KA24E Valve/Rocker noise ~18k mi after rebuild

[driverds20]

1989 240SX Currently at 136k mi.

I have consistently had valve noise right at startup for a couple seconds...used to that for the last few years. But Sunday the valve noise continued a bit longer at idle. I ran it for a minute or so at 2000 RPM to try to bleed the rocker arms, but there was no improvement. Drove a 15 minute trip, and the valves were noisy (at least I could hear them over the road noise and such) whenever the motor was over about 2200 RPM. When I shifted to 5th at 50MPH and the tach went below 2K they quieted down. Did not seem to be affected by throttle position (like spark knock is); temp gauge was ok. Today I drove the car to work, 20 min at just over 70 MPH/3200 RPM, could hear them the whole way. Once off the interstate got quiet again below 2200 RPM. Going home I noticed it seemed to quiet down when revved above about 3500 or so. So the noise is between 2200 and 3500. Power and smoothness seem fine.

All rocker arms were replaced about 18k miles ago, as was rocker shaft on the intake side, to try to get rid of valve noise at startup (which this motor didn't always do - assumed it was a wear issue). Oil pump replaced as part of rebuild 20k miles ago. Ran Pennzoil non-synthetic for 10k miles after rebuild, then Mobil1 synthetic until this last oil change (about 1000 mi ago), when I changed to Mobil Clean5000 10W-30 (non-synthetic) to save money since the car uses about 1 quart in 1000 miles (I know...too soon after the rebuild; a question for another day!).

I'm concerned about this new noise. I could replace the rockers again, but they shouldn't be bad already, should they? Should the rocker shafts always be replaced when you replace the rockers? Could I be getting a lot of oil leakage thru there, and not pumping up the rockers on the exhaust side (rocker shaft still original over there)? Maybe that's why the noise goes away at higher RPM, since the oil pressure is better? Has anyone ever gotten a bad oil pump (I'm sure I bought Nissan OEM)? Do they make high-pressure/high-flow oil pumps I could try?

Oil level is fine...I actually first noticed this just after topping off oil level. Motor currently shows about 1/8" overfilled on the dipstick.

Any other ideas?

Thanks - Mark

[sx moneypit]

Did you replace the lash adjusters(lifters)?

[driverds20]

Hydraulic lash adjusters are built into the rockers...

[sx moneypit]

Sorry ,i must have been half asleep when i posted .I was thinking KAde.

[seang]

Here is the official Nicoclub ka24e ticking lifter tech article: http://www.nicoclub.com/archives/ka24e- ... epair.html

[driverds20]

Thanks - I had seen that write-up, but since the FSM says "Bleed air off by running engine at 1000 rpm under no-load for about 20 minutes", I have used this method before, and it works well. (For instance, since my car uses a fair amount of oil, occaisionally I will go too long before checking it, and when it gets about a quart low the valve train gets really noisy. When I top up the oil, it takes just a few minutes running the engine to bleed the rockers, and they're fine again). It sounds like the procedure you linked is just trying to bleed air out as well, and is a good bit more work, so I'm not sure why one would work and not the other. FSM says if bleeding rockers by running the engine like this doesn't quiet the noise, the next step is to replace the rockers, at which point you bleed the new ones the same way, which tells me this method should work for bleeding even if the rockers start out dry.

The other thing I'm wondering is why my valve train would suddenly need bled. It went quickly from normal (noise only for a couple seconds at startup - which I took to be rockers slapping until oil pressure pumped them up) to quite noisy within about a day...

[seang]

The noise on startup, I thought, was usually the timing chain guides not being pushed on by the tensioner for a few seconds.

[sr20671]

As for your ticking prob. Did you remember to prime your oil pump after changing it you could have either: 1) air in oil pump resulting in damaged pump and lifters 2) oil pump is giving out 3) lifters are getting stuck