Thanks to all, I do appreciate your help.

To ZackeryMack: I did PM you yesterday to get a copy of that scan. You must be like me and don't notice that little envelope flashing. I once had a message that was 2 weeks old before I noticed the envelope <img src="/forums/images/graemlins/lol.gif" alt="" />.

To kravdraa: Thanks for the offer to machine me a new one! If I didn't have the credit (mentioned below)I would probably take you up on it.

It seems the consensus is the oil cooler valve/regulator. Since a replacement base and valve is only $38, and I have a credit at St. Charles that is several months old, I just went and ordered it from them. My second oil change is due shortly and I will also make use of an Isuzu/OEM filter at that time too, just to eliminate the possibility of a missing check valve in the econo-parts store filters.

Thanks again!

NCDiesel

Thanks to Paul223's help once again, I shall attempt to post this scan I have of the oil passage.
Hopefully, this is from the Isuzu manual :


This shows where the valves are in the circuit.

From that rather good diagram It would suggest to me the pressure releif valve... or maybe the oil jet regulating valve.

I got to thinking - If the 1981 manual has it in it, so should the 86 Trooper factory service manual. Sure enough, I found it. It is slightly different so here it is:

http://www.atis.net/~yostsw/Clip2.jpg
Changed this to a link because of its size -- Randii

Basically the same but the plumbing in the cooler is different and the pressure values are different. The regulater in the block feeds the oil pipes only. The tips of the oil pipes are a bit higher than the cooler base, I believe, so I don't think that if the regulator for them was leaking the leak would drain the cooler/filter, or even the galley.

So I agree - I think it has to be the oil cooler valve. The call it a regulator in the diagram but a cooler valve in the Isuzu parts book I have.

Thanks again!

NCDiesel

Hey Zack--

Glad you put up your oil system post. Good job.

And NC, nice followup. Amazing what's in those manuals.

I know you guys know this but here is a photo (I love posting photos) of two oil filters. The one on the left has no check valve and the one on the right does have one.

Notice the rubber flapper ring under the holes around the center hole. This is the valve and these holes are the inlet to the oil filter. So to make sure you have a check valve look for the rubber flapper.

Paul

Paul,
Nice picture and now I know what to look for in the oil filter.
I have been using a FRAM filter, but didn't check on the one way valve. I have an 81 PuP (LUV)
Eric

Thanks for the great pics. When I start the oil cooler base swap-out, I will of course drain the filter and remove it. I will check the NAPA(I said Wix but this was a NAPA) filter I have on it now to make sure I have the check valve. If it doesn't, I will just put on one of my Isuzu factory filters and see what happens. If it does, I'll swap out the base.

Thanks!

NCDiesel

I am about to replace the oil cooler base and was wondering: Is the the stainless upper "coolant" part of the oil cooler self contained? In other words, can I just remove the long hollow bolt holding the two halves together and not bother draining coolant and crimping off the coolant lines leading to and from the cooler?

To the best of my recollection, the upper, "water" part of the cooler is self contained and I should get no coolant leak when I remove the large center bolt and split the base from the upper part.

However, the risk of coolant contaminanted sump and crankcase is serious enough I want independant confirmation before I trust my recollection, especially considering that my recollection has been known to be wrong before <img src="/forums/images/graemlins/lol.gif" alt="" />

Thanks in advance!

NCDiesel

One other thing....

Just removed the oil filter, and I do have the larger rubber flapper under the perimeter holes as Paul223 showed us, so it isn't a oil filer draining the oil - or is it??. I did find something else. The O ring around the small neck in the center of the filter was missing from the filter I just removed. (and it isn't in the large center bolt). It was never on the filter. Would this be my problem with oil draining back into the crankcase?? Using one of my new factory filters as an example, here is a picture of the o-ring that I am talking about:



What does that o-ring do anyways??

As usual, thanks in advance,

NCDiesel

Well, I spoke with Jerry Lemond this afternoon about something else, and mentioned the oil pressure delay. He was convinced it was the oil filter and not anything else. He told me to just change the filter with the OEM filter I had gotten from him a month ago and forget the base.

Guess what. As usual he was right and the OEM filter fixed the problem.

The NAPA filter looked and felt completely right, except the misssing o-ring and the feed tube is a bit smaller. Neither of thewse created a real problem though according to Jerry. The problem is apparently there is no check valve inside of these. The rubber thing we were talking about, the "flapper", is only one of two check valve devices in these filters. The one on the main feed is up in the top of the filter according to Jerry and is often left out by aftermarket manufacturers. So stay AWAY from NAPA and WIX filters for sure, probably all the others. Just buy OEM straight from Jerry or Isuzu.

Hope this helps someone else in the future...

NCDiesel