mysterious oil loss. no oil leak

[mekaeel]

good afternoon all.

my engine loses oil noticed by drops in the dip stick level especially after highway runs approx 80 kms each time

i own a Navara AX ZD30DDT. it has 230 000km on it. full engine overhaul at 215 000 km with all nissan original parts (new pistons, rings, bearing rods, head, the works) done by a ceritified nissan tech at the local dealer. ( because thermostat got stock and the head cracked)
stock turbo and exhaust. blanked the EGR.

oil change every 5000km. i use a 15W40. (recommended by the nissan dealer for our tropical climate)

after a highway run i noticed a drop in the dip stick level and after 2 weeks time of highway runs 80 km daily the dip stick dropped by half. took 1 and a 1/2 quarts to top up. this problem continues.

so far i have searched everything in the exterior for oil leaks with no luck. have also dismounted and inspected turbo and housing for leaks. nil leaks.

no oil noticed in the exhaust nor sooth in the exhaust pipes. no noticeable blue smoke, black smoke nor white smoke.

any help or suggestions for further investigation is kindly appreciated.
thanks

 

[tweak'e]

if you keep driving does the oil level go below half?

is the turbo wet with oil or the hoses pipes just after the turbo?
really common for these to blow oil out the breather.
a common problem is people overfill with oil. every mechanic thats done an oil change on mine has over filled by a liter or so.
what i think happens is they check it after its been running, see that oil has dropped to half and put a litre in.
these engines have a really high oil level, so anything over full gets blown out he breather rather quickly.

this is why we recommend catch cans.

 

[mekaeel]

thanks for the reply.
yes if i keep driving it dips below half. at my 10 000 km after the overhaul it actually just made the lower limit.

yes its wet at the impellers of the turbo. some degree of blow by is expected with all diesels. my nissan mechanic says what i am getting is normal. a second opinion mechanic says its too much.

i actually assist/do my oil changes. drain oil warm/hot and then refill allowing sufficient time to pass so the oil settles and engine cools. but point taken about overfilling. i will invest in a catch can to see if i can account for the lost oil.

my nissan tech is opting to recheck the piston ring clearance as well as for any cracked rings/seals. but that involves the headache of dismantling the head to get to the block (more cost)

i'm wondering if i exhausted all other options before having to dig in there

 

[bods]

I wonder if the nissan mechanic offset the piston rings when fitting them... or did he just line them all up together...? Never know without pulling it apart again.

 

[mekaeel]

he off set them. i have heard about the rings still having a certain amount of play/movement. but i'm not sure if it would have this amount of oil loss

 

[tweak'e]

a decent catch can would be the first thing.
2nd is to replace the air filter and check the pre filter. the more restriction you have the more the engine tries to suck blowby out of the crankcase.

the other thing, tho its a bit late for it, is to go put a heavy load on, tow a trailer and give it a big blast. run up and down a few hills, put the boot into it. it needs to work hard, real hard.
the rings need full combustion pressure for them to wear in and if they are driven softly they don't wear in and then you get more blowby.

 

[Stelianos]

a decent catch can would be the first thing.
2nd is to replace the air filter and check the pre filter. the more restriction you have the more the engine tries to suck blowby out of the crankcase.

the other thing, tho its a bit late for it, is to go put a heavy load on, tow a trailer and give it a big blast. run up and down a few hills, put the boot into it. it needs to work hard, real hard.
the rings need full combustion pressure for them to wear in and if they are driven softly they don't wear in and then you get more blowby.

are you sure? because the owners who do it in new engines blow the most black smoke out the exhaust as well and run into problems more often!
i did as the manual said, no loads for the first kms and gentle driving switching through the gear as the manual says, for the yd25 its 1st gear 0-24km/h 2nd gear 42-40 km/h 3rd gear 40-64 km/h and 5th gear 64 + km/h.

 

[bods]

are you sure? because the owners who do it in new engines blow the most black smoke out the exhaust as well and run into problems more often!
i did as the manual said, no loads for the first kms and gentle driving switching through the gear as the manual says, for the yd25 its 1st gear 0-24km/h 2nd gear 42-40 km/h 3rd gear 40-64 km/h and 5th gear 64 + km/h.

A brand new engine is different to a rebuilt engine. The best thing is to load them up do help bed the rings in after a rebuild. Brand new engines in new cars are "run-in" on an engine dyno before being fitted. A rebuilt engine, if it is an in chassis rebuild, won't have this done. The new car run-in procedure is for the rest of the components. That being said, normally the "harder" it is run in, it will be more powerful than one that is "babied." That doesn't mean rev the ring out of it and shift gears on the rev limiter, but get it under a lot of load, without labouring it and change gear to keep the turbo in the sweet spot without letting it labour or racing it. That's also the recommend procedure for engines which are glazed up from idling for excessive periods or not being worked hard enough...

 

[tweak'e]

are you sure? because the owners who do it in new engines blow the most black smoke out the exhaust as well and run into problems more often!
i did as the manual said, no loads for the first kms and gentle driving switching through the gear as the manual says, for the yd25 its 1st gear 0-24km/h 2nd gear 42-40 km/h 3rd gear 40-64 km/h and 5th gear 64 + km/h.

the other thing is they don't want anything breaking in case something got missed during assembly. hence the 1000km first service which is really just a check to see nothing has fallen off!