Tiiiiny Bubbles.....innn the liiinee......makes me worrieddd......is my engine doing fiiine?



You have a leak downstream somewhere....

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

The primary filter will trap dissolved gas from your tank. Fuel is cool and under slight pressure by design. This is ideal for dissolving gas. When the fuel gets up to your engine it heats up and de-gasses. The primary fuel filter is designed to trap gas. That is why the outlet is low. You should not see a continuous stream of bubbles coming into the filter, but even if you get rid of all of the gas in the filter it will come back eventually.

I have seen this myself and I am sure I don't have a fuel leak before the filter.

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1991 350SD (updated rods)
Biodiesel B100 when I can find it.
Dino when really cold outside

But that's exactly what I see when the engine is running.... I do believe it's something new that was not there before... the only other thing is that I recently cleaned the vent tube (looks like a little trumpet - under the car on the driver's side rear) that vents the tank to the atmosphere - took it apart and it acted like it may be a check valve - though not a strong one as I could overpower it with my breath... anyway - I wonder if I may have re-installed that part backwards!? Possible for these symptoms?!

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1987 Mercedes 300SDL; SOLD
1985 Mercedes 300D; SOLD
2006 Honda Pilot - wife's ride; 122K;
1995 Toyota Land Cruiser - 3X locked; 182K

If the fuel is cold and the engine is hot it is possible that tiny bubbles could be de-gassing fuel, or, there could be a leak. I am not sure how a leak would not show up as dripping fuel.

BTW: About Viton

A few of the flexible OE fuel lines on my car have survived years of B100. They are
1) The flexible hose from the tank to the long stainless line.
2) The line from the long stainless line from the tank to the stainless line that goes to into the engine compartment.
3) The "cigar tube" that returns fuel to the tank.

I think the lines that connect the primary filter would have survived had my mechanic not changed them to some incompatible material. The return tubes from the injector eventually leaked, but it may not have been the B100.

The grommet around the fuel filler neck melted away immediately.

Depending on the year of your car, Viton may not be needed everywhere.

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1991 350SD (updated rods)
Biodiesel B100 when I can find it.
Dino when really cold outside

Get a piece of hose and replace the hose in the engine compartment.
Then send Bob A. some Gas-X.


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1984 MB 300SD Turbo

I thought this thread was going have something to do with Don Ho.

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Toblin

'79 300D, "Liesel von Diesel", 235K

I kid proofed the house....but they still get in

That's hilarious

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1974 240D 3.0L 4(M) - 250K -OM617.910 + 300D FW + Rajay turbo power!
1977 6.9 3(A) - 84k

Thank you. Thank you.

__________________
-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

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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!