Hey all, hoping someone has heard this. Few days ago started hearing a sort of a subtle rhythmic thump coming from the engine bay. When I popped the hood it seemed like it was coming from the serpentine belt. When I looked at it, it appeared to have slight play at the serpentine tensioner but nothing alarming. Today the sound has changed a bit and sounds more high pitched and at a fast pace. Still a consistent rhythm and it does not change whatsoever when increasing/decreasing RPMs. Went to Autozone and picked up a new belt and tensioner. As I got the front end disassembled I was pleasantly surprised to see the belt is in top shape so didn’t move forward with replacing that, only swapped out the tensioner (Home late and have an early morning tomorrow so not looking for extra work). Put it all back together only to find that the sound is exactly the same.

The video attached was taken tonight after I put it back to demonstrate the sound I’m referring to.

Any thoughts? When I had the belt off I felt the rest of the pulleys and everything seemed tight, nothing seemed loose in the slightest. Belt is on straight and appears to have basically no play in it whatsoever. Never run into this one before so hoping someone else has, or has some ideas on where I might look next.

Thanks in advance to any responses. Happy trails!

 

I can’t listen to the audio right now, but if it’s rhythmic, almost like a metronome, it’s your fan clutch.

 

If it's the fan clutch, is that normal? Or does the rhythmic thumping mean it's going out?

 

I haven't come across this particular LR3 fan clutch symptom personally houm, but a part making noise when it's not supposed to is never a good sign

 

I interpret it as the fan clutch starting to fail.

 

Thanks...mine has made that noise for years.....but for that rig years only equals a couple thousand miles, and I only hear it in the garage when all is quiet and I listen really hard. I'm sure it will let me know....

 

Back with an update.

First, thanks to all who have commented so far. Secondly, apologies for posting and then dropping off. I posted that and then had to leave town and only recently got back and have spent some more time under the hood.

Here’s where I’m at.

Based on the comments coming in, I ordered the fan clutch for install. However, it arrived after I left town so before leaving, I walked my dad through the steps to install the new fan clutch (my wife wants this fixed ASAP). He watched me pull it out the night before so he was already familiar.

He called after he installed it and said the sound was still there. I said no worries, I’ll look at it upon my return. Got back and turned the rig over and lo’ and behold she started up just fine. The initial sound seems to be gone. Only issue was that the idle wouldn’t settle down. It was idling at around 1200-1500 RPM, so slightly higher but nothing crazy. After a few minutes running, I turned the car off and tried to restart. It started, and then almost immediately died. Repeated attempts produced the same result. This made me question if the alternator was going out. Couldn’t get the car running long enough to test the alternator as it would die immediately. So, went ahead and ordered a new one thinking this was the culprit.

Alternator came yesterday and went to install today. Before doing so, thought I’d go through the motions again. This time, the car turned over and continued to run. However, it was running very rough and throwing a number of codes. Codes are:



P0102: MAF Sensor ‘A’ circuit low

P0447: EVAP System Vent Control Circuit Open

P2103: Throttle Actuator ‘A’ Control Motor Circuit High

P0607: Control Module Performance

P0121: Throttle/Pedal Position Sensor/Switch ‘A’ Circuit Range/Performance

P2105: Throttle Actuator Control System – Forced Engine Shutdown

P0459: EVAP System Purge Control Valve ‘A’ Circuit High

U2023: No idea what this is

After pulling the codes, turned it off and attempted a restart. Engine turned over and then immediately dies, just as the time before. Repeated attempts produced the same result.

At this point, put the charger on the battery for a bit to try again. This time, turned over and continued to run but not nearly as rough and wasn’t throwing the above codes after I cleared them. However, continued to idle high and heavy (minor vibration). And this time I pulled the multimeter to test the alternator and it seems fine (Just over 14 volts when running, giving gas and pulling juice for internal instruments). Let it run for 5-6 minutes then turned off. Try to start again and same behavior occurred; turned over fine but died immediately.

I suspect if I charged the battery again I would get this exact same results, yet the alternator seems to be functioning fine.

So, really scratching my head on this. The new fan clutch seems to have resolved the initial noise that prompted me to start this thread. But, now I have this new issue that wasn’t present before and I’m truly at a loss. Doesn’t seem related, seems like it’s probably some thing electrical that was compromised during the install, or perhaps a vacuum leak? I’m honestly guessing at this point and hoping someone more knowledge/experience than myself can offer suggestions.

Thanks in advance and sorry for the long post. Just trying to be as descriptive as possible so readers know how this all unfolded.

Cheers all.

 

Those are pretty much all codes you would get when wiring or a connector has been cut/broken/unplugged or otherwise disturbed. I'd give a thorough look over the engine bay, especially around the fan.

 

In this regard, check your MAF connector. I had something similar happen when cleaning it once. Forgot to plug in - would start and then immediately die.

 

Another update.

Truck is starting more frequently but all symptoms persist. Once running, high and rough idle when in Park/Neutral, once in gear idle drops but remains rough.

I’m still pulling the same codes. I use the 4Dcan software from RSW to pull/clear codes. The interesting thing is that when I clear the engine codes, the engine immediately dies. I’ve never had that happen before. When fired back up, codes remain and all symptoms remain.

I’ve inspected the MAF sensor, cleaned it, took a close look at the wiring and harness, all of which looks good. Truly stumped.

AT this point, thinking I may just take a chance and order a new MAF sensor & install and see if that gets me anywhere. Is there any way to tell if the MAF sensor is bad?

Thanks for the contributions thus far, truly appreciated.