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1989 Ford Ranger Pickup

I have a 1989 Ford Ranger Pickup, 300 cu in six, manual Transmission, 140 k original owner miles. Last week engine started losing power on hill. Stopped at a store and then when started up sounded like nuts and bolts in a grinder (very loud). Stopped the truck, got towed to my garage who has done major work on the truck over the years. Week later when they got to it said they found no problem after driving it around. Don’t really want to drive it until I solve problem. Any ideas?

Clogged catalytic converter?

Thanks for your response. Could that cause a very loud grinding noise which would abate after rest?

Only if the forces that clogged it found another area for the exhaust gases to leave the exhaust manifold…

Hmm.

Was not thinking about the noise with my first response… When the noise occurs, is it in a specific gear?

I was driving through town when the noise started. I was probably in third gear and immediately stopped and turned off the truck. I thought perhaps the timing chain snapped and the grinding noise was my valves. I thought the engine was toast but the garage mechanic said he drove it around (a week later) and could not find anything wrong.

Did they check the hypoid oil (manual transaxle/gear oil) level, and quality?

If your timing chain snapped the engine would not run. Since you are still able to drive it, and it seems to run okay now I would actually look behind the engine.

Was the noise rotational? (I know you only ran it for a short time and might not remember) My first thought on grinding noises that are loud enough to worry a driver are clutch/flywheel hardware. A bolt loosens up in there and it that flywheel becomes a lathe real quick. What it end up machining (bellhousing/engine block/transmission case) can self clearance in some cases meaning it makes a racket for a bit and then is mysteriously silent. It also takes power to machine metal so it’ll feel like the engine is bogging down.

If there is an inspection cover on the trans/bellhousing it might be worth a look.

Thanks Kyle. How about if the timing chain just slipped a cog? Or loosened somewhat? I had a new clutch installed 2 years (1500 miles) ago at the same garage. If a bolt came loose could you tell from the outside or would you have to take everything apart? I did not notice any clutch slippage during loss of power (engine was not racing when I going up a hill); I just had to shift to a lower gear.

I will ask the mechanic to check for metal chips/filings in transmission.

The noise sounded like there was a lawn mower crushing twigs right next to me…or a food processor crushing nuts and bolts.

I talked to the mechanic again yesterday and he said he started the engine and left it running for a while with no problem. He then drove it home and back (40 miles round trip) and found no problem. I asked if it might have been the catalytic converter contents coming loose and he said he would tap it and see if he heard anything.

Really appreciate your interest.