oil pressure problem update

xring 223

Member
got the packing nut installed now my pressure is about 80 lbs. operating speed and temp. up idle pressure is 40-45 when hot motor is noisy sound like hammers pounding the block compression is 120 any ideas I'm almost afraid to work it. thanks for any help.
 

It'd help to know what machine that engine is in.

Are the hammers tapping? = valve train

Or are they really pounding? = crankshaft, rods, pistons

Loose gears can also do this. Hydraulic pump drive may as well.

Without hearing it and with the description you've given it's hard to say exactly what you're hearing.
 
According to your first post a few days ago, you were down to 15 PSI at operating speeds. You didn't say how long you were running like this, but if it was for any appreciable amount of time, the damage has already been done to the bearings. Myself, I would have pulled some bearing caps off for a visual inspection while I had the pan off.

If my hunch is correct, I would not run it any longer until I took a look at those bearings. The longer you run it, the more damage you'll do to the crank.
 
15 psi at what rpm?

6 psi per 1k is a common 'rule of thumb' for minimums... ( i know, I know.. is not a set in stone guarantee number.. )

If he was running at 2500 rpm or less ... the oil pressure *may* have been sufficient.

Not saying there isn't a problem somewhere.. etc.. but we need to know more..
 
There was a big discussion about this a while back on this board, however IMHO 15 PSI while working the engine cannot be good for it, I don't care what the RPM is.

6 PSI per 1000 RPMs sounds downright scary to me. Any diesel would never live with numbers like that.
 
it really does depend on the application...

When I got my Case VAC, I thought it was ready for a rebuild because it had low double digit oil pressure.

then I find out that is the BOOK oil pressure spec.

Not every engine needs 80 psi oil pressure...
 
I agree, engines don't need 80 PSI, however most diesel engine manufacturers specify a minimum of 35-40 PSI at working speeds. If my engine is constantly running 50-60, I'm pleased.
 
I know we all like pressure.. But lets look at some real world stuff.

Ant of hp excess oil pump pressure eats?

Reading on some Chevy builders forums, at 7000 rpm, you can be giving away 10-12 hp for excess oil pump needs

Once you have your oil wedge in the bearing clearance, .. You are golden.

Look at ford oil senders.. When do they open? 6-10 psi? 14, maybee? I've seen some low opening ones.

Reading up on some race engines, common practice is 3qts oil, 7500 rpm, and virtually 0 excess psi.

Pretty interesting stuff once you start reading it.

Double digits on these old low rpm gassers dont bother me..
 
Be careful what you read on forums, including here at YT. I seriously doubted this 10-12 HP savings you quoted, so I did some of my own research and math...

A SB Chevy "high volume" oil pump puts out 23 GPM @ 6000 engine RPM (by comparison, Ford says that a 134/172 tractor engine oil pump is rated at 3.5 GPM @ 1400 engine RPM, so the SB Chevy figures sound quite reasonable). If you use the formula for hydraulic horsepower, which is HP = GPM x PSI / 1714, and plug in 50 PSI for system pressure, you will find that this high volume oil pump consumes a whopping 2/3 of one horsepower. If you double the pressure to 100 PSI, the difference between 50 & 100 PSI is again less than one HP.

More info here: http://www.hotrodders.com/forum/bb-sb-chevy-oil-pump-numbers-221702.html

With regards to oil pressure senders, keep in mind that these switches are set intentionally low so that they don't cause false alarms at hot idle. Let's say the switch in a tractor engine is set at 10 PSI, and let's also say that the relief valve spring in the oil pump is broken and/or weak. This engine might produce "good" oil pressure at idle, say 15 PSI, but the relief valve will open prematurely at higher speeds, and only make 25 PSI at higher RPMs. The warning light will never come on, and yet damage is likely being done to the engine if it's working hard. This is a major drawback to a warning light system.

The original poster said he had only 5 PSI at idle, and 15 revved up. I still maintain that this would spell disaster for a diesel engine in short order, and long-term problems for a gasser if it's worked hard. While Ford does not give a minimum allowable spec for oil pressure in these engines, the fact that the OP now has about 8 times the oil pressure after his seal repair, PLUS a heavy-duty knock that he apparently did not have before, it sure does not sound good to me.
 
(quoted from post at 08:01:56 07/19/16) Be careful what you read on forums, including here at YT. I seriously doubted this 10-12 HP savings you quoted, so I did some of my own research and math...

A SB Chevy "high volume" oil pump puts out 23 GPM @ 6000 engine RPM (by comparison, Ford says that a 134/172 tractor engine oil pump is rated at 3.5 GPM @ 1400 engine RPM, so the SB Chevy figures sound quite reasonable). If you use the formula for hydraulic horsepower, which is HP = GPM x PSI / 1714, and plug in 50 PSI for system pressure, you will find that this high volume oil pump consumes a whopping 2/3 of one horsepower. If you double the pressure to 100 PSI, the difference between 50 & 100 PSI is again less than one HP.

More info here: http://www.hotrodders.com/forum/bb-sb-chevy-oil-pump-numbers-221702.html

With regards to oil pressure senders, keep in mind that these switches are set intentionally low so that they don't cause false alarms at hot idle. Let's say the switch in a tractor engine is set at 10 PSI, and let's also say that the relief valve spring in the oil pump is broken and/or weak. This engine might produce "good" oil pressure at idle, say 15 PSI, but the relief valve will open prematurely at higher speeds, and only make 25 PSI at higher RPMs. The warning light will never come on, and yet damage is likely being done to the engine if it's working hard. This is a major drawback to a warning light system.

The original poster said he had only 5 PSI at idle, and 15 revved up. I still maintain that this would spell disaster for a diesel engine in short order, and long-term problems for a gasser if it's worked hard. While Ford does not give a minimum allowable spec for oil pressure in these engines, the fact that the OP now has about 8 times the oil pressure after his seal repair, PLUS a heavy-duty knock that he apparently did not have before, it sure does not sound good to me.

Real experience is hard to beat.. We could read the net till ell froze over the experience can pick out the good and read over the bad... In the search for a silver bullet the less experience will believe what ever is the easiest..

I have challenged Bern I don't agree with everything he post BUT do stand up and pay attention when he talks he does know a HOLE lot I don't know about tractors I may never work on...

I figure if you challenge Bern you best be ready to challenge a real world experience not sum'N you read on the net...
 
I used to worry and worry about the subject and was a thick oil nut due to that. Since then I have learned that there are numerous engineering designs in engine mechanics and the 6 psi per thousand does sound a little low. 30 psi has been around for a long time and considering an older engine back in the old days, making it's hp at 2000 rpms (Buick straight 8 for one) with 30 psig pressure, that's 15/1000. Deere 4010 and 4020 were set to 30 and ran on up around 2500 as I recall.

Obviously actual pressure depends on how fast the pump is turning and viscosity. So heat and rpm will affect it. Question then remains, is there a pressure relief valve or not.

I had Dodges and Chevs and Fords. I now know that Dodge ran high pressures ((315-360 engines) and low flow. Chevy ran high flow and low pressures (small block V8 for one). Learning that, I quit throwing rocks at Chevy designers. My dodges would jump up and hit the peg just above idle where the Chevys just mosey'd along with the rpm. I don't remember the Ford as the '88 was the only one in the mix other than a '65 "hotwater 6".
 
thanks for the comments and the info this is a 172 gas engine and from all I can gather I need a rebuild I worked the tractor with a brush hog about a month ago for 6 or 7 hr with low oil pressure and over heating problems so I think the damage is done and a rebuild is in short order. I don't have good thoughts for the person who left the packing nut off.!!!!!!!
 
I had one more thought about all of this...

I've worked on more than my share of engines with spun bearings. Virtually every time, it's a rod bearing that spun, rather than a main bearing. Why is this? One reason could be because a rod bearing gets its oil AFTER the main bearing, due to the way the oil is routed through the crankshaft. It stands to reason then that, since oil pressure is measured in the oil rifle in the block, that a pressure reading of say 10 PSI on the gauge probably really is zero or near zero PSI at a rod bearing. Stated another way, we need to have higher pressure where it's measured in order to ensure adequate pressure for a rod bearing downstream.
 
None of the info came from here, that's for sure.

Here is one place I was reading

http://www.reocities.com/pcwright77/files/oilpressure.html
 
hmm.. pressure should be pressure in a system. pressure is a resistance to flow. If the gauge reads 10 psi somewhere in the line that means that at the last location where oil is escaping, there is enough resistance to flow that the gauge can read 10 psi.
 
Think for a minute about how oil gets to the main bearing, and then a rod bearing. Oil first travels through a rifle drilling in the block, then on to the main bearing shell. Once oil enters the main bearing shell, it travels around the main journal, lubing it and the bearing. Some of this oil escapes past the sides of the bearing shell and back into the oil pan.

Some of the oil however is routed through a groove in the upper main bearing shell to a hole in the crank, where the drilled passage in the crank feeds the rod bearing. This is how a rod bearing is lubed.

My point is, since some of the oil from the block rifle passage is lost at the main bearing as it spits out over the side of the shell, the volume, and therefore pressure, drops at that point, meaning the pressure at the rod bearing will be naturally less than at the main bearing.

Taking this one step further, consider a Ford tractor turbocharged engine, such as a 7600 or TW 30. Those engines use drilled connecting rods to take oil from the rod bearing up to the top of the rod to lube the piston pin, as well as spit oil out the top of the rod to cool the underside of the piston. The oil pressure here will be even less than at the rod bearing, for the exact same reason I described earlier. Every time you lose oil (volume) at a particular point, pressure drops.

Think of it this way: Imagine taking a garden hose and attaching a lawn sprinkler to the end of it. Now turn the faucet on, and you have pressure at the end, correct? If you didn't, water would not be spraying out 10 feet or more across your lawn. Now, take a small drill and drill some holes along the length of the hose, without turning up the water volume at the faucet to compensate for your leaks. What happens to your sprinkler? Water flow drops, and the sprinkler radius is reduced because the pressure dropped, right?

In my garden hose example, the faucet is the oil pump (a fixed volume at a fixed speed), the sprinkler is the piston pin bushing on a Ford turboed engine (the final oil destination point), and the holes that were drilled in the hose represent the oil that escapes past the main and rod bearings.

Hope this helps.
 
Smokey Yunick was a highly respected engine builder back in his day. That said, the quote attributed to him about an oil pump using 10 HP cannot be correct. Either the man was misquoted, or else his understanding of hydraulics was rather limited. I suspect the former.

The formula for hydraulic horsepower (HP = GPM x PSI / 1714) has not and will not change. I plugged in the numbers in my prior post, and came up with less than one horsepower to drive a SB Chevy oil pump.

The only possible way I could see how higher oil pump pressures could contribute to HP loss like he said would be due to increased windage. More pressure equals more oil escaping past the bearings and raining down on a spinning crank. This windage sucks horsepower, and is why windage trays and dry sump systems came into existence.
 
I'm somewhat familiar about windage, and already knew the hp calc.

What I dint know is the ultimate gpm that those pumps can make.
 
I believe you are incorrect.

Volume won't drop downstream if you have sufficient flow rate.

Think of it lil a sprinkler line.

Pump pressure tank and a 100' PVC run, a sprinkler head every 10'.

Turn on water, untill you have more flow than the sprinkler heads can pass, you will have flow but no pressure ( ok, minute open channel flow backpressure). increases flow till you have more flow than can be exhausted thru the heads. Put a gauge at a few places I the line.. If you have the flow capacity, you will have pressure.. Otherwise your house plumbing would have no pressure at you sink if you were filling the tub.
 
Try this: Turn on the faucet at your kitchen sink, note the flow, then turn on your bathtub full blast. What happened to the flow at your sink? It dropped. Unless you have all 1" plumbing in your house, it has to.

You say that "volume won't drop downstream if you have sufficient flow rate". By definition, it has to if some of the oil is being lost past the bearing clearances along the way. And keep in mind, for a given engine RPM, pump flow is constant, it does not change.

One more thing to add about my garden hose/oil system analogy: If we need say 50 PSI at our sprinkler head to get decent lawn coverage, and all I have is a leaky hose to supply it with, I'll have to supply more volume from the faucet to get the job done. In the case of my garden hose, this is easy to do - simply tee in a pressure gauge right next to my sprinkler and adjust the flow at my faucet until I get my 50 PSI. In this example, I might need 100 PSI at the faucet to get this job done.

In the case of my engine, say we need 20 PSI of pressure at the piston pin bushing to adequately lube the bushing and squirt oil on the underside of my piston. This means we'll need higher pressure upstream, near the pump, to make this happen, because of all of the volume losses along the way. So, to make this happen, say we need 40 PSI as measured at the block, which is much closer to the source than it is to the final destination.

In my garden hose example, I can measure the pressure directly at my final destination - the sprinkler. In an engine, I don't have that option. I can only measure pressure much closer to the source. Bottom line is that 15 PSI of oil pressure in my block isn't going to get adequate oil pressure (and consequently, volume) to the rod bearings, as the original poster has finally and sadly concluded.
 
Your argument proved nothing.

Sure, there may be a pressure drop at the kitchen sink when bathtub turns on.. However that pressure in the house will be the same. You can't have 50 psi at the sink and 30 at the tub.

And look, I already know your reply will be disagreement. I remember our last conversation, so to speed this up.

I agree that you disagree with me.

Back to tractors reading now?
 
"You can't have 50 psi at the sink and 30 at the tub."

Oh yes sir, indeed you can. Just like you can have 11 volts at the battery and 9 volts at the starter while you're cranking the engine. Voltmeter will show 12.6 at both points until you put a load on the system.

I'm done with this thread also. Thanks for keeping it interesting and civil.
 

I'm not going to get in the fluid dynamics argument but as far as the low oil pressure concern can anyone tell me how a 550 Oliver will run for years and never have more than 12 psi of oil pressure from the day it was new.
I had a worn out 289 in a 68 Torino that I drove 250 miles to Nashville and back making 15 psi at interstate speed and less and 5 psi at idle, finally decided to replace it about a year later because the body was in bad shape but the engine never did blow up.

To xring223, You already have concerns about the engine's condition and wont be satisfied until you tear it down, so just do it, at best you'll be out $ for some gaskets or you may stop a developing problem before it gets real costly.

I rebuilt the engine in my 4000SU a year and a half ago and have used it hard at times, noticed the oil light blink a couple of times so I put a gauge on it and even warm it had 20 psi making me think everything was ok. Left the gauge on and worked it pretty hard one day and oil pressure dropped to 10 at idle.
The crank is turned .020 rods and .010 mains, I'm thinking they may have given me a full set of .020 bearings so tractors setting in front of the shop waiting to be worked on. After putting over 400 hours on it now that I know something's not right I'm afraid to use it.
 
(quoted from post at 17:17:54 07/19/16) "You can't have 50 psi at the sink and 30 at the tub."

Oh yes sir, indeed you can. Just like you can have 11 volts at the battery and 9 volts at the starter while you're cranking the engine. Voltmeter will show 12.6 at both points until you put a load on the system.

I'm done with this thread also. Thanks for keeping it interesting and civil.
hew! Just in the knick of time! I was thinking it was about to turn into a
contest.
 

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