After a week of spectacularly sunny weather with highs around 15C / 60F it is now a notably colder 10C/50F and drizzly Sunday so I’m taking the day off from boat work and enjoying being snuggled into Möbius’ toasty warm SuperSalon taking in the world outside the 360 degrees of windows.
We’ve got a bowl of buttery fresh popcorn and the two pups beside us so makes for a very comfy spot to be in. A time like this has us reflecting on the crazy and challenging times we all find ourselves living in the past few years and the past week in particular. Difficult to take it all in and make any sense of it, yet most of all we are feeling especially grateful and thankful to be so fortunate.
Turkey has treated us eXtremely well in so many wonderful ways. We have family and friends we love who virtually surround us in spite of being literally spread all over the world. In the most literal sense, we have each other and are living in this wonderful floating home.
Could we be more fortunate?
The above perspective is also very helpful in powering our patience and persistence with the challenges that we, like everyone else, do face from time to time. As many of you following our adventures here know all too well, of late one of those has been the ongoing hunt for the elusive cause of Mr. Gee’s lack of proper oil pressure. Thanks to all the comments, texts and Emails we receive from all of you I know that you are almost as anxious as we are to get to the bottom of this and put this recalcitrant problem in our wake. So, without any further delay …..
Mr. Gee Update
I last left you and Mr. Gee quite literally hanging in the Engine Room in THIS post back at the end of January and then last week I let you know that I had just returned from a short trip up to Canterbury England to spend some time with THE eXperts at Gardner Marine Diesel and bring back a few parts.
Picking up from there, here’s how all those pieces fit together this past week.
This coloured illustration of the lubrication oil pipework system from the Gardner 6LXB manual will help orient you as to how the oil flows. The marine version of the 6LXB does not have the Green ‘scavenger’ oil system so you can ignore that.
Focus on the Red circuit that goes from the oil pump inside the sump in the bottom Right corner which pumps the oil to the horizontal Red pipes and fittings you see on the bottom of the Main Bearings on the crankshaft.
Take particular note (click to expand any photo) to the cast iron fittings # 40, 41, 42 and their rubber O-rings #30 7 47.
Here is what those parts looks like in reality on the bottom end of Mr. Gee with the Oil Pump on the far Right.
This is what that whole pipework’s system looks like when removed and note the black rubber O-rings in the middle of each fitting.
As I’ve been chasing down every possible lead on where the oil pressure could be leaking out, I kept coming back to these rubber O-rings that seal the pressurized oil flowing through each cast iron fitting bolted to the Main Bearing caps.
At first glance after removing these fittings you might think that everything looks fine and you would just move on to look elsewhere. But you’d be wrong!
Looking closer you start to notice that the rubber has marks around the outer and inner diameter where the rubber seems to have been pinched and cut?
When you remove the O-rings and zoom in closer with your magnifying glass it gets worse. The rubber has been sliced open.
Oh, and did I mention that all the photos of the O-rings above are brand new and only been installed and then removed from the engine without starting it.
Here is what happens after the engine has been run for about 7 hours. The pressurized oil flowing past the cut open O-rings appears to erode the exposed inner rubber more and more until the seal is broken and the oil pressure begins to drop more and more as the engine runs.
At least that is the best scenario I could come up with. However, in the many hours of discussions I’ve had over the past few months with true experts on Gardner engines and diesel engines in general this just did not make any sense. GMD and other Gardner shops have rebuilt literally hundreds, likely thousands of 6LXB engines overall and using these exact same parts and O-rings and none of these have experienced any such problems with decreasing oil pressure, so there was no consensus on the conclusion I had come to.
What else to do but dig in deeper and continue testing and checking EVERY part of the lube oil system. Still finding no trace of other problems that would explain the loss of oil pressure, I felt it best to eliminate even remote possibilities so I replaced the oil pump seen here that checked out fine but just in case I ordered a new one …
…. and similarly replaced the copper oil cooler tube with new ones.
eXtremely looooooooong story short, the low oil pressure continued and the root cause of this remained more elusive than ever.
The damage to the O-rings continued to baffle us all and none of us could explain how or why this was happening and seeming to only happen on Mr. Gee and not on all the other 6LXB’s restored with all the same parts. Yet, I had conclusive proof that they were being damaged immediately upon installation and whether it was the cause of the low oil pressure or not, I had no choice but to resolve this and be able to know for sure that the next time I installed a new set of O-rings they would NOT be damaged.
By now I had quite the collection of O-rings from the various rebuilds and all my tests and all the evidence and data I had from all of this caused me to conclude, even though it made no sense, that there was simply more volume of rubber than there was volume of space in the groove they fit into that was machined in each cast iron fitting.
You can see this quite clearly here with a new never installed O-ring on the Right and one previously installed and removed on the left.
While I could not explain the why or how, my testing seemed to prove that this was indeed what was happening.
Here is one of my “test reports” I wrote up and sent to Michael and James at GMD and my good friend and diesel expert Greg.
Can you spot the pattern that is the clue to this riddle? Read on to see if you’ve got it.
The ONE data point we did not have was what the factory depth and tolerance was for those grooves. GMD had sets of the original drawings from the Gardner factory but this dimension was not shown. I measured the depth on the fittings out of Mr. Gee and the ever helpful James at GMD measured some he had on hand and they seemed to be about the same but I decided the best if not only thing left to do was for me to fly up to GMD and pick up a set of all these cast iron fittings they had on hand out of other Gardner engines they had dismantled.
James very kindly spent several hours with me as we went through all my photos and data as well as looking over my growing collection of badly damaged O-rings from the previous rebuilds and my many bench tests. It also helped that we had had a stripped down 6LXB that James was just starting to rebuild to refer to.
I kept hoping for some Aha! moment to happen, to find something I had not checked or replaced or some mistake I was making but I left GMD and flew back to Möbius without any such revelation or resolution. BUT, I did come back with a set of new fittings in my backpack which fortunately did not get red flagged by airport security!
OK, a long and winding road to get to this point but here is what I did upon my return.
As you have been picking up I’m sure, in the course of all my work on this oil pressure problem, I’ve become a Frankensteinian combination of a detective and a scientist so I laid out all the original fittings from Mr. Gee in the foreground here and all the new ones I just brought back from GMD in the background. The numbers are the depth of each groove in thousands of an inch.
Here is my summary of the test results.
Aha! Check out the difference in tolerances of the groove depth between the original fittings out of Mr. Gee and the new/old ones I brought back from GMD. Then check out the tolerance difference of the sectional diameter of the O-rings. I think we may finally be onto something here Watson!
Note that there is a HUGE 0.028” difference between the best and worst scenarios of how much the rubber O-rings are being compressed.!
In terms of space available for the O-ring rubber, the worst scenario would be when one of the largest or “fattest” 0.192” sectional diameter O-rings is put into the smallest “shallowest” depth groove of 0.109” as this combination would compress the rubber O-ring 0.083”. Best scenario would be if the smallest or “skinniest” O-ring of 0.178’ diameter is put into the deepest 0.123’ grooves and only compress 0.055”
Perfect Storm of Tolerances
Let me put it this way; can you be too tolerant? Let’s run one more test to find out.
I took the full set of new fittings I had brought back from GMD, installed a set of the smallest skinny sectional diameter O-rings that James had so kindly sorted through their new stock to find. These ranged from 0.178 to 0.180 diameter.
ALL the O-rings in the new and deeper groove fittings came out like new. No pinch out, no cutting, no marks of any kind!
Whereas, all the O-rings in the test using the original fittings came out damaged which matches the results of all my previous tests on the original fittings where most of the O-rings came out with cuts and slices on them.
From my perspective I think this shows that all the evidence and test results match what I kept coming back to which was the proverbial dilemma of “trying to stuff ten pounds into a five pound bag” so to speak. In this case, more volume of rubber than could fit in the space available in the grooves.
Why Me? asks Mr. Gee & Me
This is the question that has bedeviled me and everyone at Gardner and I’m not sure if we will ever know the answer for sure. Based on all my testing, my best guess is that Mr. Gee and I simply ended up with the “perfect storm” situation where we ended up having fittings with “shallow” grooves that were below the minimum tolerance and these got matched up with “fat” O-rings at or above the upper end of their tolerance. Whatever the opposite of just right Goldilocks is, fat O-rings in shallow grooves are it! Not knowing what the factory specs are for the groove depth we can’t know if the original fittings on Mr. Gee were for some reason below the minimum and I would have certainly exacerbated the problem when I flat filed them to remove their equally difficult to explain bowed out condition and make these surfaces flat.
As is the norm, “perfect storms” come about when a unique combination of factors or events takes place which makes them very rare. In the case of the Gardner LXB, it would indeed be unlikely that such a situation of overly shallow grooves would happen to be fitted with overly large O-rings and thus be extremely rare. What I have shared with GMD and any other Gardner rebuilders, is that it is well worth the few minutes it takes to use a digital Vernier caliper to confirm that the depth of the grooves is never less than 0.120 and that the sectional diameter of the O-rings is never more than about 0.185”. I would imagine that this range is the norm and so even left unchecked there would rarely ever be the kind of loss of oil pressure that has plagued Mr. Gee and me.
In any case, at last I had a path forward where I could be confident that by using all ‘skinny’ 0.178-0.180 sectional diameter O-rings and putting these in fittings with the deeper grooves, there would be the Goldilocks amount of space for the volume of rubber so there would be no squeeze out and pinching. At the very least I have now removed the O-rings from the Most Wanted list of suspects.
I think so. I hope so! But alas, I won’t know for sure if I have finally found and fixed the root problem causing the oil pressure to drop until I have got Mr. Gee up and running with full oil pressure for a few hours and then head out on some more sea trials to ensure that the oil pressure holds up under load.
At the very least I’m delighted to have at least finally resolved the mystery of how and why the O-rings were being damaged which has been the conundrum wrapped in an enigma that has been vexing and eluding me for months now.
Yesterday I spent all my time putting Mr. Gee back together again; hopefully for the last time! Tomorrow I will lower him back onto his engine bed, fill him up with oil, reconnect all the hoses and re align the prop shaft and CPP output flanges. With any luck I should be able to start him up later this week.
As is my habit every time I start Mr. Gee, I will use the hand crank first to spin him up for a few minutes and check that there is oil pressure registering on the gauge. This ensures that all the oil galleries and bearings are full of oil prior to starting and reduces the chances of premature wear in the first few seconds after start up.
If all goes well this week I will at least be able to bring you news and video in next week’s Möbius World update that Mr. Gee is back up and running AND with full 35 PSI oil pressure.
Stay Tuned for the Season Finale!
Whew! if you’re still reading, you’re to be commended for your patience and persistence. This has been an eXtremely long and winding journey for all of us and I do thank you all for joining me along the way. I will do my best to wrap up this ‘murder mystery’ series and bring you the final episode in the coming weeks. Stay tuned for that and in the interim please put your comments and questions in the ‘join the Discussion” box below.