So I'm trying to get to the bottom of the few problems. On the 5.9L I have seen and witnessed a peculiar yet perplexed problem.


After running at a higher RPM (like 3000) or so because of interstate towing with the OD in the off position. Well when coming off the RPM's like getting off the off ramp and coming to a stop there is a total and complete loss of oil pressure. Literally it bottoms right out to 0 psi!

Normal operating psi is in specifications at curb idle and at hwy speeds. Now this could also happen if abundant heat levels outside is high like 100's and sitting in traffic. The main portion of the problem is when the motor is being worked or is at high heat with low RPM.

No other associated problems or isolated problems other than hard RPM's and/or during high heat operations.

Ruled out,

1. Filter issues.
2. Gasket issues.
3. Sending unit issues.
4. Oil pump is working fine under regular use.

Now after doing extreme testing it is plausible that there is no sure reason for this phenomenon.



-------Now Hydra weighs in with more information------



After researching this issue for about 3 years the punishment is concluded.....IMHO

What about blow by?

When an engine is under stress like hard working more blow by can come into the crank case and if your PCV valve isn't working or can't remove the pressure, oil CAN and WILL foam making it possible the oil pump to lose ALL psi just like a air lock when replacing the oil pump so cavitation is plausible.


Now other things I have thought about include:

1. Bad bearings in the oil pump making the shaft move out of range to pick up oil and therefore cavitating. This could be heat related but one would conclude that under heat tolerances would be tighter not allowing this to happen.
2. Oil thinning out. Heat makes the oil thin out thus making the viscosity to thin for the oil pump to pick up.


With the same oil pump being used from 1962 to 2003 in the 5.9L (360) engine and constantly using a 10W-40 or 10W-30 I doubt it's the oil pumps make that could concur this situation.

After looking for a problem in the vacuum system I replaced the PCV valve which was very sticky. The valve had about 40k to 50k on it. So I replaced it. Well by accident I forgot to plug it back onto the intake manifold barb and started it. Well, she ran smooth and stumbled for one revolution but that would be conclusive to replacement of the PCV. Anyway, I took off the crank case breather to the air hat connection to check it out and I had a nice smoke/pressure coming out of the crank case. Got everything put back together and the thoughts finally started making sense as stated in the first part of this post.

I think it's a blow by situation and the oil is foaming thus creating the issues. The PCV valve helps to create vacuum on the crank case to remove blow by and if bubbles/foam are created the vacuum pops the bubbles.

The other thing is Silicone. Silicone is an additive that is added to oil compounds to keep foam/bubbles under control. If there isn't enough it will foam. If too much it will foam. The manufacture rides a fine line.

The Ford Power Stroke engine had this problem because the gaskets were Silicone and they would leach out into the oil creating foam/bubbles thus creating cavitation in the oil pumps the same as this?


----- Opinions wanted???? -----

 

Reject what you think..
Change the oil and filter...( Try a different style filter as well)

Trust meh, hugs kisses..

 

Done, tested, company tested, and totally proven wrong.


Thanks for the hugs and kisses!...

 

Hydra, keep it simple. The pickup tube may have a low crack in it that is fine at idle and under acceleration but when decelerating may be exposed to air. This would definitely allow a drop in pressure. The oil is actually thicker at operating temp due to an additive (I can't remember the name now). 10W40 deciphered is a viscosity index of 10 in winter (W) and 40 at operating temp. Cavitation is the implosion of tiny air bubbles on the suction side of a pump and is caused by low pressure causing the fluid to "boil" after introducing pressure again the bubbles collapse with tons of force. This would be very noticeable and would sound like your oil pump was chewing up gravel. If that was the case I would look at a restriction in the suction side.

 

I don't think it's any type of restrictions because it would do it at other times as well.


Also with higher temperatures the oil thins and lower temps it thickens.


Supporting documentation:
http://1st-in-synthetics.com/tempera...motor_oils.htm



Now a crack?....... Possible!...... But even with a crack every time the motor got hot it would do this but this is not always the case. Many times I've seen these motors get really hot like 220 and not do it. I feel that if this was the case it would always do it.


Now I question this accredited statement because if you go too thick it won't fall through the baffles and jackets correctly causing a lack of lubricant and burning therefore vaporization and failure of the lubricant and say goodbye to a lovely engine. This be extremely relevant to it's use in a cold motor in low abundant temperatures.


I found this and wanted to share:

 

This is what I'm saying. The PCV pulls vacuum to keep this from happening. If the PCV valve isn't operating correctly or not enough the air bubbles can't pop and get sucked into the pump. If this happens cavitation will occur because the pressure will drop on the suction side and therefore all pressure will be lost.

Once you hit the throttle it speeds up the rotor and forces the cavitation through the pump thus returning to operation.

 

Air bubbles that are sucked into a pump can wreak havoc but don't cause cavitation. As far as the additive I was talking about it is called a viscosity modifier. It works by causing cold oil (and were talking freezing temperatures here) to be thinner in order to flow better in cold weather. This is accomplished by the molecules in the modifier to straighten out when cold and ball up when heated. With a straight weight oil you do not have the viscosity modifier in it and you will have thinner oil as it heats. If I had 0W30 I'd want that oil to thicken up pretty quickly personally otherwise you are using almost the equivalent of water to lube the engine.

 

Thanks for all the info guys. I seem to be expericing this problem now on a trip to Disneyland. After driving through the grapevine, my 2002 RT loses oil pressure at stop signs or any time of de-acceleration and then immediatey goes back to normal. I've had the truck for about a year now and this is the first time I expereinced this. I was driving up the grapevine, and I had the OD off since I was carrying a load. When I was on the decline portion of the highway, I tried to give the motor a break so I put it in neutral and let it coast down. Almost instantly the "check gauge" light came on and I notice the oil pressure drop to low. Since that time I have been experiencing this problem whenever sitting idle or de-accerlearating.


My most important question is.. Do I need to fix this now am I damaging the motor, or can I wait until I get back home?

Thanks

 

my 2cents...

everything is STOCK.
No hi volumn Oil pumps...
when oil pressure fails any noise such as lifters ticking or rods a knocking? thinking here is the sudden change hi rpm to low and the drop in pressure the sensor may over run the low end ..... a mechinical gauge might substatute but alot of work for me who believes easy simple first.
does the visual on gauge follow that logic?

Could there be a problem with the oil pressure bi pass? Valve sticking in a somewhat "open" ...

I like simple easy diagnostics .....right before your next oil change run an extra quart of oil .....try to repeat condition....BUT dont go forever with that extra...

 

I have thought about the bypass valve sticking but even if it did you would still have SOME psi?----5psi or something not just drop off the face of the earth. It would have to be wide open which it couldn't......IMHO..... Besides during this phenomenon you can hit the throttle to get the pump back flowing then let off and it will or can drop off totally again. All you need is like 1200 rpm to get the psi back to normal and you can let off so the engine drops back to 600 RPM and then it drops COMPLETELY off again! Not the problem. This problem would be consistent with foaming and the EXACT same issue with the Ford.

kev2<------brings up some great points.

1st..... Make sure it actually is loss of pressure. In my case I know for a fact that it was at a total loss of psi. Heads rattling, motor bogging down, slapping of everything..... Basically it BOTTOMED out!....Non....Noda.....Nothing


tallon<------ This is EXACTLY what I'm talking about!.... First check the level and make sure you are right to the top line!

Change the oil and filter ASAP and change out your PCV valve. If you bottom out on psi hit the gas to get it back going or hold you foot on the throttle just a little and brake with the other foot. Go Mobil 1 Fully Synthetic 10W-30 If it keeps up you might want to put in a quart of 10W-40. I bought some Mobil 1 Fully Synthetic 10W-30 High Mileage that is supposed to be of a higher viscosity than their regular Mobil 1's Fully Synthetic 10W-30 at operating conditions that is supposed to be more resistant to burn off and brake down during blow by. I bought 2 at Wal-mart for $22 bucks for 5 quart container. It was on sale this week and they also sell the OEM Mopar oil filters (Mopar # MO-090) as well which is one of the best filters made because they are actually made of metal.....LOL


Now Fully Synthetic oil and I'm talking about is Mobil 1 only. It has more anti-foaming properties incorporated because of the oil base and additives used but each to their own.


Mean Green<------ I understand the modifiers and the need for use of modifiers for 10W for (winter) cold and a 30 for heat (basic 10W-30 oil) and everyone is currently using them as I explain this problem. This could be one of the first things that could cause this problem, but if a user installed a straight weight oil like a 30W then the hot properties are the same? The cold would be different for viscosity ratings/polymers and cold would have the think pour properties during which bearings could be fried. Besides, it's getting hard to even find the straight weights anyway.

Supporting documentation:
http://autos.yahoo.com/maintain/repa...ques120_1.html


The thing is, if you go above the NORMAL heat range it can thin out because it's past what it's rated for. Then it can vaporize after extreme heat range and it can vaporize and brake down so it thickens so it could be harder to pump.



Again tech heads, this is out of the normal realm of normal thinking. I know everyone want to go to the basics but the basics are covered. We gotta dig deep.