worse since the car was last serviced (which included an oil flush).Oil level is fine, has now done about 5,000ks on the new oil.
Any ideas what this is, or what might help!Still seems to be running fine, but I want it to keep running for a while yet !
Doesn't sound like exhaust leak or bearings etc (it's a light sound).

eddie1981, Apr 2, 9:15am
SOMETIMES THAT TAPPING CAN BE A VALVE THAT JUST NEEDS A LITTLE TIGHTEN

motorboy2011, Apr 2, 9:19am
engine flush prob knocked some of the crud that was cushioning moving parts, never do oil flushes. Proma MBL8 may quieten it down.

jasongroves, Apr 2, 9:24am
Valve clearances most likely need to be done.
What grade oil are you using!
Thicker oil or ProMa can help but only a band aid fix.

mantagsi, Apr 2, 9:30am
x1
At risk of sounding like a dumbass, don't these engines have hydraulic lifters so dont need valve adjustment! perhaps one of the lifters is a bit sticky

motorboy2011, Apr 2, 9:35am
I almost posted the same.

jasongroves, Apr 2, 9:38am
I just looked up the valve clearances on Autodata. wouldn't have them if they were hydraulic.
But I did originally think the same.
Autodata isn't 100% reliable so could be wrong.

extrayda, Apr 2, 9:39am
I havent checked re valves/lifters as far as what it has, but it does have that sound to it. admittedly comparing it to the 350 chev i had, so not quite the same tech, but same principal. I will look up lifter valve specs / config tomorrow. Thanks for ideas so far.

extrayda, Apr 2, 9:41am
i have also seen timing chain on the web as potential issue, but it sounds more like top end to me.

jasongroves, Apr 2, 9:44am
Valve clearance:
Inlet - mm: 0.26 - 0.34 cold.
Exhaust - mm: 0.29 - 0.37 cold.

After awee google, it appears they are hydraulic.so perhaps the specs are recommended tolerances!
Noisy lifters appears to be a common problem according to the same google search.

jasongroves, Apr 2, 9:52am
Do you know what oil was used!

bubbles244, Apr 2, 10:58am
noisy lifters in nissan's are a sign of lack of maintenance.

most common issue resulting from irregular oil changes is stretched timing chains.

the lifters are most likely blocked. the most common way to remedy this issue is to remove them and soak them in diesel for a day or two.remember to number them and put them back in the order they came out.

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