Jeep 4.0 finding engine noise
Cherokee Ronnie Cherokee Ronnie
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 Published On May 1, 2022

A few things to looks for if your engine is making noise:
- Exhaust Manifold Leaks
- Loose Flexplate bolts hitting bellhousing
- Cracked Flexplate
- Damaged Spark Plugs
• Damaged Valves / Valve Seats
Worn Valve Guides
- Broken / Worn Piston Rings
- Bent / Broken Push Rods
Binding / Cracked Valve Springs
- Worn / Stuck Camshaft Lifters
- Flat Camshaft Lobe
• Worn Cam/Crank Bearings
- Piston Slap

Tests you can try:
- Slow Motion Test: With the Valve Cover off, film your engine,
preferable with a slow motion setting (60fps, 120fps, 240fps,
ect) and slow it down on a computer to better see what the
engine is doing and what the sound actually sounds like.
- Timing Light Test: Count how often the noise happens
compared to a spark plug firing. 1 tap for 1 blink is half engine
speed (Camshaft or Valve Train related) 2 taps for 1 blink is full
engine speed (Crankshaft or Rotating Assembly related)
• Elimination Test: Disconnect the Spark Plug wire and Injector
wire from 1 cylinder at a time and start the vehicle to listen for
a change in noise. Go down the line for each cylinder to see if
you can find the culprit; this may narrow it down to
combustion related issues.
- Compression Test: Using a Compression Gauge, pull all
spark plugs and check each cylinder's compression. An
abnormally low reading points to a cylinder not sealing
properly.
- Leak Down Test: If a Cylinder shows low compression, turn
the crankshaft until that cylinder is on Top Dead Center (TDC)
on the Compression stroke and connect a low pressure airline
up to the spark plug hole. Try to listen to where the air is
coming out. Listen to Intake, Exhaust Pipe, Crankcase, and
check coolant for bubbles.

Camshaft Lift Measurement: Using a dial indicator
connected to a pushrod, measure the lift of each Cam Lobe to
check for severe wear.
- Lifter Preload Measurement: Check to see if Camshaft Lifters
have proper preload. Can be measured, or loosen up rockers
for one cylinder to see if noise gets better or worse.
- Worn Rod Bearing Test: Rotate the Crankshaft until the
Cylinder in question is starting to move down, then insert a
screwdriver into the spark plug hole so that it touches the
piston. Push down sharply on the piston and listen for a knock
which would indicate loose clearances on the Rod Bearing.

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