Part time engine knock

Hi Group,
I have a 1991 GMC K-2500 with the 350 CID engine {5.7 Liter}, 217,000
miles, runs great, doesn't use oil.
It developed a water leak and the garage replaced the intake gasket.
When I picked it up the oil pressure was very low, about 15 highway, 0 at
idle. I assumed they had loosened a wire or something, until the engine
started knocking.
OF course the garage claims there is no way changing the intake gast
would cause a loss of oil pressure, so I'm on my own.
I pulled the oil pan and checked the rod bearings with plasti-gauge,
number 8 was worn to much to get a reading with the green, but the others
all ran from .002 to .003. I replaced that bearing with a new standard
bearing and rechecked it, it was now .002. I installed a new oil pump and
reassembled it. Now I get several hard knocks as soon as the engine starts,
which stops as soon as the oil pressure rises. Oil pressure cold is 60 PSI.
The engine sounds perfect at all speeds cold, no trace of a knock.
As the engine warms up, the oil pressure drops a bit. At about 150
degrees the oil pressure has dropped to 45 PSi and the knocking starts
again. It sounds low, like a rod knock, increases in speed with the engine,
but is not very loud, and at higher engine speeds it can't be heard over the
fan noise.
At normal operating temperature the oil pressure is down to 15 PSI at
idle, 30 highway, with a constant knocking from the lower engine. My best
guess is that the crank itself will have to be replaced, with all new
bearings. I welcome comments from anyone who might know more than I what is
wrong.
Thanks.

The coolant is what did in the bearings:

not the shop replacing the manifold gaskets. So there are several factors at
work here, mainly. The main bearings were never checked.

Secondly, why did you only replace the one bearing, the sides of the others
could be egged at the parting line.

Thirdly, The cam bearings were also etched by the zombie juice that was in
the crank case when the manifold leaked.

So, if you would have replaced all the rod bearings, all the mains, there
would have been 12 less chances for a knock. The mains are most likely lose
and leaking pressure, and the rod bearings are more than likely egged at the
sides, so when the oil thins out at operating temperature. You lose the oil
strata that normally quiets the knock hydraulically.

You might be able to save it in vehicle, but would you want to take that
chance again, with the price of a good kit, with Sealed Power pistons, cam,
rings, bearings will most likely be sealed power and not cleveite. but, if
you want the best you'll have to pay more.

Machining it won't cost a lot and the timing chain, cam bearings and freeze
plugs will be in the kit too.

I hope this helps?

Refinish King

PS
Don't buy the kit with cast pistons, pay a few bucks more and get the :
Hypereutectic pistons.
"The Ancient One" <[email protected]> wrote in message
news:[email protected]...
> Hi Group,
> I have a 1991 GMC K-2500 with the 350 CID engine {5.7 Liter}, 217,000
> miles, runs great, doesn't use oil.
> It developed a water leak and the garage replaced the intake gasket.
> When I picked it up the oil pressure was very low, about 15 highway, 0 at
> idle. I assumed they had loosened a wire or something, until the engine
> started knocking.
> OF course the garage claims there is no way changing the intake gast
> would cause a loss of oil pressure, so I'm on my own.
> I pulled the oil pan and checked the rod bearings with plasti-gauge,
> number 8 was worn to much to get a reading with the green, but the others
> all ran from .002 to .003. I replaced that bearing with a new standard
> bearing and rechecked it, it was now .002. I installed a new oil pump and
> reassembled it. Now I get several hard knocks as soon as the engine
starts,
> which stops as soon as the oil pressure rises. Oil pressure cold is 60
PSI.
> The engine sounds perfect at all speeds cold, no trace of a knock.
> As the engine warms up, the oil pressure drops a bit. At about 150
> degrees the oil pressure has dropped to 45 PSi and the knocking starts
> again. It sounds low, like a rod knock, increases in speed with the
engine,
> but is not very loud, and at higher engine speeds it can't be heard over
the
> fan noise.
> At normal operating temperature the oil pressure is down to 15 PSI at
> idle, 30 highway, with a constant knocking from the lower engine. My best
> guess is that the crank itself will have to be replaced, with all new
> bearings. I welcome comments from anyone who might know more than I what
is
> wrong.
> Thanks.
>
>

"Refinish King" <[email protected]> wrote in message
news:[email protected]...
> The coolant is what did in the bearings:

The coolant leak was external, no coolant was ever in the oil, and the
garage changed the oil after replacing the gasket to insure there was no
contamination from the gasket change.

>
> not the shop replacing the manifold gaskets. So there are several factors
at
> work here, mainly. The main bearings were never checked.
>
> Secondly, why did you only replace the one bearing, the sides of the
others
> could be egged at the parting line.

Only one failed the plasti-gauge check, so I only replaced the one. I
expected it to still fail the test, but it did not.

>
> Thirdly, The cam bearings were also etched by the zombie juice that was in
> the crank case when the manifold leaked.
>
> So, if you would have replaced all the rod bearings, all the mains, there
> would have been 12 less chances for a knock. The mains are most likely
lose
> and leaking pressure, and the rod bearings are more than likely egged at
the
> sides, so when the oil thins out at operating temperature. You lose the
oil
> strata that normally quiets the knock hydraulically.
>
> You might be able to save it in vehicle, but would you want to take that
> chance again, with the price of a good kit, with Sealed Power pistons,
cam,
> rings, bearings will most likely be sealed power and not cleveite. but, if
> you want the best you'll have to pay more.
>
> Machining it won't cost a lot and the timing chain, cam bearings and
freeze
> plugs will be in the kit too.
>
> I hope this helps?

Every suggestion helps. Thanks.

I'm of the mentality:

If one bearing is lose, another one is lurking to get me!

So if I sounded brash, I wasn't at all. I just get nervous that something is
going to bite me in the back, and usually does.

I was married, if you get my drift?

Refinish King


"The Ancient One" <[email protected]> wrote in message
news:[email protected]...
>
> "Refinish King" <[email protected]> wrote in message
> news:[email protected]...
> > The coolant is what did in the bearings:
>
> The coolant leak was external, no coolant was ever in the oil, and the
> garage changed the oil after replacing the gasket to insure there was no
> contamination from the gasket change.
>
> >
> > not the shop replacing the manifold gaskets. So there are several
factors
> at
> > work here, mainly. The main bearings were never checked.
> >
> > Secondly, why did you only replace the one bearing, the sides of the
> others
> > could be egged at the parting line.
>
> Only one failed the plasti-gauge check, so I only replaced the one. I
> expected it to still fail the test, but it did not.
>
> >
> > Thirdly, The cam bearings were also etched by the zombie juice that was
in
> > the crank case when the manifold leaked.
> >
> > So, if you would have replaced all the rod bearings, all the mains,
there
> > would have been 12 less chances for a knock. The mains are most likely
> lose
> > and leaking pressure, and the rod bearings are more than likely egged at
> the
> > sides, so when the oil thins out at operating temperature. You lose the
> oil
> > strata that normally quiets the knock hydraulically.
> >
> > You might be able to save it in vehicle, but would you want to take that
> > chance again, with the price of a good kit, with Sealed Power pistons,
> cam,
> > rings, bearings will most likely be sealed power and not cleveite. but,
if
> > you want the best you'll have to pay more.
> >
> > Machining it won't cost a lot and the timing chain, cam bearings and
> freeze
> > plugs will be in the kit too.
> >
> > I hope this helps?
>
> Every suggestion helps. Thanks.
>
>
>

"Refinish King" <[email protected]> wrote in message
news:[email protected]...
> I'm of the mentality:
>
> If one bearing is lose, another one is lurking to get me!
>
> So if I sounded brash, I wasn't at all. I just get nervous that something
is
> going to bite me in the back, and usually does.
>
> I was married, if you get my drift?
>
> Refinish King

hehehee, oh yeah.

Another reason I only replaced one was because I figured I would have to
replace the crank anyway, and most reconditioned cranks are at least .010
undersized, so I would be wasting the money I spent on a whole set.
I just bought one so I could get an accurate reading from that journal,
and was quite surprised when it read so good.
Being somewhat eager to have my truck on the road again, and hoping for
the best, I reassembled it and went for broke.
I've made a couple of trips to town and back and the knocking is not
getting any worse yet, hopefully it will last until I can budget the funds
to fix it right, whatever it takes.

>
>
> "The Ancient One" <[email protected]> wrote in message
> news:[email protected]...
> >
> > "Refinish King" <[email protected]> wrote in
message
> > news:[email protected]...
> > > The coolant is what did in the bearings:
> >
> > The coolant leak was external, no coolant was ever in the oil, and the
> > garage changed the oil after replacing the gasket to insure there was no
> > contamination from the gasket change.
> >
> > >
> > > not the shop replacing the manifold gaskets. So there are several
> factors
> > at
> > > work here, mainly. The main bearings were never checked.
> > >
> > > Secondly, why did you only replace the one bearing, the sides of the
> > others
> > > could be egged at the parting line.
> >
> > Only one failed the plasti-gauge check, so I only replaced the one. I
> > expected it to still fail the test, but it did not.
> >
> > >
> > > Thirdly, The cam bearings were also etched by the zombie juice that
was
> in
> > > the crank case when the manifold leaked.
> > >
> > > So, if you would have replaced all the rod bearings, all the mains,
> there
> > > would have been 12 less chances for a knock. The mains are most likely
> > lose
> > > and leaking pressure, and the rod bearings are more than likely egged
at
> > the
> > > sides, so when the oil thins out at operating temperature. You lose
the
> > oil
> > > strata that normally quiets the knock hydraulically.
> > >
> > > You might be able to save it in vehicle, but would you want to take
that
> > > chance again, with the price of a good kit, with Sealed Power pistons,
> > cam,
> > > rings, bearings will most likely be sealed power and not cleveite.
but,
> if
> > > you want the best you'll have to pay more.
> > >
> > > Machining it won't cost a lot and the timing chain, cam bearings and
> > freeze
> > > plugs will be in the kit too.
> > >
> > > I hope this helps?
> >
> > Every suggestion helps. Thanks.
> >
> >
> >
>
>
>

Just remember:

When it knocks like that, a rod is getting egged. So it will pay you to have
all 8 rods reconed when you do the motor.

Refinish King


"The Ancient One" <[email protected]> wrote in message
news:[email protected]...
>
> "Refinish King" <[email protected]> wrote in message
> news:[email protected]...
> > I'm of the mentality:
> >
> > If one bearing is lose, another one is lurking to get me!
> >
> > So if I sounded brash, I wasn't at all. I just get nervous that
something
> is
> > going to bite me in the back, and usually does.
> >
> > I was married, if you get my drift?
> >
> > Refinish King
>
> hehehee, oh yeah.
>
> Another reason I only replaced one was because I figured I would have to
> replace the crank anyway, and most reconditioned cranks are at least .010
> undersized, so I would be wasting the money I spent on a whole set.
> I just bought one so I could get an accurate reading from that journal,
> and was quite surprised when it read so good.
> Being somewhat eager to have my truck on the road again, and hoping for
> the best, I reassembled it and went for broke.
> I've made a couple of trips to town and back and the knocking is not
> getting any worse yet, hopefully it will last until I can budget the funds
> to fix it right, whatever it takes.
>
> >
> >
> > "The Ancient One" <[email protected]> wrote in message
> > news:[email protected]...
> > >
> > > "Refinish King" <[email protected]> wrote in
> message
> > > news:[email protected]...
> > > > The coolant is what did in the bearings:
> > >
> > > The coolant leak was external, no coolant was ever in the oil, and the
> > > garage changed the oil after replacing the gasket to insure there was
no
> > > contamination from the gasket change.
> > >
> > > >
> > > > not the shop replacing the manifold gaskets. So there are several
> > factors
> > > at
> > > > work here, mainly. The main bearings were never checked.
> > > >
> > > > Secondly, why did you only replace the one bearing, the sides of the
> > > others
> > > > could be egged at the parting line.
> > >
> > > Only one failed the plasti-gauge check, so I only replaced the one. I
> > > expected it to still fail the test, but it did not.
> > >
> > > >
> > > > Thirdly, The cam bearings were also etched by the zombie juice that
> was
> > in
> > > > the crank case when the manifold leaked.
> > > >
> > > > So, if you would have replaced all the rod bearings, all the mains,
> > there
> > > > would have been 12 less chances for a knock. The mains are most
likely
> > > lose
> > > > and leaking pressure, and the rod bearings are more than likely
egged
> at
> > > the
> > > > sides, so when the oil thins out at operating temperature. You lose
> the
> > > oil
> > > > strata that normally quiets the knock hydraulically.
> > > >
> > > > You might be able to save it in vehicle, but would you want to take
> that
> > > > chance again, with the price of a good kit, with Sealed Power
pistons,
> > > cam,
> > > > rings, bearings will most likely be sealed power and not cleveite.
> but,
> > if
> > > > you want the best you'll have to pay more.
> > > >
> > > > Machining it won't cost a lot and the timing chain, cam bearings and
> > > freeze
> > > > plugs will be in the kit too.
> > > >
> > > > I hope this helps?
> > >
> > > Every suggestion helps. Thanks.
> > >
> > >
> > >
> >
> >
> >
>
>