Oil in Intake Manifold?

I have a '97 with 205,000 miles on it. It has been consuming anti freeze recently (very slowly), so I removed the upper plenum this afternoon. I found antifreeze in the plenum (small amount) and oil. I presume the oil is coming through the PCV valve--not sure. Has anyone experienced oil in the intake manifold?

The new plenum comes with a new PCV valve, so possibly, this will resolve it. I hesitate to put a new plenum on with so many miles, but the compression is good and the car has has, otherwise, been running great.

I have a '97 with 205,000 miles on it. It has been consuming anti freeze recently (very slowly), so I removed the upper plenum this afternoon. I found antifreeze in the plenum (small amount) and oil. I presume the oil is coming through the PCV valve--not sure. Has anyone experienced oil in the intake manifold?

The new plenum comes with a new PCV valve, so possibly, this will resolve it. I hesitate to put a new plenum on with so many miles, but the compression is good and the car has has, otherwise, been running great.

The inside is normally covered with a heavy layer of black oil. Remember to put both o-rings on the PCV valve! Occasionally someone overlooks the lower one.

Are you changing the lower gasket under the metal LIM?

Did your intake come with a reduced diameter EGR tube to fit into the LIM?

Soak up the antifreeze and change the oil right away to avoid damage from any residue that's in the oil pan from working on it or burning it.

Did you get new o-rings for the injectors with the UIM? Those should be replaced.

I had not planned to change the metal gasket under the LIM. Do they leak usually?

I have the a reduced stovepipe in placefrom the last time I worked on the UIM. I put in the Kenco kit and epoxied the UIM and sanded it down. It looks like the epoxy is giving away around the diameter of the stovepipe. The material is pitted and somewhat soft. It looks like it is recessed and may be leaking around it. It has had about 80 or 90,000 put on it since the kenco kit repair. I do have some new o-rings.

I will look for the o-rings for the pcv. I probably won't work on it for a few days due to the cooler temps coming in.

Remove the 2 corner inside lower manifold bolts and usel sealer on the threads, oil can migrate up these bolts and puddle in the corners.

Thanks. Should I not pursue replacing the LIM gasketl? From what I have always read, the UIM, near the stove pipe, is the weak point.

Correct on the stove pipe issue, but the lim gaskts although less of an issue can be problematic.

All finished. It runs great and no leaks.

Soak up the antifreeze and change the oil right away to avoid damage from any residue that's in the oil pan from working on it or burning it.Did you follow the advice above? I hope so, it would not be a bad idea to change the oil/filter again after about 500-miles!

I found that the lower PCV o-ring was compressed and was sideways. Also, there was no spring on top of the valve (at all). I don't recall that there was ever one in there. I changed the PCV valve once, many years ago.

I just tightened each lower manifold bolt slightly and put the upper manifold back on. There was no indication of antifreeze in the valve covers--just black, dirty looking oil. I am fairly sure the leak was only occurring in the UIM. If the LIM starts to leak, I'll just pull it all off. It really doesn't take long to remove the fuel rail and UIM, especially if the throttle body is left attached to the UIM. It seems to be doing fine now. I do need to change the oil soon.

Sounds like everything is OK. In case someone else reads this in the future, I personally wouldn't do a UIM, without doing the Lower.
The gasket GM used back then has problems. My experience is, if the LIM isn't leaking, it's getting ready to.
Chris.