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1984 6.9 idi rebuilt and now has about 3k miles since the build. The engine runs smooth, no unusual noises, and delivers 21 mpg highway. Recently the oil pressure has dropped to the bottom line of the normal range on the factory gage. I figured it was just the factory gage being nothing more than an indicator that oil pressure is present. I put on a new sending unit and this did not change the reading. I checked voltage at the wire that connects to the sending unit and voltage is present (this is an indicator that the ICVR is operating). This old truck has a low voltage instrument cluster with a voltage regulator that feeds the temp, fuel, and oil pressure gages. I installed a direct reading gage and confirmed that at idle the pressure is not enough to register, and high rpm the engine develops about 17 psi. My diagnosis is probably a stuck oil pressure regulator. When I pulled the oil cooler I found that the pressure regulator is staked in and not easily removable. A search around here disclosed that a replacement part is not available for this engine. Ford has discontinued this part and no alternate part is available. And there is no overhaul kit to renew the existing regulator. My idea is that I need to get the existing regulator out of the oil cooler header without bugging it up. Then I MAY be able to polish the plunger and bore, if necessary, find a replacement spring. My question is: has anyone else had this problem, and what was your solution? Thanks for any advice that you all may provide. Is this Ford's way of telling me to buy another truck?
 

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Aimless Wanderer
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1984 6.9 idi rebuilt and now has about 3k miles since the build. The engine runs smooth, no unusual noises, and delivers 21 mpg highway. Recently the oil pressure has dropped to the bottom line of the normal range on the factory gage. I figured it was just the factory gage being nothing more than an indicator that oil pressure is present. I put on a new sending unit and this did not change the reading. I checked voltage at the wire that connects to the sending unit and voltage is present (this is an indicator that the ICVR is operating). This old truck has a low voltage instrument cluster with a voltage regulator that feeds the temp, fuel, and oil pressure gages. I installed a direct reading gage and confirmed that at idle the pressure is not enough to register, and high rpm the engine develops about 17 psi. My diagnosis is probably a stuck oil pressure regulator. When I pulled the oil cooler I found that the pressure regulator is staked in and not easily removable. A search around here disclosed that a replacement part is not available for this engine. Ford has discontinued this part and no alternate part is available. And there is no overhaul kit to renew the existing regulator. My idea is that I need to get the existing regulator out of the oil cooler header without bugging it up. Then I MAY be able to polish the plunger and bore, if necessary, find a replacement spring. My question is: has anyone else had this problem, and what was your solution? Thanks for any advice that you all may provide. Is this Ford's way of telling me to buy another truck?
That valve sticking open dumps oil pressure from the pump right back into the pan. I had an 83 and lost the engine over that. After rebuilding it but not realizing that valve was stuck open, I lost oil pressure shortly after the rebuild. After pulling the engine from the chassis again, I found the cam bearings down to copper, mains scrubbed pretty good, and the rods almost perfect. I was able to get the new valve at the time, (1992) replaced all the bearings, and all was fine for almost 60K more before I sold the truck.
 

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Discussion Starter #3
That valve sticking open dumps oil pressure from the pump right back into the pan. I had an 83 and lost the engine over that. After rebuilding it but not realizing that valve was stuck open, I lost oil pressure shortly after the rebuild. After pulling the engine from the chassis again, I found the cam bearings down to copper, mains scrubbed pretty good, and the rods almost perfect. I was able to get the new valve at the time, (1992) replaced all the bearings, and all was fine for almost 60K more before I sold the truck.
The parts department at the local ford dealer says that the header went out of production about two years ago. I really don't want to pull the engine again. I work in my home two car garage. The truck stays outside and only the engine gets in the house! I have read that volume of flow in this engine is probably more important that pressure. I have not loaded the truck down since I put it back in service, so there has not been prolonged periods of high power requirements. If I can find another cooler in a salvage yard, that may correct the issue, but I may end up with the same problem that I have now. There is probably a reason for that old engine being in salvage?
 

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The parts department at the local ford dealer says that the header went out of production about two years ago. I really don't want to pull the engine again. I work in my home two car garage. The truck stays outside and only the engine gets in the house! I have read that volume of flow in this engine is probably more important that pressure. I have not loaded the truck down since I put it back in service, so there has not been prolonged periods of high power requirements. If I can find another cooler in a salvage yard, that may correct the issue, but I may end up with the same problem that I have now. There is probably a reason for that old engine being in salvage?
The one in salvage could be cooked from busted heads, blown head gaskets, melted pistons, or a few other items that plagued the early 6.9 diesels. I'd bet there is an NS1 part someplace. Check with a dealer and ask them to run under that search. The 7.3 used the same cooler so should be readily available. My valve was jammed open from chunks binding it's operation from the engine letting go prior. Lot's of early to mid 1990's IH school busses used the same engine and there should be some of those around also.
 

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Discussion Starter #5
The one in salvage could be cooked from busted heads, blown head gaskets, melted pistons, or a few other items that plagued the early 6.9 diesels. I'd bet there is an NS1 part someplace. Check with a dealer and ask them to run under that search. The 7.3 used the same cooler so should be readily available. My valve was jammed open from chunks binding it's operation from the engine letting go prior. Lot's of early to mid 1990's IH school busses used the same engine and there should be some of those around also.
Thanks, those are very good points and I will give it a try.

Question: with the header in my hand, I push in with a brass rod and I felt the plunger move to the bottom of the bore (where it stayed). did I open or close the port through which the oil flows?
 

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Thanks, those are very good points and I will give it a try.

Question: with the header in my hand, I push in with a brass rod and I felt the plunger move to the bottom of the bore (where it stayed). did I open or close the port through which the oil flows?
You opened the port and if it stayed recessed into the bore, a good portion of the oil flow will bypass the engine and be returned to the pan.
 

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that confirmed what I thought I understood about the way the regulator operates. I hate to lose the truck engine for the sake of a simple spring loaded valve. especially since there are designs that ford could have used that permit the rebuilding or replacement of the regulator valve. a simple spring loaded ball on a machined seat works just a well, and some of those were adjustable by shimming the pressure spring or turning the plug in a little deeper.
 

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that confirmed what I thought I understood about the way the regulator operates. I hate to lose the truck engine for the sake of a simple spring loaded valve. especially since there are designs that ford could have used that permit the rebuilding or replacement of the regulator valve. a simple spring loaded ball on a machined seat works just a well, and some of those were adjustable by shimming the pressure spring or turning the plug in a little deeper.
That valve is just staked in place so would be easy to replace with a ball and seat cartridge although you may need to open up the hole in the casting to make it fit. If not, plug the original hole, drill and tap though the mounting boss, (end cap) and run an external line back into the oil pan which would require welding on an external bung and a line. Not really hard to do just takes a little ingenuity of which I lack......
 

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I have been soaking the spring and plunger port with CRC "Break Er Loose" penetrating oil. While I was spraying the oil I noticed a small port on the filter side that goes into the valve chamber. I applied compressed air to that port to make sure it is open, and the valve activated. I tried it several times and sometimes it opens, and other times only partial opening and sometimes nothing at all. I think a small slide hammer puller may take the sleeve out of the hole. I gently pushed the steak dimples back by tapping the seam line between the sleeve and the header assembly lightly using the corner of a small chisel like a wedge so that it did not cut into the soft header metal. There is a small dimple in the end face of the sleeve. I put the end of a ***** punch in that dimple and gave a light tap and observed that the sleeve rotates fairly easily. That is good news to me! I do not have a slide hammer, but I am going to look for a small one like could be used to remove small bearings for pressed assemblies. I think the sleeve will come out with the proper tool. Then I will try to polish the parts and the bore to achieve freedom of movement. IF I can do that, then I will reinstall plunger, spring and top sleeve by re-staking the rim of the valve and give it a try. Does anyone see any obvious flaws in this procedure?
 

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The penetrating oil has been "soaking" for about 4 hours. I tried to wiggle the valve again and was able to hook it in one of the 3 holes near the top of the bore and got it started out. I placed an open end wrench at the bottom of the top lip and used a socket as a fulcrum point to lift the valve free of the header. There was a fairly heavy coating like a varnish on all of the surfaces that was binding the valve. I polished all of the mating surfaces to a nice bright clean finish and periodically ran the plunger in to check the fit. Once it was all clean and with a light coat of oil the plunger falls out of the sleeve with gravity. There is no radial play that I can detect. The spring did not show any scuffing on the outer circumference so I think it is good. I gave everything a good coat of clean engine oil and put the valve back in the header bore and re-staked it there. Out of curiosity I measured the outside diameter of the exposed sleeve at the staked end and found that it is larger than the hole to which it mates on the engine block. I think this could have been installed without re-staking, but would have been more difficult to reassemble to the engine without the staking of the valve. So the header is ready to go back on the engine. I hope it works to boost oil pressure! That truck is not leaving my yard until it has oil pressure!
 

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Navistar is a lot better than Ford for keeping parts available for these engines, I go to the Ford dealership for chassis parts but never for engine parts.
 

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Navistar is a lot better than Ford for keeping parts available for these engines, I go to the Ford dealership for chassis parts but never for engine parts.
I havent't worked with one in several years and am unaware of parts availability at all. Usually aftermarket unless proprietary to the vehicle.
 

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None of the aftermarket sources were able to get anything that would help with this particular problem. I have bought temp sensor and switch from International. The parts from international were less expensive than what ford offered.
 

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None of the aftermarket sources were able to get anything that would help with this particular problem. I have bought temp sensor and switch from International. The parts from international were less expensive than what ford offered.
I've found the OEM dealers to be price competitive on many routine service items also. For many years I've ran OEM branded filters on engines being Mack, Case, IH, John Deere, and now Perkins. Aftermarket is not always best and it can pay to shop around if you don't have a lot of overhead costing money during the research.
 

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Another good place to look for Navistar parts is eBay seller "u-techcenter." He deals more in 7.3l parts than 6.9l and it's all Navistar (no Ford), but a lot of them will fit with minimal mods and the prices are pretty good.
 

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Discussion Starter #16
I have attempted to show some pictures of this project. The three internal parts of the regulator valve all cleaned. the order of assembly and the exact location on the header where the work was done.

I have the truck back together. initial start on a direct reading gage showed 15 psi at cold idle and near 40 at high rpm. Hot idle was under 10 psi but the pressure goes quickly to just above 30 at cruising rpm. I think that is the best I could hope for. Maybe the pressure would be higher if I put a ship in the bore before installing the valve components? As it is I am pretty pleased. If this happens again before I get rid of this truck, I will try a ship to see what it does to the pressure.

Thanks to all who replied to requests for information. Just hearing from you all cheered me up. I was afraid the engine was done (only about 3k since overhaul) for the sake of a few old parts that are not readily supported. I plan to visit Southern International to inquire if the oil filter header can be obtained or is it really a dead issue?
 

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Aimless Wanderer
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Boy if that don't just look familiar. Think I may have to go heave after seeing another.....

Glad you got it repaired. You didn't reuse the piston cooler jets during the rebuild did you? I've seen those blown out and this causes an immediate loss of oil pressure down to about what you have. They are an interference fit and are not supposed to be reused as all.
 

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Yes, I did re-use them. I wonder if a flexible magnate could "search" through the oil drain hole? None of the jets went in very easy, and I was careful to make sure each one was completely seated.

Just when I was sitting back quite content with myself, now I have visions of engine oil squirting directly onto the crank. Hey, , , maybe that is why I did not burn up the crank with low pressure. Splash lube! ! !
 

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Yes, I did re-use them. I wonder if a flexible magnate could "search" through the oil drain hole? None of the jets went in very easy, and I was careful to make sure each one was completely seated.

Just when I was sitting back quite content with myself, now I have visions of engine oil squirting directly onto the crank. Hey, , , maybe that is why I did not burn up the crank with low pressure. Splash lube! ! !
It seems some of the oil pans used on those engines had an upper baffle plate. If this is the case it may be tough to find one. The oil pressure you have is low and mine never was below 30psi at hot idle. I'm thinking the oil pressure was around 60psi at road speed but it's been a long time and my mind has been the second thing to go.
 

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no baffle on this engine. It is just a big open pan, I also rebuilt a 7.3 idi on my 89 f350 dually. No issues with that one, all is well. on the 6.9 the pan looked exactly like the pan on the 7.3. I wonder if it is just a weak spring in the regulator? I don't really want to pull the pan off to see if piston jets have come loose. In the 7.3 the jets are held in with a bolt, that was the big difference I saw between the two builds. I thought it was kind of strange that the jets in the 6.9 were just pressed, but then I am not an engineer and trusted to International that they knew what it needed. I was working on a shoestring budget and so I reused as much as possible. the 6.9 had a broken rod when I got it, but it was still running on 7. The milage on the truck says about 28,000, I do not know if it is 128, 228, or 328?

At the moment I am contemplating my options, (1) sell the truck (it needs a paint job). (2) shim the regulator spring with a washer at the bottom of the bore. (3) drop the oil pan and check for loose piston jets. Another option is if I can find someone with a borescope that could look in throung the drain plug to see if jets are sitting in the oilpan. ? ? ? ?

As it is the factory oil pressure gage runs in the bottom of the normal range, the F350 with a 7.3 is never below mid-range.

These are the only two diesels of this design that I have broken down to the block, so my experience is limited with no fleet knowledge. The local ford dealer told me there is no one in his shop old enough to have ever worked on these.

I can't bring myself to sell the 84 with what I think is a known problem. I will not mis-represent the truck as being mechanically sound when I can't get a normal indication on the oil pressure.
 
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