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valve train noise or worse ?



 
 
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  #1  
Old July 22nd 05, 11:52 AM
carl
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Default valve train noise or worse ?

Hi,

Can I bring another question to this forum ? I looked at the archives, but
found nothing similar for this noise pattern or situation. And I wonder what
a mechanic would say, given lash values are correct for most of the dealers.

My car has had valves tightened a bit too much, now they're at correct valve
lash. For a while, I hear too much noise coming from the cover. Valve lash
increases with temperature ( is it always so ? ) and seems lower in
frequency and much less noticeable when warm

It is loudest on a cold engine, and in the afternoon, with engine still
warm, is never that loud again. It also becomes very high in frequency when
cold when the throttle is released, after driving in low gear and low load,
the clatter increases just after release in volume and frequency, and
diminishes after about a second ...

Does the noise pattern, like after throttle release, point to something
worse ( low- high end or main bearing ) ? I thought they would make heavier
noise. There could have been oil issues in the past. Also, timing could have
been too early 4 degrees for a long time, or late 4 degrees for 1000 miles
now, giving more than normal bearing load ?

Now this valve train has a OHC, two rocker shafts and 12 valve rockers with
4 exhaust ones. The rockers are cast aluminium, with iron or steel adjuster
screws. I imagine it is not such a big deal to install new rockers and
shafts, and even a camshaft, and adjust valve lash again. But from where can
this noise come when valve lash is correct ? The car has 35 k miles and oil
was changed just at 33k5 miles. Is there something with aluminium rockers
and steel adjustment screws, which should not be overtightened ( they
tighten even further when hot ) ? They could have been.

Looking forward to any advice,

MTIA,

Carl


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  #2  
Old July 22nd 05, 12:13 PM
N8N
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Posts: n/a
Default



carl wrote:
> Hi,
>
> Can I bring another question to this forum ? I looked at the archives, but
> found nothing similar for this noise pattern or situation. And I wonder what
> a mechanic would say, given lash values are correct for most of the dealers.
>
> My car has had valves tightened a bit too much, now they're at correct valve
> lash. For a while, I hear too much noise coming from the cover. Valve lash
> increases with temperature ( is it always so ? ) and seems lower in
> frequency and much less noticeable when warm
>
> It is loudest on a cold engine, and in the afternoon, with engine still
> warm, is never that loud again. It also becomes very high in frequency when
> cold when the throttle is released, after driving in low gear and low load,
> the clatter increases just after release in volume and frequency, and
> diminishes after about a second ...
>
> Does the noise pattern, like after throttle release, point to something
> worse ( low- high end or main bearing ) ? I thought they would make heavier
> noise. There could have been oil issues in the past. Also, timing could have
> been too early 4 degrees for a long time, or late 4 degrees for 1000 miles
> now, giving more than normal bearing load ?
>
> Now this valve train has a OHC, two rocker shafts and 12 valve rockers with
> 4 exhaust ones. The rockers are cast aluminium, with iron or steel adjuster
> screws. I imagine it is not such a big deal to install new rockers and
> shafts, and even a camshaft, and adjust valve lash again. But from where can
> this noise come when valve lash is correct ? The car has 35 k miles and oil
> was changed just at 33k5 miles. Is there something with aluminium rockers
> and steel adjustment screws, which should not be overtightened ( they
> tighten even further when hot ) ? They could have been.
>
> Looking forward to any advice,
>
> MTIA,
>
> Carl


A rapping noise on overrun as you describe sounds like rod bearings to
me, GF had the same noise on her Corrado and new rod bearing shells
made it go away

nate

  #3  
Old July 22nd 05, 01:54 PM
carl
external usenet poster
 
Posts: n/a
Default

>
> > Carl

>
> A rapping noise on overrun as you describe sounds like rod bearings to
> me, GF had the same noise on her Corrado and new rod bearing shells
> made it go away
>
> nate
>


Thanks, Nate,

If you're talking about low end bearings, it is relatively good news for
repair. But how did it come ? Bad oil, bad load ? As I drive at low rpm, on
low throttle, would that be enough for damage to occur in a short period of
time ? I imagine oil pressure then doesn't get that high , ie. high enough.

This car ran fine for a long time, until there was an oil problem and fuel
system issue, then after a power test it ran worse. It is possible the
damage dates from then. But after letting the car sit for two years, at
first there was no noise. I'm worried timing has been altered by someone
turning the distributor 4 degrees, any-clockwise.

This distributor has a camshaft sensor, which doubles as a crankshaft sensor
with magnetic markings. A mechanic said you could turn it as much as you'd
like, the computer would still find the right TDP ? If not, could this have
any influence on rod bearings wear ?

Thanks again,

Carl




  #4  
Old July 22nd 05, 02:10 PM
John S.
external usenet poster
 
Posts: n/a
Default



carl wrote:
> Hi,
>
> Can I bring another question to this forum ? I looked at the archives, but
> found nothing similar for this noise pattern or situation. And I wonder what
> a mechanic would say, given lash values are correct for most of the dealers.


Is the valve lash correctly set? Was it set to the correct gap with
the engine at the proper temperature?

>
> My car has had valves tightened a bit too much, now they're at correct valve
> lash. For a while, I hear too much noise coming from the cover. Valve lash
> increases with temperature ( is it always so ? ) and seems lower in
> frequency and much less noticeable when warm


How do you know the valves were tightened too much.

>
> It is loudest on a cold engine, and in the afternoon, with engine still
> warm, is never that loud again. It also becomes very high in frequency when
> cold when the throttle is released, after driving in low gear and low load,
> the clatter increases just after release in volume and frequency, and
> diminishes after about a second ...


A rattling or rapping sound can come from a lot of sources besides
valves. An exhaust leak can make a rattly sound when cold, as can
loose wristpins, main and connecting rod bearings as well as valves
that are not correctly gapped.
It is all but impossible to correctly diagnose the cause of noise from
a written description on this or any other forum. I would suggest that
you have an experienced mechanic disgnose the problem, preferably one
familiar with whatever make of car you have.

>
> Does the noise pattern, like after throttle release, point to something
> worse ( low- high end or main bearing ) ? I thought they would make heavier
> noise. There could have been oil issues in the past.


What is an oil issue. Do you mean the engine was run without oil, or
the oil was never changed?

> Also, timing could have
> been too early 4 degrees for a long time, or late 4 degrees for 1000 miles
> now, giving more than normal bearing load ?


How did you determine the ignition timing had been reset over such a
wide range.

> Now this valve train has a OHC, two rocker shafts and 12 valve rockers with
> 4 exhaust ones. The rockers are cast aluminium, with iron or steel adjuster
> screws. I imagine it is not such a big deal to install new rockers and
> shafts, and even a camshaft, and adjust valve lash again. But from where can
> this noise come when valve lash is correct ? The car has 35 k miles and oil
> was changed just at 33k5 miles. Is there something with aluminium rockers
> and steel adjustment screws, which should not be overtightened ( they
> tighten even further when hot ) ? They could have been.


Don't start adjusting valves and replacing rockers before you know what
the problem is. I would strongly suggest that a mechanic with the
proper tools and training take a look at the car.

  #5  
Old July 22nd 05, 02:43 PM
carl
external usenet poster
 
Posts: n/a
Default


> >given lash values are correct for most of the dealers.

>
> Is the valve lash correctly set? Was it set to the correct gap with
> the engine at the proper temperature?


Yes, measured hot, set cold and verified hot. And reverified cold.
> >

>
> How do you know the valves were tightened too much.
>

Because of the above, they were checked after a mechanic had adjusted them.
They were 2/1000th of an inch too tight, some 3/1000th.

> A rattling or rapping sound can come from a lot of sources besides
> valves. An exhaust leak can make a rattly sound when cold, as can
> loose wristpins, main and connecting rod bearings as well as valves
> that are not correctly gapped.
> It is all but impossible to correctly diagnose the cause of noise from
> a written description on this or any other forum. I would suggest that
> you have an experienced mechanic disgnose the problem, preferably one
> familiar with whatever make of car you have.
>

I'm trying to find someone. Had a bad experience with the last one.

> >
> > Does the noise pattern, like after throttle release, point to something
> > worse ( low- high end or main bearing ) ? I thought they would make

heavier
> > noise. There could have been oil issues in the past.

>
> What is an oil issue. Do you mean the engine was run without oil, or
> the oil was never changed?
>

The oil was overfilled to a level at least half an inch too high. in the end
it, or what was left was removed, but the car consumed the quantity between
the dipstick markings in about 1000 mi. There was no interest from the
dealer to look into it, although it was strange, but I did not see this
dramatic drop again (yet).

> > Also, timing could have
> > been too early 4 degrees for a long time, or late 4 degrees for 1000

miles
> > now, giving more than normal bearing load ?

>
> How did you determine the ignition timing had been reset over such a
> wide range.
>

The distributor has been turned that much. But was it turned along time ago
and has someone reset it to its correct position, or was it turned a while
ago and reset, or is it set to less advance now ? I could not get an answer
from the dealer, because he said turning a distributor does not affect
advance on this ECU engine.

>
> Don't start adjusting valves and replacing rockers before you know what
> the problem is. I would strongly suggest that a mechanic with the
> proper tools and training take a look at the car.


I did have to have the valve lash adjusted because it was much too tight. I
asked some mechanics to look at it, but they are confident that this type of
engine can stand anything, and never has problems.

Thanks again,

Carl


  #6  
Old July 22nd 05, 02:56 PM
N8N
external usenet poster
 
Posts: n/a
Default



carl wrote:
> >
> > > Carl

> >
> > A rapping noise on overrun as you describe sounds like rod bearings to
> > me, GF had the same noise on her Corrado and new rod bearing shells
> > made it go away
> >
> > nate
> >

>
> Thanks, Nate,
>
> If you're talking about low end bearings, it is relatively good news for
> repair. But how did it come ? Bad oil, bad load ? As I drive at low rpm, on
> low throttle, would that be enough for damage to occur in a short period of
> time ? I imagine oil pressure then doesn't get that high , ie. high enough.
>
> This car ran fine for a long time, until there was an oil problem and fuel
> system issue, then after a power test it ran worse. It is possible the
> damage dates from then. But after letting the car sit for two years, at
> first there was no noise. I'm worried timing has been altered by someone
> turning the distributor 4 degrees, any-clockwise.
>
> This distributor has a camshaft sensor, which doubles as a crankshaft sensor
> with magnetic markings. A mechanic said you could turn it as much as you'd
> like, the computer would still find the right TDP ? If not, could this have
> any influence on rod bearings wear ?
>
> Thanks again,
>
> Carl


Actually in the case I'm referring to it was just a bad batch of
bearings from the factory and a common, known problem with the G60
motors. I don't know if incorrect timing could affect bearing wear or
not; I suppose if it were advanced enough that it was always detonating
that that might happen.

nate

  #7  
Old July 22nd 05, 03:21 PM
carl
external usenet poster
 
Posts: n/a
Default

> > Carl
>
> Actually in the case I'm referring to it was just a bad batch of
> bearings from the factory and a common, known problem with the G60
> motors. I don't know if incorrect timing could affect bearing wear or
> not; I suppose if it were advanced enough that it was always detonating
> that that might happen.
>
> nate
>


Possibly it did. Nice to have someone confirm my thoughts.

Thanks.


  #8  
Old July 22nd 05, 05:07 PM
Brian Stell
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Posts: n/a
Default


> It is loudest on a cold engine, and in the afternoon, with engine still
> warm, is never that loud again. It also becomes very high in frequency when
> cold when the throttle is released, after driving in low gear and low load,
> the clatter increases just after release in volume and frequency, and
> diminishes after about a second ...


I can see valve noise being influenced by RPM
(more RPM => more noise) but I'm unfamiliar with
valve noise being influenced by throttle.

My experience with rod bearing noise is it is
loudest when accelerating / hill climing
(more engine power => more noise) and is quiet
when off throttle.

I've been told the main bearings tend to be
noisy all the time.

Now the "diminishes after about a second" makes
me think gear lash. As in something is spinning
and the normal resistance keeps the "front"
side of the teeth engaged. When going off throttle
the spinning item's inertia keeps it spinning so
the gear is bouncing between the "front" and
"rear" side of the teeth. When the engine speed
stops dropping it's back to resistance / "forward"
teeth. If the slowing is heavy then the inertia
can keep the "rear" side of the teeth engaged.

Driving down a grade, off throttle, at a constant
speed would create a similar force on the bearings
as off throttle but no inertia / spinning changes.

Do you get the noise under this condition?

Or only when the engine is dropping RPM?
  #9  
Old July 22nd 05, 06:56 PM
Peter
external usenet poster
 
Posts: n/a
Default

Hi,

That's a thought. This gearbox has given me trouble in the past.
When starting up the car again, I will try what it's doing under the
conditions you describe.
A way to find out is IMHO to disengage the clutch and see if the sound has
gone. If it is engine bearings - whichever - the clatter should persist, at
least some.

Thanks for the idea.

Carl

"Brian Stell" > schreef in bericht
m...
>
> > It is loudest on a cold engine, and in the afternoon, with engine still
> > warm, is never that loud again. It also becomes very high in frequency

when
> > cold when the throttle is released, after driving in low gear and low

load,
> > the clatter increases just after release in volume and frequency, and
> > diminishes after about a second ...

>
> I can see valve noise being influenced by RPM
> (more RPM => more noise) but I'm unfamiliar with
> valve noise being influenced by throttle.
>
> My experience with rod bearing noise is it is
> loudest when accelerating / hill climing
> (more engine power => more noise) and is quiet
> when off throttle.
>
> I've been told the main bearings tend to be
> noisy all the time.
>
> Now the "diminishes after about a second" makes
> me think gear lash. As in something is spinning
> and the normal resistance keeps the "front"
> side of the teeth engaged. When going off throttle
> the spinning item's inertia keeps it spinning so
> the gear is bouncing between the "front" and
> "rear" side of the teeth. When the engine speed
> stops dropping it's back to resistance / "forward"
> teeth. If the slowing is heavy then the inertia
> can keep the "rear" side of the teeth engaged.
>
> Driving down a grade, off throttle, at a constant
> speed would create a similar force on the bearings
> as off throttle but no inertia / spinning changes.
>
> Do you get the noise under this condition?
>
> Or only when the engine is dropping RPM?



  #10  
Old July 23rd 05, 09:41 PM
Brian Stell
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Posts: n/a
Default

> That's a thought. This gearbox has given me trouble in the past.
> When starting up the car again, I will try what it's doing under the
> conditions you describe.


Does your car have a gear or chain driven cam?

A chain could also produce a "bouncing" between
"front" of the chain pulling against normal
resistance and "rear" of the chain pulling
against the inertia to slow the rotation during
dropping RPM.

Also, if the chain were stretched or the
tensioner weak on dropping RPM the "front" side
of the chain could loose and be flapping or
banging around.

Again the condition would be dropping RPM (as
opposed to constant RPM with engine braking).
 




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