Cat MT665B tractor UOA

[sdan27]

This is a Cat tractor with a Sisu CTA8.4L engine. When we first got this tractor, the manual called for 400 hour change intervals that we stuck to. Just past 1000 engine hours, it threw a rod and we got the engine warrantied. They told us to cut back to 200 hour oil changes. At about 2000 hours, the engine developed a terrible knock as the valves were not getting enough oil and were terribly out of adjustment. I think that one got covered under warranty as well. I've done two UOAs and they've both come back real good. Do you think it'd be safe to go up to 300 or 350 hours? We're using Service Pro 15w-40 and 900mL MoS2. Have 2516 hours on the unit and 220 hours on the oil.

Iron 29
Chr 1
Alum 1
Cu 2
Lead 1
Tin 1
Sil 6
Sod 4
Moly 86
Bor 10
Mag 1161
Cal 1550
Phos 1340
Zinc 1504

Fuel Soot 1.5%
Vis 100c 15.3
TBN 7.4
Oxidation 10
Nitration 16

 

[tomcat27]

I dont think they're gonna warranty another engine for you. I'd stick with 200 hours as suggested.

 

[Chris142]

Where are Sisu engines made?

 

[sdan27]

They are Swedish made. Cat ag equipment is under the Agco umbrella. They still use some Cat engines in the Lexion combines and the larger 700 and 800 and 900 series tractors. The warranty was for the first 2000 hours so it's past that now.

 

[Chris142]

Given this engines history I would not push my luck with it.

 

[Mokanic]

My understanding was that the Sisu engine is their premium engine now.

 

[dnewton3]

I'd have to say that this UOA shows very reasonable wear for 220 hours on a piece of heavy equipment. To answer your direct question, I believe you can safely push out the OCI. This is at 220 hours. Try 275 hours next UOA. Then work your way up.

Now, let me add a bit of more detailed opinion:

If a catastrophic event were to happen soon, and this UOA is present, just where is the evidence of a problem? No contamination; no high wear metals. Where do "they" get off wanting to blame an OCI duration with data like this?

If there were no history of poor mechanical life, we'd all be praising this UOA and likely offering advice to push the OCI out. But because there is "history" suddenly the OCI becomes suspect? Not in my mind.

A thrown rod is likely not caused by OCI duration. Valves out of adjustment aren't caused by OCI duration.

The distinction I'm trying to make is that OCI duration is not = to lube condition. I understand and agree that OCI duration is a contributing factor to oil condition, but it is NOT the only thing. One load of oil can be in great shape in one engine, and in poor condition in another, after the exact same exposure timeline. Or, you can vary the time line, but have them similar in condition. The point is that this UOA shows the oil is good for continued use, period. A shorter OCI isn't warranted, and even if a mechanical event happens, this load of oil (or others like it) are NOT the problem!

Sounds like either poor design, or poor construction/manufacture. I know zero about this engine, but I'm always suspect to motives when someone want's to blame the lube, especially when the lube is within spec and PM'd according to OEM plans. Is there any market history on this engine? Are they "new"? Are they failing in other fields? Are they used in other industries? I guess I see the reduced OCI suggestion as an attempt to blame the lube/maintenance plan for other underlying issues.

This UOA shows very good lube performance and no contaminaion. In any other engine, we'd all be suggesting continued use of the lube and lengthening the OCI. So how does this suddently become an oil/OCI problem?

Let me pick just one example, even though I don't know the source of the comment. You said that the valves went out of adjustment due to oil not getting to the valves. How does shortening OCI duration cure this issue? It doesn't! Either it's a poor design, or perhaps a lighter grade oil might help, but OCI duration has ZERO to do with oil getting to the valves. If oil can get to the valves in the first 10 hours, it can get there at 100 hours or 1000 hours. Now, if there were evidence that the oil went grossly out of grade (way too thick) then I'd possibly agree, but this oil is in great shape. You also indicate that this is not the only good UOA (I presume that they are similar in respect to data, or you'd already have mentioned some difference?).

If there is another "mechanical problem", and your engine service company wants to blame the oil maintenance plan, I'd ask them to point to where the lube failed with EVIDENCE, and not wild conjecture.

 

[sdan27]

From what I've read online, Sisu is a pretty well regarded engine. The dealership we got it from has been real cool and didn't think the engine threw the rod due to the longer OCIs. Sometimes it's harder for them to get paid for the warranty work if Agco would have had a problem with it though. They said the original engine did have some sludge in it but since then they installed a centrigual oil bypass as a recall and not much soot shows up in the UOA. I have no idea why we had the valve train issues. They thought we were letting the turbo get too hot and it was getting the engine oil too warm. With a 5-gallon oil capacity, I think you'd need a turbo about the size of the engine to do that. I think I'll shoot for 275 to 300 hours for the next oil change and see how that works out. We use this tractor a lot in all year round except in the winter so it builds up hours pretty fast.

 

[dnewton3]

Well - it's out of warranty, so everything is in your hands now.

The dealership we got it from has been real cool and didn't think the engine threw the rod due to the longer OCIs.
I can't find any lack of logic here.


They said the original engine did have some sludge in it but since then they installed a centrigual oil bypass as a recall and not much soot shows up in the UOA.
You were changing oil at the recommended OCI (400 hours) per the manual. If it sludged up, that would be a design issue, would it not? Or at least an error in the OEM recommended OCI duration? (Presuming you're using OEM spec'd fluids).


I have no idea why we had the valve train issues.
They apparently blamed the oil not getting to the valves (which I don't think any of us believe, including you). If the oil was NOT getting to the valves, that would be a design issue. No OCI duration is going to make that better or worse, presuming they have spec'd a correct fluid.


They thought we were letting the turbo get too hot and it was getting the engine oil too warm.
The turbo should be designed by the OEM to stay cool enough that both it, and the oil, stay in good shape for the recommended OCI (which was 400 hours via the manual). The volume and flow rate of the oil in the turbo should be sufficient to cool the turbo; if not, it is again a design error. Your OCI has nothing to do with this. A turbo that is too hot may cause a sludging factor of the oil, but that is NOT the OCIs fault. It's a design issue in that the cooling capacity of the oil velocity and volume may not be great enough through the turbo. Presuming that all mechanical systems are operating as designed (water cooling, oil pump, etc) the engine should be operating within it's designed load factor. Watching the EGTs is important, but unless that unit is supplied with an EGT gage from the OEM, I don't see how they expect you to monitor it. I would presume that if it DID have an EGT gage from the OEM, then there would be some type of monitoring system for warning if EGTs get too hot. Again, design issue, because if they want you to monitor the EGT, they should provide you with a way to watch it!


With a 5-gallon oil capacity, I think you'd need a turbo about the size of the engine to do that.
5 gallons for 8.4L is a pretty good capacity, and this would go to show that the oil should NOT be sludging due to a low capacity. So if the oil IS sludging, then it's the EGT issue I covered above, or a contributing factor like poor oil return (yet again another potential design issue).


I think I'll shoot for 275 to 300 hours for the next oil change and see how that works out.
Given this UOA, and the other that I presume is similar, I'd say that is a very reasonable decision.


Overall, it seems to me you've thought this through pretty well. I think that some anomolies occured with the engine (the origin of which may have been poor design or manufacture). But your OCI, as I previously stated, likely had nothing to do with it. If you have problems with this engine, and your UOAs are as good as this one, then I have to disagree with others, and say this engine design isn't all that great. You may want to add an EGT gage if you don't have one already.

 

[Mokanic]

Originally Posted By: sdan27
From what I've read online, Sisu is a pretty well regarded engine. The dealership we got it from has been real cool and didn't think the engine threw the rod due to the longer OCIs. Sometimes it's harder for them to get paid for the warranty work if Agco would have had a problem with it though. They said the original engine did have some sludge in it but since then they installed a centrigual oil bypass as a recall and not much soot shows up in the UOA. I have no idea why we had the valve train issues. They thought we were letting the turbo get too hot and it was getting the engine oil too warm. With a 5-gallon oil capacity, I think you'd need a turbo about the size of the engine to do that. I think I'll shoot for 275 to 300 hours for the next oil change and see how that works out. We use this tractor a lot in all year round except in the winter so it builds up hours pretty fast.


Sisu is not alone in these type of problems. JD has had numerous cranks snap in two on the 300 series engines. There are only a few old-school engine builders left that still over-build the engines stronger than they have to be. Sisu is supposed to be top-notch. I don't know.

 

[PandaBear]

For legal liability issue (in case it is a material or design defect) I would not run an hour past any vendor recommendation just in case they want to use that as an argument against you.

Could it be anything else like cooling? wrong application, wrong parts, overloading, operator error, running lean/rich, or anything like that? Are you (or the operator) using it different than any body else?

 

[dnewton3]

Well, he's out of warranty (at least that's my presumption, unless he got some extense with the "new" engine. I say "new" because it's not clear if it was a true new engine or a rebuild of the initial one). So there is no real "legal liability issue" here that I'm aware of.

And, as I noted, the manual calls for 400 hours OCIs, but someone (the shop? the dealership?) told him to cut that in half. It's my understanding that was NOT OEM info, but rather some "kneejerk" advice from the place doing the work. That is why I question the validity of "blaming" (for a lack of a better term) the problems on the OCI.

If it was the OEM that suggested the reduction in OCI, then I'd have to seriously question what has happened in the market place for them to make that statement. One of two things could be the reason behind that.
1) they sold him a lemon engine initially, and had no other leverage point to blame, so they blamed the OCI
2) they are discovering historical evidence (problems) with this engine design, and realize that shorter OCIs might be warranted (because they may have over-spec'd the OCI initially, but that should result in a consumer notice campaign at the very least).

 

[sdan27]

They said the shorter oil changes were recommended in a TSB that came out. I think they found that the oil was getting overly loaded with soot from the EGR system the engine uses. That was also why they had the bypass filter added on as a factory recall. From the UOAs I've done though, the oil seems to be in pretty good shape yet with low soot and no increase in viscosity or anything like that.

 

[dnewton3]

Interesting.

So, the OEM came out and recommended a shorter OCI (at half the original duration) and also added bypass filters? I would think that adding a bypass filter would greatly INCREASE the OCI duration, not shorten it.

But, "bypass" is a relative term. There are some bypass filters to go down well below 3um absolute. And there are others that only go 10um nominal. "Bypass" is simply a term that describes the function, not the level of performance.

If all the OUAs are looking this good, I don't see why you cannot continue to use the oil.

 

[m37charlie]

Originally Posted By: dnewton3
Interesting.

So, the OEM came out and recommended a shorter OCI (at half the original duration) and also added bypass filters? I would think that adding a bypass filter would greatly INCREASE the OCI duration, not shorten it.

But, "bypass" is a relative term. There are some bypass filters to go down well below 3um absolute. And there are others that only go 10um nominal. "Bypass" is simply a term that describes the function, not the level of performance.

If all the OUAs are looking this good, I don't see why you cannot continue to use the oil.


Not to be nitpicky, but...
the "bypass filter" is centrifugal. Whose function depends more on density than particle size.
The density of carbon soot is ~1.1
Incidentally 1.5% soot seems high for only 220hrs and a centrifuge. Are you sure it was installed correctly?
OTOH the oil may be doing its' job well and dispersing soot in such tiny particles that they are too small to respond to the acceleration field of the centrifuge (viscous resistance >>mw**2R).

Charlie

 

[dnewton3]

Thanks, Charlie.

In general, the centrifuge systems work well with a constant velocity, resulting from consistent RPM. In this application, does that make more sense?