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Discussion Starter · #1 ·
Hello - I've got a 98 Rodeo with 135k, 3.2L V6. Recently it has started this problem where it sounds fine on startup, but after the engine has warmed up to operating temperature, a tapping noise starts up. It's a very audible tapping noise, almost makes the engine sound like a diesel. I've read about the common problem with Isuzu engines and valve tapping, but I'm not sure this is that.

I've put my stethoscope on both valve covers, the tapping is more noticeable on the left side (passenger), than the right. I was running 10W-30, but switched to 5W-30 today, but the tapping is still there. Also noticed that the tapping noise was very noticeable when I put my stethoscope on the oil pan. Having a hard time pinning down where the noise is originating from.

What I really can't figure out is if it's a serious internal engine problem, why is the noise not there when the engine is cold, but is there after the engine warms up?

Any help is appreciated. Thanks.
 

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If your oil pressure is still good, it's probably the hydraulic belt tensioner(s). A noisy tensioner will sound like a conn rod going bad (yes, they are that noisy!). If your oil pressure is dropping drastically once the motor is warmed, there may be something else going on. Does the noise go away if the motor is revved? If so, that's a real good clue it's a bad tensioner.

BTW later model 3.2's had a bucket-and-shim type of valve actuation and the noise problem isn't present in this motor. Some slight ticking might be present but that's normal. Definitely doesn't sound like it's a valve train noise, unless something has busted or come undone.

HTH........ed
 

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Discussion Starter · #3 ·
Thanks! I thought about the tensioner, but had done a timing belt change recently, new belt, hydraulic tensioner, tensioner pully, water pump, plus camshaft and crankshaft seals. In fact ending up doing the timing belt 3 times, because Haynes manual info. is wrong and I had it all out of time. Got it back in time and it ran nice and smooth for about 2-3 weeks, then this loud tapping noise started.

You might be on to something there with the oil pressure. Did notice today that if I rev the engine, at some rpm level (couldn't tell the rpms because I was under the hood with my stethoscope and throttling by hand), the tapping subsided. Let the engine idle back down and the tapping comes back.

Oil pump gone bad maybe? How do I check the oil pressure?

Thanks.
 

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If the engine is the same as my 2000 Passport, the oil filter is on the front and you can put a pressure gauge into the oil sending unit hole after you remove it. Pretty easy spot to check the oil pressure with a gauge.
 
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