Oil & Fuel Another diesel leak in my 5740's fuel tank

Unclebuck257 · Jul 5, 2009

As some of you know, on July 8, 2008, just about exactly a year ago, I repaired a leak in the fuel tank on my 2005 5740C. It was the standard reason these plastic fuel tanks begin leaking on the 5740Cs, in that the molded plastic tank has molded into them the place where the screws holding the protection plate and support structure are screwed into on the tank itself. Now, after I returned from a month out of town, with no one driving or even starting my tractor, I find a big diesel mark on my barn floor again, and after checking in the light, the diesel tank is definitely leaking (dripping) again from the corner of its support structure. This is getting old real quickly for me!

Last time we took some good apoxy, after draining the tank and removing many support screws, and filled in that molded screw hole along with the one half inch crack out from it, and there were no more leaks for the past year.

I haven't drained the fuel tank yet this time, nor have I checked closely yet to see which screwhole is leaking this time yet either. Any ideas from anyone on fixing it?

I guess my other questions are..What is the cost of a new fuel tank from Montana..Anyone know? And does anyone know IF a metal equivilant is made anywhere to replace it too?

tack 350 · Jul 7, 2009

I had the same problem as you only I compounded the problem. I had my tank shields off putting every kind of sealer I could find on the molded nuts to stop the seepage. My son had an emergency and I helped him out and I ended up driving a piece of rebar in the bottom and out the top just in front of the filler hole. We bought a plastic welder from Harbor Freight and modified it slightly and filled in the holes. We still used a plastic tank sealer from the auto parts place, even though it didn't say it was for fuel. It has held up for four months. I priced a tank from Dugan Brothers here in Florida and it was just under $400. By the way, they have sold several. I looked all over the net, but never could find a replacement. I will probably build one out of aluminum, before I spend $400. Hope this helps. This is a great tractor except for the tank and seat.

Unclebuck257 · Jul 8, 2009

Tack350,

Thank you for the info. I agree that before I spend $400.00 on a new plastic tank, I'll get a metal shop around here to make me one in aluminum. In the meantime, I may try some of that plastic sealer you mentioned. Thanks again.

tractorbarry · Jul 11, 2009

Get a hold of your dealer and have them call Montana this will be a warranty if is a year to two years from date of delivery. the have come out with a revised tank

Unclebuck257 · Jul 15, 2009

tractorbarry,

Thanks for that info, but my 5740C was bought in Feb 2005 and is beyond warranty. BUT, it's ALL PAID FOR now!! LOL!

I mowed a little more than half my pastures yesterday and the leak apparently got worse. Not sure if I can continue and finish mowing the way it is, but I'll check in about an hour and see. I was too tired yesterday evening to do anything but put a diesel can under where it drips to catch the diesel dripping.

Hopefully I can finish mowing my pastures before we get this cold front in here and it rains this Friday or Saturday, again hopefully. After that, I'm pulling the present factory tank off and having a welder make me one identical in shape to the plastic factory one on there now. Tractor will be down a week or so when I do that though. I'm real tired messing with this plastic piece of junk the factory put on it!

Unclebuck257 · Jul 15, 2009

Well, I went out to see how my diesel tank leak was doing to see if I could mow the rest of my pastures and it was literally dripping like a siv. The one diesel can I had under one corner of the big drip spots was half full and there was at least another 2 gallons of diesel on the concrete floor of my barn. I decided that I better not attempt to do anything until I got the tank problem fixed. My brother in law and I pulled the tank and dumped about another 7 gallons of diesel into two five gallon cans. I then had a welder who lives out here come out and pick it up to use it as a model and make me one out of 3/16 inch steel, exactly like, shape wise, that plastic piece of junk. The cost will be about $600.00 instead of the $400.00 he initially told me on the phone because of all the cut ins and cut outs and that long thin portion of the tank he didn't expect to find. Dang!! those tanks look somewhat like a guitar case, with the long thin section that goes to the rear of the tractor!

Anyway, it's being made out of 3/16 inch steel so I won't need the guard pieces either, but I won't have it running again until at least Saturday to finish my mowing. The welder said he'd have the new tank back to me Friday evening.

Unclebuck257 · Jul 20, 2009

An update on my new steel diesel tank. It took an additional day to get it and then when the welder delivered it to my place, we then decided that with the weight difference between the hard plastic and the steel, ( about 75 lbs) we'd better beef up the one main tank support that bolts to the frame. We welded a piece of steel down the center of the underneath of that original support piece for strength and then made another piece that fits on an angle from that, back to the frame itself, below where the original support piece bolts onto the frame. It too was made so it bolted onto the frame and bolted onto the support piece. It had to be made to bolt on because that original support piece cannot be put into place until the tank itself is back up in place. That original support piece is made to help hold the tank in place too. We held the new tank up initially while putting it in place with a floor jack on the front end and used the big U clamp in the rear for the old tank to hold up the back, "thin" end on the tank itself, but didn't tighten it down all the way at that point. Worked like a charm. Oh, and we lined the U clamp in the back and the original support piece with a heavy duty 3/8 inch black mat material I bought at Tractor supply for cushioning for sound and wear reduction now that the new tank is metal too.

JDeerekid · Jul 20, 2009

Great news on the new tank!!! Now where are the pictures??? I have the 4340C and am worried everytime I get into a little brush or rough and bumpy field conditions that I will hurt the tank. A metal one seems like the key.

Unclebuck257 · Jul 20, 2009

JDeerekid,

Ironically, I spoke to a Montana Factory Tech Rep this afternoon on the phone to get those A/C pressures I needed and he said the same thing regarding the new steel tank. Apparently, those hard plastic ones have been a nightmare for Montana and many many people are having all kinds of problems with them leaking like I did, and for the same reasons.

I'll get some pics of the finished deal, and those new support braces I mentioned, but in this Texas heat, all I wanted to do was get the thing installed and I didn't take any pics of the new tank before it was installed. You'll get a real good idea from the pics I do take now though.

John Reiss · Sep 12, 2009

Unclebuck257 said:
An update on my new steel diesel tank. It took an additional day to get it and then when the welder delivered it to my place, we then decided that with the weight difference between the hard plastic and the steel, ( about 75 lbs) we'd better beef up the one main tank support that bolts to the frame. We welded a piece of steel down the center of the underneath of that original support piece for strength and then made another piece that fits on an angle from that, back to the frame itself, below where the original support piece bolts onto the frame. It too was made so it bolted onto the frame and bolted onto the support piece. It had to be made to bolt on because that original support piece cannot be put into place until the tank itself is back up in place. That original support piece is made to help hold the tank in place too. We held the new tank up initially while putting it in place with a floor jack on the front end and used the big U clamp in the rear for the old tank to hold up the back, "thin" end on the tank itself, but didn't tighten it down all the way at that point. Worked like a charm. Oh, and we lined the U clamp in the back and the original support piece with a heavy duty 3/8 inch black mat material I bought at Tractor supply for cushioning for sound and wear reduction now that the new tank is metal too.

I have a2006 model 5740C which I bought new from the dealer in Ocala Fl on July 13,2007. I have a farm and small Airport here in North Central Fl. I use the tractor mostly to mow the runway. After 254 hour the fuel tank started leaking at the famous front screws. I called the dealer and they said the price of a new tank would be $480 not including labor and transport fees. I call the rep in Arkansas and they have offered to only charge me 1/2 the cost of a new improved tank model. I guess that all I can do for now since my tractor is 2 months out of the 2 year warranty. Let me how you new steel tank works out, since I may have to go that route in the future.

Unclebuck257 · Sep 13, 2009

John,

That new steel tank is working out real fine for me. The only thing that I'm going to have to go back and do, additional to what I've done already, is to take some of that 3/8 inch black rubber matting I used for cushioning and sound control and put some of it on top of that thin part of the tank, at the rear of the tank, by the U joint. I have it lining the actual U joint itself already. As I stated in an earlier post, that part of the tank is held up by a big U joint that bolts on the top to the frame of the tractor. Since putting in the new steel tank, I've mowed about 100 pasture acres and I've noticed sound coming from under the tractor at about that point, and it sounds like the top of the metal tank hitting on the frame in the rough pasture areas. Once I do that, there won't be anymore sound at all. Otherwise, the steel tank is working out fine for me.

Ironically, my buddy who bought a 2006 5740C after borrowing mine a couple years ago, called me this weekend and he has the infamous "tank leak" too. Same problem, from the same source, and he lost 13 gallons of diesel in his stone and dirt driveway over it too. He called Montana and they offered to sell him a new tank, that supposedly had the problems eliminated from it for half cost, or approx $150.00, since his tractor is out of warranty too. It would still be hard plastic though and he's kind of like I am about that situation. Right now, he used epoxy to fix his old one temporarily and is making some other adjustments like eliminating the guard plates where they are now, etc. He's seriously looking at having a metal tank made for his too, in the longrun.

Ron Blacic · Oct 21, 2009

I also have a leaking problem with the poor design of the fuel tank.Montana knows they have a problem(will not admit to it).They sent me(I paid $182 for shipping) a replacement tank,do not see any design changes,there seems to be residue or future leak at the screw locations for the protector plates.only time will tell. I own the LS4950c

FLHayman · Nov 19, 2009

I have a 2006 5740C, bought used. After reading about the tank, I looked at mine, no leaks. But, the guard seemed to be attached to the problem area, so I took it off. I know, I know, it's a compromise solution, but it looks like a branch pushing against the tank or guard would have put some stress on it. Yes, more damage is likely on a direct hit without the guard.
Maybe there is something to be gained from enlarging the guard holes, (in case thermal expansion/contraction adds stress, too) and mounting the guards with nylon screws? It would break the guard off in a prying impact, but keep it on for a direct hit, the breaking nylon screws would possibly protect the threaded plastic recesses in the tank from bending too much.
Also, I'd love to hear more about the plastic welding that was mentioned earlier. I thought that it was tough to find compatible welding material, since the chemical makeup of different plastics varies a lot. Please post more about this, if possible.
Thanks to all.

Unclebuck257 · Nov 20, 2009

FL,

The problems with removing the guard plate for me here where I live in Texas could be great. I live in an area known as The Barnett Shale with a lot of natural gas and oil. That also means shale rock, and a lot of it. Frankly, removing, and leaving off that guard plate is not an option for me with the rocks. That's why I never considered it.

I believe that the problem with those hard plastic tanks these tractors come with cannot be eliminated unless a person lives where the ground the tractor is used on is relatively smooth and even, because the stress that causes the tank to leak comes from just using it and the resulting vibrations.

I first repaired mine with very good plastic apoxy and that lasted about a year before I had the problem again, only much worse. I filled in the particular screw hole that was cracked and leaking, along with the crack out from the molded screw hole, and did NOT put a screw back in that hole at all. As I said though, a year, almost to the day later, I had severe leaking from another couple of screw hole areas. That's when I had a metal tank welded to the exact shape of the plastic one and then installed it on my 5740C.

You can get that apoxy at most auto and farm equipment stores. I forget the name of it though because my buddy already had some of it in his shop when we did those initial repairs. I remember it comes in its own siringe type dispenser too. I know he told me it was "high quality" and high dollar stuff too.

jc7622 · Nov 29, 2009

Leaker here. I thought I was the only one, I gues not. I took off the guard and sealed it up.

Amblansman · Aug 15, 2014

jc7622 said:
Leaker here. I thought I was the only one, I gues not. I took off the guard and sealed it up.

And the same problem continues. This will be the first problem I've had with my 5740 that was not due to normal wear and tear since I bought it new in 2007. I will try the Permatex or Versachem fuel tank patches first, but plan on finding a fab shop to make me an aluminum replacement.

cotman1 · Aug 9, 2017

I walked outside today and noticed mine dripping too, gonna look into a temporary fix (for now) and aluminum maybe as a replacement.

Unclebuck257 · Aug 15, 2017

Cotman,

I wish you luck finding an aluminum replacement tank. Be sure and check to make sure ANY replacement tank you are looking at buying will fit into the area where your old tank is. That steel tank I had made in 2009 was made to the exact same shape as the old hard rubber one so it would fit into the tank area. It is still going strong and I haven't had any leaks since putting it in eight years ago. Good Luck and please let us know what you do and how it works out for you.