Concerned over oil pressure

[Valence]

I'm a bit concerned with the high oil pressure readings in my 1972 M35A2. The engine is a Continental LDT-465.

After an oil change, a split upper canister gasket (over tightened operator error), and a bunch of oil on the engine/drive way I decided that it would be worth my money to purchase a spin-on oil filter conversion kit, if anything, to greatly reduce my chances of screwing up in such a fashion again.

I feel a bit foolish for not really making note of what my oil pressure was previously (I know it wasn't low or high, but I cannot remember a specific number). With the conversion kit installed, I run about 60 psi at 900 rpm (idle), and 80-90 psi on the highway (2100-2400 rpm). My gauge will read from 0 to 120 psi.

The filters are Wix 51458, rated at 11-13 gallons per minute, 21 micron.

I'm a bit confused by the TMs though.

Page 1-33 of TM9-2330-361-20 lists the oil pressure of: Idle @ 200F 10psi min; Full Load @2600 40psi min, 75psi max

Page 1-11 of TM9-2320-209-10-2 agrees pretty closely to the previous TM, stating:
"Normal oil pressure with engine running at idle speed is about 10 psi (69 kPa). With engine running at road speeds, engine oil pressure should read about 45 to 60 psi (309.275 to 413.700 kPa)."
"Some engines have normal oil pressure readings between 40 and 75 psi (275.800 and 517.125 kPa) at road speeds..."

Page 3-39 of TM9-2320-209-10-1 however shows that just after warming up the engine at 800 rpm, the oil pressure gauge should show between 30 to 40 psi (if I were to guess, this was probably about what my truck ran at before while idling. However, as I said, I foolishly did not take note of it before ).


Are these TM differences purely the difference of the type of motor? And do you think that the spin-on oil filter conversion kit I got may damage my engine?

I have driven the truck about 20 miles, and let her idle for 25 minutes with no abnormal sounds or temperature readings.

 

[steelandcanvas]

Although I don't understand your "high" oil pressure concern, I sincerely doubt swapping over to a spin-on oil filter conversion kit would damage your motor. Too bad you don't have a baseline to go by.

 

[tie6044]

See if you can find any numbers on your sending unit on the passenger side of the block, I've seen trucks that had mis-matched sending units and gauges. There are 60 psi units and 120 psi units, if the gauge does not match it will give a false reading. For example, if you have a 60 psi sending unit and a 120 psi gauge and it puts out 30 psi of pressure it will read 60 on the gauge because 60 is right in the middle where the 30 is on the matching gauge.

Did I explain that ok or just confuse things???

The spin on kit will not hurt your motor in any way, it will just protect it at startup.

 

[Valence]

Although I don't understand your "high" oil pressure concern, I sincerely doubt swapping over to a spin-on oil filter conversion kit would damage your motor.

Ah, my apologies, I wasn't clear enough. I'm concerned that I'm seeing 60-90 psi readings, when the 2 1/2 ton Multifuel TMs state that I should be running at (approx.) 30/40-75 psi. So, to me, the high pressure seems like there is a great restriction in the oil flow - and if there is the damage would come from not getting enough oil to the engine as it needs/requires.

 

[M35A2-AZ]

I have a 0-60psi gauge in my M35A2 and at 2100 my gauge is past 60psi.
At idle it is around 45psi.

 

[Valence]

See if you can find any numbers on your sending unit on the passenger side of the block, I've seen trucks that had mis-matched sending units and gauges. There are 60 psi units and 120 psi units, if the gauge does not match it will give a false reading. For example, if you have a 60 psi sending unit and a 120 psi gauge and it puts out 30 psi of pressure it will read 60 on the gauge because 60 is right in the middle where the 30 is on the matching gauge.

Did I explain that ok or just confuse things???

The spin on kit will not hurt your motor in any way, it will just protect it at startup.

Oh no, tie6044, you made perfect sense. TM9-2320-209-10-2 talks about exactly that, (mis-matched sending units an gauges). I hadn't considered that, I had just made yet another mistake, thinking it should be right straight from the UT National Guard . But the only way to really know is to check. I shall look when I get home.

Thank you.

 

[Valence]

I have a 0-60psi gauge in my M35A2 and at 2100 my gauge is past 60psi.
At idle it is around 45psi.

M35A2-AZ, do you know if your sending unit and gauge match? TM9-2320-209-10-2, page 1-11, says:

"If your oil pressure gauge has a maximum reading of 60 psi and the needle peaks at 60 psi, notify organizational maintenance. They will replace the gauge and sending unit with one that can measure a higher range of oil pressure."

 

[tie6044]

Also, I have never put a whole lot of trust into the factory gauges (especially the fuel), to get a true reading one would need to hook up a mechanical gauge at least temporarily to see what it reads.

 

[M35A2-AZ]

M35A2-AZ, do you know if your sending unit and gauge match? TM9-2320-209-10-2, page 1-11, says:

"If your oil pressure gauge has a maximum reading of 60 psi and the needle peaks at 60 psi, notify organizational maintenance. They will replace the gauge and sending unit with one that can measure a higher range of oil pressure."

No I have not check it out.

 

[Josh]

My truck runs oil pressure anywhere from 20lbs at idle on a hot day, to 100psi at start up on a cold morning. Tends to even out around 60ish psi after up to temp and running down the road. I've put about 20,000 miles on my truck the last few years and have not had a single issue with the motor. I change the oil every 10kmiles or 1yr.

 

[Valence]

Well cool, thanks everyone who replied. I will check my sending unit and gauge.

Though, might have to change the thread title to "No longer concerned...."

 

[tie6044]

Be concerned when you DON'T see oil pressure

 

[Valence]

 

[Castle Bravo]

I have a 60 lb gauge and I'm not sure what the sending unit is. When it is warmed up, I get 15 psi at idle and 30 psi at throttle. If its cold, it stays near 30 psi at idle and throttle. I don't know if this is "normal" or not, but I've always heard "Some at idle, more at throttle" is okay.

 

[Amram]

Mine is the complete opposite. I read the same techmanual that said if the engine doesn't reach 30 psi during warmup shut it down and contact maintenance activity. So naturally I was concerned when my truck sat ariund 15psi when idling and it stays between 25-29 psi when running down the road at 2k rpm.

 

[sandcobra164]

My motor's a New in 92' Hercules with a 120 psi gauge and sending unit. Cold, 90 psi whether at idle or governor so I suppose the pressure relief must be set at that. Warm, 20 or so at idle and almost 60 going down the road. Some say that's low but it's run hundreds of hours with no issues that I can tell. I've got spin on adapters as well, same pressures before and after but much quicker oil pressure on a cold start.

 

[rlwm211]

"Also, I have never put a whole lot of trust into the factory gauges (especially the fuel), to get a true reading one would need to hook up a mechanical gauge at least temporarily to see what it reads. "
__________________
Scott

I agree wholehearredly with "TIE6044" that the only way to be sure of anything with an oil pressure concern is to use a quality mechanical gauge to be sure you have oil pressure. While the electrical gauges in these trucks are very sturdy and normally accurate, it is too easy to simply put a line pressure Gauge in to be certain. I would guess $20 or a little less at an autoparts store. If you are truly concerned, compare the cost of the gauge, which you may find another use for, versus the cost of an engine.

Just my two cents and maybe a little more....

 

[shenkmen]

Definitely hook up a mechanical gauge in place of the sending unit to verify.

While the sending unit is out test it with an Ohmmeter. Info on this test (my test) is here -
https://www.steelsoldiers.com/showth...=1#post1065168

 

[panshark]

https://www.steelsoldiers.com/showth...ml#post1065168

Here Katadyn says that if you have insufficient flow at the filter you would have a drop (not a rise) in oil pressure. Can anyone confirm that the pressure sending unit is downstream of the filters?

 

[rlwm211]

Page 12 of the Multifuel troubleshooting manual from Continental located in
the Deuce TM section of www.jatonkam35s.com has the oil system diagram. This may be helpful in this question.