OM606 fuel lines - skip the o-rings & use epoxy? - Page 3 - PeachParts Mercedes-Benz Forum

nhdoc · #31 09-05-2008, 01:28 PM

As hard as it is to believe, based upon your isolation of the problem and having replaced the filters and o-ring previously the source of the air leak was most likely in the prefilter housing itself...like you said either some porousity in the casting or a crack or other defect which allowed air to get in from it. It really isn't a problem with the o-rings or the design per-se, it must be a defect in the housing itself.

mcreynol · #32 09-05-2008, 02:15 PM

Quote:

Originally Posted by nhdoc

As hard as it is to believe, based upon your isolation of the problem and having replaced the filters and o-ring previously the source of the air leak was most likely in the prefilter housing itself...like you said either some porousity in the casting or a crack or other defect which allowed air to get in from it. It really isn't a problem with the o-rings or the design per-se, it must be a defect in the housing itself.

Exactly what I'm thinking too. Though I'm not giving MB a pass on the crummy design.

As part of my diagnosis I jerry rigged a vacuum gauge into the line from the fuel heater to the coarse filter. At idle the intake suction bounces from 0inHg to 10+inHg at about a 4Hz rate (once per IP revolution). That pulsation has to move the o-rings around in their seats. Add some road grit (or many hundreds of miles of desert dust) to the picture and you have wear in the O-ring mating surfaces. I'm guessing this is where the leakage comes from.

PS: At reasonable RPMs (1200+) the intake suction was 5inHG. That seems like a lot of suction on a fuel line. Whenever I redo the lines & o-rings on the E class I'll see is what the suction is on it's shorter and lower fuel line.

nhdoc · #33 09-05-2008, 02:37 PM

There's no way the soft rubber of an o-ring will "wear into" the mating surfaces, whether they are plastic or metal. The o-rings will wear out before that happens so I think your theory is flawed there...I'd still look closely at that pre-filter housing and find the flaw in it, that's where your air is leaking from.

TMAllison · #34 09-05-2008, 02:59 PM

I misunderstood earlier and thought you meant you had isolated the leak to the outlet of the Main filter; I now understand you are calling the pre-filter the "coarse" filter.

Based on what you said you've isolated the leak to the line entering the pre-filter, the prefilter itself, the line exiting the prefilter and the cast housing.

Buy a new (or "another" new) pre-filter and see if that stops the bubbles. THey have been known to be warped and have poor seals right out of the box before. I've had to tweak the hold down washer to create additional downward pressure and resort to some silicone grease to get them to seal.

jon606 · #35 10-28-2008, 02:02 PM

I had trouble with air getting in the pre filter in exactly the same was as described earlier in this thread and was absolutely sure the o-rings were fine. I came up with the same idea- buy a little plastic strainer and ditch the one in the filter housing.

That said, does anyone know where I can buy a viton o ring kit in the UK, or where there is a list of the sizes I need?

Also, does anyone know whether I need to switch the o rings in the IP to viton to run SVO (as well as all the other kit)?

Thanks

Jon

TMAllison · #36 10-28-2008, 04:50 PM

use my name under advanced search and search for 606.962 oring sizes.

It ought to pop up.

check out fryerpower.com for the orings. Operated by a froum member.