96 Saturn engine knocking

Hello:

I have a 1996 SW2 that had low compression and high oil consumption. Last
summer, I pulled the engine, tore it down and sent the block, crank, head,
etc off to a machine shop. It came back with a rebuild kit, bored out block,
rebuilt head, turned crank, etc. It took a few nights to put it back
together, but it when I put it back in, it started on the first try. It had
good compression and the oil consumption stopped. As a side note, I replaced
every sensor, gasket, etc. that I could find on the engine before
reinstalling it.

A few weeks later, I noticed the head gasket leaking antifreeze most of the
way around. I took the head off again and went to the dealer and bought head
gasket and new head bolts. I noticed the dealer gasket was thicker than the
rebuild kit one and seemed to have an orange "rubber band" running through
it. I reinstalled the head and other stuff and the leaks were fixed. It was
running as good as new.

Now, its a year later and my wife mentioned a "knocking" noise. I took it
for a drive the other day and sure enough, I thought the engine was falling
apart. It has good performance, good milage, isn't using any oil, no
antifreeze missing from the coolant tank and no trouble codes set. But, when
cruising, it knocks so loud I think it's falling apart. Under load, the
noise completely disappears. Under idle it's fine, but rev the engine to
about 1200 rpm and it shows up.

Should I be worried? Any suggestions on where to start? Is it possible the
head gasket is leaking again?

A friend suggested a problem with the lifters. Another said the pistons were
loose. How would I know? By the way, I bought a new torque wrench for this
project and carefully observed the specs and procedures in two different
manuals.

Thanks in advance.

You can email me directly at

 

It could be just about anything. What is the quality record of the engine
rebuilder that you used? What warranty did they provide to you?

You really need to isolate the source of the noise using a stethoscope to
determine its cause. Could it be an exhaust manifold leak or something else
non-internal to the re-built engine?

Bob

 

Knocking that stops under load is exactly what happened to me - and it was a
rod bearing that had spun. Here's what it sounded like at idle:
http://www.evilplastic.com/sounds/knock.wav

A tip - don't drive it that way and fix it as soon as possible, or the bits
of the bearing that wear away will circulate and cause more damage.

Lane [ lane (at) evilplastic.com ]

 

Internal noises that sound like lower end problems MUST be diagnosed ASAP to
prevent further catastrophic damage. When a crankshaft bearing fails it
usually takes a lot with it. DO NOT DRIVE THIS CAR.

Read what the others have said here.
Put the car on some planks to give yourself some clearance to work under
front. Chock the wheels, you will be doing a lot of running in neutral and
your parking brake can fail.
Check the easy stuff first, engine and accessory and exhaust mounts.
Install a real oil pressure test gauge, position it so you can read it as
you start the motor.
Make a test log to record some after start tests.
Have a real good listen to the motor, try to determine the source location
of any noises, if you have knowledgeable friends get their help to listen.
Piston and crank failures have pretty distinct sounds, they are usually very
sharp and vary substantially when engine speed changes. They even sound
expensive. Write down the results of following tests.

Start engine and run @ idle, observe when the oil idiot light goes out and
how long it takes for the engine oil pressure to build and what is max @
idle & 1000 & 1500 @ 2000 rpm

Blip the throttle and listen for internal noise with a mechanics diaphragm
probe stethoscope (a piece of hose works but is harder to interpret).
Listen particularly for sounds on rapidly closing the throttle, this is when
the con rod bearings are unloaded and can float loosely, pistons are also
free to slap and these sounds are often difficult to distinguish. Record
what the oil pressure does as you vary the engine speed and how fast it
drops to idle pressure. (rapid pressure drop can indicate excessive bearing
clearance)

Examine the plugs and do a compression check.

Have a look inside the valve cover, failed valve train can make strange
noises into the manifolds, drop in power is not always large. Use some
plastic to catch the oil spray and have a look while the engine is running,
use your hose to listen to each valve tip.

Drain the oil into a clean container. Allow to settle and check for coolant
as you strain the oil through a cloth, check with a magnet and for other
particles of metal or other.

Cut apart the oil filter (use a pipe cutter or a cold chisel, do not use a
saw or grinder) and wash the paper in a clean can of solvent. Examine the
filter with a magnifying glass. Run the solvent though a coffee filter and
check for particles.

Review your results and make sure you have not overlooked something easy.

Remove the oil pan (you may need to raise the motor?) and check the crank
assembly and piston undersides, rotate the crank and inspect piston skirts
and cylinder bores with a strong light.. Check for loose bolts. Remove
bearing caps to check bearing wear surface and crankshaft for smoothness and
color. Check bearing clearances with plastigage.

Faulty assembly is always suspect in crank failures. Were the con rod bolts
removed? Did YOU check the bearing clearances at assembly? How? Did you
torque the bolts dry? or with Loctite? Did you add a litle for mother?
Faulty machining many be the cause of the failure but the assembler usually
carries the can, consider yourself lucky if a failed bearing does not damage
the crank.

Just my .02, Good luck

 

At the suggestion of a friend, I ran another compression test - it's within
spec. I also checked the plugs - couldn't be burning better. Now for the bad
news. I listened carefully while it was idling. It seemed to be coming from
the head directly above the number one cylinder. I took the valve cover
gasket off just to take a look. Start with the easy stuff, I thought. At
first I couldn't see anything wrong, but then I noticed one of the bolts
holding the timing chain guide was broken. Coincidently, these bolts hold
the first cam shaft bearing cap on. When I tried to remove the other bolt,
it broke as soon as I put a wrench on it. Must of been cracked.

Any suggestions for removing broken bolts from an aluminum head? I drilled
one and tried to use a bolt extractor. It won't even budge. I'm afraid I'm
going to twist off the extractor. Should I just get a new or rebuilt head?
Maybe reuse the cam shafts? Any suggestions are welcome.

Thanks

 

snip
When I tried to remove the other bolt,

The best way I know of to remove broken bolts is to weld a washer on to the
broken bolt. Allow to cool, clean weld, then weld a large nut (or a bolt)
onto the washer. Allow to cool before using a wrench to turn out the (now
hopefully shrunken) broken bolt. Some prefer a wire feed welder for this
job.

Works better than ANY extractor I have ever tried and eliminates the (good)
chance that you will drill off center or break the drill or extractor which
are hardened and brittle. Works good on hardened bolts and sometimes on
broken drills and extractors.

I have had some success with (larger) bolts broken below the surface by
fitting a small piece of steel pipe to the broken bolt and then raising the
heat and sticking the rod down inside the pipe and welding by sound.
Usually takes multiple tries. Caution, do not burn through the side of the
pipe.

YMMV