Engine Knock Right at Engine Start only!!

#1

I'm trying to get as much research for this as I possibly can before taking
action. Any info you guys could provide would be greatly appreciated!

My Situation:

Sometimes when I go to start my truck, I will turn the engine over and when
it fires up there are a series of 4 knocks and then it goes away. Each and
every time it does it, it's four knocks. It usually happens after the engine
has been sitting for the night. I took my truck to a mechanic concerning this
"knock". He said it sounded like front/rear main bearings or possibly the
crank shaft, but he could not tell which area it came from. What puzzled him
is that it only "knocked" four times and then went away. After that,
everything sounded perfect. Absolutely NO ENGINE NOISE WHAT SO EVER. He
commented that the truck ran remarkably well.

Info I recieved from another forum:

this is most likely a problem with the crankshaft main bearings. general
motors had a bulletin on this when these engines were new and the fix was to
measure the main bearings and install oversized bearings on the mains. they
also note that this will not affect the longevity of the engine. bottom line
is leave it alone.

Do you guys concur with this response?

Thank you for your input!

Phil

#2

On May 5, 1:07*am, "Dunamis" <u43397@uwe> wrote:

Quote:

I'm trying to get as much research for this as I possibly can before taking
action. Any info you guys could provide would be greatly appreciated!

My Situation:

Sometimes when I go to start my truck, I will turn the engine over and when
it fires up there are a series of 4 knocks and then it goes away. Each and
every time it does it, it's four knocks. It usually happens after the engine
has been sitting for the night. I took my truck to a mechanic concerning this
"knock". He said it sounded like front/rear main bearings or possibly the
crank shaft, but he could not tell which area it came from. What puzzled him
is that it only "knocked" four times and then went away. After that,
everything sounded perfect. Absolutely NO ENGINE NOISE WHAT SO EVER. He
commented that the truck ran remarkably well.

Info I recieved from another forum:

this is most likely a problem with the crankshaft main bearings. general
motors had a bulletin on this when these engines were new and the fix was to
measure the main bearings and install oversized bearings on the mains. they
also note that this will not affect the longevity of the engine. bottom line
is leave it alone.

Do you guys concur with this response?

Thank you for your input!

Phil

Sounds like classic bearing rattle to me. You get it at startup till
the pressure builds up.

Longevity? Hard to say. Were it me, Id think about using a heavier oil
and see if that helps any.
Maybe a can of oil treatment. You want to prevent the rattle. I have
to assume when it rattles it is potentially scarring the bearing. For
putting around town you may get by for a long time, Id be afraid to
make any long distance trips.

Id also think twice before I gunned it to get around grandpa.

#3

Thanks a lot! I appreciate the info!!

--
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#4

Thanks a lot! I appreciate the info!!

--
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#5

"Dunamis" <u43397@uwe> wrote

Quote:

I'm trying to get as much research for this as
I possibly can before taking
action. Any info you guys could provide would
be greatly appreciated!

My Situation:

Sometimes when I go to start my truck, I will
turn the engine over and when
it fires up there are a series of 4 knocks and
then it goes away. Each and
every time it does it, it's four knocks. It
usually happens after the engine
has been sitting for the night.

I know this sounds kind of weird----but have you
had any work done on the AC?
If there is a bit too much oil in the AC system,
it will settle in the pump lower
cylinder overnight, and knock a few times on
start-up. Had it happen on my
94 K1500.

Bill

#6

No work done to the A/C. As a matter of fact my air hasn't worked in a long
time. I'm just to lazy to replace the sensor on the drier unit.

BillM wrote:

Quote:

I'm trying to get as much research for this as
I possibly can before taking
[quoted text clipped - 10 lines]
usually happens after the engine
has been sitting for the night.

I know this sounds kind of weird----but have you
had any work done on the AC?
If there is a bit too much oil in the AC system,
it will settle in the pump lower
cylinder overnight, and knock a few times on
start-up. Had it happen on my
94 K1500.

Bill

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx/chevrolet-trucks/200805/1

#7

"Dunamis" <u43397@uwe> wrote

Quote:

I'm trying to get as much research for this as I possibly can before
taking
action. Any info you guys could provide would be greatly appreciated!

My Situation:

Sometimes when I go to start my truck, I will turn the engine over and
when
it fires up there are a series of 4 knocks and then it goes away. Each and
every time it does it, it's four knocks. It usually happens after the
engine
has been sitting for the night. I took my truck to a mechanic concerning
this
"knock". He said it sounded like front/rear main bearings or possibly the
crank shaft, but he could not tell which area it came from. What puzzled
him
is that it only "knocked" four times and then went away. After that,
everything sounded perfect. Absolutely NO ENGINE NOISE WHAT SO EVER. He
commented that the truck ran remarkably well.

Info I recieved from another forum:

this is most likely a problem with the crankshaft main bearings. general
motors had a bulletin on this when these engines were new and the fix was
to
measure the main bearings and install oversized bearings on the mains.
they
also note that this will not affect the longevity of the engine. bottom
line
is leave it alone.

Do you guys concur with this response?

Thank you for your input!

Phil

It is simply the hydraulic lifters pumping back up after leaking down
overnight. Engines have been doing this ever since hydraulic lifters were
invented. There is nothing wrong, they are working like they are supposed
to. See http://en.wikipedia.org/wiki/Hydraulic_lifters if you don't
understand.

Randal

#8

How about the year and engine?????, some 4.8 and 5.3 engones had an issue
with the oil pump to block seal which caused some start up issues
"Dunamis" <u43397@uwe> wrote

Quote:

I'm trying to get as much research for this as I possibly can before
taking
action. Any info you guys could provide would be greatly appreciated!

My Situation:

Sometimes when I go to start my truck, I will turn the engine over and
when
it fires up there are a series of 4 knocks and then it goes away. Each and
every time it does it, it's four knocks. It usually happens after the
engine
has been sitting for the night. I took my truck to a mechanic concerning
this
"knock". He said it sounded like front/rear main bearings or possibly the
crank shaft, but he could not tell which area it came from. What puzzled
him
is that it only "knocked" four times and then went away. After that,
everything sounded perfect. Absolutely NO ENGINE NOISE WHAT SO EVER. He
commented that the truck ran remarkably well.

Info I recieved from another forum:

this is most likely a problem with the crankshaft main bearings. general
motors had a bulletin on this when these engines were new and the fix was
to
measure the main bearings and install oversized bearings on the mains.
they
also note that this will not affect the longevity of the engine. bottom
line
is leave it alone.

Do you guys concur with this response?

Thank you for your input!

Phil

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#9

It's a 95 K1500 w/ 5.7 350 engine. 203K miles on the truck, but I put in a
new "crate" engine about 8 years ago. I think it MAY have 50K on it. The
issue is that I bought the truck when I was a young punk and only had one
thing on my mind and it wasn't the truck. So, the truck has been neglected in
the past. Now I'm trying to bring the truck back up to its former glory. I
want to get everything under the hood where it needs to be to get optimum
efficiency and functionality before I start working on the outside of the
truck.

--
Message posted via CarKB.com
http://www.carkb.com/Uwe/Forums.aspx/chevrolet-trucks/200805/1

#10

On May 5, 11:57*am, "Randal O'Brian" <ROBRI... (AT) austin (DOT) rr.com> wrote:

Quote:

"Dunamis" <u43397@uwe> wrote in messagenews:83af08b03e6ec (AT) uwe (DOT) ..
I'm trying to get as much research for this as I possibly can before
taking
action. Any info you guys could provide would be greatly appreciated!

My Situation:

Sometimes when I go to start my truck, I will turn the engine over and
when
it fires up there are a series of 4 knocks and then it goes away. Each and
every time it does it, it's four knocks. It usually happens after the
engine
has been sitting for the night. I took my truck to a mechanic concerning
this
"knock". He said it sounded like front/rear main bearings or possibly the
crank shaft, but he could not tell which area it came from. What puzzled
him
is that it only "knocked" four times and then went away. After that,
everything sounded perfect. Absolutely NO ENGINE NOISE WHAT SO EVER. He
commented that the truck ran remarkably well.

Info I recieved from another forum:

this is most likely a problem with the crankshaft main bearings. general
motors had a bulletin on this when these engines were new and the fix was
to
measure the main bearings and install oversized bearings on the mains.
they
also note that this will not affect the longevity of the engine. bottom
line
is leave it alone.

Do you guys concur with this response?

Thank you for your input!

Phil

It is simply the hydraulic lifters pumping back up after leaking down
overnight. *Engines have been doing this ever since hydraulic lifters were
invented. *There is nothing wrong, they are working like they are supposed
to. * Seehttp://en.wikipedia.org/wiki/Hydraulic_lifters*if you don't
understand.

Randal- Hide quoted text -

- Show quoted text -

Well...now theres "rattle" and there's "tick tick tick". If its rattle
rattle rattle, Im leaning towards rod/crank bearing. If its "tick tick
tick" then definately lifters. This has been my experience anyway.