I'm getting lots of loud clacking on a 96 Nissan Sentra 1.6 Liter. Sounds like it's coming from the head. It has overhead cam, I believe. I had thought OHC did not use hydraulic valve lifters, so I thought sludged up lifters would NOT be causing the clacking.
The clacking comes and goes, does not follow a predictable pattern. It has been happenning for about 2 years, and is slowly getting worse.
The head looks clean when you remove the oil filler cap and look in with a flashlight, and plenty of oil splashes out all over everything if you open the cap with the engine running.
Oil and filter changes have been done every 5K to 7K.
Backbone's reply is right. To furthur the discussion, your engine uses replaceable shims to control valve adjustment. They don't usually wear. If one did wear, it would probably mean that it's companion cam lobe was worn, too. A more likely cause of your random noise, assuming it is valve related, is that you have massive carbon build up on the backs of the intake valves. This keeps the valves from fully seating, and can turn a recommended lash of .010" into .030" over time. The carbon is forgiving enough that it can allow the valve to close sometimes, and can hold it open others. Temps and fuel soaking have a role in how hard or soft it gets.
The valve followers or 'buckets' that move up and down in the head can get stuck, but it's unlikely if you did regular oil changes and the head looks clean through the oil cap as you state.
Adjusting valve clearances on this engine is an ordeal. I would have someone verify that it sounds like a valve noise, then investigate top engine cleaners, Chevron Techron additive, or a Motorvac service to try to break loose the carbon on the valves. You could then *check* the clearances (fairly easy) and make sure they were in spec.
If your second opinion doesn't agree with the valve noise diagnosis, you may have a stretched timing chain or broken guide. I don't know the reason, but I have seen stretched chains cause a similar noise that 'comes and goes'.
BTW, I have yet to see a Sentra of that bodystyle that wasn't leaking at the front crank seal. Just a FYI, you might want to check that when you are done with the noise issue.
Woody and Backbone : the mechanics keep telling me there is no adjustment to be made to the valves. One of them is a former Nissan mech, too. I guess they just don't want to mess with it. :) They didn't mention checking the valve clearance either.
Yes, the manual says for the ga16de engine, that if the valves get noisy, to inspect valve clearance. I don't know if I have the ga16de though. It's a 4 cyl 1.6 Liter automatic trans.
Toyota MDT : I also get a rasping, buzzing, sound , like a baseball card in the spokes of a wheel, often in the high rpms of each gear, only at light throttle. Could be the timing chain ?
Valve cover looks easy to remove. Is there a way to manually rotate the crank with a wrench, to get the valves in the right spot to check ?
That's what you have. There may have been a 2.0 available that year, but the 1.6L in 1996 is a GA16DE.
I would think the timing chain would be noisier with engine at idle, listening under the hood.
Yes, you manually rotate it with a wrench. Get a Nissan/Mitchell/Motor service manual or copies of the appropriate pages from the library. While checking clearance is easy and requires few tools or savvy, it should only be attempted by a beginner after reading/following the procedure right out of the manual.
MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.