I have a dime-sized bubble in the clear plastic primary filter running or not. Is this a sign of air infiltration? I have been chasing an air problem, and if the bubble is not normal while running, then I have it narrowed down to the tank-to-hardline connector over the pumpkin.

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327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
- Albert Einstein

take a walk down memory lane...

BUT the prevailing opinion is that a small air bubble in the Primary is O.K.

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'84 300SD sold
124.128

normal

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1984 300D Turbo - 231k....totalled 11/30/07 RIP

A 1-4 bubbles in the top of the filter is fine and there isn't anything worth doing about it. When there is a stream of bubbles, then you have a problem to worry about.

I almost always have a little air in the primary filter. Doesn't seem to do any harm.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Normal.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I was hoping that it was normal. I have ordered the 3 clear IP to secondary FF connectors with banjo fittings from the dealer. All three are hard and not clear any more. They are not leaking fuel, but I still want to replace them to continue ruling out causes for this pesky air problem. Any other places I should look? The IP pump has no visible leaks, yet somehow air is getting in there and collecting in the secondary cannister.

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327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
- Albert Einstein

take a walk down memory lane...

I've had one (well, not the same one) since 1983.

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Charles
1983 300D, bought new, 215k+ miles, donated to Purple Hearts veterans charity but I have parts for sale: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/296386-fs-1-owner-83-mb-300d-turbo-rebuild-parts.html

What is this "air infiltration" problem? From the tank to the IP, diesel flows by gravity. Any holes that would let air in would first let diesel out, wouldn't it? Does the IP pull fuel faster than gravity can feed it? I wouldn't think so, you could drain the tank in a few minutes by opening the line to the primary filter. And once you shut down the engine, you'd have a leak on your hands if there was a problem in the lines.

Just curious...

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mjk

'84 300SD 119KMi (Liesl der Diesel)
'84 300D 326KMi when the oil left (former parts car)
'82 300SD 253KMi (new parts car)

evidently, air can be sucked in (in minute amounts) where diesel can't get out. my problem is finding where this is occurring.

__________________
327K on 1986 W201, 602.911, 722.414 2.5 190D ("The Red Baron")
139K on 1993 W124, 104.942, 722.433 2.8 300E ("Queen")

http://farm5.static.flickr.com/4081/...0bb92d3c_m.jpg http://i370.photobucket.com/albums/o...g?t=1325284354

Do not worry about your difficulties in Mathematics. I can assure you mine are still greater.
- Albert Einstein

take a walk down memory lane...