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Old 02-08-2007, 10:26   #16
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Not exactly - your mechanic was talking about an Anti-Drainback Valve; whereas Wheels was differentiating between Full-Flow & Bypass type Filtres.

Anti-Drainback Valve:
Some oil filtre mountings (such as those mounted orifice down, or cartridge above horizontal) may allow oil to drain out of the filtre through the oil pump when the engine is stopped. When the engine is next started, oil must refill the filtre before full oil pressure reaches the engine.
The anti-drainback valve prevents oil from draining out of the filtre. This A-D valve is a silicone flap that covers the inside of the inlet holes of the filtre. When the oil pump starts pumping oil, the pressure will unseat the flap. The purpose of this valve is to keep the oil filter & engine galleries filled at all times, so when the engine is started there will be an almost instantaneous supply of oil to the engine.
Some engines have anti-drainback valve mounted on the oil filtre mounting plate.
To test the filtre’ anti-drain back valve, simply blow into the filter to see if the A-D valve seals the filtre.

Full Flow Filtre: All of the engine oil is filtered as it passes through the filtre into the engine. The entire oil supply is filtred each time it passes through the engine.

Bypass Filtre: The filter operates by filtering oil on a "partial-flow" basis, wherein a small percentage of the engine oil passes through a “finer” filtre to the engine , and the balance is returned to the sump. Often used in conjunction with a full-flow filtre.
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Old 02-08-2007, 12:46   #17
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Gord is correct, but I will take that one step further.
There are two terms of "bypass" used. One as Gord stated. The other is a pressure protection mechanism. Depending on the engine design, the "relief valve" can be found in either the engine, or it maybe found in the filter it'self. The Oil pumps are a "positive displacement device". Meaning that every rotation, the pump delivers a set measure of oil. The fast the rotation, the more oil pumped. This means that if the flow is restricted in anyway somewhere down stream of the pump, the pressure will keep building till something blows or breaks. The filter is the usuall place of restriction, due to blockage. If the pressure continues to climb due to the filter getting blocked, it will either rupture the case, or worse, it will fail internally allowing sludge and paper to flow through the engine and possible damaging it. So a relief valve is fitted. Once the filter restricts the flow to much, it overcomes the valve and and the oil bypass the filter and flows through the engine. It is better to have unfiltered oil than no oil at all. Now, this relief or bypass valve can be found in some filters, or it can be found in the engine it'self. If there is no engine fitted valve, and a filter with full flow through is fitted, low fluctuating oil pressure may result.
There is one other valve as well. this is the pressure valve that sets the actual working pressure of the pump. As I said above, the pump is positive displacment. So it pumps a set amount of oil every rotation. At a slow idle, this displaced flow my not be a lot to keep up with all the galleries in teh engien, so you get a low pressure reading. When you rev the engien, more oil is pumped. The galleries have to be able to get rid of the flow or seals will be blown out and damage to the pump may result. So the pressure relief valve allows the over flow to bypass back to the sump. It is this valve that sets the upper pressure limit. In some more simple designs, this valve can do both jobs. But I imagine the later model perkins you have would be a litte more sophisitcated than that.
Sorry, I can not help with what scenario you have. I have not been inside one of these engines nor seen a manual.


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Old 06-10-2007, 18:59   #18
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Hi, I have the same engine, and my oil pressure is around 65-70 lbs at start up. This engine need 6 liter of engine oil, and the original Perkins filter has a valve, and I was warned by Perkins that using the wrong(valve less) filter may ruin this engine. So I stick with Perkins parts, or the equivalent Volvo MD22 series engine(same engine in Volvo green paint). Are you assured that this beeping at startup is not related to an alternator trouble, or simply to an delay in the start up of the charging process? (Balmar and other smart regulators do that!). This engine is quite common in England and is used in Austin Montego and some Land Rover from 1993 to 2000 I believe. On Ebay UK you would easily find parts, and manuals including a well made workshop manual. Good luck. Elie.

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