hey everyone - i searched for a while through the forum and couln't find this addressed anywhere...please redirect me if this has been covered a million times...

I have a huge bubble in my pre-filter. My 82 300DT sometimes stumbles a little bit when first started, this morning it started and stopped after turning over on its own a few times. Otherwise it starts and runs OK. This is more of a PM thing. I have not done a filter change yet, and all of the PO's (or POs mechanics work) is suspect.

I primed the system the best i knew how following my Haynes manual. I loosened the spin on filter bolt, and pumped the primer a bit (PO installed the black updated primer). A little diesel spat out the bolt, and eventually no more diesel came out the top bolt. Air bubble still there. Am i doing something wrong? I re tightened the bolt to come online to look for an answer...

Any thoughts? Do I need to remove the PF to get rid of the bubble?

thanks,
dd

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

Man, that's a tough one...is the bubble new? I'm thinking line leak somewhere between that filter and the tank: not enough to leak fluid (you're not leaking fluid, are you?), but enough to let air in. Also, make sure your tank strainer (inside the tank, use the search) and vent line is clear. Could be the filter, too. Change it out and see if it changes anything. Good luck!

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1989 300E 144K

A single bubble in the prefilter is normal. It should not affect performance.

A filter change is very near in my future anyhow. Fortunately, I am not leaking fuel anywhere.

FI - the bubble is big, maybe 1/10 the volume of the filter or more - is this still okay?

Why wouldn't bleeding the system get this sucker out?

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

As long as it's not a stream of bubbles (One single bubble that stays in the highest point of the filter), normal.

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A single bubble "1/10 the volume of the filter" sounds about normal. Mine always has a "pea size" bubble. If you see bubbles moving through the filter, you have an air leak upstream. Priming the pump will not do anything about the bubble in the pre-filter.

Its not a bubble. Its a gel-point indicator.

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Paul
2004 E500 4matic; 72,000mi

I have a slight air pocket in mine too. I wouldn't worry...

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I'm not a doctor, but I'll have a look.

'85 300SD 245k
'87 300SDL 251k
'90 300SEL 326k

Six others from BMW, GM, and Ford.

Liberty will not descend to a people; a people must raise themselves to liberty.[/IMG]

Me, too. About 1/8th of the entire volume. Runs like a champ.

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1998 E300 +310,000K
1996 E300 +460,000K

i am now officially not worried about it anymore.

my occassional starting stumble must be something else. perhaps IP timing.

it's down there on the list right now.

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'85 300D, 'Lance',250k, ... winter beater (100k on franken-Frybrid 3 Valve Kit)
'82 300D, 'Tex', 228k body / 170k engine ... summer car
'83 300TD Cali Wagon 210k, wife's car

I'd bet you could have up to about 1/4 of the filter as air.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)