Fuel Tank Leak

Hi guys, I've recently discovered that my fuel tank has rusted through... 1987 BMW 535is

A new (used) tank is fairly expensive or a decent trip to to get it, so I think I'm going to drop the tank and use a sealer to fix the issue.

What sealers have you guys used? I would guess that the POR 15 kit is good, but it's twice the price of other sealers. Is it worth it?

Only one I will use is Caswell platings Phenol Novolac Epoxy I like it in red as its easy to see if I've got it coated well. In fact I was just drilling out the vent line on a fiberglass motorcycle tanks I coated last night. http://www.caswellplating.com/restoration-aids/epoxy-gas-tank-sealer.html

I've used it in 21 tanks now and there all holding up great even the 4 that sit with modern pump fuel all the time.

44Dwarf—

Did you get the Caswell kit from a local outlet or buy it on-line?

I need to seal up the old tank in my Austin A35 and was looking for a recommendation like yours. So many time you hear stories about the new formulated fuels eating away at the tank coating, nice to know that there's one out there that honestly performs as advertised.

AWSX1686 wrote: Hi guys, I've recently discovered that my fuel tank has rusted through... 1987 BMW 535is

I'm guessing it's rusted around where the fuel pickup hoses connect into the top of the tank, sort of behind the passenger side rear wheel - that's a real common thing on e28s. Mine is starting to go in that area as well, I need to get it fixed soon.

I have no personal experience with this company but they have franchises across the country: http://www.gastankrenu.com/ They may be worth checking out if there's one in your area.

I will look into that.

The leak I know of is at the seem where the top and bottom of the tank come together. It is certainly possible that there's some up top too.

Once saw Wayne Carini on TV repair a leaking gas tank in an original Cobra using JB Weld.

For what it's worth . . .

Buy a new tank. Way less aggravation in the long run.

New tanks are still available from BMW, but they sell for ~$375.00.

stuart in mn wrote: New tanks are still available from BMW, but they sell for ~$375.00.

That's not a bad price at all. If you have to do it twice, it will cost way more than that just in aggravation.

How big of a hole? Only bad in one spot?

I found a used gas tank, supposedly rust free but it's like a 2 hour drive to get it. The guy seems a little sketchy though.

My main concern about a used tank is that a lot of them rust in the same spot so the used tank could rust out too.

From what I can see the rust hole is not huge. I can only see that it's bad in one spot.

JB weld (or the putty version) and brass or aluminum screen will fix a small hole.

I would replace it. Have you looked on Amazon or Rock auto? If new from BMW is less than 400 aftermarket is probably cheap.

TeamEvil wrote: 44Dwarf— Did you get the Caswell kit from a local outlet or buy it on-line?

I buy it on line. is quick and easy.

Have you check the regular parts store or Rock Auto "spectrum" has some low cost tanks. I put one in my 96 ford f150 is was LOW COST and I still see that truck driving around today...on its 3rd owner after me.

As with anything its all about prep!! if tanks is dirty don't expect the best results you need to clean clean clean... One steel tank I use evapo-rust and let is sit over night then pop the tank in a different side go to work and flip it again until I'm sure it has sat on each side 6-12 hours. then wash dry and acetone wash and dry.

I've checked autohausaz and Rock Auto, both with no luck on a gas tank. Ebay, Amazon, and Auto Parts warehouse have the original BMW tank for ~$650.

I found car-parts.com which shows places that are parting out cars and you can search for a specific part. Found a used tank for $150, but it's a 3-hour drive to go get it. The guy contacted me and said that if I wanted to make the trip he'd pull that tank and smoke test it.

I'm looking for one that's closer, but I'll make the trip if I have to once I figure out that it is the best choice.

If the rust hole is in the middle of the tank then it's easy to patch. But a leak at the seam is not. The rust is in between the two layers of metal and once it has a foothold it won't stop. You can patch it now but it will develop a leak somewhere else soon after. Get a new tank or a good used one.

I usually solder them myself.

I finally dropped my tank. It seems like the leak is coming from the seam.

I found a used tank for cheap, and only an hour away, so I went to go get it this morning only to find that while it might not leak, the rust is even worse. (I didn't buy it.)

After I talk to my mechanic I will probably end up using a sealer, as well as cleaning up the tank a lot and using a rust converter on the outside to stop rust. I may also coat the outside in bed-liner to prevent future rust. This particular tank sits right behind the right rear wheel and collects a lot of dirt, which the bed-liner should help protect against.

I'll try an post pictures as I go.

Here's the different sealers I am looking into:

POR-15

Caswell

Eastwood (and possibly for the outside)

And aparently NAPA has a sealer as well, but I couldn't find the link.