AWD - Hairline crack in fuel tank hose bib weld

Volvo AWD V70-XC70 Forum

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Hairline crack in fuel tank hose bib weld V70-XC70 2004

I tried a fuel-compatible epoxy (Perma-Chem), but it failed to adhere.

No less than 3 Volvo shops advised me that the fuel tank would have to be replaced, estimates around $3200 (the Haldex and propeller shaft have to be removed, as well as the rear seats, fuel pump and level sender).
The new tank assy. part was quoted at $1400.

I was able to fix the leak using plastic welding.

I went to the junkyard, and sawed out a 6"x 6" (150 x 150 mm) piece of fuel tank from the same MY, thus assuring plastics compatibility.

Since the leak was along a circular joint around the filler vent hose bib, I cut a donut shaped patch out of the scrap material. I used a 2" (49mm) dia. hole saw to cut a circular disk, then used a 13/16" (21mm) dia. boring bit to cut out the donut hole. I judged the patch to be too thick to melt, so in a vise I sawed it into two donuts half as thick, and only used one. The patch was about 2mm thick.

The car's rear end was jacked up about 6", and the pass. side wheel removed. This is so that I could address the repair from both the side and underneath.

At Harbor Freight, I bought the Chicago Electric 80W plastic welding iron ($16). The tip is just the right size, but I advise getting some practice with scrap material. It's low enough power, there is little risk of burning through the tank (1/4" thick fiberglass-reinforced high-density polyethylene).

The hose must be removed from the bib to get the donut patch on. I used a Dremel cutter to release the factory crimp-style hose clamp. It's safer to do the welding with the hose put back on the bib (closing off gasoline fumes).

The welding was a bit messy. The hose bib was likely a different kind of plastic as the tank, and didn't blend as easily into the weld.

That said, the Check Engine Light faults have stopped (with tank between 15-85% full), and so the plastic weld did the trick.

(I'll have to pay the Volvo dealer $95 to clear the SRS "urgent service needed" code. I drove the car with the rear seats removed to the shop to get a smoke-pressure test - you have to pin down a hairline leak this way. Only the Dealer-enabled VIDA can reset SRS faults, and it leaves a record attached to the VIN at Volvo Corp.
SOmething to think about before removing the seat(s)).


New Hairline crack in fuel tank hose bib weld [V70-XC70][2004]
posted by  pbierre  on Mon Feb 11 19:58 CST 2019 >

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