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Oil pressure drops


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Having a issue with my oil pressure.. 40 psi at start up then about after 15 mins driving it drops way down.. At idle its down low around 2 or 3 psi hit the peddle it pops right up to around 20psi.. It almost seems to me that the gauge is clicking the needle, ie; it'll be low at 3 psi then bring rpms up and the gauge kinda "pops" back up, but only to 20psi... Any ideas on what to check??? Think it may just be the gauge or sensor????

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As in all electronic gauges, most problems w. inaccurate readings are caused by a faulty sensor or impedence between the sensor and the gauge. The gauge only reports the resistance reading of the sensor it sees, plus the built-in circuit resistance. The gauges are usually pretty reliable. Check for tight cluster connections and clean up any corrosion first. But you already know that. :cheers:

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How many miles are on the engine, and do you have any idea how well (or poorly) the previous owner took care of it? Low oil pressure usually means bearings. I know several people from NAXJA who dropped the oil pan and replaced the bearings to get back their disappearing oil pressure.

 

Try the mechanical gauge first. If it confirms the low pressure, don't panic. It means some work, but it doesn't mean you have to start shopping for a $2500 rebuilt engine.

 

What weight oil do you run? Do a change, and throw in Mobil-1 15W50. See if that helps.

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Out of curiosity, what brand oil filter are you running?

 

What weight oil do you run?

 

Not being a smartass, but... ;) :cheers: :razz:

 

 

Not been running long on new oil change,, purelator filter, Rotella 15 40 diesel spec'ed oil..

 

 

Did this only start after you put the diesel oil in it? Just wondering because the oil may be too heavy and you may have to back off to a regualr 10-30.

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Yeah Brent I changed to the Rotella first thing when I got the truck. I'm using the Rotella because of its high Zinc content. I've been using it in my Rodeo for about 2 years, because of a top end lifter tap.

 

I've heard of replacing bearings with engine still in, but never tried it. I think I could do it with a lil info..

 

1) Will I have to get deferent sized bearings?

2) Do the main and rod bearings??

3) Torque numbers on the caps

4) Do I have to remove the front axle beam?? (2wd)

 

I have no problem doing this I've just never have before..

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Interesting info... I have never heard of anyone running diesel oil in a regular engine before.

 

I know the bearing job can be done without removing the axle as our engine guy at the dealership has done several of them like that since I have been there, but I don't know all the specific answers for you on the other stuff.

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Out of curiosity, what brand oil filter are you running?

 

What weight oil do you run?

 

Not being a smartass, but... ;) :cheers: :razz:

 

Not been running long on new oil change,, purelator filter, Rotella 15 40 diesel spec'ed oil..

 

 

 

I found the problem with my post: "Posted: 13 Sep 2008 03:14 am" Gotta find a way to resist having one more look before bed. :D

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I guess I can try the Lucas before I dig into the engine.. I really feel thats just a band-aid though. Maybe it'll give me a cushion to find a engine core and rebuild it.

Brent think you can talk to that Technician and get the specifics of doing the bearings?

 

just make sure to run the lucas with 10-30oil because the lucas is extreemly thick 100% petrolium :brows:

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You do not have to drop the front axle to change the bearings. It does help to jack the vehicle up and let the axle droop, for pan clearance. The PITA part is maneuvering the pan off with the oil pump pickup in place. The other issue is getting the pan loose. The factory pretty much glued it on. It's hard to remove without mangling the flange. Best approach is to loosen the bolts but leave them in the hole. Then get something thin but stiff (like a paint scraper but not flexy like a putty knife), get it started, and then just chase it all the way around until you have it loose.

 

Once it's open look at the main bearings. You'll probably be through the bearing material and showing copper. Unless your crank is fubar, replace with stock size bearings. Keep in mind the factory occasionally used cranks that were ground .010 under, so check the codes on the bock near the distributor to see if you need stock or 10-under bearings.

 

If the rod bearings look bad, replace them too. I would expect that they are probably okay.

 

When you button it up again, get the '95+ one-piece pan gasket. It's much easier to work with, and it provides a better seal. And while the bearing caps are off (for obvious reasons, only do one bearing at a time), it would be a good idea to replace the rear main seal while you have everything accessible.

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Since it started after the oil change. I would swap in a new oil filter before doing anything else. It could just be a bad filter and they are cheap too.

 

I agree with Maddzz. And if it doesn't get better I think Sunpro sells a mechanical gauge that screws into where the sender is to tell you if the gauge is off. I think I saw it on Amazon.com the other day.

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I guess I can try the Lucas before I dig into the engine.. I really feel thats just a band-aid though. Maybe it'll give me a cushion to find a engine core and rebuild it.

Brent think you can talk to that Technician and get the specifics of doing the bearings?

 

just make sure to run the lucas with 10-30oil because the lucas is extreemly thick 100% petrolium :brows:

 

I guess Ill go ahead and change oils then.. I'll probably go with that Brad Penn this time.

 

You do not have to drop the front axle to change the bearings. It does help to jack the vehicle up and let the axle droop, for pan clearance. The PITA part is maneuvering the pan off with the oil pump pickup in place. The other issue is getting the pan loose. The factory pretty much glued it on. It's hard to remove without mangling the flange. Best approach is to loosen the bolts but leave them in the hole. Then get something thin but stiff (like a paint scraper but not flexy like a putty knife), get it started, and then just chase it all the way around until you have it loose.

 

Once it's open look at the main bearings. You'll probably be through the bearing material and showing copper. Unless your crank is fubar, replace with stock size bearings. Keep in mind the factory occasionally used cranks that were ground .010 under, so check the codes on the bock near the distributor to see if you need stock or 10-under bearings.

 

If the rod bearings look bad, replace them too. I would expect that they are probably okay.

 

When you button it up again, get the '95+ one-piece pan gasket. It's much easier to work with, and it provides a better seal. And while the bearing caps are off (for obvious reasons, only do one bearing at a time), it would be a good idea to replace the rear main seal while you have everything accessible.

 

Got it.. IF I do the bearing change (for some reason the oil change and oil pressure test show it positivity needs it) Think I should do the oil pump while in there?

Also I need some torque #'s if by any chance you know them.

 

Another quick question.. When I take main cap off how do I get the top half of the bearing out?? Just spin it on around the journal?

 

If I need to pull the crank, is there a easy way to get the timing chain off??

 

 

 

You could always stop by Harbor Freight for one of these.

 

 

 

92687.gif

 

I called Advanced and I swear... some of those guys do not need to be working there.. The guy I usually talk to won't be back till Monday... I might try to stop by sears or western auto to see if they have one..

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i have the exact same problem. driving me crazy, did an oil change and it seemed to go away for a week, then came back, going to drop the oil pan and clean out all the gunk if there is any in a while, i hope i don't have to replace the bearings, i'm a carpenter, not a mech. but i think i beter get savy quick with this truck.

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i have the exact same problem. driving me crazy, did an oil change and it seemed to go away for a week, then came back, going to drop the oil pan and clean out all the gunk if there is any in a while, i hope i don't have to replace the bearings, i'm a carpenter, not a mech. but i think i beter get savy quick with this truck.

Welcome,, and tell me how that works out for you.. I going try an oil change and run a can of the Lucas oil treatment.. If it stays low after 20 miles then going to commit to surgery..

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