MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG TD TF 1500 - Fuel tank leak

I have a small leak in my gas tank on a '53 TD. It produces about 1 or 2 drops of gas each day. I can't seem to find where it is leaking from. I put in a new sending unit gasket as well as gaskets on the drain and filter fittings. They are bone dry. The gas appears to be coming from under the horizontal stiffner that runs the width of the tank. Any ideas as to how to locate the leak? If I can find the leak, I might be able to fix it without removing the tank. I really don't want to remove the tank and take it to a shop. I know that it will have to be repainted and I don't know the color that it was done with some 20 years ago. I guess that if I had to remove the tank and fix it myself, that it would be okay because I might be able to eliminate a paint job if I was careful but I'm trying to eliminate work on car that is just a driver.

I'm afraid that the general response is to take it off, but maybe someone has some different ideas.

Mark
Mark Strang

mark, chances are if it is leaking..it is rotten. best of luck. regards, tom
tom peterson

Mark, I had just repainted my car and discovered a gas leak such as yours. I wiped the bottom of the tank over several days and found I had a small stress crack as the paint started bubbling. I scrapped the paint off and sanded the area and then used JB Weld to seal it off, no leak in over 12000 miles since. JB is still there where I patched it. Look for bubbling paint.
Tom Maine (TD8105)

On other cars, I have fixed gas-tank leaks with the "Tootsie-roll" style marine epoxy....Never leaked again, and stopped the leak in 5 minutes...Buy it at any hardware store.
Edward
E.B. Wesson

The last tank I did had a tiny leak, but when I sanded down the paint on the bottom I found swiss cheese and rusty metal. Sitting with a small amount of fluid for a long time is a killer. Expect the worst, and you may be lucky!

Tom Lange
MGT Repair
t lange

I gave up and removed the tank. After removal and inspection, I still couldn't find any leaks although after sitting for 20 years most of the paint was bubbled along the entire stiffner area. Hard to determine where the leak started.
I put about 3-4 pounds of air in the tank and used a soap solution to check for bubbles. Couldn't find any. I think now that maybe the leak is in the cavity between the walls of the stiffner. This is spot welded on along the entire length as near as I can tell. I suppose that I could purge the tank and cut the stiffner off at its flange and look there. If I can find it and fix it, I could just weld the stiffner back on.

I'm still going to look for it on the outside for a while though before major surgery.

Mark
Mark Strang

Tom L. What did you do when you found the "swiss cheese" problem? Fix it or scrap it? The real question is is it fixable?

Mark

Mark Strang

Nobody has mentioned the tank slushing process that can seal up a small pin hole leaks quite effectively. It requires removal of the tank and removal of the sending unit. I did this with a replacement tank I fitted to my TD 30 years ago and so far no problems. The best part is it doesn't require repainting the exterior.
John Quilter (TD8986)

I just had my body man put a new bottom in my tank. Can't tell the tank was ever repaired and it doesn't leak.

Wish there was some process you could replate the interior of the tank with some electroplating process so it would be like the tinplating they use now on gas tanks.
Cheers,
Bob
Bob Jeffers

I did what Bob did - my shop guy cut out the entire bottom of the tank, shaped a new bottom piece, welded it in, smoothed it and painted it, and it is invisible. I did also coat the inside of the tank, to be sure it didn't happen again.

Tom Lange
MGT Repair
t lange

Thanks for the info on the repair. Looks as if I'll just remove the old bottom and put in a new one if it come down to that. Not a big deal but just a PIA to do. I'd like to do the sealer but I just don't know the extent of the damage that exists.

Mark
Mark Strang

If your tank inside is clean and free of rust you can seal the inside by slushing. I used the Bill Hersch product as it will not be affected by alcohol in the fuel. Was easy to do, just follow the directions.

I had some light rust in my tank and after using the sealer no rust has been showing in the fuel filter.
C.R. Tyrell

Well, I decided to clean the inside of the tank after looking at all of the postings. Apparently someone had sealed the tank in the past-as much as 25 years ago. I could see the sealer pulling away from the sides. With nothing to lose I put in a gallon of MEK along with 200 sheet rock screws and plugged all of the openings. Swished the contents around like Larry Shoer mentioned in Ttalk. After about one hour of playing with it I could see that the old sealer was dissolving nicely. Kept at it for about another hour and the old sealer was pretty much gone and steel was showing all over. Drained out the MEK, dried it with air, and fished out the screws with a magnet. I then added a quart of muriatic acid and went at it again. After about another hour the inside looked really good. I rinsed it out several times and it is now drying. I didn't see a lot of rusted areas so the little leak that was appearing can't be very large. It seems as if the basic structure is sound.

After studying all of the web sites and this site I ordered a Caswell fuel tank sealer kit. I spoke with them and it seems like this product will work okay.
If this works it will sure beat the cut/weld process.

Mark
Mark Strang

mark, did you google "caswell fuel tank sealer failure"? lots of posts under that google search. whether it is a good thing or not, after reading those i went with bill hirsch. i have not used the product yet..as soon as my driving season is over i will be able to tell more. regards, tom
tom peterson

MARK,
If you looked in your tank, I'm sure that you have seen the baffles that you must get the sealer around,,, if any one has not seen them, go to Bud's TTALK,,

http://www.ttalk.info/FuelTankInnards.htm

P.S. Bud,, thanks for maintaining your great reference site!!!!

SPW
STEVE WINCZE

Sounds like you have the hard part done. In my opinion I would stay away from the polyurethane based sealers. I did use the Bill Hersch Tank Sealer in mine and put in the entire quart to make sure the baffles got covered. Ended up with a third of a quart that was recovered after dumping the excess. It left a nice thin film in the tank and can be removed easily later by washing out with MEK. And as I said before no more rust in the filter.

Poly sealers can separate from the metal leaving a loose "balloon" inside the tank which is almost impossible to remove because of the baffles. They will seal the tank though.

Best of luck with whatever you choose from this point....cheers.
C.R. Tyrell

My body guy also cut out and replaced the bottom plus the lower section of the sides. He then sent it to a place that sealed the inside with a red oxide looking sealer. Is this the good sealer (alcohol resistant)or bad that was used?
R Taylor

I can report that after 4 1/2 years the Caswell tank sealer is still performing flawlessly. The TD is filled with gasoline year-round. I also use Techron, Red Line lead substitute, and Stabil. The tank sealer is not affected by them.

I chose the Caswell system because I wanted a two-part epoxy system and one that was explicitly described as unaffected by gasoline containing ethanol.

While some may blame the gas tank sealer if it appears to fail, it is also possible the surface was not prepared properly. Make absolutely sure you prepare and dry the surface well. Do not scrimp. What I describe on TTalk worked well for me.

Good luck.

Larry
Larry Shoer

One other thought. Muriatic acid is hydrochloric acid. MEK and the acid should do a great job of cleaning the inside of your tank. What they won't do is etch the metal. I strongly encourage you to do that. I used POR15 products to prepare the tank, Marine Clean and Metal Ready. Metal Ready is a proprietary aqueous phosphoric acid solution. I'm sure there are other equally good metal etching products you can use. After etching, the tank must be washed out and, of course, thoroughly dried.

The metal etch greatly enhances the ability of the coating to "grab" the metal. This could spell the difference between a coating that remains firmly attached to the metal and a coating which bubbles up.

Larry
Larry Shoer

Larry,

That sounds like a good idea. I suppose that the etching also increases the surface area that the epoxy adheres to as well. I'm going to get some etching material and use it.

Mark
Mark Strang

Hi Guys
All acids remove rust to some degree. Phosphoric acid converts rust to ferric phosphate FePO4 which is black in color and may be painted over. There are all kinds of products which use this as the main ingredient and make it sound like a secret thing! I use the real McCoy when I can find it and save a few bucks. After the rust is removed the surface is pretty rough and holds onto most coatings. Check it out on Wikipedia.
Chuck
cj schmit

chuck, don't you have to remove the scale before using phosphoric acid? all of the commercial products containing phosphoric acid require removal of loose scale..when i have used the products it seems the surface is converted, but just beneath is iron oxide. regards, tom
tom peterson

Like many metals, iron (steel), copper, and aluminum, react with oxygen in the air to develop a thin layer of metal oxide on the surface. In many situations, the oxide layer protects the underlying metal by not allowing oxygen to penetrate. Brightly polished metal that then becomes dull is displaying this very process of "oxidation."

Over-cleaning metal, to the point where it is bright and shiny, is likely counterproductive. The remaining oxide layer may be sufficiently thin that treatment with phosphoric acid is not as able to "rough up" the surface (increase the surface area) to provide significantly improved opportunity for the coating to bind.

On the other hand, significant remaining surface rust is likely to leave a less physically strong interstitial layer, even after treatment with phosphoric acid, between the coating and the underlying, good metal. That is why surface preparation prior to treatment with phosphoric acid usually involves mechanical removal of the more gross surface rust.

Larry
Larry Shoer

Hi larry
You are right about polishing smooth surfaces. Also, a coating of aluminum oxide gives a smooth, hard, clear surface that resists further oxidation. They call it annodized.
That's not what we are dealing with inside our gas tanks. It would be great if we could get inside our tanks and remove the scale of rust mechanically (and quit before we enlarge the pin holes) Sand blasting is the best way i've found on accessible areas of the body. Not practical in the tank, however.
The disc sander works pretty good on body parts but cant get into the pits of rust. This is where converting the rust helps give you something inactive FePO4 to coat. There are electrolosis methods that work really good too.
I have had good luck with fiberglassing the whole bottom of gas tanks that were almost lace. I got 10 more years out of one tank. my nephew just got his powder coated on the outside after coating the inside with a poly product. Looks good! Time will tell...
Chuck
cj schmit

See this URL:
http://www.masterseriesct.com/page7.html
I have heard wonderful things about this stuff being used to seal gas tanks. Even ones with pinholes! I have used the stuff on my TF frame and many other ferrous parts and it goes on like glue and you can't get it off. I plan to use it (per the web site instructions) on my gas tank, when I get there.
Regards
Rod Murray
Rod Murray 54TF 3006

This thread was discussed between 16/10/2012 and 26/10/2012

MG TD TF 1500 index

This thread is from the archive. The Live MG TD TF 1500 BBS is active now.