DD 6-71 Oil in Airbox (2024)

Re: DD 6-71 oil in airbox

Blower seals.

Pull the air intake off of the blower so you can look at the rotors. If you look in at an angle, you should see oil on the inside of the blower end housings, if the seals are bad.

Rick

Re: DD 6-71 oil in airbox

Yep, you got BAD Blower Rotor Shaft Seals in there somewhere. DO NOT run the engine until you replace the seals, ALL OF THEM, as if you do, your are cruis'en for a "Scream'en Jimmy Run-a-Way, and those are about as fun as a Hand Granade, in a closet..... Just Say'en......

Re: DD 6-71 oil in airbox

Yup, what Bruce said above..... fix it first!
JH

Re: DD 6-71 oil in airbox

Thanks will look at that next weekend.

Re: DD 6-71 oil in airbox

What kind of oil are you running? these engines need a straight-weight SAE 40 in the summer...it could be wiping oil off the rings into the airbox, if the rings aren't seated yet. Make sure the airbox drain is not plugged, like the others said, it's not a good situation...

Re: DD 6-71 oil in airbox

Dirk if your 6--71 DD oil leak in air box is not fixed check if the rebulder of your engine have not used a standerd outside diameter sleeve in an oversised block hole' P erhaps you can mesure the old sleeves to know if this hapened Hi Rodrigue

Re: DD 6-71 oil in airbox

Yep........I agree, I sounds like blower seals.Has the blower ever been tripped or air intake been covered when running at a higher RPM? I have heard of them sucking the seals out of the blower from this.

Re: DD 6-71 oil in airbox

Depending on the age of the blower, new teflon seals and wear sleeves are available to replace the polyacronide seals which most likely came with the engine.
If the seals are completely shot, when you remove the air intake manifold, oil will be pooled at the bottom of the blower.
If the rotors are blackened, your seals are just at the point of failure, and ought to be replaced.
If the blower is clean, and there is no oil on the rotors, you airbox is full of oil blowby which cannot escape out of the slobber tubes. Be sure they are clean and free of debris. Stick your air compressor nozzle at the end and blow in for a second or two to be sure they are clear. You can also use a little kids pipe-cleaner if you are not inclined to using an air compressor.

As others mentioned, you want a rather clean airbox, or else you are feeding the engine more oil to burn. I have had good luck cleaning the air box with paper towels, and a spray can of diesel fuel. Be meticulous and clean everything. It can take some time.

1 gallon of oil consumption per hour is alot. Are you sure that you are filling your engine up properly. On any 53/71/92/110/149 the full mark is calibrated to the point 1" below the machined deck of the block, (the point where the oil pan bolts to)
You should only use Chevron Delo 100 or other suitable straight weight 40 oil with very low ash content. I am using Chevron URSA which is more readily available than the old Delo 100, and I have had no problems with it.

Chris

Re: DD 6-71 oil in airbox

another source of oil is the wrist pin retainers, if whom ever overhauled the engine did not use the proper tool and vacume test the retainers then it could be your problem. also no matter what; you will have oil out of the airbox if you do not quick put oil in it as it is out of oil.

Re: DD 6-71 oil in airbox

Easier to check the blower seals first before getting to deep...( look for the little things first ) I have an 8V-92 in a 4200 transtar that use be the biggest wrecker in my area, "the 92 is a transplant" the original owner had it delivered to a shop on a pallet to be overhauled completely and from the time it was fired up untill now it slobbered oil like crazy and it only has about 65-68,000 miles on it, Dad is a retired diesel mechanic...40yrs... we looked it over and it seems that the wristpin seals are leaking, just like what Bruce said in the post above, Hope you dont have to go that deep.

Jim

Re: DD 6-71 oil in airbox

Let's not forget When It comes to a 2stroke Detroit there are a few rules to abide by... 1. There are 2 kind's of people, Those who Swear BY Them, and Those who SWEAR AT THEM!!
2. If it ain't leaking oil somewhere, then it's probably out and
3. The only way to drive it is by slamming your thumb in the door before getting in the cab, so that you are pissed off

One exception to rule #2, is having the right Detroit mechanic can keep them from leaking... I knew a good one, that would get about a half dozen tubes of silicone whenever over hauling one in order to prevent leaks. And my one instructor @ college was a Detroit trainer who loves 2strokes (Terry Boroff)... I heard he overhauled a 6-92 for a guy, and a couple yrs later the guy learned how Boroff kept it from leaking when he removed the valve covers... "I had to scrape off about 4 layers of paint to get them covers off", but it never leaked

Re: DD 6-71 oil in airbox

Another issue not mentioned is the type of oil being used. All 2 cycle Detroits must use single weight low ash oil, #30 in winter and #40 in summer. Multi grade oil (15w-40) will cause greater oil use and will lead to cylinder/piston scuffing. Also, light to no load running will cause some additional oil use as the pistons don't get to operating temp and they pass oil by the rings. Under what load condition is the engine using this amount of oil? What is the water temp? Should be 165-185 at the least.

Sorry; didn't see K-tron's comment at the bottom of his post about the oil.

Re: DD 6-71 oil in airbox

What you can do is get an air tank "with a Gage and safety valve"fill it half full with 30 weight oil pressurize it to 60 psi drop the oil pan " easier than taking off the head" port the tank via a hose with a valve on it into the oil galley, open valve look for drips coming down from liners, look into blower, and take air box covers off and look into the liners themselves.
Bernie

Re: DD 6-71 oil in airbox

To find the cause of oil consuption that severe, I would start with the rebuilder. A 6-71 that old would have had figure eight liner ports and probably HV7 injectors and a 2 valve cylinder head when it was new. The rebuilder has changed a lot of parts and I wonder if all the parts are compatible. I'm guessing the rebuilder was not a Detroit Diesel dealer. You are in for a real nightmare I'm thinking.
Camshaft and injector timing may be a partof the problem I wonder how well the engine starts and runs. Was the engine run on a dyno after rebuild?? Does it have a good load now when it runs??
I had a mysterious 4-71 oil consumer problem to solve once and what it came down to was to find out where the oil was getting into the air box. To do that, I made and installed clear plastic airbox covers on the engine and dyed the engine oil with a red dye from a Caterpillar dealer used to dye track roller oil. The source of the oil in the airbox was a failed gasket on the rear timing gear plate, at the rear camshaft bearing. The gasket was installed with silicone, the silicone made the gasket slippery and the pressure oil pushed part of the gasket into the airbox. It is not impossible that your engine may have a similar problem, for what it's worth Good luck

Re: DD 6-71 oil in airbox

One last thing that hasn't been mentioned. The pistons should have been installed from the Bottom not from the top, as this can damage the oil control rings, which never pass the liner ports.

Re: DD 6-71 oil in airbox

I have thought about this engine overnight and remembered one other thing that caused quite a few oil consumption problems in the mid nineties. For a short while, Detroit Diesel produced crosshead cylinder kits with the piston skirts having no drain holes in the oil ring grooves, for 71 and 92 series engines. Strangely, engines assembled with these "updated" cylinder kits ran ok for the first 500 hours or so but then, oil consumption problems and excess oil draining from airbox drains became issues with many customers. The customers with the most problems were oilfield service rig engines that spent considerable time at low idle speed. I recall a customer with an 8V92T truck engine that became so bad it would actually run wild for a short burst, after idling a short time, because there was so much oil in the airbox. There was detonation happening inside the engine, it sounded horrible for the short duration,with a big cloud of blue/grey exhaust smoke, it was a miracle that the engine didn't destroy itself with bent conrods or something. Detroit Diesel stepped up and supplied new cylinder kits to replace the problem ones but a lengthy protocol detailing hours worked and oil consumed had to be followed to document the problem. The dealer (me) supplied the labour.
I learned later that some aftermarket cylinder kits were produced with the same issue, no oil holes in the oil ring grooves.

Re: DD 6-71 oil in airbox

I have a 6v71. And I have oil coming out the exhaust. I am afraid it is the wiper rings. I changed the blower gasket and it doesn't look like the blower shaft seals are bad. Anyone have any other ideas ??

Re: DD 6-71 oil in airbox

wrist pin retainers

Re: DD 6-71 oil in airbox

What oil is in it?