oil pressure drop 77 diesel

deene · May 20, 2018

I bought a 77 diesel last yr and was told it ran and worked well with no problems. it does run ok but after after a cpl hours brushogging would lose oil pressure. this was after I put on 2 new filters..new oil and a new oil pressure gauge. so I brought it back home and let it cool down and the next time same thing. I took out the oil bypass spring and plunger and stretched the spring and it worked for a little longer and did the same losing of pressure after a cpl hours run time. i figured it might be a weak spring that after heating up was losing tension,so today I went and got a stiffer spring and cut it to length and installed it instead of shimming the old one. I started the tractor and had good oil pressure for about a minute of run time and then it went to nothing on the gauge again. I have also checked this gauge against another and they read about the same...what am I missing here...any insight would be helpful and a thanks in advance

Olliejunkie · May 20, 2018

Sounds funky. I would get the right spring or put the old one back in to see what it does.

chucksoliver77 · May 20, 2018

Maybe the transfer pump is leaking fuel into the oil!!!

J. Schwiebert · May 20, 2018

Send me an email I think you are looking in the wrong place. How many pounds of pressure when it is cold? Remember that is a bypass system. Also pressure is caused by resistance to flow!

deene · May 20, 2018

transfer pump has been bypassed with an electric by previous owner but good thinking on your part...thanks for the insight

oliver90owner · May 21, 2018

I think John is going to say the wrong filter type, the restrictor for the filter volume rate or something similar.

Please note that any spring operated PRV will have a seat which seals or allows oil to pass. That seat may be failing, not just the spring.

If it were fuel dilution you would notice the increase in crankcase oil level, I would have thought...

ss55 · May 21, 2018

What do you call low oil pressure? Some of those engines never used high oil pressure (maybe only around 15 PSI at full throttle?). Check your operator's manual or service manual for what pressure it is supposed to have, and compare that to what your new gauge shows. Also check what the range is on the original gauge. An acceptable 5 PSI at idle could look way too low on a 60 PSI gauge, but look just fine on a 20 PSI (factory original?) gauge. Again, start by checking what oil pressure the factory recommends.

Also make sure the line to the new gauge is not plugged or restricted.

oil pressure drop 77 diesel

deene

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Olliejunkie

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chucksoliver77

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J. Schwiebert

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deene

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oliver90owner

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ss55

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