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Disappearing rattle

Hello Car Talk community! I’m having the strangest problem, or lack thereof, and I wonder if you could advise…

About two months ago I noticed a transmission-y rattle coming from my 1982 Isuzu P’up (diesel). The rattle wouldn’t start right away, you had to drive the truck for 4 or 5 miles before it would kick in. And it wasn’t always there, it would sort of go away and come back intermittently, although this pattern repeated every time I drove the car. The noise was present in every gear, including 4th.

I took it to a transmission guy, who claimed to have heard it coming from the engine, not the transmission, while it was up on the lift. Later I took it to another mechanic, who insisted it was in fact the transmission, and that the transmission guy didnt know what he was talking about.

Stuck in a contradictory limbo, I drove the car around for a few days, trying to make notes on the problem.

And then the car had an electrical problem, which kept me from driving it for about 2 weeks. The guy who did the electrical doesn’t speak english very well, but as I understand it he fixed something that recharges the glow plugs? Or recharges the battery? Not sure.

But here’s the thing:

The noise is gone.

I’ve been driving the car for two weeks now, taken a longish (80 miles round trip) freeway drive and I keep waiting for it to come back. But no noise! So what’s going on??? Where did my noise go?

I put my fate (or at least my transmission’s fate) in your hands!

Thanks in advance! IR

It sounds like much coincidence and a sticking lifter. Did the oil get changed at the glow plug fix? Does the noise vary with engine speed? Since the noise went away my best guess is a sticking lifter and would recommend 3000 mile oil change interval, and watch and wait.

There’s not enough known to make much of a guess but I have seen some knocking in diesels that was caused by a fuel injector fault. It would sound exactly like a rod bearing knock and could be intermittent in nature.

Sometimes the faulty cylinder/injector could be picked out by examining the glow plug as the faulty injector would often erode the tip of the glow plug.

I’m not familiar with Isuzu diesels so I’m speaking from a Volkswagen perspective here. Maybe the symptoms and causes are similar.

If it comes back, somebody’s gonna have to put it on the lift and use one of those car-stethoscopes to find exactly where the sound is coming from.

There’s an off-chance the non-English-speaking mechanic did something with the alternator (which recharges the battery). Sometimes alternators can make weirdclicking and clanking noises. Sometimes it is the belt is too tight or too loose or worn out. Sometimes it is the alternator insides that are coming loose. He might have done something to the alternator or the drive belt which also fixed the noise. Alternator noises can be diminished when the car is cold, and get louder as the car warms up.

Therre ‘s two reasons my explanation isn’t entirely consistent with what you say though. First, an alternator noise is usually audible even at idle. You don’[t have to be going very fast to hear it. And second, alternator noises sound like they are coming from the front of the car, not the mid-car where the transmission is.