83 SD-25 engine pushing oil out Dip Stick tube.

SD diesels were widely available in the US in the 1981-86 Datsun/Nissan 720 pickups, and in Canada through '87 in the D21 pickup.

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charmalu
Posts: 166
Joined: 9 years ago
Location: Soquel, Calif

83 SD-25 engine pushing oil out Dip Stick tube.

#1

Post by charmalu » 6 years ago

A few weeks ago I bought an 83 Nissan long bed PU from the original owner. 134,595 miles. Picked it up for $1800.
I have been going through everything to get a base line to start from.

Removed the Carpets and Seat and Shampooed them with a Bissell Little Green Machine. Removed the Mouse Condo under the Passenger seat. Didn`t seem like they were in there long enough to do any damage.

Removed the floor drain plugs and scrubbed and hosed out the cab.

Got that back together, still a sort of mouse odor. maybe the Dryier Sheets will mask it.

Steam Cleaned the engine to get rid of 30yrs of oily neglect, and discovered an engine under the hood.

This being a Calif model. as I seem to understand, it is the inly one with the EGR and vacuum hoses and vac pods etc...

I removed all this crap except for the EGR. soon to make soon block off plates for that. on the hunt for some none EGR Manifolds.

removed the Air Filter housing and washed it out in a pan of gas, along with the Valve Cover to clean up that mess.

There is a metal tube from the rear of the VC with a rubber hose connecting to the Crank Case vent from the L/R of the engine. The SD-22 has a large Draft Tube, where on the SD-25 it has this small vent tube coming out the top about the size of my little finger.
The Crank Case/Blow By gassed are routed into the VC.

On the top rear of the VC is this round assembly that meters the Blow BY fumes into a little box next to and attached to the Air Cleaner via a short rubber hose. Then the fumes are sent to the Air Cleaner and directed down the intake to be burned.

Now I washed all these parts in a pan of gas, blew it out with spray Carb Cleaner to get any oily residue off. I even removed the assy off the top of the VC and washed it out and replaced it. I did notice it has a rubber Diaphragm inside it. this unit is not one to be taken apart, the top is crimped on.

Now I did adjust the valves, and got this all put back together. yesterday took it on a run to warm up the eng oil to be changes along with the filter.
I noticed oil on the R/F corner side of the VC, and the Dip Stick tube pushed up. that would be caused by pressure in the Crank Case.

Last week I took it on a 100 mile run and ran ok w/o this oil problem.134,595K to 134,825K it did ok.

I did something to create this problem with the Dip Stick. Iam thinking maybe it is the unit on the top rear of the VC that could be the problem. maybe the rubber diaphragm didn`t like the gas and Carb Cleaner wash job and is sticking. to this unit as a Air Control Valve.


OK Iam a little long winded here, but wanted to lay out what I have done so far. So any of you SD-25 engine experts out there have this problem?

The Mercedes Diesels in the late 70`s just ran the Blow By from the VC straight into the air tube just before the Turbo. then later they ran it to an oil separator in the Air Cleaner, then some condensed and drained back into the pan.

I don`t know why this tube from the Crank Case that is routed into the VC on this SD engine couldn`t just be routed straight to the Air Cleaner.



Here is what is in the FSM:

The closed-type crankcase ventilation system is utilized as a crankcase emissions control system.
The closed type crankcase emissions control system prevents blow-by gas from entering the atmosphere and keeps the internal crankcase pressure constant.
During the valve operation, the blow-by gas is fed into the intake manifold by the air control valve.
This is activated by the internal rocker cover pressure. When the intake air flow is restricted by the throttle chamber, the internal rocker cover pressure decreases. At this point, the crankcase emission control valve keeps the internal rocker cover pressure constant so that air or dust is not sucked in around the crankshaft oil seal.

Inspection Air Control Valve

!. remove rocker cover.
2. Remove air control valve from rocker cover.
3. After plugging the center hole with adhesive tape, check that air flows from inlet by orally sending air from the outlet and that air does not flow sucking air in.


OK, diving back into this thing and see what I can screw up today. ;>)


Charlie
82 Datsun KC 483K lost #2 cyl blowing blue smoke :cry:
83 Nissan LB 134K SD-25 as of 10-21-13
78 240D Mercedes $300 Parts?
80 240D 360K
80 240D Parts? $750
82 240D Parts? $440
84 300SD 270K
85 300D 363K
86 Ford F250 6.9 Diesel 221K

charmalu
Posts: 166
Joined: 9 years ago
Location: Soquel, Calif

#2

Post by charmalu » 6 years ago

I removed the air cleaner and valve cover along with the Air Control valve.

removed the valve from the VC. I can blow or sick air both directions. When I stick my thumb over the center hole of the air valve and blow, air goes through, but when I suck on the hose easy a slight bit of air will flow, how ever when I suck harder, then the air flow totally stops.

So this is exactly what the FSM mentions to check.

Now Iam at a loss.

Maybe just run a draft tube.

I did find this thread on the SD-22 and SD-25 emissions.

http://nissandiesel.dyndns.org/viewtopic.php?t=267

Charlie
82 Datsun KC 483K lost #2 cyl blowing blue smoke :cry:
83 Nissan LB 134K SD-25 as of 10-21-13
78 240D Mercedes $300 Parts?
80 240D 360K
80 240D Parts? $750
82 240D Parts? $440
84 300SD 270K
85 300D 363K
86 Ford F250 6.9 Diesel 221K

charmalu
Posts: 166
Joined: 9 years ago
Location: Soquel, Calif

#3

Post by charmalu » 6 years ago

I was looking at this Air Control Valve. Iam thinking the only thing that is causing the back pressure could be the rubber diaphragm. So poking it a little to see what it does with a small screwdriver, it tore almost like the rubber was soft. HMMM, well what do you know? a Wardrobe malfunction. :>0

So it was easy to pry it around enough to grab it with some Needle Nose pliers and yank it out. Then all that is left is a flat metal plate with some holes.

Put it all back together, and ran her down the hill to the Freeway and gave her a good run and back up to the house. Not one drop of oil and the Dip Stick stayed put.

Now was it the right thing to do? Probably not, but can`t have it blowing oil out the tube. Not really sure why it suddenly started the problem when it wasn`t doing it before cleaning things up. maybe the Carb spray was too much for the rubber? who knows.

Charlie
82 Datsun KC 483K lost #2 cyl blowing blue smoke :cry:
83 Nissan LB 134K SD-25 as of 10-21-13
78 240D Mercedes $300 Parts?
80 240D 360K
80 240D Parts? $750
82 240D Parts? $440
84 300SD 270K
85 300D 363K
86 Ford F250 6.9 Diesel 221K

ehtrain
Posts: 141
Joined: 7 years ago
Location: regina, sk

#4

Post by ehtrain » 5 years ago

sounds to me like you have excessive blow by from the bottom end... ie piston rings. could be wrong though. you could try a leak down tester if you can find one that fits diesel.... if 155psi shop air is enough even. works on a gas motor no prob

the valve cover diaphram is there to regulate the crank case pressure. my engine after rebuild wouldn't bypass that valve until the oil was hot. and even then there wasn't much blow by in comparison to say a tractor

does it smoke blue?

charmalu
Posts: 166
Joined: 9 years ago
Location: Soquel, Calif

Re: 83 SD-25 engine pushing oil out Dip Stick tube.

#5

Post by charmalu » 5 years ago

No it wasn`t blowing any blue smoke when I was driving it.

Since I last posted on this, I pulled the engine/trans and replaced the Clutch Disk, Pressure plate, release bearing, Pilot Bushing, and resurfaced the FW.

Then took the transmission apart and replaced the Input Shaft and Counter Shaft Bearings. Got that back together, then replaced the Water Pump, and thermostat housing with a better one w/o corrosion. Painted the Block, and a few other Brackets. Washed up the power Steering reservoir and painted it. Replaced the By-Pass hose and the "J" hose for the Oil cooler.

Since the Hood was off for the eng/trans R&R, I got carried away and pulled off the air grill below the windshield, and whadaya know? there was another Mouse Condo, along with piles of Douglas Fir needles packed in there. Pulled that out, vacuumed and scrubbed and hosed it out. Had a pile as large as a basket ball in the Wheel barrow.

The original owner lives under a bunch of Douglas Fir trees, so 30 yrs worth and dirt. yuk.

I have the fenders off to address a little rust issues, then one thing leads to another, bought a Soda Blaster to blast off the paint primer on the inner fenders etc... then a small Sand Blaster to hit the rusty spots. 20 gallon Compressor is way too small, and found a 60 gal 3.7hp upright Compressor off CL for $150. same one Lowes sells for $499.00. guy used it very little then stored it. In the process of getting this hooked up now.

I`ll get back to the Nissan when I can, too many other priority projects keep popping up. :>/


Charlie
82 Datsun KC 483K lost #2 cyl blowing blue smoke :cry:
83 Nissan LB 134K SD-25 as of 10-21-13
78 240D Mercedes $300 Parts?
80 240D 360K
80 240D Parts? $750
82 240D Parts? $440
84 300SD 270K
85 300D 363K
86 Ford F250 6.9 Diesel 221K

elminero67
Posts: 143
Joined: 9 years ago

Re: 83 SD-25 engine pushing oil out Dip Stick tube.

#6

Post by elminero67 » 5 years ago

I'm a little confused-had you solved the problem before pulling the motor?

Also-I still have that radiator if you need it.

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