I had the jeep since 2003, pryer to that I have no idea. Before engine rebuild, oil was changed every 6 mtns. Piston fell apart in the engine a year ago this week. The shop did a complete master rebuild. Sine then, I put about 4000km since then. roughy 4 mtns after did oil change. I've put most the km's on the engine in the fall during hunting season. I had a small oil leak in november. Oil was a quart down topped due to leaking,that leak was fixed. Since then I changed oil filter/oil, tried Lucas, did another oil changeto get rid of lucas. Here were are today. Oil pressure(18psi)it better, but I haven't been on a really long drive.
high then low oil pressure
- Thread starter Jeeplander
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It sounds quite normal to me....for a well worn engine.
10 psi at 1000 rpm is all thats needed to float the bearings.
My Sierra, with 300k miles also shows high pressure when cold. But as it warms up, the pressure falls to about 13-14.
Thats normal. oil is thicker when cold and doesn't flow as easily as when hot. Hot oil loses its viscosity, flows like water and squeezes through gaps easier.
But again, 300k miles. The bearings are slightly worn and they'll bleed off pressure at every bearing.
I really have to question if the bearings were really replaced in this total rebuild of the engine. I would guess not.
10 psi at 1000 rpm is all thats needed to float the bearings.
My Sierra, with 300k miles also shows high pressure when cold. But as it warms up, the pressure falls to about 13-14.
Thats normal. oil is thicker when cold and doesn't flow as easily as when hot. Hot oil loses its viscosity, flows like water and squeezes through gaps easier.
But again, 300k miles. The bearings are slightly worn and they'll bleed off pressure at every bearing.
I really have to question if the bearings were really replaced in this total rebuild of the engine. I would guess not.
Originally Posted By: JimPghPA
When the oil pressure drops, pull over and quickly pull the dip stick, wipe it and re-insert it, and pull it to measure the level. It would be best to do this with the engine still running if you can. If it is real low it means the oil is not getting back down to the sump fast enough. This could happen when the engine warms up because the oil thins when hot. When thin it flows up through the engine with less restriction, and does not open the relief valve on the pump. If the upward flow rate exceeds the downward gravity return rate the sump will run out of oil, suck air, and the pressure will drop.
There are several things you can do if this is the problem. You could go with an oil that does not thin out as much when hot. And / or, you could increase the gravity return passage(s) ID.
??? Thin oil not getting back down fast enough? I highly doubt that 4 to 5 quarts of oil are being suspended in the valvetrain area. Not only are the oil return passages on this engine big enough to fit your fingers and thumb in, it would smoke like a banshee.
Originally Posted By: Jeeplander
I had the jeep since 2003, pryer to that I have no idea. Before engine rebuild, oil was changed every 6 mtns. Piston fell apart in the engine a year ago this week. The shop did a complete master rebuild. Sine then, I put about 4000km since then. roughy 4 mtns after did oil change. I've put most the km's on the engine in the fall during hunting season. I had a small oil leak in november. Oil was a quart down topped due to leaking,that leak was fixed. Since then I changed oil filter/oil, tried Lucas, did another oil changeto get rid of lucas. Here were are today. Oil pressure(18psi)it better, but I haven't been on a really long drive.
I "T'ed" off my sending unit with a mechanical gauge and recommend you do the same. Then there will be no doubt of the status of the pressure. EDIT: Re-read your first post. Pull the pan and make sure that the oil pickup tube is fully engaged into the pump body. That could be a viable source of pressure loss. Might want to replace the oil pump. It's about $60 and takes about an hour or two. I recommend the one piece Felpro rubberized gasket with the bolt grommets to avoid over tightening. I would still add a dab of RTV at the front and back around the ends where the bearing caps are. I used this gasket on mine and friends Jeeps and have had zero leaks.
Dang, if I were close, I'd help you out.
When the oil pressure drops, pull over and quickly pull the dip stick, wipe it and re-insert it, and pull it to measure the level. It would be best to do this with the engine still running if you can. If it is real low it means the oil is not getting back down to the sump fast enough. This could happen when the engine warms up because the oil thins when hot. When thin it flows up through the engine with less restriction, and does not open the relief valve on the pump. If the upward flow rate exceeds the downward gravity return rate the sump will run out of oil, suck air, and the pressure will drop.
There are several things you can do if this is the problem. You could go with an oil that does not thin out as much when hot. And / or, you could increase the gravity return passage(s) ID.
??? Thin oil not getting back down fast enough? I highly doubt that 4 to 5 quarts of oil are being suspended in the valvetrain area. Not only are the oil return passages on this engine big enough to fit your fingers and thumb in, it would smoke like a banshee.
Originally Posted By: Jeeplander
I had the jeep since 2003, pryer to that I have no idea. Before engine rebuild, oil was changed every 6 mtns. Piston fell apart in the engine a year ago this week. The shop did a complete master rebuild. Sine then, I put about 4000km since then. roughy 4 mtns after did oil change. I've put most the km's on the engine in the fall during hunting season. I had a small oil leak in november. Oil was a quart down topped due to leaking,that leak was fixed. Since then I changed oil filter/oil, tried Lucas, did another oil changeto get rid of lucas. Here were are today. Oil pressure(18psi)it better, but I haven't been on a really long drive.
Dang, if I were close, I'd help you out.
Originally Posted By: highmilegeguy
10 psi at 1000 rpm is all thats needed to float the bearings.
The 2.5L Jeep spec is about 37+ psi at 1600 RPM.
10 psi at 1000 rpm is all thats needed to float the bearings.
The 2.5L Jeep spec is about 37+ psi at 1600 RPM.
The oil pump was replaced.
Is possible debris from the piston, could be in a oil line?? Is there any way to remove this. SeaFoam worth try'n?? I guess if something is inthere, the engine would have to be dismatled....
Before the engine had to be rebuilt, I had no oil pressure issue's stayed between 30 & 45 psi.
Is possible debris from the piston, could be in a oil line?? Is there any way to remove this. SeaFoam worth try'n?? I guess if something is inthere, the engine would have to be dismatled....
Before the engine had to be rebuilt, I had no oil pressure issue's stayed between 30 & 45 psi.
Originally Posted By: Jeeplander
The oil pump was replaced.
Is possible debris from the piston, could be in a oil line?? Is there any way to remove this. SeaFoam worth try'n?? I guess if something is inthere, the engine would have to be dismatled....
Before the engine had to be rebuilt, I had no oil pressure issue's stayed between 30 & 45 psi.
Anything is possible, but the particles from the piston would fall directly into the pan. Anything small enough to make it into the oil pickup screen would get sucked into the pump and then go into the filter. Most rebuilding facilities do a decent job at cleaning the block during rebuilds. If it is something lodged somewhere, Seafoam would have no effect on it.
I'm going to stick to my original recommendation of replacing the oil pump, or in the very least, inspecting the oil pick up tube. There is also a gasket that goes between the oil pump and block and if this was omitted during the rebuild, would cause a drop in oil pressure.
It really is a simple system. Just start from the bottom up and eliminate as many possible causes as you can.
The oil pump was replaced.
Is possible debris from the piston, could be in a oil line?? Is there any way to remove this. SeaFoam worth try'n?? I guess if something is inthere, the engine would have to be dismatled....
Before the engine had to be rebuilt, I had no oil pressure issue's stayed between 30 & 45 psi.
Anything is possible, but the particles from the piston would fall directly into the pan. Anything small enough to make it into the oil pickup screen would get sucked into the pump and then go into the filter. Most rebuilding facilities do a decent job at cleaning the block during rebuilds. If it is something lodged somewhere, Seafoam would have no effect on it.
I'm going to stick to my original recommendation of replacing the oil pump, or in the very least, inspecting the oil pick up tube. There is also a gasket that goes between the oil pump and block and if this was omitted during the rebuild, would cause a drop in oil pressure.
It really is a simple system. Just start from the bottom up and eliminate as many possible causes as you can.
I replaced the oil pump & gasket after lucas didn't make any noticable difference. Neither did the replacement of the oil pump. I in the conclusion that it's either cam or main bearings.......
I would still measure the oil level when the pressure has dropped to insure that oil is not trapped above. It is a no cost thing to check, and allows you to rule something out once you check it.
Were any parts that were replaced in the rebuilt not the same design as before the rebuilt. Different style of rockers, or anything else.
Trying to figure out what is going on with this engine without having it to look at is to put it in engineering terms taking one giant step in the wrong direction with signal to noise ratio.
Any information you can provide regarding anything different from normal that has been done to this engine could be helpful for someone to help you figure out what to look for.
BTW you still have not said what oil you have used in the past and what oil you are using now.
Were any parts that were replaced in the rebuilt not the same design as before the rebuilt. Different style of rockers, or anything else.
Trying to figure out what is going on with this engine without having it to look at is to put it in engineering terms taking one giant step in the wrong direction with signal to noise ratio.
Any information you can provide regarding anything different from normal that has been done to this engine could be helpful for someone to help you figure out what to look for.
BTW you still have not said what oil you have used in the past and what oil you are using now.
I have always used Castro 10w30 with a change every 6mtns. All parts used were from Master Rebuild Kit from Engine Tech. Engine temp is normal. What oil should I use to bring up pressure?? Will this cause my startup pressure to go even higher...
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Well, you still don't know you have a problem to treat. It's more a curiosity about "what's up". It would bug the heck out of me too, but without apparent symptoms, what is there to really do besides some detective work ..as in an ongoing work in progress? Now IF I heard lifters rattling at hot idle, then I would have bona fide cause to feel that something was harmful.
You've eliminated all the usual suspects.
You can use a 40 weight synthetic. That will surely raise your hot idle viscosity. It will have you slamming against the same limits that you are now. You will probably be at the relief level longer.
The only other explanation that I could pull out of my behind would be if you, for some odd reason, were seeing some oddball oil temp. This would produce the radical difference in visc that was not apparent otherwise.
Another would be if the bearing side leakage increased as you "wore it in". Again, you're not hearing any lifter rattle, so flow to the top end is adequate.
You've eliminated all the usual suspects.
You can use a 40 weight synthetic. That will surely raise your hot idle viscosity. It will have you slamming against the same limits that you are now. You will probably be at the relief level longer.
The only other explanation that I could pull out of my behind would be if you, for some odd reason, were seeing some oddball oil temp. This would produce the radical difference in visc that was not apparent otherwise.
Another would be if the bearing side leakage increased as you "wore it in". Again, you're not hearing any lifter rattle, so flow to the top end is adequate.
I do not own a Jeep, but many here on BITOG who have Jeeps like Shell Rotella T 5W-40 synthetic engine oil. Shell just changed the formula from T5 to T6, but the T6 really is suppose to be compatible with older engines. You can get it at Wall mart, and Pep-Boys, and several other places.
Any Jeep owners out there care to comment?
Any Jeep owners out there care to comment?
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Go to the third main forum and the first topic Pasanger car motor oil, click on that and go to the sixth one down about using RTS in a Jeep in northern climates.
BTW here on BITOG Shell Rotella T Synthetic is refered to as RTS
BTW here on BITOG Shell Rotella T Synthetic is refered to as RTS
That thread moved down a few. Look for "Rotella 5w-40 too thick for Northern ontario?"
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The stuff survived over one year with shorter trip usage in my 2.5. The used oil analysis wasn't stellar, but the stuff was still a solid 40 weight and there was no consumption. I did this twice back to back. This was the SL formula ..so it's long gone.
Read "Motor Oil by A E Haas". You can find it on google.
If you have an oil pressure gauge and a tack, you can chose your oil so the oil pump pressure limit opens at the normal maximum RPM your engine sees. As long as the lowest oil pressure is not too low this would be an improvement in the internal cooling of your engine, because oil does not just lubricate, it also cools internal parts. My choosing oil so the pressure limit trips at max rpm you also chose the oil that has the maximum flow and thus the maximum cooling.
If you have an oil pressure gauge and a tack, you can chose your oil so the oil pump pressure limit opens at the normal maximum RPM your engine sees. As long as the lowest oil pressure is not too low this would be an improvement in the internal cooling of your engine, because oil does not just lubricate, it also cools internal parts. My choosing oil so the pressure limit trips at max rpm you also chose the oil that has the maximum flow and thus the maximum cooling.
Typing error, should of read: By choosing oil so the pressure limit trips at max rpm you also chose the oil that has the maximum flow and thus the maximum cooling.
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Ideally you would have a spec'd oil that matched the demands of the engine and totally "fit" through the engine without going into relief over the full range of operation. The Asians seem to do this well. The Euro's appear to do it well for those who actually use their full range of operation ..but domestics appear to have other influences in visc, oil pump volume, and relief limits. I'm talking about your generic pushrod engine of no particular distinction. This engine would qualify in that class.
Hey guys thanks for all the help!!! I just had the thought. Is it possible the block could be cracked?? I guess you would see oil in the coolant, which I don't......
Hey guys Still got the same problem, no better. I have been doing some basic reading on syn. oil. If I switch over to Syn oil. would this help me in keeping a higher idle oil psi???? I'm new to this idea.
Originally Posted By: Jeeplander
Sorry guys... when I was saying "When driving it runs 35 - 55 psi but drops hard to 15psi" it drops hard when I come to a stop at lights etc. jeep idles at 15psi...... Is it possible that one of the bearinngs has spun..... I went from haveing 35 - 55psi to 15 at idle and 35-55psi driving over night.....
I wonder if it is Engine-Specific.
My Jaguar has Full Oil Pressure at Start-up.. Gauge goes STRAIGHT to 65Psi (When its "Cold." I tru to let it warm up for 5-10 minutes; sometimes, i only let it warm up for one, and drive very Slowly. I run 10W-40, i think that is as thick as i feel comfortable going. (My Car SAYS 20-50, but thats Jaguar. The Relief Pressure for my 4.2L Inline 6 Engine is 65Psi.)
After its warmed up for liek "20 Minutes," I see 15-20 Psi at the Light, Hot, Idling. Step on Gas.. it goes 40-60, MAYBE 65, Psi. So, i wonder if that is "NORMAL" for mine (If its in the first 10 or 15 minutes and im driving on the Highwway, Oil Pressure is a full 65 Psi, meaning Relief Valve is open.)
So.. Maybe it is Engine Specific.
Is it better to have HIGH Oil Pressure than LOW Oil Pressure?
Ive seen Plenty of Ford engines where Oil pressure is at 80 Psi, and i wonder what the HIGHEST Oil Pressure an Engine has seen is.. also if it can make an engine "Blow Up." My OLD oil produced very LOW Pressure, and i always thought Higher pressure was Good...
I wonder if there is a "Universal Normal Range."
Sorry guys... when I was saying "When driving it runs 35 - 55 psi but drops hard to 15psi" it drops hard when I come to a stop at lights etc. jeep idles at 15psi...... Is it possible that one of the bearinngs has spun..... I went from haveing 35 - 55psi to 15 at idle and 35-55psi driving over night.....
I wonder if it is Engine-Specific.
My Jaguar has Full Oil Pressure at Start-up.. Gauge goes STRAIGHT to 65Psi (When its "Cold." I tru to let it warm up for 5-10 minutes; sometimes, i only let it warm up for one, and drive very Slowly. I run 10W-40, i think that is as thick as i feel comfortable going. (My Car SAYS 20-50, but thats Jaguar. The Relief Pressure for my 4.2L Inline 6 Engine is 65Psi.)
After its warmed up for liek "20 Minutes," I see 15-20 Psi at the Light, Hot, Idling. Step on Gas.. it goes 40-60, MAYBE 65, Psi. So, i wonder if that is "NORMAL" for mine (If its in the first 10 or 15 minutes and im driving on the Highwway, Oil Pressure is a full 65 Psi, meaning Relief Valve is open.)
So.. Maybe it is Engine Specific.
Is it better to have HIGH Oil Pressure than LOW Oil Pressure?
Ive seen Plenty of Ford engines where Oil pressure is at 80 Psi, and i wonder what the HIGHEST Oil Pressure an Engine has seen is.. also if it can make an engine "Blow Up." My OLD oil produced very LOW Pressure, and i always thought Higher pressure was Good...
I wonder if there is a "Universal Normal Range."
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