6CTA8.3's Engine Rebuild Info

[Iggy913]

Ladies and Gentlemen,

My 923A2 has been suffering from an oil/coolant mixing issue recently and I wanted to share the results of what I've found and provide some info to hopefully help others.

Over the past month I've noticed my engine oil becoming an increasingly milky mix of oil/water. Initially the water would "boil out" or evaporate after running the truck down the road getting it good and warm, however as time progressed the "milk" got thicker to the point where I had to do some investigating.

You can get a coolant pressure testing kit which will allow you to do just that and pressurize your cooling system and begin to search for leaks. Before I bought/rented that I pulled the oil pan to begin looking around. I quickly noticed coolant running down the cylinder liners of #1 and #2 cylinders. That's a pretty tell tale sign of a damaged liner or liner o-ring. In either case the only repair option is to take the motor down to a bare block to get to those parts.

Over the last few weeks I've dedicated a few hours each day to the teardown process. I was a certified diesel tech at one time so I wasn't going at it blindly. Before anyone else attempts an "in chassis" rebuild let me make you aware of a few issues your likely to find.

First some good, these motors are commercially available Cummins 6CTA8.3's and there is nothing "military" about them so please don't be scared thinking you have to find "government issued" parts from years past. There is a serial number located on the fuel pump housing and if you give that to any reputable diesel parts supplier they can set you up with everything you need. I ordered all my parts from "Cummins Parts Direct" pricing was the best I found, customer service was great, and the parts aren't made in China. I ended up with a complete overhaul kit, including cylinder liners, rod bearings, all gaskets and seals, thermostat, oil cooler, and various other hoses and fittings, all were spot on perfect replacements.

Now the bad: you will have to pull the injectors to remove the cylinder head, they will be stuck due to age/corrosion. Don't be fooled into thinking you can twist or pull them out by hand or some wrenches. I ended up dropping a piece of chain over the head of the injector, threading on a nut, and attaching the other end of chain to a 25lb dumbell and used it like a massive slide hammer, still wore me out completely by the time all 6 were out. Do send your injectors out for rebuild after this, due to this corrosion and unknown age we had all ours serviced just in case.

Next the exhaust manifold, you will break some of the bolts holding it to the head unless your some kind of magician. Don't fool with EZ outs or extractors, I tried and nearly broke some of them too, just take the head to a machine shop and have the broken bolts removed, its a good chance to also have the head pressure checked for leaks, and decked for flatness.

At this point you'll be ready to remove the liners themselves, here again don't be fooled by back yard mechanics saying you can drive them out with a hammer/punch or chunck of wood and a floor jack. I bought a puller off ebay for cheap that the seller made perfect to measurements I took on the motor and gave him. The liners were all out in 10 minutes with the puller and no damage done.

Before reassembly I meticulously cleaned and lubed everything making for a very plesant process. Just take your time, use the right tools, and this massive job is actually pretty easy compared to some automotive tasks.

Sorry for the length but I thought it would be helpful to some, if anyone needs more help feel free to PM or email me.

Mike

 

[M35A2-AZ]

Mike, Good write up, look forward to the reassembly write up with pics.

 

[Iggy913]

Taking pictures with a brief description for each is no problem. Uploading them all here is somewhat tedious. Is there any other way to do it faster/easier then taking the picture with my phone, uploading to photobucket, then bringing them over here in a post?

 

[gringeltaube]

Yes, email them to me and I can/will post them where you want.



G.

 

[Iggy913]

To anyone who may be having this milky oil issue, if you want to pull your oil pan to see if you have a liner/o-ring issue you cannot remove the pan completely with the truck sitting on its wheels. The pan will hit the front axle and the pickup for the oiling system itself housed inside the oil pan.

To remove the pan you must either lift the front of the truck via the frame or bumper to allow the suspension to drop down and give the neccessary clearance. This is difficult and dangerous due to the weight your playing with and the height you need to lift it.

Option #2 is to lower the oil pan until it sits on the front axle, this will give you enough room to reach inside and remove the entire oil pickup assembly from the engine block, its 3 8 or 10mm bolts. The pickup assembly will then fall into the oil pan and you can wiggle the whole pan out from under the truck.

Once its gone its very easy to look up at the bottom of the motor and see if you have coolant leaking into your oiling system.

I should also mention I'm using a Cummins dissasembly, inspection, abd rebuild manual circa 1986 to continually reference. If I can answer any questions for anyone please ask.

Mike

 

[JohnnyBM931A2]

Very helpful information. Thank you I hope I will never have to use it..

Is this a common issue for these engines? I thought only the 14 liter engines had liner related problems.

 

[Iggy913]

The problem with any heavy duty diesel is the coolant system itself, they are very very sensitive to a proper coolant being used and monitored on a regular basis. In fact a lot of manufacturers will add a filter inline with the coolant system which both filters and adds in a chemical to keep the coolant itself at the proper PH to keep from having oxidation and electrolysis issues leading to damage to the block, liners, water pump, and varios seals throughout.

 

[JohnnyBM931A2]

The problem with any heavy duty diesel is the coolant system itself, they are very very sensitive to a proper coolant being used and monitored on a regular basis. In fact a lot of manufacturers will add a filter inline with the coolant system which both filters and adds in a chemical to keep the coolant itself at the proper PH to keep from having oxidation and electrolysis issues leading to damage to the block, liners, water pump, and varios seals throughout.

With that in mind, do you plan on installing an inline coolant filter during your rebuild? If so, pictures would be great

 

[Bandit02]

I'm very surprised Cummins was the cheapest. I would have figured IPD would have been the seller on your inframe kit.

 

[Iggy913]

The parts did not come directly from Cummins, it's a company called "Cummins Direct" it's actually an offshoot of a much larger diesel engine parts supplier who's name escapes me, but Cummins Direct is how I found them.

I did not install a coolant filter, if you keep an eye on your coolant including using PH strips you can replace and flush your coolant system before any damage is done. Use of distilled water and a commercially available "heavy duty diesel" coolant will help avoid issues as well. Still, if I was keeping this truck I would install one, there are commercially available filter setups that would fit very easily into the heater lines running up the passenger side of the block, in fact Cummins even makes a direct fit setup.

 

[Iggy913]

Ladies and Gentleman,

The truck is up and running again! Nearly 9 months since I began disassembly I have completed the project and am happy to report the truck runs without issue. I do have some photos I'll try and put up here as I have some time, however a complete "guide" on how to do it would be impractical and hugely time consuming. As a reference the book I used to complete this from Cummins is nearly two inches thick! There are just so many things to note, proper order of things, orientation, torque specs, bolt sizes, and I would hate to be responsible for someone else trying a rebuild using my information and damaging something.

With all that being said I'd like to offer help and a rebuilding service to anyone who is interested. Now that I've completed this and purchased quite a few tools that work for these motors only I'd like to potentially make use of them more than once. I'm not sure how much detail I can get into without running into an issue where I would be considered a "Vendor" by our moderators, and I certainly don't want to offend anyone by overstepping my boundaries. I have a background in diesel engines and equipment, a decent set of specialized tools now, and firsthand knowledge of these trucks, and a desire to help my fellow man and do a superior job over some subpar diesel shops.

To our mods, please advise with a PM if this is overstepping and how to correctly place an add for a rebuilding service.