Evap Gone Wild!

Evaporative Emissions Systems stink, and that's when they're working correctly. There is some complication to them, but they serve an important purpose: give a hoot, don't explode.

When your fuel tank gets hot (like sitting all day in an asphalt parking lot in August) the liquid gasoline is trying very hard to becomes gaseous. Without a way to vent the tank, the tank could bulge or spring a leak. But just drilling a vent into the tank is a poor method as well, and dumping combustible gas on the ground is not only throwing your money away, its a real hazard for anyone nearby. (Flick a butt under your are and watch all the fuel vapors ignite in a flash: FOOP!) "Am I missing an eyebrow?"

The VW evaporative system (which has evolved, but is still in use in today's cars) allows the fuel tank to vent flammable gas out of the tank safely, first to long copper tubes that travel out to the sides and then back to the rear of the bus, then up to condenser chambers in the air inlets at the rear corners. Here it has a chance to re-condense and run back down into the tank. If the vapors are quite thick, they'll travel down again, joining up and entering a holding tank.

That tank is the carbon canister. Depending on your year and model, it may be in a few different locations in your engine bay. Thus, you don't waste fuel by venting it to the air around your car, your car doesn't stink because its sitting in a haze of its own fuel, and you don't deform your fuel tank because you give the fumes someplace to go. And you don't explode.

Of course, there are two assumptions here: one is that all of your evaporative emissions hoses are in place and that they 'air tight' so you're not leaking fuel fumes in to your engine compartment, or worse, into the cab of the vehicle.

The other assumption is that your carbon canister is up to the task of trapping the fumes. If it is plugged up or the carbon is just OLD, it can't do its job. VW recommended replacement of the sealed canister every 48,000 miles. You can imagine how often this maintenance got skipped.

The real tender part is that all of those blue, red, green and purple hoses have to be replaced because they've  been rotting for more than three decades. The purple ones are especially exciting, since they are your fuel fill hoses and if one of them fails, you can take a left turn a little too fast and leave $20 of fuel on the ground.

I went through the whole gymkhana of replacing all of these hose links with Ethanol resistant hose, so I won't need to do that again for many years. Only the blue rear three hose links and the red hose can be replaced with the engine in situ ; all others require the engine to be removed first. Amazingly awkward.

I was especially pleased to find that both of the purple hoses were in very bad condition, so the effort was worth its weight. Once the fuel level sensor (on backorder for the last month, dammit) gets here, I'll get that screwed in and the fuel tank can be remounted and strapped back into place. Finally, the firewall can go back in and we'll be back to just dealing with the engine. As if that isn't enough.

Another thousand words

091 Transmission retored to its rightful place. CV joints were cleaned and repacked, and I took about two
pounds of sludge off of them. No, it is not necessary for me to buff the outside of the CVs with a polishing
rag and jeweler's rouge. But I did make sure they were utterly clean, and having inspected the boots,
I'm content that they've got a lot of life left in them.

I've been stampeded enough lately that, even when I have taken the opportunity to stop and take pictures of the work I'm doing, while I do it, the copy doesn't get written to go with it. So the pictures languish and so does this blog.
So this is my second 'catch up.' There was a three week delay between the time I got the transmission back in place, and the time this got written, and most of it was dealing with sick kids, broken dryers, postponed day trips and crushing work hours. So here's the work 'to date.'

With the shifter and transmission back in place, it was time to move on to the next item to be buttoned up: the fuel tank. (Can't put the engine back in with the fuel tank out.)

So the replacement tank, which had light rust inside, was scoured with a slurry of water and roofing nails to knock the rust scale off. With that removed, I placed an order for POR15 PrepNReady and US General Tank Sealer.

Because there are so many steps in the tank work, I pushed ahead right away, knowing that something would slow me down. I was right. The dryer died.

The interior of the replacement fuel tank. Not dirty, just rusty. This is after the nails had been through to
remove the scale across the bottom. So this was my starting place.

I gave the tank an overnight with a gallon of 'Safer Muriatic Acid.' 'Safer' my tired feet. It barely touched it. I went back to Lowes and got a gallon of the full-on rotgut stuff used to kill algae in pools (dilution 10,000:1.) This stuff vaporized alarmingly when I took the lid off, like a King Cobra raising its hood. At a dilution of 13:1, it rapidly chewed its way through the rust.

Just the fumes that escaped from the cover I put over the sender hole chewed the paint off of the exterior of
the tank. And there was also the matter of the moderate amount of surface corrosion on the tank, too.

I ordered all new fuel line while the tank cooked in the back yard. I recommend Gates Barricade, so that you don't have to replace your fuel lines every year from running E10 fuel.

After a mere 4 hours, the tank was considerably improved. Now quickly, rinse that stuff out and neutralize it!

Of course, as soon as you get water all over the inside, you're going to flash rust like crazy! So after a through rinse, move quickly on to the next step: Zinc-Phosphate!

The tank evaporating out after the zinc-phosphate has been added. Note that the area that the
acid had taken off and then flash rusted is "bare" metal. Not really. There is a thin layer of
zinc-oxide that is keeping the O2 from getting to it and causing it to rust again. The whole
interior of the tank is protected like this now. But zinc-oxide won't endure fuel or water, so the final
layer has to go on: an epoxy based sealer.

To get the tank bone dry, it went on top of my kerosene heater for three hours.

The interior of the tank, sealed from the fuel for
 the first time ever. Of course, the exterior still needs help.

Tank in primer.

Having gotten the tank all Bristol style on the inside, I went to work on the outside: two coats of rust catalyzing primer to get at the slight corrosion, then two coats of flat black.

The final product, left in the garage for the epoxy in the tank to harden over the forthcoming week.

There is still a brace of work to do on the fuel tank compartment, including replacing seals,etc for the filler, evap lines, etc. I'll work those this week while the tank sealer hardens. Maybe have the whole 'firewall forward' area buttoned up by Sunday?