Dumb Secondary Fuel Filter Question - PeachParts Mercedes-Benz Forum

JHZR2 · #1 11-28-2010, 10:36 PM

Hi,

On 617 engines, to replace the secondary filter, you loosen the bolt and spin off. Fill with fluid of your choice (or not), prime a little or a lot depending upon how much you filled it, then crank until you get it to fire.

Some instructions state to crack the bolt attached to the filter a bit, and pump until no bubbles come out with the fluid coming from around the bolt.

My issue is that the times Ive tried this, more fuel comes out of the seal area where the filter touches the mount than from the bolt area. Does this mean that somehow the spin-on filter isnt arranged correctly or somehow it is not installed exactly right?

In reality is there any reason to waste that fuel? The air would just go out the cigar hose anyway, right?

Is it possible to tighten the bolt down too much? Is there a torque spec for it?

Thanks!

jt20 · #2 11-28-2010, 10:44 PM

The filter bolt gets tightened. Not too hard, no more than you could apply to the filter by hand.

The bolt with the arrow pointing 'out' gets loosened, and air escapes there.

after that, you could also do the bolt on top on the return line.

jt20 · #3 11-28-2010, 10:46 PM

arrow pointing 'out' is visible towards the center of your image.

...and as a reference, that filter bolt has seen way too much torque if proper wrenches / sockets were used.

JHZR2 · #4 11-29-2010, 09:25 AM

I saw that... Wonder if that could effect air leaks? Is there a p/n for that bolt?

Likely a big adjustable was used instead of a socket... At least that is how it looks to me based upon rounding/gouges...

mespe · #5 11-29-2010, 09:50 AM

If you fill the new filter completely with fuel, no need loosen the bolts air will go out the cigar hose when you prime.

If you loosen any banjo bolt, you run the risk of developing a leak and may need to anneal the washer.

Biodiesel300TD · #6 11-29-2010, 10:05 AM

I never crack open the banjo bolt on the return. The air will return through the cigar hose. You just end up with fuel that you have to wipe up, and it's never really helped me any.

JHZR2 · #7 11-29-2010, 04:29 PM

I really thought it was the top bolt... After all, the housing has a tapered lip, thought it was to let the fuel fall off to the ground.

Otherwise why is it shaped the way it is?

Problem is, loosening it or the banjo with the arrow will both cause spoilage not easy to clean up, while if it came out the top bolt, a rag may be all that is needed.

Seems with the new style primer it is no big deal anyway...

tangofox007 · #8 11-29-2010, 04:57 PM

Quote:

Originally Posted by JHZR2

I really thought it was the top bolt...

The 617.95 Engine Manual calls for loosening the filter housing discharge line.

layback40 · #9 11-29-2010, 05:59 PM

In practical terms. If the car is on the flat or nose down hill, just filling the filter right to the top has worked for me for the last 30 years.
If you have a weak primary pump, have the car facing up hill, dont fill the filter right up, have air leaks, have a non standard fuel system, leave the filter off for an extended period, have a weak battery or are using something other than diesel you will have problems and will need to bleed the system.

snookwhaler · #10 11-29-2010, 06:28 PM

I'm sure glad I'm not the only one that has a rounded off filter bolt. The PO (or someone) did the same thing to mine. It was probably done with a crescent wrench instead of the "proper tool".

sd300td · #11 11-29-2010, 07:35 PM

I crack the banjo bolt, per FSM instruction. Once running, if the filter bolt leaks I will tighten until it no longer leaks.

Diesel911 · #12 11-30-2010, 01:46 AM

Because I would most likely spill I do not fill the Secondary Filter at all. I just pump with the hand primer.
If I happen not to have pumped on the Hand Primer enough and got some Air in the Hard Lines I loosen 2 of the Hard Line nuts at the Injectors and crank a bit. Tighten the Nuts and it starts.
I have never loosened the return Banjo Bolt and used the hand Primer until Fuel Comes out just to bleed the Air out.

JHZR2 · #13 02-06-2011, 06:39 PM

Quote:

Originally Posted by jt20

...and as a reference, that filter bolt has seen way too much torque if proper wrenches / sockets were used.

Well youre right. Ever since that day there has been a small leak of fuel from the filter. The big bolt and the top part are dry, but the sides of the filter, the little trough around the top of the filter, and the sides of the filter (and everything below) is wet. I havent used the car hardly at all since doing the filter but the tank Ive used since only got me 25.5MPG of mixed use. Im used to more like 28 MPG in mixed use.

This was the first time I did the filter on this car. Perhaps there is something wrong with the mount, which is why the PO had to crank down on it so much? Should I tighten it down, or look to do something else? Can I just replace that bolt?

Some iphone pics:

Need to take care of this quick - I have diesel fuel on my $$ new engine shock mount, AC lines, compressor and rubber AT cooler hoses, and dont want it to harm the compressor seals or spring a leak in the rubber...

Should I just crank down to start, or just replace the bolt? Mount?

Biodiesel300TD · #14 02-06-2011, 07:41 PM

There is a crush washer under that bolt. Try replacing that first.

JHZR2 · #15 02-06-2011, 08:00 PM

Thing is the leaking is not from the bolt. There is no leajkage on the upper part of the filter mount. I tried to capture the color of the diesel in the "trough" at the rim of the filter. IMO it is a sealing issue, but there is an overtightening issue here that is part of the car's history that I do not know... All I know is that the bolt was overtightened in the past and now that Im doing it, it leaks...