|
Maintenance is something you perform on the car before something breaks, in exchange for not having to fix the car when something
*does* break. While doing maintenance on the car isn't quite the funnest thing in my book, it is much better than having to
fix something that has broken down. This, my first level of engine maintenance/upgrading (is it upgrading if I make it run
closer to new without adding anything non OEM? hmm...) is an engine timing rebuild/maintenance and replacement of the old
injectors. I'm a bit dissapointed because this work was a combination maintenance/fix. The injectors simultaneously wore out
while my engine developed the dreaded Nissan--KA at least--timing chain rattle. Not a happy turn of events.
The car occupied some garage space at my father's house, who helped me with the rebuild and repairs as a birthday gift.
It was a real learning opportunity because I honestly don't know very much about engines. So far I'm most knowledgable about
suspensions and what to tune to get more from them. Engines are still sort of a mystery to me. I know the basics alright,
but knowing the basics will not help you fix anything, should something break.
We started with the engine timing. Taking off the valve cover and front engine covers exposed the timing equipment. Just
getting to the covers took a little work, as the intake and fans had to come off as well as what, atthe time, seemed like
a myriad of other little random things.
Once the covers were off we could see the layout of the timing equipment. At the camshaft, two cam gears were connected
by a chain to a central gear below them, which was connected by a seperate chain to a gear at the crankshaft. These gears
and chains kept the crankshaft and injectors pumping happy and kept the valves safe from becoming piston fodder.
At the cams, a tensioner and two guides kept the chain in shape, and at the crankshaft a single tensioner with a large
guide against it aimed the chain properly. It was the tensioners that caused the problem. All chains have a tension side and
a slack side, picture a bicycle chain. The botom side has slack and some bikes have a tensioner there for the chain. Tensioners
keep the slack side pressed in enough to stay under tension, otherwise you run the risk of the chain jumping some teeth and/or
coming loose altogether which would detroy the valves once the timing got off enough. Destroying the valves would mean a costly
rebuild, it would likely total the engine. When a tensioner wears out or gets stuck the chain has slack on the slack side,
which is what leads to this scenario. With the KA's, you can hear the lower chain slapping against the inside of the front
engine cover if the lower chain's tensioner has gone south.
Fortunately for me, once we pulled all the chains, tensioners, guides, and gears I was able to see that one of the tensioners
had gotten stuck, but wasn't out of commision. Inside the cover, oil is being slapped around everywhere to keep things moving
smoothly. Over the miles--150K+ in my case--a "varnish" of this oil developed on everything that was constantly
exposed to the lubrication, which is why silver metal parts in an engine are often a tint of brown. Oil "varnish"
buildup. This varnish had actually caused the timing problem, by gumming up the piston that the tensioner rides on. Allow
me to elaborate: The tensioner is basically a base with a spring in it, conected to a piston with the guide on it. It's designed
so that the tensioner's guide has a range of motion, so that the chain is constantly under pressure and doesn't have slack.
Simple enough, right? Problem was, the oil varnish gummed or clogged up the piston connecting the base to the guide; the part
that does the tensioning. Something occured that forced the tensioner to bottom out and become fully compressed, and it became
stuck in this position by the thicker width of the piston made by the oil varnish. We got it unstuck and cleaned it with a
brush and degreaser to remove the oil varnish from the entire tensioner but especialy the piston area. After this, the tensioner
worked as strongly if not stronger than the replacement (non-OEM) tensioners dad had ordered. We cleaned the other tensioner
and replaced the old chains with the new ones, everything else was just "rebuilt".
That completed the rebuild, but there was still one problem: The injectors were wearing out, and fast. One was already
completely shot. Since the injectors all see the same conditions we knew it wouldn't be long until the other 3 were gone as
well. The solution? Brand new OEM injectors from Nissan. Wow, this made a nice difference. The car runs like never before.
Remember this car was already 10+ years old when I started driving it, so I've never seen it run so well. I am *very* pleased
with the new engine performance from the fresh timing equipment and injectors. Removing the old and installing the new was
fairly easy; the biggest challenge was yanking the old injectors out. They really didn't want to leave thier natural environment.
It can be done with some pulling and a good -gripping pair of pliars though.
That covers my engine maintenance/"upgrades" step one.
But wait!
A bonus feature!
Just what caused the tensioner to be fully compressed and stick? And is there anything you can do to avoid having the
same thing happening to you? If you drive a manual car, there is something you can be on the lookout for!
Here's how it happened: After a long time of thinking about it, there was only one thing we could think of that was very
likely to have caused the problem. An engine turns the same direction, all the time. Even when in reverse, it's not as thought
the direction of engine rotation changes, obviously. Still, the tensioner would become fully compressed if the tension side
and slack side somehow switched places. How could this occur? The engine turning over backwards. Why in the heck would I turn
my engine over backwards? There are two possibilities that come to mind fairly quick: Connecting the battery backwards, which
would spin the alternator backwards if I am thinking of this correctly, thus spinning the engine backwards, or something harsher,
a spinout.
In hindsight I am pretty sure it was a spinout that caused the tensioner to get stuck. I *know* I never connected the
battery wrong. The tensioner probably wouldn't have stuck without the oil varnish but here it is. The car spins out at speed.
I autcross and I try to learn more about car control by practicing drifting on the track as well as going for best time runs,
so there're chances for spinouts to occur. If I messed up and the car began to spin, I could have been distracted and/or slow
in getting my foot on the clutch pedal. If the car spun enough for the tires to turn backwards and the clutch was engaged--so
would the engine. There you have it, a spinout and engaged clutch when I was autocrossing and driving hard, must have just
forgotten about it.
So what can you do to avoid your manual having the same problem? If you start to slide out or spin out and you cannot
recover, get on the clutch as soon as possible. You *do not* want to turn the engine over backwards, whether or not it gets
anything stuck it's just not fun. So to especially fellow beginner drifters out there, learn from me and keep aware of the
clutch when you practice. If you can't hold or recover from the slide and it turns into a spin:
Step on the clutch. Your engine will thank you for it.
By: Ben C.
|
