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2000 986 oil vapor separator

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car symptoms:

- CEL and ODB2 codes 1128 and 1130

- excessive smoke from exhaust at startup

- oil puddle on top of engine below throttle body

I pulled the short hose connecting the oil vapor separator to the intake

and there's liquid oil in the hose. Is that normal?

next I was going to remove the throttle body/intake and see how

much oil is laying around in the system.

I don't know if the separator is not working right, or the oil is just normal accumulation

from 5 years of vapor condensation. Any way to test the separator or other suggestions?



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search for oil bellows tube. no direct answer on why this could cause oil to be sucked into intake, but I'll pull the separator again and check the tube.

if someone can explain how oil in the intake gets there, that would be helpful, instead of the generic "the oil separator failed, replace it". A new separator comes with a new bellows tube, so what is really at fault?

Edited by notmycar2
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NotMyCar; Next time you send a renTech an email, manually type in your EMAIL address in the message so they can reply, instead of having to track you down on the board.

I had a blown motor.

Bad Rings or hole in piston was pressurizing the block, thus forcing Oil out

of the breather [oil separator] along with the exhaust gasses and per US Emissions regulations, the

breather must feed back into the intake so the escaping gasses will get

burnt. That is how oil gets into the intake.

The other possibility for your friend, is that the oil separator has failed

or its return is clogged. They are not too expensive ~$120 I think, and not

to hard to replace ~2hrs. If you disconnect the hose from the intake to the

separator and see if there is pressure coming out of the block, you can

determine if the motor is failing. There is only one hose from the oil

separator to the intake, near the throttle body, real easy stuff.

Ignore the other stuff in the pics, the engine was supercharged [TPC System

$6K], 0-60 in 4.95 sec 289HP, VERY fast, but it probably helped my engine





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  • 3 weeks later...


I cut open the round top of the separator. Inside is a diaphram and restriction mechanism. It appears the purpose is to throttle the air flow through the separator when the intake vacuum goes up.

Assuming the tear I found in the diaphram wasn't created by my chopping the thing open, the symptoms are all explained.

The tear acted like a vacuum leak to the intake, hence the lean condition and codes P1128 and 1130. Since the diaphram mechanism was not blocking the vacuum, oil was simply sucked into the intake where it puddled.

The oil vapors that accumulate after engine shutdown burn off when the car is started again, resulting in a rather impressive smoke-screen.

The only thing not explained by the separator is the oil puddle on top of the engine. That appeared to come from the oil fill tube joint. The latest version of the tube doesn't look like it will help a lot - the updated tube is easier to pull apart, but the basic design is still "a pretty stiff plastic tube getting clamped around a solid plastic tube" ... not good considering which way the oil is flowing.

Anyway, some notes:

you can replace the oil separator from the top. However, it's easier if you disconnect the oil fill tube. Assuming you don't have the latest fill tube and neck, use a hairdryer to soften the plastic a little before attempting to pull the pieces apart. It's not mandatory to split the fill tube, it just gives you more room.

If you have oil in the intake, remove the intake pipes from the throttle body forward, including the cross pipe. You'll need to mop out the oil, and when the intake plumbing is off, you have lots of room to deal with the separator.

Buy a pair of locking hose clamp pliers with ends that can swivel...you really need them. I tried using some small vice grips, and invented a couple dozen new four letter words before popping out to the tool store. The pliers do what they are supposed to.

When replacing the separator, install the bellows hose first before inserting the plastic drain pipe into the engine. That will let you tilt the separator and get your arms down both sides to push on the hose.

If you do replace the oil fill tube and are reading the TSB, you don't need two people. However, to get the new tube onto the service port unit, you need those locking pliers to hold the clamp open from the engine bay side. A second person would be handy to hold your glass of scotch, though.

If you also replace the fill tube neck (the part that connects to the top of the engine) because, for example, you leaned on it and cracked it, you'll need a crows-foot wrench to remove one of the bolts.

If someone needs my old bellows tube, toss me a message and you can have it. It's got 45K miles on it, and is still soft with no evidence of cracking. Apparently you cannot buy the hose itself, you have to buy a separator to get a new one.

total cost of repair around $150 for a new separator ($88), oil fill tube, and fill tube neck.

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