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Restore Rusty Mondial Expansion Tank

Discussion in 'Mondial' started by cockrill, Mar 3, 2010.

  1. cockrill

    cockrill Formula 3
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    Jan 23, 2008
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    Frisco, TX
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    Jeremy Cockrill
    Hello:

    My car's expansion tank has a bit of rust on/in it. I'm planning on removing it and strip/repaint the outside. For the inside, I'm going to throw in some nuts and bolts and shake it up for a bit. Once I remove the rust on the inside, is there anything I can do to help prevent rust from coming back? I can't think of anything to coat the inside of the tank with that wouldn't eventually make its way into the rest of the coolant system.

    Thanks for any advice.

    --Jeremy
     
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  3. AZDoug

    AZDoug Formula 3

    Jun 17, 2009
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    As far as keeping rust from coming back, Eastwoods makes a two part gas tank sealer that would seem to work well for this, I would check with them for this application. It is clear, you poor it is, and hold the tank in various positions for a full coating, then let the rest drain out, you would want to make sure the radiator cap area is wiped clean of the stuff before it cures.

    I used this stuff on an old Honda CT-90 gas tank once, worked great, I mixed up a bunch of pea gravel,and 1/2" ball bearings and some water and put it inside the tank and shook vigorously for 10-15 minutes to break off any loose rust. I could have used some HCL pool acid, also, but didn't want to risk damaging the tank, as I didn't know how thin the metal was, and timing is critical on acid dips.

    Doug
     
  4. cockrill

    cockrill Formula 3
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    Jan 23, 2008
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    Thanks, Doug! I just read about the tank sealer stuff and it looks perfect. If it stands up to gasoline then I'm sure that it'll work fine for the expansion tank. (The website states that it can be used for "nonpotable" water tanks.)

    I'll post pictures once I restore the expansion tank.
     
  5. fiatbrett

    fiatbrett Karting

    Aug 20, 2009
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    Brett B
    Just to share-I had the same rust problem with my expansion tank for a 308 QV and ordered a new aluminum one from Superformance amd had it powder coated black to match the original. It turned out nice and cost less than any original (steel) tank I could find at the other sites.
     
  6. Meister

    Meister F1 Veteran
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    I repainted the outside of mine with POR-15 high temp paint. The stuff is tough as nails and IMO works much better than a rattle can high temp paint. Might not be exact OEM color, but I'll never have to do it again.

    The eastwood gas tank sealer is something I would do also, but didn't/don't have any interior rust.

    Good luck
     
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  8. Brian Harper

    Brian Harper F1 Rookie
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    Feb 17, 2006
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    Whoa, I didn't know those existed. Very cool. And the same or less than the original steel. I need one of those. Mine has a couple of pinholes that I'm trying hard to ignore.
     
  9. cockrill

    cockrill Formula 3
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    Brian, you may want to check into the tank repair kit from Eastwood that I ordered. It claims to repair pinhole leaks.

    Also, there is another thread on FerrariChat where someone took their tank in to a radiator shop and had the tank soda blasted, inside cleaned, holes welded closed, and repainted for under $60. I'm sure that I'll wish that I went this route before it is all over...
     
  10. Brian Harper

    Brian Harper F1 Rookie
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    Feb 17, 2006
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    My tank has been to a radiator shop once already when it sprang it first pin-hole. They repaired it, but now it leaks from several spots. I think putting money into a rusty old tank is a bad idea. The top of the GT4 tank has several concave ribs. I think that when my car sat for a long time that water condensed on the top of the tank, and drips hung out from the bottom of these ribs rusting all of them. All of the pin holes are along the center of these ribs. On today's drive the tank was really steaming and bubbling from several spots. I ordered the aluminum tank this evening. I'll post pics when I get it and put it in. Aluminum is the correct material for this anyway. Steel rusts and plastic gets old and brittle.
     
  11. Brian Harper

    Brian Harper F1 Rookie
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    #9 Brian Harper, Mar 14, 2010
    Last edited by a moderator: Sep 7, 2017
    I ordered the tank from Superformance and got it a week later. Funny how stuff comes just as fast from halfway around the world ans it does from halfway across the country. Except for being aluminum it is just about exactly the same as the OE tank. The only thing missing on the Superformance tank is the MAX and MIN levels embossed on the side, but I didn't really find those useful anyway. I suppose I should order the replacement sticker someday as well. The new tank looks to be very well made, the aluminum nipples and cap neck look to be very well done. It is in the car and was a perfect fit!
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  13. i-velocita

    i-velocita Formula 3

    Sep 9, 2006
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    I took my badly corroded tank to a radiator shop. They resoldered and repainted it for about $60. Works great!
     
  14. cockrill

    cockrill Formula 3
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    Brian:

    That aluminum tank looks very nice. If mine turns out to be in too bad of shape I'll order the aluminum one. (I think that my tank is salvagable, though, as it doesn't leak and doesn't have rust on the outside.)

    Thanks for the picture!

    --Jeremy
     
  15. HPINFO

    HPINFO Rookie

    Mar 31, 2007
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    Seattle, WA
    Can you tell me how you removed the level sensor from the top of the tank? I have a thread going currently, but so far no response.
     
  16. StuR

    StuR Formula Junior

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    #13 StuR, Apr 14, 2010
    Last edited: Apr 14, 2010
    Hi, busy house renovating so my mondi (QV) rebuild is on hold. However, this was one of the (many) fun issues I came up against. The rust problem is really the internal one (cause of most pin holes and difficult to see through green coolant whilst looking through the filler cap). The internal rust is caused by a chemical reaction between coolant and air. I found few (well, none) petrol tank sealers that could prevent eventually producing detached/chemically melted lining getting into the coolant system. The problem is exasperated if coolant is topped up with water, and if the cars sit around alot. That said, as bad as mine was, it had lasted since 1982! Aftermarket alu wasn't an option, as they were fine for 308s, but didn't have the hole for the mondi coolant level float sensor. Mine is under several boxes of parts, but I think (I know that's not exactly helpful) it 'simply' prized out. The float sensor (rod and plastic end caps) was shot, so I ordered a replacement. Unfortunately I could only get one from a horizontal tank version (US/3.2?), but was able to make a new float rod of the correct length. The tank itself, I ended up getting OEM, best price actually Ferrari. On the basis that it will last another 10-20 years (once the car is rebuilt!) it wasn't so terrible. I also replaced all coolant hoses with silicon (including the long under car ones that looked ok, but were shot from the inside out and braking down). For the lower rad joint I had a custom bend made (not expensive). Recored the rad, replaced thermometers, rebuilt pump, etc. Who knows, it might make a difference...
     
  17. HPINFO

    HPINFO Rookie

    Mar 31, 2007
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    #14 HPINFO, Apr 15, 2010
    Last edited by a moderator: Sep 7, 2017
    Thanks for the info. I actually found a great pic of the item on the Ricambi site (see below) that shows it just pushes into place. It will be interesting to see if it will pry out without breaking. It still works, so I hope so ($ 105 new.)

    The horizontal tank is for the cab I think (like my car) and the vertical is the coupe. Not sure why they would be different, but apparently they are...
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