Detroit Diesel 8-71T Oil in Air Box

Tim in Mexico

New member
Hi Smokstak Form,
I recently bought a Terex 72-61 80C wheel loader powered by its original 8-71T, I am bio stranger to the Detroits by any means, but this one has me scratching my head a little. When I checked out the machine prior to the purchase I noticed two things about the engine;
1- heavy oil (more than just the normal drips) coming from the air box drain only on left side.
2- about 2-3 gallons low on oil.

Just figured oh well its got some hours on and I'll check this in our shop and end of story. Got the machine at our place and decided to put it to work for a while to best find all its real issues, so 400 gallons of fuel, new filters and oil and off to work. Plenty of power, smoked like hell, and every time I checked the oil before starting the machine it was always 2-3 gallons low.

That soon got expensive not to mention a pain, so back to the shop with the monster loader… Quick look in the air box to find only light carbon, obviously the oil has been keeping things washed pretty well… No real issues found visually with liners, piston tops dry and compression rings looked reasonably good. Then checked the intake system, turbo dry but blower black and gummy (typical of bad seals). Replaced the blower, filled with oil and first 2 minutes of running put about 2 gallons of oil on the shop floor from the left air box drain….

Then I started the engine with left air box covers off, found cylinder 2 pumping out heavy amounts of oil from the cylinder liner ports, some from others on this same side but this may have been from the vast amounts of oil from cylinder 2 (can't be sure).

So then here we go breaking the engine down… Got all the cylinder kits out and carefully dis-assembled them wanting to find broken oil rings or one of the tin plates on the side of the piston had dis-lodged SOMETHING OBVIOUS but not the case… Everything still looked fairly reasonable to me just well used and in my mind nothing that would by itself cause such a vast amount of oil wastage.

I did find oil control rings not matched as they should be (two smooths together and vise versa), liners with about .020" wear steps, rings and lands wore pretty good, also when testing by filling the crosshead pistons up with diesel there was seepage from piston crown to skirt seal and also on a few of the tin piston pin plates, but what I really wanted to find was the problem for sure rather than a bunch of little things. I find it hard to believe that the persons running the machine prior to me would let the engine get so worn out that this was all coming from simply wore out cylinder kits??? New kits should be here in a couple days then I'll get it put back together, and see.

It just bugs me to think that I might start it up to find the same oil puddle under the air box drain because of the fact that I didn't find a real broken part yet! While waiting for parts I have been all over the block for hours looking for some damage, crack or otherwise that might explain this oil, but can't find anything at all. Everything I have seen and done says the cylinder kits are simply worn out and thats that, end of story. But figured it couldn't hurt to share this to see if anyone out there has been down this road to find a different source of the oil issue??

Thanks
Tim
 

Toesmack

Subscriber
Been down this same route plenty. I have found over the years many owners that will just keep running their equip until it flat out quits. Oil is cheaper than an engine overhaul, so they choose to go that route regardless what the mechanics have to say. Usually at that point the mechanic is expected to pull a rabbit out and put on a $10 bandaid in under an hour that will get it running again for at least 6 months. When owner has "time" to repair it properly. Then 6 months later, same story.

Sounds like you are on the right track with your screamin' green machine, obviously not your first rodeo. However I would also verify the correct dipstick is in there. Measure actual oil in it and compare to OEM specs. Complete new power packs should certainly cure the problem. High dollar to be sure, but a really long term fix likely to deliver 10 to 20,000 hours of production. That Detroit will run LONG after it should give up.

Just keep a good supply of earplugs handy.
 

Tim in Mexico

New member
Been down this same route plenty. I have found over the years many owners that will just keep running their equip until it flat out quits. Oil is cheaper than an engine overhaul, so they choose to go that route regardless what the mechanics have to say. Usually at that point the mechanic is expected to pull a rabbit out and put on a $10 bandaid in under an hour that will get it running again for at least 6 months. When owner has "time" to repair it properly. Then 6 months later, same story.

Sounds like you are on the right track with your screamin' green machine, obviously not your first rodeo. However I would also verify the correct dipstick is in there. Measure actual oil in it and compare to OEM specs. Complete new power packs should certainly cure the problem. High dollar to be sure, but a really long term fix likely to deliver 10 to 20,000 hours of production. That Detroit will run LONG after it should give up.

Just keep a good supply of earplugs handy.
Thanks for the reply Toesmak! Yes everything I know says quit worrying and just rebuild and go, but like I said looking for some feedback like yours.

The oil level was in fact verified (so I thought) when I first changed the oil and filters, I always figured about 8 gallons on a small diesel like this! I added about 8 and the dipstick was at full.

GUESS WHAT? Your suggestion made me look a little harder and checking the Terex 80C literature they list the engine oil capacity at 5.5 gallons! Ooooops. Looks like two things are going on here;
1- Crank was throwing that oil up onto worn cylinder kits that couldn't handle it. Thats why only on side was sobbing wet I bet.
2- Im just overhauling something that actually needed it anyhow, getting this out of the way before any big jobs.

Ok no downstairs to the shop to have a long hard look at the dipstick

Thanks again for your reply, it helps to listen to input sometimes! Oh and yea and the ear plugs, you know when this thing is running for sure, no mistaking the sound.

Tim

---------- Post added at 02:10 PM ---------- Previous post was at 01:15 PM ----------

Oh well, the relief and possible solution was short lived, dipstick has been positively confirmed correct :(

Was easy as the engine is apart in the shop, Terex literature list 5.5 gal (21 lts), just added 21 lts exactly to the pan with dipstick tube installed and right on the mark. So back to hoping the cylinder kits will be the cure.
 

andrewmackeyjr

New member
2& a half gallons of overfill??? WOW :eek: youare lucky the engine did not pick up the vaporizing oil and run away! vaporized oil becomws fuel real fast! glad you looked in the book huh? nothing like rebuilding an engine and then watching it blow itself to bits!:rant:
 

K-Tron

Active member
Take the oil dipstick out and bend it along the path of its tube. The full mark should be 3/4" below the mating surface of the oil pan/block, and the low mark should be 1/2" below that!

Overfilling the crankcase will cause abnormally high oil consumption, high oil temperature, and premature failure of crankshaft oil seals. When the oil level rises to the point that the crankshaft is submerged in oil, the oil will become churned and aerated by the rotating crankshaft, resulting in lower oil pressure and increased oil temperature. Foamy oil lacks the lubrication of liquid oil!

Chris
 

Tim in Mexico

New member
Guys thanks for the input, but the oil level is not an issue, as I replied yesterday as follows;
"Oh well, the relief and possible solution was short lived, dipstick has been positively confirmed correct

Was easy as the engine is apart in the shop, Terex literature list 5.5 gal (21 lts), just added 21 lts exactly to the pan with dipstick tube installed and right on the mark. So back to hoping the cylinder kits will be the cure."

Oil type is straight weight, being here in SE Mexico where its always hot we run SAE 50 in Detroits here, especially when they are well used. Might change up to SAE40 once its re-assembled as the bearings will be new resulting in better oil pressure.

Thanks for your replies, any other ideas for another possible cause???

Tim
 
J

Joe Bali

Guest
Hi Tim,
The 8v71T engine is known for fairly high oil consumption even when it is up to specifications. I hope II am not too late to offer some help. The most critical part of this egine is the oil control rings, the piston crown to skirt rings, the wrist pin retainers and the blower seals which are metal. When assembling you new cylinder kits, make sure that the piston assembly is loaded into the liner from the bottom. The oil rings should never be pushed past the ports in the liner because the fine wiper edge will be damage on the rings. Also, use the proper Kent-Moore tool for installing the wrist pin seals. Hope I was of some help.
 

Tim in Mexico

New member
Thanks Joe,
We are on the same page it seems. Looks like I won't have time to get the overhaul out of the way for about two week due to other paying projects here that need to come first. As soon as I can get back to this project and crank up the fresh overhauled version of what i'm hoping to be just a well worn out engine, I will reply and let you know what the result is.

Ive spent hours looking for some other cause because its just beyond my way of thinking that someone could actually run ann engine so worn out without stopping to correct it… With this type of oil consumption I was looking for something obviously broken, cracked, or an internal plug that had came out. But nope!

Blower and Injectors are OEM Reliabuilt, all other overhaul components are FP Diesel. We'll see soon enough I suppose.

Regards,
Tim
 

Tim in Mexico

New member
OK so its been a while to reply, always something around here BUT the Detroit is back to new state with 0 abnormal oil consumption. Always a little but air box drains dry and piston tops perfect. Actually right now the biggest oil loss is a nuisance drip on the old style oil filter, just need to get time to install the new style spin on adaptor kit and get the machine back to work!
 
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