Very Low Oil Pressure after Changing Oil Cooler and Filter

[AZDIRT]

UPDATED W/ PICS! Very Low Oil Pressure after Changing Oil Cooler and Filter

Hey guys, My oil cooler sprung a pretty bad leak, so I pulled the entire cooler off of my 1992 7.3L Parts engine. I cleaned it up really good and replaced the O-Rings, and swapped out my leaky 1985 6.9L oil cooler for the 1992 cooler.

I changed the oil, switching from Rotella to 15W-40 Super Tech. I also replaced the stock filter with a Motorcraft filter for a Super Duty (holds an extra quart).

I did all of this, backed off the pump quite a bit (had it up 3 flats), and increased the timing a dime's width.

I then took the truck for a ride, with new oil cooler, oil change, and adjusted fuel and timing. The truck ran out very nice, but upon my return I noticed the oil pressure dropping almost to non-existence.

I then disconnected and removed the factory oil pressure sending unit and installed a mechanical gauge. Cold idle was 10-15, with up to 75psi showing at 3300 RPM. Hot, oil pressure drops to less than 5lbs at idle, getting up to 40-50psi at 3300 RPM.

Before changing the oil cooler, oil change and filter change, and adjusting fuel and timing, I have put about 20,000 miles on the engine and NEVER had the oil pressure drop at all.

Is it possible that the bypass valve in the rear header of the oil cooler is different from the 92 7.3L to the 85 6.9L? Should I try changing the rear header? Would this even matter considering how low my hot idle oil pressure is?

Has anyone ever had a problem going to the Super Duty oil filter? Would this even matter considering how low my hot idle oil pressure is?

I was just getting ready to sell truck (already bought another one), and now am worried I may have a bad engine...

Thanks

 

[agp23109]

Could be the oil. Some people on here have used that Super Tech which have given them oil related problems. Switch back to Rotella or Delo would be what I would do. I'm sure someone with more info on the coolers will chime in shortly. As far as the filter that shouldn't cause the problem. Not all oil is created equal and given the rather small price difference I would stick with the trusted diesel oil. It's cheap insurance.

 

[burtcheca]

I'm having the same problem with my van. Sometimes after an oil change, if I used Super Tech or Chevron, the reading of the oil pressure is very low. It's amazing that even with new oil, in a week or two the needle is barely touching the line before the NORMAL. Sometimes I think something is wrong but I learned in this forum that that needle does not reflect the real amount or volume of oil being pumped. I know that you can have low pressure with good volume but still it worries me. I was talking about this with a friend at NAPA and he said to try straight 40 next time and see what happens. I would like to add a pressure gauge that will give me a more reliable reading. I need to learn how to do it and where to get the stuff I need.

Burt.

 

[gonecrazyi]

Just go down to autozone and get an oil pressure guage. You will need a brass tee that matches the threads on the stock oil sender behind the cdr on the back of the intake. Took be about 20 minutes to track down the fittings in my garage and to get it all hooked up.

 

[icanfixall]

The stock dash gauge is not showing pressure. It tells you the system has 5 lbs and that it. Install a real gauge.... Yes... When you changed the oil cooler the rear header has the bypass valve in it and also the oil pressure regulater in it. Should have kept the oem unit but thats yeaterdays thought. In the regulater there is a spring. That spring wears flat because it drags on the sides of the valve port. As it wears thin the pressure drops. A new header is around $300.00 now. They can't be "fixed" but.... I removed mine and shimed it up 70 thousands. More oil pressure than I will ever use or need. Not many guys have tried doing this because your breaking down a new header. The aluminum is staked around the valve and any mistake grinding away the stakes and you buy another header. These motors push 18 gpm of oil thru the motor at 3000 rpm so don't be concerned about the crappy factory gauges on the dash. Just install an electrical or mechanical gauge and believe in it.... Not the dash... After all what temp is the coolant when the needle is on the "R" or the oil pressure needle is on the "N".....

 

[AZDIRT]

I then disconnected and removed the factory oil pressure sending unit and installed a mechanical gauge. Cold idle was 10-15, with up to 75psi showing at 3300 RPM. Hot, oil pressure drops to less than 5lbs at idle, getting up to 40-50psi at 3300 RPM.

I know it was a long post, because I included a lot of detail...

Also, you can see in my original post that I still have the original oil cooler, and the one I put on was from a 1992 7.3 engine. So I have access to two oil coolers.

 

[Black dawg]

the oil pressure switch started in the 87 body style. His has a sending unit that measures pressure.

 

[AZDIRT]

As I wrote in the original post, as soon as the factory gauge showed low oil pressure I replaced it with a mechanical gauge and recorded the oil pressures above.

I guess to make it clearer, I am asking:

1. Has anyone ever had any experience where changing brands of oil caused the oil pressure to drop?

2. Has anyone ever had an experience where oil pressure was low after changing or rebuilding their oil cooler? If so, why?

3. Does anyone know if the pressure relief in the rear oil cooler header is different between a 1985 6.9 engine and a 1992 7.3 NA, and could it cause lower oil pressure?

4. Has anyone ever had an experience or know of any issues with running a Motorcraft Oil Filter that is Spec'd for a Super Duty (holds an extra quart)?

5. Regarding the changes I made prior to the low oil pressure, does anyone have any other ideas as to the cause of the low oil pressure?

Synopsis:

I put 20,000 miles on the truck BEFORE making the changes/repairs listed in the top post, and never had the gauge drop below the "M" in normal. After making the changes/repairs in the top post, I took the truck for a drive, and the oil pressure began to dip periodically, especially at low rpm. I then installed the mechanical gauge and confirmed the low oil pressure at hot idle (less than 5 psi), but good oil pressure at higher rpms (both cold and hot).

Either it is a coincidence that I just finished the repairs and now the engine is showing signs that it needs to be rebuilt, or some part of the changes/repairs caused the drop in oil pressure.

Thanks

 

[jhnlennon]

I would be scared to let that thing idle with that low of oil pressure. I know lifters need a certain amount of pressure to keep them pumped up. Obviously something happened when you did the oil cooler swap. I would change the oil to a different brand first, as this is easiest. I doubt you will notice a differance though. I run nothing but supertech in all the diesels I ever had and never hadda a prob with pressure. My guess is the oil cooler pressure relief valve. Might be that its on the worn side and you motor clearances might be a little on the high side causing the problem.

 

[Diesel JD]

Hey AZdirt, I felt like I understood you from the beginning. First, the WalMart super tech oil is diesel rated if I'm not mistaken it's CI4+. It should not hurt your truck. For whatever reason some trucks do seem to "like' some brands of oil better than others. I'd expect and have seen my truck burn off more lower quality oils such as Pennzoil and Wal Mart super tech than it would Amsoil or Rotella, but oil pressure has been somewhat lower with some combos at times. Your mechanical gauge probably proved that you do have somewhat lower oil pressure at idle than you should, however it is still not terrible where it is. Personally I like to see good oil pressure at cold startup and when I'm working the engine at 2000 rpm and up...why? Because there is where your wear could happen. Your engine has obviously been ok for the last 20,000 miles, and the only thing you really changed was the oil cooler headers. If you re-read icanfixall's post you know you're on the right track thinking it's the rear header. Personally I would swap the 85 rear header back in. Everything else you did seems excellent. The FL1995 filter is one of the best upgrades you could do for your truck. It has finer filtration in addition to the extra volume. If anything this will help rather than hurt your oil pressure. I would not have any other filter on my truck. You're on the right track you just have to keep with it.

 

[hesutton]

Gary, isn't there an oil pressure sping deal in the rear head of the oil cooler? Think that the new cooler may have an issue there? I seem to remember you (Gary) posting that the spring can be shimmed to increase the oil pressure or something like that. I don't know if I'm even remembering this correctly. I haven't sleep all weekend and this cold is killing me.

Heath

 

[icanfixall]

Sorry your ill Heath.... I already posted all about shimming the spring in the regulater found in the rear header. What I would do is remove the filter and test the bypass vlave. Its the wafer type valve that allows dirty oil to reach the main oil galley... Dirty oil is way better than no oil if the filter plugs up. If that is found to be ok then I would pull the oil cooler and swap out the rear header for the one that worked better. BTW.. Whats the motor rpm set at. If its set too low the oil pressure at idle will be low also. Mel likes the idle set at 650 rpm..... I like 750 rpm..... Don't bother with the dash oil pressure injicater... Nobody knows what any letter in that means and it really isn't telling you that you have a particular pressure. Its not designed for that. It wont tell you that the r means you have 50 lbs or the n means you have 5 lbs... As some have explained, these dash gauges are nothing more than an idiot lite with a pointer. All of mine still work but I depend on my Isspro gauges now. And I'm much happier.....

 

[hesutton]

Sorry your ill Heath.... I already posted all about shimming the spring in the regulater found in the rear header.

Sorry man. Like I said, I've been in a huge fog all day. Sleep would be good right now, but work is work eh?

Heath

 

[icanfixall]

Heath... Sometimes I'll bet your work really stinks but it puts bread and butter on the table.... I guess you just have to dive on in and just do it... Just think about all the really good days at work... They can't all be bad days now can they.....

 

[Knuckledragger]

AZDIRT,

Since the only thing that changed substantially is the oil cooler, I would look there.

Different makes of oil may have a slight difference in their performance, but none of us on this forum would be able to tell. The oils sold in the US are rated by the SAE and oil industry, any deviations of a gross magnitude would call for different ratings. I.E., if you are using Chokenpuke oil that is rated at 15w-40, it is going to perform exactly the same as Whizbang oil rated at 15w-40, nevermind that the whizbang ads have prettier girls with bigger boobs.

I'm guessing that the bypass in your new cooler is stuck open slightly, or the spring is very worn. Check that first off. Ford does not sell replacement springs, they want to sell entire headers. With a little creativity, you can probably find a spring with the same characteristics in a catalog.