Someone help diagnosing this squeak...

fsflip13

Well-known member
Aug 31, 2005
154
1
31
Nashville, TN
I have a squeak that can be heard in the videos below. It's not a belt/pulley, as it remains when running with no belt. I have no misfires/codes showing any issues. Compression is good on all cylinders, but could be possibly a head gasket or intake gasket? I've stethoscoped all potentially obvious external sources (haven't found an exhaust leak) and I believe it could be the crank pulley or a headgasket. I have no issues other than the noise at the moment, but wanted to check with the discoweb board for ideas. Thanks.

https://youtu.be/10lMyACJ874

https://youtu.be/fiiY6kU2SKg
 

seanmcd

Well-known member
Apr 24, 2006
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0
It is hard to hear man but to me it sounds like an idler pulley or water pump bearing, it definitely sounds like a bearing. I am not sure how far you drove it without the belt on? Is it under the hood?
 

fsflip13

Well-known member
Aug 31, 2005
154
1
31
Nashville, TN
I drove it up and down the street without the belt, and also revved it in the driveway without the belt. The squeak persists without the belt, so it should cancel the possibility of idler pulleys and water pump. I will likely retest this though as the squeak has gotten worse in the last few days. It only squeaks under load/acceleration/revving, even sitting still. This should cancel out the u-joints (new front driveshaft).

I swapped the manifold to y-pipe gasket, but haven't yet swapped head to manifold exhaust gaskets. This is what it honestly sounds like most, but I haven't figured out where with the stethoscope. It could be a headgasket letting go, but I haven't seen any misfires or signs of bad headgasket. It is very loud from outside the truck, to the point it is embarrassing to drive, but I'm going to keep chasing down the squeak. This weekend I will swap the head to manifold gaskets and go from there.
 

squirt

Well-known member
Nov 13, 2008
792
0
Los Angeles
If you think it's one of the manifold gaskets, you should be able to use a short piece of tubing on your ear and detect which exhaust port is causing the noise. If your stethoscope is like mine, it terminates in a solid rod and is most useful for ticking or vibrating noises.

Another possibility is a loose O2 sensor. I've had a chirping sort of sound from that before. In fact, based on the noise frequency in the videos I'd be leaning more toward this(or something that is not tied to a single cylinder) than a single exhaust gasket leak. In the video at ~1100-1200RPM you're getting about 6 squeaks per second. A single cylinder causing the noise would only produce a frequency of 1-1.5 squeaks/second at that engine speed.

1200RPM/60seconds/8cylinders/2(because 4 stroke)=~1.25 exhaust shots per second per cylinder
 

fsflip13

Well-known member
Aug 31, 2005
154
1
31
Nashville, TN
This sounds very possible. It is coming from what sounds like the passenger side of the engine. Will try the stethoscope around the o2 sensor, I haven't even tried or thought of that yet. My stethoscope is the type that ends in a solid rod and has been very useful so far in finding what is not squeaking. I will update this once I take a look at that.
 

fsflip13

Well-known member
Aug 31, 2005
154
1
31
Nashville, TN
Update: https://youtu.be/DG-_OU6xo6U
Note that I'm trying to hold the mirror still in this video, the compression/exhaust air is bouncing it around forcefully.

The squeak got much louder on my drive home today. It was becoming more obvious that it was some sort of exhaust leak, and when I got home I pulled out the stethoscope and couldn't find any obvious noise again or see any escaping gasses. Looking for hopefully a loose spark plug or something of the sort, I ran my hand by the exhaust and felt what was obviously the exhaust leaking. It is leaking externally from the headgasket. This is fairly obvious now, but I was hoping it was something much simpler to fix. This external leak is new to me, as I've had internal head gasket leaks before. This will be something like my 4th set of head gaskets in the two discos I've owned, lucky me. Off to replace the head gaskets this weekend.
 

p m

Administrator
Callsign: AK6PM
Apr 19, 2004
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La Jolla, CA
www.3rj.org
I had an external head gasket leak on the Classic, near #1. No fluid leaks - just exhaust blowing outside between the block and head.