Originally posted by BadaBing
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What kind of motor oil do you use?
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Originally posted by jbsoukup View PostI'm thinking the only way to be sure of correct oil pressure is to install a new gauge and matching sender.
Catalina Direct has a nice oil pressure gauge which matches the fuel gauge I installed last season, but the sender is metric thread.
Will any sender work?(Maybe)
You answered your own question. The sender and gauge must be matched (ie from the same manufacturer)for accurate readings.
That having been said some sending units and gauges are interchangeable because they have the same parameters. If you know the manufacturer of the sending unit and gauge you might be able to cross reference.
TRUE GRIT
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Not exactly.
If the sender and the gauge are both the same range and both the common 240-33 ohms, then they should work fine together. I went through 3 gauges on my old engine with the original sender and they all worked fine. Nothing wrong with getting all new though if you are not sure what you have. Remember 33 ohms is full scale, so if you have a 100 PSI sender and an 80 PSI gauge your readings will be off.
Originally posted by JOHN COOKSON View PostJohn
You answered your own question. The sender and gauge must be matched (ie from the same manufacturer)for accurate readings.
That having been said some sending units and gauges are interchangeable because they have the same parameters. If you know the manufacturer of the sending unit and gauge you might be able to cross reference.
TRUE GRITJoe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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I have virgin early model A4 and have always had "mechanical" oil pressure gauge with connected copper tubing w/compression fittings. Gauge is on cockpit wall exposed to weather during the season. Am on my 3rd gauge in 42 years with same 3+ ft tubing [tee'd off to OPS]. Used Stewart- Warner gauges, sometimes a little hard to find "mechanical" type. FYI, engine is on slight aft tilt and have always used 4qt name brand 30W or 10-30W w/ 1 bottle of STP. Oil pressure is about 35psi at start up, 30+ psi at cruise and around 20psi at idle. Once in a great while I get a very small leak with this set up and a fitting needs a little tightening. I believe you get a accurate reading with the mechanical gauge vs electrical and matching the right sending unit.
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Apologies for resurrecting an old thread.
Originally posted by hanleyclifford View PostWe have had other members report that oil pressure increases with time and temp increase after start up. I have tried to make sense of this because it is counter intuitive to my understanding and experience that viscosity decreases with temp and hence pressure should also decrease. One factor that keeps coming to mind is the nature of the oil pump intake. The "bottleneck" is the 1/8" NPT 90 degree street ell coming right off the oil pump. Since that fitting is a casting, it's cross sectional area is subject to the irregularities of the casting process. Even a small burr in the oil stream could have an influence on flow especially at cold temperatures. Because of the foregoing "theory" I have modified my oil pump to use a 1/4" NPT fitting. The difference in oil flow was impressive and could account for the big pressure differential I live with between start up and cruise. I live with it and enjoy the (relatively) massive flow and pressure increases as well.
I sent off the oil pump to MMI (courtesy of the Amish ones ) for testing and the result are it landed on the 'correct' side of the bell curve. But looking at Hanley comments about reducing the inlet restrictions and the 1/4" NPT street Ell... has anyone else done this?
BTW, when I build my first custom car, I did a "high volume, standard pressure" oil pump on the blueprinted engine. It has been a great motor, no leaks and still lots of pressure (75 PSI cold, drops to 40 PSI hot at idle and 50-60 PSI when running through the gears. Is a similar performance (but not exact PSI) possible on an A4?
... this is coming from a person after two A4s with low oil pressure after 2-3 hours of cruise.Thanks,
Ron
Portland, OR
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Originally posted by ronstory View PostApologies for resurrecting an old thread.
As a person about to assemble a rebuilt A4 engine after the last one lasting 45 years... I will hopefully be dead before anyone needs to rebuild it again.
I sent off the oil pump to MMI (courtesy of the Amish ones ) for testing and the result are it landed on the 'correct' side of the bell curve. But looking at Hanley comments about reducing the inlet restrictions and the 1/4" NPT street Ell... has anyone else done this?
BTW, when I build my first custom car, I did a "high volume, standard pressure" oil pump on the blueprinted engine. It has been a great motor, no leaks and still lots of pressure (75 PSI cold, drops to 40 PSI hot at idle and 50-60 PSI when running through the gears. Is a similar performance (but not exact PSI) possible on an A4?
... this is coming from a person after two A4s with low oil pressure after 2-3 hours of cruise.
You may want to look at an oil temp gauge and an oil cooler. The temp gauge is on my list and maybe a cooler depending on what I find.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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Joe--
I wish had your oil pressure, then I would only be dealing with a bit of blow-by. I manage that by having vent cap with a hose connection that I put in the bilge blower inlet. Looks similar to:
I have 80PSI cold when warm up the engine and drop to 40-45 in 5 mins. When running for more than hour at cruise I'm at 20 PSI. At idle when I'm maneuvering into the slip, I'm at so low on oil pressure that I'm worried about the OPSS killing the engine.
Now back to the question: Has anyone else done the larger 1/4" NPT Street ell into the oil pump?Thanks,
Ron
Portland, OR
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Originally posted by ronstory View PostJoe--
I wish had your oil pressure, then I would only be dealing with a bit of blow-by. I manage that by having vent cap with a hose connection that I put in the bilge blower inlet. Looks similar to:
I have 80PSI cold when warm up the engine and drop to 40-45 in 5 mins. When running for more than hour at cruise I'm at 20 PSI. At idle when I'm maneuvering into the slip, I'm at so low on oil pressure that I'm worried about the OPSS killing the engine.
Now back to the question: Has anyone else done the larger 1/4" NPT Street ell into the oil pump?Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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Could be bearings clearance or it could be the oil pump. Ken's thoughts were that pumps do go wear out.
I already installed an indigo remote oil filter plus their oil cooler in an attempt to stave off the rebuild. I'm also using the Indigo thermostat, so I have nice toasty and consistent 180F water temp with their electric FWC.
So I'm heading down the rebuild path on the spare motor... and trying learn as much as possible about 'best practices' from the forum. I have all the MMI tech tips archived, but looking for do's & don't from our very knowledgeable members.
... and I will make positive to install all three internal oil plugs.Thanks,
Ron
Portland, OR
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Been using 15W40 Diesel oil for 13 years now. Have not had one mechanical issue with the engine...3 black iron hot exhausts later, a fuel pump, bunch of filters, generally maintenance and a raw water pump. I've changed the oil at 25 hrs and to be honest it's hard to see where it is on the dipstick it's so clean...been clear for years now. Been a good engine. Still a great running engine.
EDIT: The engine developed a head gasket leak (air only) under the T-stat area where the head was weakened from years of salt water running through it. When the gasket was changed I couldn't get to torque two studs and found a small crack near the exhaust ports between two stud holes...again, worn thin from years of salt water. I changed the engine out and put in my spare. The internals are all still good on that and I've been told the right guy with a brazing rod can fix that issue. The issue it experienced had nothing to do with the oil I use. 15W40 is in the new one I put in as well.Last edited by Mo; 04-22-2021, 04:57 PM.Mo
"Odyssey"
1976 C&C 30 MKI
The pessimist complains about the wind.
The optimist expects it to change.
The realist adjusts the sails.
...Sir William Arthur Ward.
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