Just rebuilt d750 in my b7100 with new head and have quite a bit of white smoke for a few minutes after start up. Any ideas
B7100 rebuild
- Thread starter DukeHigbee
- Start date
North Idaho Wolfman
Moderator
Staff member
Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
What all did you do to the engine? new sleeves, rings, pistons?
How does it start, easy ( light amount of cranking) or hard (lots of cranking).
Have you done a compression test?
Did you use new glow plugs?
Are you using the old injectors or new injectors?
How does it start, easy ( light amount of cranking) or hard (lots of cranking).
Have you done a compression test?
Did you use new glow plugs?
Are you using the old injectors or new injectors?
85Hokie
Moderator
Staff member
Lifetime Member
Equipment
BX-25D ,PTB. Under Armor, '90&'92-B7100HST's, '06 BX1850 FEL
any head shaving done?
Did you plasi-gage the bearings?
As NIW mentioned....... give us ALL the particulars in the rebuild
New sleeves,pistons,rings,seals,gaskets, and whole new upper end. Tried some new aftermarket injectors that didn't work. Put old ones back in. Starts pretty quickly. Only has maybe 2 hrs on rebuild. Smoke stops after a couple minutes.
Everything was gauged, and mixed. The block was decked. Everything torqued to specs.
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
North Idaho Wolfman
Moderator
Staff member
Lifetime Member
Equipment
L3450DT-GST, Woods FEL, B7100 HSD, FEL, 60" SB, 743 Bobcat with V2203, and more
Did you add the shims to make up for the decked block?
You needed to add the same amount they took off the block, to the head and to the injection pump.
If you didn't your timing is off.
And get a set of injectors as those sound like they are leaking.
You needed to add the same amount they took off the block, to the head and to the injection pump.
If you didn't your timing is off.
And get a set of injectors as those sound like they are leaking.
If it only smokes after a couple minutes, it is oil getting into the exhaust AFTER the combustion chamber, which means exhaust valve guides. Oil going into the combustion chamber gets burned right away and smokes right away at startup. Oil that gets into the exhaust stream after the combustion chamber will not smoke until the exhaust manifold gets hot enough to burn it.
Since your smoke clear up after a while, it is likely that your exhaust valve guides are letting some oil drain into the exhaust ports/manifold while the tractor is off, and then once running and the initial accumulation of oil has been burned, it does not leak quickly enough to add noticeable smoke to the running engine.
This would lead me to the followup question of, is something preventing the top of the cylinder head (under valve cover) from draining oil down into the block properly? It's possible something like a glob of RTV that was squished out into a fluid passage between two mating parts has constricted the flow of oil draining from top to bottom, leading some of it to drain through valve guides before the oil level drops below top of valve guides.
Since your smoke clear up after a while, it is likely that your exhaust valve guides are letting some oil drain into the exhaust ports/manifold while the tractor is off, and then once running and the initial accumulation of oil has been burned, it does not leak quickly enough to add noticeable smoke to the running engine.
This would lead me to the followup question of, is something preventing the top of the cylinder head (under valve cover) from draining oil down into the block properly? It's possible something like a glob of RTV that was squished out into a fluid passage between two mating parts has constricted the flow of oil draining from top to bottom, leading some of it to drain through valve guides before the oil level drops below top of valve guides.
I would not call oil smoke black. It is usually white with a blue-ish tinge when it gets heavy. Burning coolant is also white-ish although it appears 'lighter' (rises and dissipates more quickly once it leaves the exhaust pipe).
Dark grey to black smoke is usually unburned fuel (running VERY rich).
Excess fuel runs a spectrum, though. It can start fairly light and progressively get darker the richer the engine runs. On a small cylinder-count engine like a 3cyl you can also usually identify identify an issue that only comes from one cylinder because at low rpms it will be a noticeable 'puff' of smoke/sound/color instead of all blended together at high rpms.
I would suspect valve guides/seals first. Things that can cause near immediate failure are if the guides are set a little too low in the head and the seal doesn't have as much to grab onto and starts going up and down with the valve instead, or if they are set a little too high the bottom of the retainer can come down and smash the seal. I dont know if the b7100 guides have some kind of positive retention or marking (some have a groove etc) so that's just generic possibilities, like the RTV thing.
Since the engine has recently been apart i imagine all the exhaust bolts are not seized. I would remove the muffler. When you cold-start the engine next time, see if oil dribbles out the bottom of the outlet flange on the exhaust manifold in the first couple minutes of running. If the manifold happened to have been cleaned during the rebuild you could also tell if it's had oil in it just by looking in with a flashlight. Could also pull the oil fill cap after a hot shutdown and see if it looks like oil is pooling up in the head. Sometimes oil accumulates in cylinder heads because there is some kind of oil restrictor between the block and head (to prevent excess oil flow into the head) that either gets removed to clean an oil passage and never reinstalled, or someone sees an orifice in a headgasket and assumes its a mistake or oversight and drills it out, or occasionally installs something about the rocker arms incorrectly etc. Again just generic possibilities.
I'm an ASE Master Certified technician just trying to be helpful. One of my very first jobs was a summer job in an automotive machine shop 22 years ago. I have not rebuilt a D750. But i'm very sure I can.
Dark grey to black smoke is usually unburned fuel (running VERY rich).
Excess fuel runs a spectrum, though. It can start fairly light and progressively get darker the richer the engine runs. On a small cylinder-count engine like a 3cyl you can also usually identify identify an issue that only comes from one cylinder because at low rpms it will be a noticeable 'puff' of smoke/sound/color instead of all blended together at high rpms.
I would suspect valve guides/seals first. Things that can cause near immediate failure are if the guides are set a little too low in the head and the seal doesn't have as much to grab onto and starts going up and down with the valve instead, or if they are set a little too high the bottom of the retainer can come down and smash the seal. I dont know if the b7100 guides have some kind of positive retention or marking (some have a groove etc) so that's just generic possibilities, like the RTV thing.
Since the engine has recently been apart i imagine all the exhaust bolts are not seized. I would remove the muffler. When you cold-start the engine next time, see if oil dribbles out the bottom of the outlet flange on the exhaust manifold in the first couple minutes of running. If the manifold happened to have been cleaned during the rebuild you could also tell if it's had oil in it just by looking in with a flashlight. Could also pull the oil fill cap after a hot shutdown and see if it looks like oil is pooling up in the head. Sometimes oil accumulates in cylinder heads because there is some kind of oil restrictor between the block and head (to prevent excess oil flow into the head) that either gets removed to clean an oil passage and never reinstalled, or someone sees an orifice in a headgasket and assumes its a mistake or oversight and drills it out, or occasionally installs something about the rocker arms incorrectly etc. Again just generic possibilities.
I'm an ASE Master Certified technician just trying to be helpful. One of my very first jobs was a summer job in an automotive machine shop 22 years ago. I have not rebuilt a D750. But i'm very sure I can.
Last edited: