1997 4.0 V6 - Knock that isn't a knock? W/ quality video.

Jman4647 · #1 02-20-2017, 01:31 PM

Hey guys, I have a 1997 Ranger with the 4.0 V6 that makes a noise at idle.

Once it's warmed up, at idle, it almost sounds like a diesel. The truck runs just fine, it has the appropriate amount of power, everything is all there... It just sounds odd when it's running.

I made a video for you guys

, using some decent audio equipment, and a microphone that records directly what it's pointed at.

LargeR · #2 02-20-2017, 11:14 PM

Quote:

Originally Posted by Jman4647

Hey guys, I have a 1997 Ranger with the 4.0 V6 that makes a noise at idle.

Once it's warmed up, at idle, it almost sounds like a diesel. The truck runs just fine, it has the appropriate amount of power, everything is all there... It just sounds odd when it's running.

I made a video for you guys here, using some decent audio equipment, and a microphone that records directly what it's pointed at.

After listening to that I say rod knock/spun bearing. How many miles on it? Did you run it low/out of oil? What grade of oil are you using? Any oil additives?

cowboybilly9mile · #3 02-21-2017, 10:09 AM

It does sound like a rod bearing is on it's way out. A couple things you can do, a) hook up a mechanical oil pressure gauge and compare the reading against the manufacturers spec b) if it's been awhile since the last oil change, send an oil sample to Blackstone labs for an analysis (UOA). The analysis can determine if there is an abnormal of metal in the oil that happens to be....the same material that the bearing inserts are made of.

UOA at Blackstone is something like, $25 or 30 US

http://www.blackstone-labs.com/

Jman4647 · #4 02-21-2017, 12:37 PM

Quote:

Originally Posted by LargeR

After listening to that I say rod knock/spun bearing. How many miles on it? Did you run it low/out of oil? What grade of oil are you using? Any oil additives?

I have a little less than 104400 miles on it, and its being doing that for the last 15,000 miles for sure. I've had the truck for 5 years now, and it's pretty much always done that. I've never run it low/out of oil, and I use 10w-30. No oil additives used either.

Surely if it was rod knock or a spun bearing, it wouldn't have lasted this long or run this well?

----------

Quote:

Originally Posted by cowboybilly9mile

It does sound like a rod bearing is on it's way out. A couple things you can do, a) hook up a mechanical oil pressure gauge and compare the reading against the manufacturers spec b) if it's been awhile since the last oil change, send an oil sample to Blackstone labs for an analysis (UOA). The analysis can determine if there is an abnormal of metal in the oil that happens to be....the same material that the bearing inserts are made of.

UOA at Blackstone is something like, $25 or 30 US

http://www.blackstone-labs.com/

I used a mechanical oil pressure gauge recently when I was having issues with my oil sender (idiot gauge was reading 0, or fluttering). Everything seemed healthy, and if I remember correctly, to manufacturer spec. A new oil sender unit solved that issue.

I just changed my oil about 400 kilometers ago, so I won't be able to do that just yet.

Some guys on the Ford Ranger Subreddit suggest it could be pulleys. Any thoughts on that?

cowboybilly9mile · #5 02-21-2017, 12:57 PM

I've never heard of it on an OHV 4.0 but now that you mention pulleys I did have a crank pulley on an SBC crack between the mount bolts (I found it before it launched through the radiator or the hood of the car) and it make attention getting noise, more of a metal-on-metal slap. Would take minimal time inspect yours and/or remove the belt if there is any doubt.

LargeR · #6 02-21-2017, 01:58 PM

You seem to be pointing more towards the back of the engine, is that where the sound is? I think a pulley would sound like it's coming from the front but again just take the belt off and see if sound goes away. Is it auto trans? Does the engine feel smooth or is there vibration? Sometimes the rubber in the harmonic balancer (part cowboybilly9mile mentioned on sbc) can come get dry/crack and allow the balancer to shift causing a vibration and possibly sound associated with it. Just throwing out ideas to help narrow the problem down.

cowboybilly9mile · #7 02-21-2017, 02:42 PM

Actually, the balancer on the SBC that had the failing pulley mounted to it was one where the pulley bolted directly to a steel hub that was also common to the crank, and there was a steel ring around that hub with a belt of rubber separating the two pieces. IMO, OP needs to get in there and further try to pinpoint the source of the noise. Also, despite hooking up a real oil pressure gauge for diagnosing the last concern, IMO, it's time to hook it up and use it to help diagnose this concern.

Jman4647 · #8 02-22-2017, 05:18 PM

Hey guys, thank you all so much for your replies.

I was just under the vehicle. It doesn't seem to make the noise much/at all at cold start, but will do it later.

I can pretty much confirm it's not any of the pulleys out front. My guess would be that it's from towards the rear of the engine. I can hear it particularly well from under the truck. It has a manual transmission, in case that makes a difference. It has a new clutch, slave cylinder, and release bearing as well.

LargeR · #9 02-22-2017, 06:21 PM

Did the sound start or change at all after the new clutch? Did you resurface the flywheel?
Does the sound go away or change when you put the clutch in?

cowboybilly9mile · #10 02-22-2017, 08:37 PM

It it really as loud when standing by the vehicle as the mic makes it sound or is that mic uber sensitive and making it appear to be much louder than it really is? I ask because, some 4.0's from the mid 90's developed a slight tap that was attributed to either the tolerances used on the wrist pins and/or the pistons, of which somewhere along the way Ford revised the skirt on them.

Jman4647 · #11 02-23-2017, 05:38 AM

Quote:

Originally Posted by LargeR

Did the sound start or change at all after the new clutch? Did you resurface the flywheel?
Does the sound go away or change when you put the clutch in?

It wasn't a bright idea... but I didn't get the flywheel resurfaced.

The noise existed before the clutch, and didn't change after the clutch. The noise doesn't change at all when the clutch is pressed, or if it's in gear.

To answer Cowboy, it's not REALLY loud, but it is noticeable. My mic is really quite sensitive and directional.

LargeR · #12 02-23-2017, 07:43 AM

Quote:

Originally Posted by Jman4647

It wasn't a bright idea... but I didn't get the flywheel resurfaced.

The noise existed before the clutch, and didn't change after the clutch. The noise doesn't change at all when the clutch is pressed, or if it's in gear.

To answer Cowboy, it's not REALLY loud, but it is noticeable. My mic is really quite sensitive and directional.

okay, follow the advice above and do UOA'S. best practice would be to test at about 1600km and again at 5000km. when testing you should use the same process for obtaining your sample, ie pumping through dipstick (cleanest way I think) or draining a bit from plug. The trouble with draining from the plug is that you may lose more oil than needed for the sample and have to add fresh makeup oil.

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