Timing belt tip for CA20, may apply to other Nissan engines

[goodolboydws]

While changing the timing belt in my wife's '88 Stanza Wagon with a CA20 engine, I ran into an interesting situation.

Her timing belt had broken, and I had chalked it up to a tensioner that had gone bad. This irked me more than a little because I had changed this same engine's belt 27K ago, when replacing the water pump. I had cleaned up the entire area under that timing cover, checked for leaks of the seals, and examined the tensioner closely before deciding to reuse it. Now I was kicking myself for not changing the tensioner at that time (which, along with the cam and crank front seals, I would still recommend for any vehicle over 150K by the way)

So yesterday I was reinstalling the new belt and trying to time the engine and tension the belt, after installing the crank and cam seals, and the new timing belt tensioner. I was getting frustrated because no matter how I tried to vary the tensioners' pressure, the belt always would track to the engine side of the cam pulley.

This really frustrated me, because I had spent quite a lot of time cleaning, and derusting the 2 pulleys, removing burrs, etc, in an effort to remove all trace of the pattern that the OLD belt had made, by also running to the same side of the top pulley especially. I remembered that the previous time I had changed the belt, THAT one also had been running off center, but I hadn't thought much about it at the time, it was still working fine, but we had just bought the vehicle with 164K (and I didn't know how long that belt had been in, and wasn't taking chances) and I've seen timing belts on other well running engines running off center

Anyway, now this new one I'm trying to install is running even farther off center, to the point where it's actually starting to hang off the back edge slightly. This CAN'T be good. I'm thinking that either the cam shaft is sticking too far forward, or the crank is possibly too far back, and that's causing the belt to run off center on the cam pulley. So I looked to check the wear pattern on the cam, and assured myself that IT wasn't the problem. So what's left? Crank? Not likely, as the engine was running so well previously.

I took out the timing chain tensioner and looked at it closely, comparing it very closely to the old one (which still didn't look all that bad to me, BUT it too had the same off center wear pattern left from the previous belt/belts) when a thought occurred to me. Could it be as simple as someone putting the timing tensioner SPACER in upside down who knows how many miles previously? That's what it was.

For those of you who haven't changed the belt on one of these engines before, there is a thick, cast iron spacer (maybe 1" thick x 2 " high x 3" long) behind the tensioner that I had always assumed was ground with both faces parallel to one another to keep the tensioner running in the same plane as the 2 pulleys. Evidently it's ground at a very slight angle from parallel, and because of this when it's in the correct way the belt will run centered, and when it isn't, the belt tracks to the rear.

So if you get to changing one of these belts, look for the off center wear pattern on the pulleys and if you see that the spacer is probably in backwards.