Tip of the day, killing cylinders.

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SC-AL

Registered User
Cut some vacuum hose, and make extenders between the coil towers, and slip over the wire terminals. I only do 3 at a time, (one bank). The ignition KV travels right up the vacuum hose, so plugs keep firing. Now carefully take a grounding probe, or (small/medium screwdriver, with a jumper lead, to a good ground) Touch each vacuum hose extender. This will kill that cylinder, and you will hear, and feel the drop in rpm. Make sure your screwdriver is well grounded, and not near any other wires, or electrical components!

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S

SC-AL

Registered User
That is true about using the scan tool for the EEC-lV cylinder balance test, but I have found that the offending cylinder has to be contributing very little to be recognized. What I was doing in this test was trying to identify rod bearing noise at 2,500 rpm, by killing one cylinder at a time.
 
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DOUG H

SCCoA Member
Oh that make sense then. Is the knock only in or around that RPM range? That doesn't sound good. My Dad used to call that "Thunder in the basement". I had a 93 that I put what was supposed to be & appeared to be a rebuild with less then 3,000km on it. It started making a simular noise 3 weeks or 750km later. Cut oil filter apart & full of metal. # 3 main which is also the thrust bearing was wiped out-down to the brass. The rest of motor was in fact fresh rebuild & perfect. The only things I replaced other then the crank & bearings were the oil pump & cooler
 
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KMT

Registered User
Back in the day, we would alternate between loading and unloading the engine to flush out a rod know. Like a low engine speed stall test.
 
S

SC-AL

Registered User
This is the mystery engine, that I bought over 12 years ago. that appeared to be near new, and never apart.

Mystery Engine

I bought this complete 3.8 SC engine, years ago, and I am finally going to install it in my 1989 white, 5 speed SC, with a bad rod knock. The story when I bought it, is these airplane guy's bought 6 of them on pallets, that were from the factory, and never used. I pulled all the plugs, and the...
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Oil pressure is good at 70# cold, and 34# hot, at idle. Starts, and idles nice smooth, and quiet, even hot. Bring the rpm's just past 2,000, and you start to hear some noise, but at 2,500, it is making a fast clatter, and some vibration. By floating the load, it doesn't have that rod bearing growl, or rap. Take the oil fill cap off, and at 2,500 it is pretty noisy in there. Sounds more like rocker arm clatter, but I think it's just loose in the bottom.
 
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DOUG H

SCCoA Member
Manual or auto? My 93 with bad thrust bearing was a 5 spd & you could feel the vibration in the clutch pedal & even diminish the noise a bit by depressing it -pushing crank ahead.
 
S

SC-AL

Registered User
At 2,500, sounds like crank speed. I just started it cold, and even with thicker oil, the clatter is there, and the vibration in the shifter. Also a low hollow sound.
 
D

DOUG H

SCCoA Member
My suggestion would be to stop running it any further ( & possibly doing more damage) & just pull the motor out for any further diagnosis. With vibration's & sounds you are describing it has to be crank related. Even if you just cut the filter apart, I'm sure you'll find metal in it. Just my 2 cents.
 
S

SC-AL

Registered User
I think pulling the engine is what I'm going to do. The engine was so clean, inside, and out, that I just rolled the dice, and installed it on faith. There were two red flags though. The oil in the filter, and the little amount still in the pan, was black. Also, the oil pressure sending unit,(switch), was missing. I will cut the original oil filter open, as well as the one I ran at first. The engine that came in the car had a really bad rod knock, that must have been driven that way for a while. I removed the pan last week, and the #5 rod bearing was completely missing, shell, and all. The rod journal had .013" ground away!
 
S

SC-AL

Registered User
Yeah, I know. I'm not going to let this beat me. I will turn my 1990 SC auto, with 168K miles on it into a parts car, if have to. I haven't licensed it a few years, but still runs, and drives good. Leaks everywhere, engine mounts shot, supercharger need oil, now and then, etc. I've had it since 1995, and replaced the trans., water pump, belts , a hose or two, brakes, radio twice, re-glued power windows, and clutch kits. That's about it. Never even tuned it. Original plug wires, and fuel pump.
 
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