Another oil pressure thread

[snailexpress]

I don't think the sum of slightly bigger gap in main and rods will take pressure down so much.
As you can see on my picture it was 3 or 4 injector cam bearings completely out and pressure wasn't so bad.
But I may be wrong.

[Rawze]

(11-15-2018 )Peashooter67 Wrote:  ...
Because of Rawze, his suggestion with explanation, I’m plastigauging main and rod bearings.
His theory and explanations made since and fit the symptoms.
...

Just repeating what I have seen in the past, or others have shared with me. I have never claimed to be any kind of professional, just someone who tries to help others with the little bit of twisted knowledge I have stuffed into my head.

(11-09-2018 )Peashooter67 Wrote:  ...

Cold at start up oil pressure is 45-50 psi at 600 rpm.
This is measured at sensor on driver side and on main oil gally on passenger side with mechanical gauge.
Once water reaches 180 and oil 220 degrees oil pressure drops to
8 psi at 600 rpm and max is 22psi at 1400 rpm.

No matter where you test the oil pressure it’s 8 psi at 600 rpm.

This would indicate you have shimmed the pump with the equivalent of 6 dimes?. When cold, it is regulating the pressure to 45~ish psi?. Does it stay at same pressure when cold and you rev it up?. -- If so, then that is an indication that the oil is flowing into the engine, down the back side of the gear cover, then back to the regulator inside the pump properly anyways. Would indicate there was no restriction (bad o-ring floating around) in the regulating feedback circuit.

Maybe someone flipped the end piece for the regulator if they had it out while shimming the pump?.




You also mention there is a lot of oil up top in one of your posts?. Maybe compare it to your other isx?. If there is a lot more oil flow in the top of the head than your other one, that is an indication something in (or something installed into) the new head may be incorrect / still hemorrhaging oil?.

Has anyone blocked off the turbo feed line to see if the pressure comes back?

Maybe drop an inspection cam into one of the drain ports on the side of the block to see the oil flow out of the engine, turbo, and other areas going into the pan?

lastly, has anyone considered sending oil off to see if it is diluted / getting thinned out with fuel? - just more blind guessing here.


Possibly something wrong with the front gear cover/housing itself and its cross-channels?.

Just more guessing here. I know if it were mine, I would have been driven crazy until I found it too.

There used to be animations / videos on youtube of the oil flow and feed system for the ISX that a person could watch with full detail through the block, head, engine brakes, etc. but it has since been taken down. Maybe someone can PM you a link to it if they still have a copy of it saved somewhere, since it is not public any more.

[Rawze]

I also did some digging and found out why it is recommended to replace the oil cooler if you have low oil pressure issues...

It has been known that an abused engine, where the oil filters are not changed often enough, the oil bypass plug (the one you say got updated) will vibrate all the time, bypassing oil from the partially clogged oil filter (or simply if the spring gets weak) and eat up the inside of the housing, creating a hole / internal leak, bypassing the filter or if it eats a hole, draining back to the pan. - The same thing can happen to the high pressure relief valve (the one located to the right of it, shown here in this picture...



OR -- If the valve has failed in some way, will bypass oil right back into the oil pan, creating lower than normal oil pressure. It is the smaller of the 2 valves located at the top of the oil filter, and usually, no one ever checks / replaces it during an inframe. For all anyone knows, it may be simply full of trash?. Also, if the valve was replaced, it could be the housing partially eaten up, bypassing oil.


-- Maybe this bit of info helps to resolve your issue and why it is recommended to replace the oil cooler. Not so much the oil cooler, but the housing itself, I would suppose.

the oil cooler element(s) could also cause restriction if they become impacted with metal shavings or other contaminants, making oil flow problems too.


thats at least another thing to consider heavily if you have not replaced that oil cooler housing.

[Peashooter67]

Thanks for more things to look at Rawze.
We had the oil cooler out and it was clean inside and out. There was a little hard water evidence in the water jacket there and the cooler o-rings were starting to fail so that was a ticking time bomb avoided.

I’m in Colorado city waiting on tires for the company trailer. Someone in maintenance decided it was a money saving good idea to use recaps and I had the predictable tire failure and it almost took out the tire next to it. Fortunately the tire man only took an hour to get from Abilene to Colorado city “wow! He had to be really cooking it”.....

Anyway when I get back this week end we will go over what we have done and these new things to check. Yeah not near as much oil ontop of the Pete as there is on the kw.... thanks for the suggestion/s as we already had that thought just to get an idea of what normal should look like.

The kw isx is max 40psi and minimum 18psi idle and x amount givin x rpm.
We have been using this one as our compairitor.

[Brock]

I had a mechanic install my camshaft dry which caused the cam bearings to spin even though everything was new..... causing low oil pressure.

I had a friend get a full in frame done at Peterbilt and they didn't pop out the oil galley plugs before assembly...... his top end ran dry, not sure if it lowered or raised oil pressure though.

[Peashooter67]

I think we found the problem Rawze sir.

All main bearings plastigauge at .002
Rod bearings #’s 1-2-3 at .002
4 & 5 at .006 and # 6 at .002.

Going to reinspect crank jurnal and install .004 under rod bearings, plastigauge adding to verify .002 gap.
Close it up and heat cycle the motor. Fingers crossed

[Rawze]

(11-17-2018 )Peashooter67 Wrote:  I think we found the problem Rawze sir.

All main bearings plastigauge at .002
Rod bearings #’s 1-2-3 at .002
4 & 5 at .006 and # 6 at .002.

Going to reinspect crank jurnal and install .004 under rod bearings, plastigauge adding to verify .002 gap.
Close it up and heat cycle the motor. Fingers crossed

That does not sound like that much excess clearances for that much oil loss, but you never know. I have not had to face that situation myself. - If I had found this extra 0.004" on a couple journals on my own engine, I would have wanted it fixed too though, even if that was not the issue.

All I can say is that this is likely the most thorough discussion about oil pressure loss issues that I have seen so far. Maybe when you finally solve it, then it will help others out there who may end up with a similar problem.

[Peashooter67]

The more I think about the more I think you may be right.
They only come in 10-20-30..........

Next step will be the front cover I guess?
Compressor?
Turbo?

Thanks for the call.

I did get my 72 c10 back together today. The ne rear end works great.

[Rawze]

As a last resort, maybe take it over to Mr. hags shop just s.e. of atlanta?. Maybe get a second set of eyes on it.