The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone above 3800 when the engine is hot. I use multigrade 10w40 oil. What could be the problem?

thanks in advance Jos


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First verify the electric gauge reading with a non-electric gauge. If
it is truly low, try changing the oil.

josZ wrote:
The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone above 3800 when the engine is hot. I use multigrade 10w40 oil. What could be the problem?

thanks in advance Jos


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After you verify that you do have pressure at the higher RPMs your next
thought might go to the pressure sender. They sometimes do strange things.
Easiest way to test them is to replace it with a known good sender.

"josZ" wrote in message
t...
The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone
above 3800 when the engine is hot. I use multigrade 10w40 oil. What could be
the problem?

thanks in advance Jos


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"josZ" wrote in message
t...
The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone
above 3800 when the engine is hot. I use multigrade 10w40 oil. What could
be the problem?


If your engine has bad mains or rod bearings then oil will be slung out of
the bearings at higher RPMs and your oil pressure will drop. You should
hear the rod bearing as a low pitched ticking at idle with hot oil. High
pitched ticking is generally the valve train. If you had a car I'd tell you
to put the car in gear, put one foot on the brake and press down on the
throttle slightly. If the rod bearings are bad then you would feel/hear the
slap of the rods.

You should be using a 20w40 oil in any case.

At this point you can probably pull the engine and replace the ROD bearings
(they cost about $90) and mains very easily. Just remove the oil pan. I
did my dodge van (318 V8) in two hours from lift to drop. I didn't have to
pull the engine but did have to remove parts of my tailpipe. It took more
time to remove the tailpipe than to replace the rod bearings.

Before bearing replacement I had 40 pounds oil pressure cold, 15 pounds hot
at idle. When hot I had ticking (slap) of bad rod bearings at idle. Oil
pressure hot was 40 pounds at speed.

After replacement of bearings and oil pump, 40 pounds cold, 40 pounds hot at
idle and 55 pounds hot at speed.

I'd be checking the crankshaft and rod bearings. Sounds like when
things get hot, clearances get large and simply let all the oil flow
freely out of the bearings, as the crank is spinning on a layer of oil,
within the bearings. It won't be long before you spin a bearing and
ruin the crankshaft.
Jim

josZ wrote:

The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone above 3800 when the engine is hot. I use multigrade 10w40 oil. What could be the problem?

thanks in advance Jos


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Far more likely, IMO, is an instrumentation issue. If the clearances in
your engine were so worn as to cause an oil pressure loss when hot with
10W40 oil you'd not have pressure when starting. As engine speed increases
the oil pump output increases. A relief valve keeps the pressure from going
too high. No offense Jim but you clearly know very little about engines.
Better no reply than a totally unfounded reply.

Butch
"Jim Goodall" wrote in message
...
I'd be checking the crankshaft and rod bearings. Sounds like when things
get hot, clearances get large and simply let all the oil flow freely out
of the bearings, as the crank is spinning on a layer of oil, within the
bearings. It won't be long before you spin a bearing and ruin the
crankshaft.
Jim

josZ wrote:

The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone
above 3800 when the engine is hot. I use multigrade 10w40 oil. What could
be the problem?

thanks in advance Jos


--------------= Posted using GrabIt =----------------
------= Binary Usenet downloading made easy =---------
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"Butch Davis" wrote in message
ink.net...
Far more likely, IMO, is an instrumentation issue. If the clearances in
your engine were so worn as to cause an oil pressure loss when hot with
10W40 oil you'd not have pressure when starting. As engine speed
increases the oil pump output increases. A relief valve keeps the
pressure from going too high. No offense Jim but you clearly know very
little about engines. Better no reply than a totally unfounded reply.

Butch, at first thought you would think the oil pressure would increse as
RPM increases but rod bearings when very bad SLING oil. Like if you (after
priming) sling a hose around your head it will pump water out of the hose.
This causes a loss of oil pressure! Very bad engines can have 15 pounds of
oil pressure at idle and that will drop when you accelerate the throttle.
I've read about it and finally saw it recently. Usually it's also very
noisy.

I'd certanly check oil pressure with a mechanical gage if the engine is not
noisy. If oil pressure is low I'd pull the pan and check clearances on the
bearings and if good suspect a slipping shaft to the oil pump.

Butch
"Jim Goodall" wrote in message
...
I'd be checking the crankshaft and rod bearings. Sounds like when things
get hot, clearances get large and simply let all the oil flow freely out
of the bearings, as the crank is spinning on a layer of oil, within the
bearings. It won't be long before you spin a bearing and ruin the
crankshaft.
Jim

josZ wrote:

The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone
above 3800 when the engine is hot. I use multigrade 10w40 oil. What could
be the problem?

thanks in advance Jos


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Jeff,

No argument. Consider, however, that the engine is lubricated by 10W40
weight oil. When cold the oil is 10W (mas o menos) and loose rod bearings
would not hold pressure well if at all. When the engine is at operating
temperature the lubricating oil is 40W or so. It's difficult for me to
visualize an engine with 10W at idle cold having pressure much higher than
the same engine with 40W hot at 3800 RPM.

Seems to me the rods would be banging like the devil at virtually any RPM.
My experience with engines is that it is very rare for all rod bearings to
fail together. It is almost always one bad bearing. I guess an exception
would be when the engine is operated with a very low oil level but that
would also destroy crankshaft and cam bearings, no?

Thanks.

Butch
"Jeff Rigby" wrote in message
...

"Butch Davis" wrote in message
ink.net...
Far more likely, IMO, is an instrumentation issue. If the clearances in
your engine were so worn as to cause an oil pressure loss when hot with
10W40 oil you'd not have pressure when starting. As engine speed
increases the oil pump output increases. A relief valve keeps the
pressure from going too high. No offense Jim but you clearly know very
little about engines. Better no reply than a totally unfounded reply.

Butch, at first thought you would think the oil pressure would increse as
RPM increases but rod bearings when very bad SLING oil. Like if you
(after priming) sling a hose around your head it will pump water out of
the hose. This causes a loss of oil pressure! Very bad engines can have
15 pounds of oil pressure at idle and that will drop when you accelerate
the throttle. I've read about it and finally saw it recently. Usually
it's also very noisy.

I'd certanly check oil pressure with a mechanical gage if the engine is
not noisy. If oil pressure is low I'd pull the pan and check clearances
on the bearings and if good suspect a slipping shaft to the oil pump.

Butch
"Jim Goodall" wrote in message
...
I'd be checking the crankshaft and rod bearings. Sounds like when
things get hot, clearances get large and simply let all the oil flow
freely out of the bearings, as the crank is spinning on a layer of oil,
within the bearings. It won't be long before you spin a bearing and
ruin the crankshaft.
Jim

josZ wrote:

The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone
above 3800 when the engine is hot. I use multigrade 10w40 oil. What
could be the problem?

thanks in advance Jos


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Butch Davis wrote:

Jeff,

No argument. Consider, however, that the engine is lubricated by 10W40
weight oil. When cold the oil is 10W (mas o menos) and loose rod bearings
would not hold pressure well if at all. When the engine is at operating
temperature the lubricating oil is 40W or so. It's difficult for me to
visualize an engine with 10W at idle cold having pressure much higher than
the same engine with 40W hot at 3800 RPM.


10W-40 weight oil is not more viscous at temp than when cold.
It's less. What multi-weight oils do is thin less with temp.
So, 10W-40 is (theoretically) as thin as 10W is when 10W is cold
and, when hot, it's as thick as 40W is when 40W is hot. That's
still thinner than 10W cold, but not as thin as 10W hot.

-Raf

--
Misifus-
Rafael Seibert

http://www.ralphandsue.com

"Butch Davis" wrote in message
ink.net...
Jeff,

No argument. Consider, however, that the engine is lubricated by 10W40
weight oil. When cold the oil is 10W (mas o menos) and loose rod bearings
would not hold pressure well if at all. When the engine is at operating
temperature the lubricating oil is 40W or so. It's difficult for me to
visualize an engine with 10W at idle cold having pressure much higher than
the same engine with 40W hot at 3800 RPM.

The base stock for a 10w40 is 10 weight oil. To that is added long chain
polymers that unwind when hot causing the weight of the oil to increase. So
when cold the oil acts like a 10 weight oil that is cold. When hot it acts
like a 40 weight oil that is hot. The point is that 10 weight oil cold acts
alot like 40 weight oil hot. The reason 10w40 is NOT recommended for most
engines is that there are too many long chain polymers added to the oil and
they breakdown at high temps and cause accelerated wear in engines. The
recommeded oil is now 20W40. This doesn't apply to synthetic oils like
mobil 1 that has no polymers added to their 15W50, or 5W30.


Seems to me the rods would be banging like the devil at virtually any RPM.
My experience with engines is that it is very rare for all rod bearings to
fail together. It is almost always one bad bearing. I guess an exception
would be when the engine is operated with a very low oil level but that
would also destroy crankshaft and cam bearings, no?

Seems so but the engine I saw act up had 15 pounds at idle and no knock and
when the engine RPM increased the pressure would drop and at about 5 pounds
would knock like the devil (oil starved). You can have all sorts of middle
ground between this case and a good engine. In the case we are discussing,
there is obviously enough oil for there to still be a cushion of oil in the
bearing thus little or no noise. In most engines the sling effect IS offset
by the increased volume of oil pumped by the oil pump at higher RPMs.


Thanks.

Butch
"Jeff Rigby" wrote in message
...

"Butch Davis" wrote in message
ink.net...
Far more likely, IMO, is an instrumentation issue. If the clearances in
your engine were so worn as to cause an oil pressure loss when hot with
10W40 oil you'd not have pressure when starting. As engine speed
increases the oil pump output increases. A relief valve keeps the
pressure from going too high. No offense Jim but you clearly know very
little about engines. Better no reply than a totally unfounded reply.

Butch, at first thought you would think the oil pressure would increse as
RPM increases but rod bearings when very bad SLING oil. Like if you
(after priming) sling a hose around your head it will pump water out of
the hose. This causes a loss of oil pressure! Very bad engines can have
15 pounds of oil pressure at idle and that will drop when you accelerate
the throttle. I've read about it and finally saw it recently. Usually
it's also very noisy.

I'd certanly check oil pressure with a mechanical gage if the engine is
not noisy. If oil pressure is low I'd pull the pan and check clearances
on the bearings and if good suspect a slipping shaft to the oil pump.

Butch
"Jim Goodall" wrote in message
...
I'd be checking the crankshaft and rod bearings. Sounds like when
things get hot, clearances get large and simply let all the oil flow
freely out of the bearings, as the crank is spinning on a layer of oil,
within the bearings. It won't be long before you spin a bearing and
ruin the crankshaft.
Jim

josZ wrote:

The oil pressure in my engine, a volvo penta 3.0gs from 1996, is gone
above 3800 when the engine is hot. I use multigrade 10w40 oil. What
could be the problem?

thanks in advance Jos


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