Motorboat sound, putt-putt over 15 mph

[NormB]

Took truck out for a ride a couple weeks ago, went grocery, apple pie apple shopping, on the way back from the orchard on a dirt road I heard what sounded like a metallic plate clang, like a muffler thing go bang (I do have the transfer case protector mounted, a little loosely, but have never hit it that I know of, or could tell), so I got out to look around and underneath, nothing seen loose or hanging, and proceeded to drive the 3 miles home.

As I accelerated to the first intersection out of the lot, I heard this kind of weird putt-putt motorboating sound as I got over about 15mph. Didn't seem to rob any power I could tell, but I kept the speed down to about 20-25 mph until I pulled into my driveway, where I parked the truck, and proceeded to give things a good listen and feel around the exhaust headers, flanges, shined a light where I could see injectors/lines, and I couldn't find a single leak, hot spot, or make the noise occur with the engine run up to about 2800 rpm while parked.

Weird.

No fluid leaks. Nothing loose/rattling. Engine spools up, drops back to idle.

Oil is black (changed a few months back, due around April or so), coolant looks like coolant with some Bars Leak stuff in it (long story, I poked a hole in the head water jacket over a year ago trying to drill out a broken header stud, threaded the hole and put a stop screw in place), and I ran a coolant check today with an exhaust gas detector - no color change.

So, I'm thinking MAYBE an injector. Or the Injector pump.

Haven't taken it out of the drive YET, as I'm anticipating badness (yeah, I'm insured, can get it towed, just don't have the time dedicated to dorking around with such a condition).

Weird.

Any - helpful - suggestions?

Place to start in the manual?


Been off the board for a while doing other things - like driving, not doing so much repair on the truck, working a LOT (I'm a front line medical worker, I see a lot of worried well over this new head/chest cold coronavirus scare), into some other hobbies (like collecting Vinyl and finding better speakers for my HiFi set) and hanging out on Fakebook/Parler/Twitterverse too much.

And seeing several pain specialists, but that's another story.

Thanks in advance.

Norm

 

[TOBASH]

Exhaust leak?

 

[MattNC]

I’m with TOBASH. Sounds like my other truck did when the exhaust manifold developed a crack. The only thing that’s off is not hearing it when parked and reving the engine. Mine was louder under load but I could still hear and see it when parked.

 

[NormB]

I’m with TOBASH. Sounds like my other truck did when the exhaust manifold developed a crack. The only thing that’s off is not hearing it when parked and reving the engine. Mine was louder under load but I could still hear and see it when parked.

YES!

Under load is the key, I thought. But revving up to 2800 rpm "should have" made SOME noise?

I once owned a POS Subaru Outback that burned up injectors, O2 sensors, igniters, plugs with alarming - warranty-covered - regularity.

Years into this routine, I drove through a local tunnel and w/ window rolled down, by a Jersey wall, I heard the unmistakable header/exhaust leak tick-tick-ticking sound. Subaru replaced the broken header, I traded it in immediately for another car.


I've heard that - SOFTLY - from my engine for years, others have said this is probably the injection pump, I've LOOKED for header leaks.

Now I've gotta REALLY look for something.

Well, I usually park the truck in the garage during the winter anyway...

 

[REF]

I had a similar situation, Turned out to be the balance weight on the rear drive shaft was just touching the metal shield on the side of the fuel tank. couldn't see a rub mark on the shield but the weight was shinny. Key was the put-put got faster as I speed up

 

[NormB]

I had a similar situation, Turned out to be the balance weight on the rear drive shaft was just touching the metal shield on the side of the fuel tank. couldn't see a rub mark on the shield but the weight was shinny. Key was the put-put got faster as I speed up

You know...

if I were still living anywhere close to my sister, I'd be checking the driveshafts for zip-ties.

She's got that kind of sense of humor.

Judging from what I'm reading, I've probably got an exhaust leak - just surprising I'm NOT hearing it while stationary.

I'm off four days next week, I'll plan on some quality temp spent underneath the truck again and report back.