"In addition to the EGR in test mode, I have the PCV line in test mode and I'm evaluating that now. The oil cap does not get sucked down as before but it's not doing the tea pot dance either, it just kind of rattles a little bit. We'll most likely fab up some kind of oil separator since I was getting a lot of oil into the compressor intake elbow. "

By test mode do you mean that it is still on just not working? I am exempt from emissions testing BUT I still need to have the original parts on car. It also depends on who does the state inspection.

Please explain test mode, Also on your 300 does that have the same motor as mine? 603xxx

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86 300SDL. 250,xxx on #14 Head. One eye always on temp gauge.. Cruising towards 300K

I've gotta disagree with Sean on this one...
Oven Cleaner is a Super "Base" (Opposite of Acid) Cleaner...

I will not recommend it's use when the possibility of "NON-COMPLETE" removal
exists.

"I ain't gonna trust my intake tract/engine to my ability to "Rinse" a BASE out
with a Carwash."

If you've got the Intake Off...
Take it to a Radiator shop and have it "Hot Tanked",problem solved.(Maybe $20.00 USD)

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'84 300SD sold
124.128

I agree with Compress, simply removing the crossover and having it hot-tanked will get all the guk out from the knooks and crannies. I had my intake manifold "617" tanked for 10 bucks, looks like new too!

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Regards,
Ian White

1995 E300 Diesel w124 OM606
2014 E550 w212 M278 biturbo

2001 BMW 740i E38 M62 (past)
1981 300SD w126 OM617 (past)

For a DIYer on a budget not wanting to go to a radiator shop (BTW if you find one who WILL do it - two turned me down when I showed them what I had.)

*clarification* IF the oven cleaner contains "sodium hydroxide, lye, soda lye, caustic soda, NaOH" or any other ingredient containing NaOH DO NOT use it. The key here is "foaming" oven cleaner. Many foaming ones on the market use potassium amines or "caustic potash" as the active ingredient instead of sodium hydroxide.


I should add- at the car wash use the hot, high pressure soap setting first and hold the intake parts down with your foot.
Since the intake is aluminum the main concern is not alkali but acidic cleaners. I do understand your concern but chemically speaking, they don't to the same thing to aluminum.

DO NOT USE DRAIN CLEANER (chemically classified as a strong base-usually NaOH or caustic soda lye) at all. DO NOT use oven cleaner (chemically classified as a weak base-usually some combination of potassium amines) IF YOU DO NOT USE SOME KIND OF HOT HIGH PRESSURE WASHER to clean it out. DO use some thought - wash and rinse it thoroughly and don't let it sit for more than 15 minutes or so. In the many times I've both seen it used and used it myself, I've seen oven cleaner etch one intake that was polished to a mirror finish, another polish and it was good as new.

AND, if you are worried about oven cleaner you should avoid radiator hot tanks just as much. Acid is a great way to remove the ceramic scale in a radiator but acidic hot tanks WILL etch aluminum. They are NOT just water.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

On the 603, there is an oil separator in the valve cover. The black plastic elbow feeds crankcase vapor into the air intake elbow in front of the turbo compressor. On older engines, where the separator isn't working so well anymore, it also feeds a good amount liquid oil in. Pull your elbow off and check it. This also contributes to a soot filled intake (but not as much as the EGR.) The factory separator has a spring loaded mechanism in it instead of just a set of baffles and duct work like most others. It's also riveted in on the inside. It is still in place and not bypassed. I have to have the "in place" inspection in NC, also. What I have is the hose going into a vented catch can and not into the intake elbow upstream of the compressor intake. The intake is capped off during the testing so I do not draw in unfiltered air. What IS bypassed is that intake elbow. I'm testing how much oil comes out in a given time in order to gauge how big an external oil separator/catch can I'll need. ALSO there is a chance we'll plumb the oil back into the engine so we don't need to drain the can periodically.

If you loosen the oil cap and let it sit in place you can guess-timate the engine blow by according to how much the cap 'dances' like it's on a boiling tea pot. No dance = good. BUT, in the 603 the PVC hose elbow ends right by the cap so it gets sucked down by the intake vacuum. When you eliminate that intake vacuum, (remember - up stream of the turbo's compressor is the other end of that hose) the oil cap will not get sucked down. You'll also get a much better indication of blow by. I've seen a few gas and diesel, you actually had to hold the oil cap down to keep it from flying off.

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1987 300D (230,000 mi on a #14 head-watching the temp gauge and keeping the ghost in the machine)
Raleigh NC - Home of deep fried sushi!

How do you disable the EGR? Pulled my intake the other day to diagnose a glow plug issue and also found a fair amount of black goo in the intake and cross-over pipe. I have a 1990 350SDL with the 603.970 motor.