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Old 16-09-2017, 23:04   #1
DGH
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Volvo Penta TAMD31 Oil Pressure

I have a Volvo Penta TAMD31M with close to 6000 hours on it. Had it from new in 2001. As always, it starts and runs perfectly (touchwood!) and does not use any oil. What does concern me though is that indicated oil pressure running at 1800 to 2000 rpm is about 2.8 - 2.9 bar. At hot idle its about 1.9 bar. How worried about this should I be? Any expert opinions gratefully received.
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Old 17-09-2017, 09:07   #2
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Re: Volvo Penta TAMD31 Oil Pressure

I have worked on some pretty expensive engines and a 27psi idle and 40 psi at cruise is about what I would expect from a 6,000 hr engine. It really does not take that much pressure to keep things lubed. I think about 1/2 of what you have would be about the end.
I would be checking the oil filter for metal and maybe start testing the oil. Towards the end of life you will start seeing a more rapid increase in metals.
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Old 17-09-2017, 13:59   #3
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Re: Volvo Penta TAMD31 Oil Pressure

Since you have had it since new, what did the oil pressure used to be?
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Old 17-09-2017, 15:28   #4
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Re: Volvo Penta TAMD31 Oil Pressure

It's my understanding that the high pressure you see on the gage is the relief valve pressure inside the pump. A good pump should be able to maintain relief valve pressure while everything else wears out, to a point. Then again the pump can wear out and so can the stupid relief valve. Sometimes it's not a worn out engine but a worn out oil pump.
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Old 17-09-2017, 15:33   #5
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Volvo Penta TAMD31 Oil Pressure

Assuming it's running lower than it used to, the very first step if your concerned is to plumb in a mechanical gauge to verify your gauge.
I've seen thousands of dollars spent when all it was was a bad gauge.

The pressure relief valve Guy speaks of is also often called a cold oil relief valve, it of course only allows oil pressure to go only so high, one way usually to determine what it's setting is is to run a cold engine at relatively high RPM, oil pressure should go up with RPM but stop at some point, that should be when the relief valve opens. Ideally at cruise RPM with a motor in very good condition, you should see oil pressure close to the valve relief setting.
However as you have already noted, best way to determine wear is to observe low idle pressure with hot oil, that is when a worn engine will show itself.
Very often knowledgeable people will run a thicker oil to offset this wear and keep pressure higher, you may want to consider a straight 30 or even a 40 weight oil as opposed to a multi Vis 15W-40, unless of course your cruising in very cold water
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Old 17-09-2017, 17:32   #6
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Re: Volvo Penta TAMD31 Oil Pressure

The Volvo manual doesn't give an idle oil pressure, the pressure at 'operating speed' is listed at 61-73 psi hot (4.2-5.03 bar).

My manual is a bit older and doesn't list the 31M, but I believe the pressure is the same.

Given that you are only running the engine at about 55-60 percent (if your full load speed is 3250), I'd be comfortable with the numbers you post. As a check, run the engine up to speed and see what the oil pressures is at, say 3000 rpm. If you get up to 55-60 psi, I wouldn't worry at all.

My TAMD41B runs at about 30-35 psi idle hot and 55-60 psi hot at speed.

There are actually 3 valves in the lubricating system; a main relief valve right after the pump, apparently to limit the pressure to protect the oil cooler from overpressure, another relief valve to limit the pressure to 73 psi, and a piston cooling valve that opens at 35.6 psi. This valve remains closed at low speeds and low engine loads, but opens at higher speeds and loads to spray cooling oil into the underside of the piston domes.

Any of them could give problems, sticking or weak springs and such, but if you've kept up with oil changes and not abused the engine I wouldn't worry about them.

The most common early warning sign for oil system issues (unless you do scheduled oil analysis), is rumbling or changing noises from the bottom end (crank and rod bearings)...

At 1800-2000 rpm, you're just getting into boost on the turbo. I'd guess you've got another 6000 hrs to go if you continue to use the engine like that.
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Old 17-09-2017, 20:51   #7
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Re: Volvo Penta TAMD31 Oil Pressure

Thank you very much Guy, a64pilot and jimbunyard for all your very useful suggestions and comments. I will do everything suggested for the tests, including another gauge. Also I like the idea of the single grade oil seeing that I'm only operating in warm water areas.
Unfortunately I never recorded the original oil pressures but I seem to recall that at my normal operating rpm of 1800-2000 it was around 3.8 bar. Can't say that I recall seeing 4. Can't recall the idle pressures at all. I have always done oil and filter changes about every 200 hours or twice a year but have only really started to take notice of the oil pressure in the last year or so. Very rarely run it above 2000rpm.
Can you suggest a take-off point for another pressure gauge?
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Old 18-09-2017, 14:11   #8
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Re: Volvo Penta TAMD31 Oil Pressure

I have just had a similar problem with my 1600hr Yanmar 4JHE. It was running 10W-40 oil and pressure dropped off completely when hot. Had it checked with a mechanical guage and all was well. Changed to 30 grade all - problem fixed.
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Old 18-09-2017, 15:27   #9
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Re: Volvo Penta TAMD31 Oil Pressure

I would temporarily install a mechanical gauge, just remove the existing one and plumb it into there. It's just to run a short while to verify the electrical one is accurate is all, then you remove it.
Unplug the buzzer too.
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Old 18-09-2017, 18:46   #10
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Re: Volvo Penta TAMD31 Oil Pressure

[QUOTE=a64pilot;2481597]I would temporarily install a mechanical gauge, just remove the existing one and plumb it into there.

Permanently is a different deal. You can't use automotive plumbing, 1/8"plastic or copper tube etc., it would defeat the purpose. If you were to install a mechanical gauge, it needs to be remote from the engine because of the vibration and the stress on the meter movement. That means high quality hoses and fittings, probably 3/16 or 1/4"hose. Even then, you have to have an orifice in the engine fittting. This is very important. You don't want a 1/4" hose spraying oil all over if something breaks. For boat guys, a little fishing weight in the end of the fitting with as small as possible hole in the middle keeps things under control if the Chinese meter broke off and it does not change the reading at all.
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Old 18-09-2017, 22:17   #11
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Re: Volvo Penta TAMD31 Oil Pressure

Thanks again guys. I will try the cold high revs test later this week and next Mon - Tues get into the more involved stuff. Will advise outcomes.
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Old 18-09-2017, 23:33   #12
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Re: Volvo Penta TAMD31 Oil Pressure

I have a TMD31 which suddenly suffered low oil pressure. Down from about 60 psi plus, which is the workshop manual norm, to 25/30 psi at 2000rpm and much lower on tickover - really worrying.

I found the problem was a hairline groove in one of the oil pressure relief valve seats. It was almost imperceptible to the eye (hard to believe this was the cause of low pressure). When we installed new seats/ pistons and springs the change was instantaneous. Back to normal. You can do no harm replacing these anyway.

I cannot say this is your problem but it was certainly mine.

Best wishes.
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Old 19-09-2017, 04:59   #13
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Re: Volvo Penta TAMD31 Oil Pressure

Sirs,
, l run my TAMD 31LA (1997).
I hate pushing over 2000rpm

My oil gauge reads the maximum as soon as I turn the key.

What should l look at, first ?
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Old 19-09-2017, 06:15   #14
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Re: Volvo Penta TAMD31 Oil Pressure

Quote:
Originally Posted by TheThunderbird View Post
Sirs,
, l run my TAMD 31LA (1997).
I hate pushing over 2000rpm

My oil gauge reads the maximum as soon as I turn the key.

What should l look at, first ?
I take it you mean before the engine starts?

If so, first check the power supply and ground to the gauge, then the sensor, wiring harness and connectors. It's an electrical problem...
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Old 19-09-2017, 16:19   #15
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Re: Volvo Penta TAMD31 Oil Pressure

Quote:
Originally Posted by jimbunyard View Post
I take it you mean before the engine starts?

If so, first check the power supply and ground to the gauge, then the sensor, wiring harness and connectors. It's an electrical problem...

No, it's the way the meter movement, (d'arsonval) works. There is nothing to move the meter to 0 until it gets power again, by then the engine is running.
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