Definitely NGC..Cummins 6BTA 5.9 oil pressure help. Maybe Solved!

[Tom H]

I know that there are people here that have expertise in all sorts of things.

Before I take forever typing out the symptoms (very slow at typing). Does anybody here know 1994 Cummings 6BTA 5.9 300 something HP and especially the M2 engine. If there is I will give the details of the issue. I have spent hours searching the net for answers already, but none really seem to match the problem.

Thank you.
Tom

[Moparnut72]

What is the problem? These are pretty basic engines. Actually most sought after for hot rodding etc.
kk

[Tom H]

This is a M2 in a boat with about 1300 hours. This is a twin engine boat.

The issue is that it has no oil pressure on the electric gauge for umm, umm about 15 seconds. Haven't timed it. The other engine comes up normal/quickly. This is with a cold start. Once started, even not running for an hour or so, the pressure come up quickly, but not as quick as the other engine.

This did not happen overnight, but when the delay became noticeable, it seemed to get worse quickly. But it has not become worse since.

Once the pressure comes up. Cold oil pressure is about 35# IIRR, which I believe is in spec. Hot idle is at least 10# at about 800 RPM. I don't think the pump is the issue.

The pressure and delay was confirmed by a mechanical pressure gauge. The auto parts store kind with the clear plastic hose.

The one really odd thing. When you turn the key to shut off the engine and wait for the engine to stop turning. The VERY quickly turn the key back on to get the gauges back on, the oil pressure comes down umm, umm slowly. Maybe 1 or 2 seconds. When you do the same with the other engine, the pressure drops instantly.

First thought was a bad pump, but pressure is within spec. Second may be the pressure relief valve sticking open or not closing fully or gunked up. The last option, which is VERY hard to check is the oil pick up tube in the pan being clogged or cracked.

To pull the pan, you have to lift the engine.  I'm pretty sure there is not enough clearance to work the pan off, much less get a good look under the engine. If your going that far you may as well pull it out and just rebuild the whole thing. When the other engine was done, pulling, labor and rebuild was over 10K.

Lets say I didn't mention some likely culprits. Where would you start??

Thank you!!
Tom

[mondtster]

Before you do anything to the engine I would be putting a mechanical pressure gauge on the engine and starting it to see how quickly the pressure rises on it.

These engines don't always build pressure the fastest, but 15 seconds sounds like a long time. Does the engine sound any different when you see pressure start to rise on the gauge? I've always found the 6BT to have an audible difference in sound with no oil pressure vs. with oil pressure.

[80CX100]

     I don't know sh*t from shineola about these things, but I noticed you mentioned a few times, stuck, gunk, clogged etc all to do with the oil system assembly.

     I've heard of quite a few old time mechanics who are big believers in flushing old engines & oil galleys out by running ATF through it, straight or 50-50 75-25 I don't recall.

     That could be death to your engine, if the thing sealing it and making it run well, is the old carbon

     It sounds like a big dollar unit, I'd be running a mcgyver flush by someone you trust first, fwiw.

     My first thought, especially if it's the easiest part to get to, verify the gauge and the port and line feeding the gauge.

     Good luck

     Kelly

[Tom H]

I did add a mechanical gauge to it to confirm that the electric gauge was correct. Also I mentioned that it takes a second or two with the engine off and not turning for the pressure to come down. Also confirmed by the mechanical gauge. The other engine, when shut down drops pressure instantly. The issue engine almost acts like something is clogged and not allowing the oil to move freely. But at the same time, once it gets pressure, it appears to be in spec.

I kinda thought about the oil filter being a problem. There is a bypass valve. The problem is that I can't remember for certain if the issue came after the oil change. All though, I'm fairly sure it was before.

I kinda like the idea of a flush, but you have to pump the oil out, not just pull a drain plug. Not sure if all the flush liquid would come out. Not so bad to do it once, but at 15 quarts a shot, it gets a bit pricey to do it twice. But then again, not as expensive as a engine rebuild.

Thanks again so far.
Tom

[mondtster]

Filters have been known to cause problems on these engines. I’d stick to OE filters as a result and I’d probably give filter replacement a shot before going further into the engine.

[Ryan]

It sounds like a flow resriction, like a spring-loaded check valve, that takes full pressure to open. Then it flows okay. When you shut down, it snaps closed preventing bleedback so it takes a little while to bleed off the pressure. I have no idea if this emgine or filter has any kind of check valve in it, but I would find out and check it for free operation. Do you have the same filters, bypasses, etc on both engines? Is there an oil cooler with a thermostat valve?

[Tom H]

I should have mentioned this at the start. It's my friends boat, he keeps all the records for it. We normally go out every weekend, but the rest of the week it just sits in it's slip. It's a 32 foot boat.

I will be bringing up what has been said so far to him. I know he did an oil change on both engines a few weeks ago, but IIRR we came to the conclusion that this was an issue before the oil change. I do know that we looked at the filter box to decide if the filter had a bypass built in, the box was not clear. "IF" I understand this engine, the FILTER BYPASS is not in the filter, but in the filter mount. One the same note, the pressure regulator valve is in the same area I believe. Even if the bypass for the filter was an issue, all that it's supposed to do is allow the engine to keep oil flowing if the filter get clogged for some reason. Better to keep dirty oil flowing than none at all from what I have read about the bypass.

Ryan, I was thinking about your idea as well. A check valve. I will have to dig deeper into this, but from what I have read about this issue so far, there is not a check valve. The closest is the pressure relief valve. Again, I'll have to dog into this some more.

With all the searching and reading that I did about the symptoms, one thing that did come up was a cracked pick up tube in the pan. But, we have the added symptom of the pressure slowly coming down compared to the other engine. If it was not for this, I would kinda believe the pick up issue.

I really do think it's something easy and simple. A flow restriction somewhere.

Keep up the ideas!

Again, Thank you so far,
Tom

[pat80flh]

Quite a few modern engines have a screen of some kind in the gallery below the sending unit/switch. Possibly plugged up/restricted?

[Rough Edge racing]

  Rather than shooting darts in the dark....Might be best to ask on a dedicated Cummins Diesel Forum,they are dozens of them on the Internet..

[pressureangle]

Quite a few modern engines have a screen of some kind in the gallery below the sending unit/switch. Possibly plugged up/restricted?

Does the pressure rise and fall more quickly when the oil is hot? If so, suspect restriction in the pressure circuit for the gauge.
Did you take mechanical pressure from the same port as the electronic gauge? I would find access to pressure at a distance from the electronic gauge to install the mechanical gauge and compare them in real time. Rough Edge is right, of course- there is a lot more experience and specific knowledge on the Cummins forums, if you can stand it long enough to find a pearl.

[John A]

Just a guess of course but is the oil pickup sealed by an o ring?  Maybe it has a suction leak there or maybe someplace along it. After re reading the symptoms, I don’t think it’s that unless an o ring is moving.  Maybe the attitude of the engines is different so the oil level in the sump is different and if there is a leak on the suction side covering and uncovering the leak could correspond to the symptoms.  However I think the bypass valve would be the most likely culprit

[Tom H]

The mechanical gauge is connected into the same block that has the electric. I think there is another place to add a gauge, I'll look.

I decided to ask about this here instead of a Cummins forum because there is a wealth of experience here that I feel I can trust. People here have pretty much seen this and done that, so I thought someone may have had the same problem on their tractor, heavy equipment and would be able to tell me what fixed their problem. I searched for hours using various terms and browsing the forums. The answers that I was reading were about the same as I'm getting here. The was not a resident mechanic that said, oh yeah, this is the problem. Change this and all is fixed.

I did find a solution that did seem to come up fairly often. The pick up tube. If it was not for the slow drop in pressure with the engine shut off and not turning, I would be looking at that first. But again, I think we at least have to lift the engine to get the pan off. Did I mention the engines are under the floor in the cabin.

That you all again so far!!
Tom

[Rough Edge racing]

  Ok,I poked around and got some info....Cummins says the minimum hot oil pressure for a  6B serie is 10 psi at idle and 30 psi at rated power...On the oil pressure dealy there's talk of restricted oil coolers, oil filter adapter issues and the type of oil filters...

[mondtster]

I did find a solution that did seem to come up fairly often. The pick up tube. If it was not for the slow drop in pressure with the engine shut off and not turning, I would be looking at that first. But again, I think we at least have to lift the engine to get the pan off. Did I mention the engines are under the floor in the cabin.

I don't think I'd bother with that yet. While the suction tube does occasionally cause trouble I don't think it would act like you describe. You may have a delay in building pressure with a suction problem but I think you'd have continuous problems while the engine is running and it wouldn't cause the delay in pressure drop off after the engine is shut down.

The good news is, much of the oil system is contained on the plate with the filter header on it. I suspect your problem lies there, although I'm not positive. That should be much easier to pull and inspect than lifting the engine to drop the pan.

How much has this engine been run since the problem developed?

[Tom H]

Thanks for the replies.

RER, I found some about the filter, but not about the cooler. That is something we need to look at.

mondtster, Thanks for the info. It does seem that all the flow and filter is in one place.

I looked at a workshop manual for an engine like the one we have. Difference is the oil gauge "plate". The plate we have has about 3 or 4 holes to mount sensors. I did my best to find some sort of "check valve or ball" that would cause the oil pressure to come down slow. I can't find one. The only thing close to a check valve is the pressure relief valve. This, if stuck, I would think would cause a low oil pressure issue. I don't think it would cause a delay in pressure.

Again, thank you VERY much so far!
Tom

[Ryan]

I thought some more about this today. Fluids don't compress, so once the engine stops, oil pressure should drop, too. If there is still pressure after shutdown, it has to be caused by either a "reservoir" of oil being pressurized by a pocket of heated air, or a mechanical force that keeps pushing oil in the passages that would maintain pressure briefly. So, could there be a pocket of air in a filter? As long as the pressure is holding after shut-down, it would have to be a large air pocket or a mechanical system with a long stroke.

I don't know what this means to your issue, but it is food for thought.

[Tom H]

I had a long chat with my friend after he read this post.

We have decided to move the mechanical pressure gauge to the top of the oil filter. That is the closest to the oil pump as we can get. Then see what pressure we get. We are both thinking that it could be a clog somewhere, maybe, as mentioned, in the plate that the electric gauges screw into.

What I found yesterday:
Pressure takes about 40 seconds to show up on the mechanical gauge that is in the plate. Again, we will move this to the oil filter and check again.

Once pressure is up....COLD...Aprox. 58# at 1000RPM. Aprox. 60 at 2400RPM
At normal operating temp.... Aprox 50# at 2400RPM. About 10# at idle

The pressures are within the spec for the engine. Minimum 10# hot idle and is well over the hot minimum of 30#. Again we are at almost 60#. I think we can rule out the oil pump for the moment until I get a reading from the oil filter housing.

The other engine was rebuilt about 2 years ago. Once the old engine gets the pressure up, the pressure, per the electric gauges, are about the same and do follow each other.

We thought about the delay in pressure. Could be a bad oil pick up in the pan. We don't think so. One the engine is warm, the pressure comes up quickly even if the engine was shut down for an hour or more. Also, the oil pressure doesn't fall quickly then shut down, it takes about 1-2 seconds for it to drop to zero. The rebuilt drops instantly.

We have more testing to do. I'm really thinking that the engine is getting pressure from cold start up and the delay may be caused but gunk behind the plate where the gauges are screwed into. If this is the case, we'll pull the gauge plate and then flush the engine with ATF and see what happens.

Thanks again!
Tom

[Don G]

Well here is my take on it, my employer runs about a 1000 of these Cummins engines in the oil industry, look in the photo and you will see where your oil pressure pick up should be, that is right off of the main galley. As far as pressure dropping off gradually, that is exactly what you want to see, that means that there is sufficient restriction to pressure loss due to the oil clearances being correct. I would put a new oil filter on and then see if your pressure comes back, we had a rash of low oil pressure scares in the 5.9G and 8.3G engines due to too long a run time on the filters.  DonG

[Tom H]

I wanted to mention that once we move the gauge over to the oil filter top and check the pressure. We also planned to change the oil filter. It's a new filter so there shouldn't be a problem. We also are pretty sure that the delay in startup pressure was there before we did the last filter and oil change. We'll check the pressure with a new filter and go from there.

DonG, I read about some filters having problems or being restricted and causing a low oil pressure issue. The issue we have is no so much low pressure, it is that there is an aprox, 40 second delay for the pressure to read on a mechanical gauge as well as the electric when the engine is first started for the day and cold. Once up to temp, the pressure comes up "ummm...normally", but just a tad slower than the rebuilt engine.

Thanks again,
Tom

[boatdetective]

No one has mentioned an oil sample- send something out to check for contaminants/wear metals. I use Polaris in Indianapolis- excellent. You can go to Boatdiesel.com- lots of info there. One of the moderators, Tony Athens in San Diego is a Cummins guy and very helpful.

[Tom H]

I hooked up the mechanical gauge to the top of the oil filter, no change. Next is to change the filter and see what happens. Probably get to that this weekend.

Thanks again,
Tom

[Tom H]

For those still interested.

It appears that the new oil filter was the issue. After changing the filter to a Wix brand and running it for about an hour with 5qts of ATF (remember the engine holds 15qts), we get pressure within a few seconds when hot. With the engine completely cold it takes aprox. 5 seconds for the warning buzzer to stop. The pressure when you shut it down still goes down a bit slow compared to the other engine. We'll see where that goes after the ATF has had time to work.

Thank you all again for your help!!!
Tom

[Ryan]

Thanks for the update.

[oldbike54]

 

 Dusty

[80CX100]

After changing the filter to a Wix brand and running it for about an hour with 5qts of ATF (remember the engine holds 15qts) after the ATF has had time to work.

     Tks for the update, Glad to hear it's coming around cheaply.

     "Wix" is not a common filter in this area, but I think I can get it by mail order; are they highly thought of down there? The reason I ask is, I recently bought a tractor with HST, the dealer HST filter is almost $200, but I think I can locate a matching jobber "Wix" filter online for $45-50, if they were good quality it would be worth the hassle.

   How did you arrive at the 1 to 3 ratio for the ATF/oil, was that a WAG or prior knowledge?

   How long will you run the ATF or let it soak in the engine system?

   My G5 had really dirty oil when I got it, I ran diesel oil through it for a while to clean it up a bit, but I'm almost thinking of running a bit of ATF though it.

   Hope the oil system continues to improve for you.

   Tks

   Kelly

     

[Tom H]

Kelly,

Wix has been around for many years. It was not normally sold in the local auto parts store, but by places that sold to auto repair businesses. I don't know for sure what the quality level is, but then again, Fram has been around a long time and when I was searching for an answer to my problem, Fram was frowned upon for this engine. I don't know why. BTW, Wix makes a filter size for the Guzzies.

My friend has used ATF in gas engines before. In a 5qt system he would use 1-2qts. He plans to run the ATF until the next scheduled oil change. I'm a little nervous about that. We do plan to monitor the hot pressure level for idle and cruising. If it seems a bit low, we'll change it shortly.

I've read that diesel will work as well, but I think I'd change that out in a few hours of running at least. On a side note, I cleaned my Eldo with gasoline in the oil. Well, not intentionally. Forgot to turn off the fuel at a lunch break and rode about 100 miles and decided to check my oil. It poured out of the fill hole. Yes, I did change my oil right there at the parts store.

Tom

[80CX100]

I've read that diesel will work as well, but I think I'd change that out in a few hours of running at least.

       What I used wasn't deisel fuel it was a 10w40 Deisel Oil with heavy detergents (no name Rotella), I'm hoping it cleaned a lot of crap out and didn't loosen any important bits 

       Tks for the info

       Kelly

[rocker59]

   On the oil pressure dealy there's talk of restricted oil coolers, oil filter adapter issues and the type of oil filters...

This is where I would look.  Starting with the oil filter.  Then the adapter.  Then the cooler.