Ideas for repairing radiator? REPAIRED!

[ROUSTABOUT]

I am not doubting nor know any of these will work but 07wingnut's recommendation would be along the line I think makes good sense. You should install large flat washers on the machine screws (stainless) and drill the holes snug so they would remain in place as you install them using the hole from inside the radiator. Have them long enough so you could use vise grips pliers to hold the screws to tighten the nut. Would suggest a good gasket being used.

Along the concerns of another failure the biggest concern I would have is not the cracking coming back but the nipple totally breaking off. Temperature gauges normally measure the coolant temp not the engine temp so loss of coolant would allow the engine to be very hot before you noticed it.

I had a nice old truck I bought. Put new belts and hoses. But, heater hose fitting broke off at intake. It was over soon thereafter. Never showed hot.

 

[RancherGuy]

Update: FYI -- and for people reading this in the future.

Upon close examination of the exploded diagrams, the L2800/3400 series radiators (TC020-16000) are different. One of those would require modification of other parts on an L3200.

On the other hand, there is no discernable difference looking at the L3200/3800 (TC420-16000) and L3301/3901 (TC620-16000) diagrams. Everything appears to be identical -- except the newer model rads sell for half the price, roughly $300.

Still mulling a repair, but it would nice to know for sure if the new rad is backward compatible one generation.

I assume you know that the primary difference between L3200 & L3301 and L3800 & L3901 is the emission stuff. But I'm not knowledgeable enough to say if the radiators are identical.

This topic got me to thinking of a different approach than reinforcing the existing plastic. Seems that this is a "stubby pipe and flat washer" design concept. If you are into custom fabrication, I could see a round washer (or flat sheet with rounded corners) piece of brass and a stubby brass tube or pipe fitting brazed together. The home supply stores might carry a good candidate for the brass pipe fitting. Then the new custom piece is glued to the existing flat surface on the radiator tank, creating a significantly large bonding surface.

 

[Doc G]

Guys, thanks for all the input. I have a plan for a repair -- back at you in a couple of days!

 

[Doc G]

OK -- for those waiting with bated breath (I know you were) here is my final solution! I hope this helps someone in the future.

To recap, the basic options were repair or replace.

Replacement Options:

• Aftermarket: Not available as far as I could see. This tractor was sold new as recently as 8 years ago, so there may be patents covering some aspect of the radiator design.
• Previous generation (OEM TC020-16000): will not fit. Would require mods on the tractor.
• Same gen (OEM TC420-16000): guaranteed to fit, but over $600. (Sheesh!)
• Next gen (OEM TC620-16000): should fit, but not positive. Around $300.

Repair Options suggested by you guys:

• JB weld or similar rigid epoxies: I love JB! But its rigidity is not ideal for this problem.
• Cyanoacrylate: The prime ingredient of most super glues. A better match (does not cure as brittle/rigid) and can be reinforced with silica fiber or beads. But these products are really not good gap fillers and do not stand up well to harsh environments, e.g. hot water and glycol.
• Plastic weld: If this were an open crack in the middle of the tank, I'd have tried it. In fact, I brought the radiator to a rad shop that repairs plastic, but they were unwilling/unable to try welding an inside corner. I can understand why.
• Cut off the nipple and build a replacement consisting of a flat metal "washer" (or disc) with a tube or bolt. I thought long and hard about this, but it has downside: the radiator sits on rubber grommets, with the nipples poking through the grommet center. A fix like this would raise the radiator vertically by the thickness of the washer, and there isn't any slop in mounting screw alignment (at least on my tractor). This would also move the fan shroud marginally closer to the fan, which might or might not be problematic. Kubota designed fairly tight tolerances here.
• And there's the solution I came up with, below!

The way I see it, there are two fundamental problems. (1) The adhesive problem. It needs to cure with some flexibility, be water and glycol resistant, stand up to thermal cycles, adhere to nylon 6/6, be able to fill gaps, and ideally have a similar thermal expansion ratio as the plastic itself. (2) The structural problem. The "fix" needs to be able to withstand the forces and vibrations that caused the failure to begin with.

Regarding (1), I think this is one of those times when we just need an epoxy that's better than the stuff in farm and hardware stores. I selected BONDiT B-45TH (see ADHESIVES for Nylon), part number 7513A1 from McMaster. Expensive ($80) but tailor made for this job. Requires that you abrade the gluing surfaces, which I did with a wire brush on a Dremel.

Regarding (2), I noticed something: there is a 45-degree bevel on the inside of the grommet. So I bought a rod of nylon, fired up my trusty old Harbor Freight mini lathe, and made the following pieces, one for each side.

Above: The grommet, and a small piece of nylon that fits into the beveled depression in the grommet.

Above: the fillet piece sitting on the existing nipple. After fabrication on the lathe, I sanded the ID so that it is a friction fit at the bottom of the nipple. (Note the nipple is slightly tapered, wider at the bottom.)

Above: pressed into a layer of epoxy. This should provide superior mechanical strength for the nipple, and is how Kubota should have molded these nipples to begin with.

Above: A shoutout to my FEL cylinder safeties. Always used whenever the FEL is up for engine service!

Bottom line: Installed radiator, flushed, refilled, drove around high speed over bumpy ground, no leaks the last couple of days! Total repair about $85. Thanks again everyone for your suggestions.

 

[zzvyb6]

What about the plastic cement used for plumbing ?

 

[Boss 302]

Impressive, let us know how it works out. You may be on to something

 

[Doc G]

What about the plastic cement used for plumbing ?

That's an interesting question, which I should have included in my list of possibilities. Plumbing cement (like for PVC or CPVC, I assume you mean?) is actually not an adhesive -- it's a solvent. It chemically dissolves, or "melts", the PVC so the two parts are in fact welded. So it is a form of welding.

However, I too wondered about solvents for Nylon, and here is the low down. Bottom line -- not practical for normal folks unless playing with formic acid is your thing.

"At room temperature, bonding using conventional solvents will not provide effective bonds on nylon. Some non-conventional solvent cements are sometimes used. Nylon dissolved in formic acid forms a high strength bond, but the cement is very toxic and highly corrosive, which makes it unfavorable for most modern manufacturing environments. A solution of resorcinol or calcium chloride and ethanol offers a less toxic formulation--the bonds are best when cured with heat. The other major issue is the solvent adhesives tend to form brittle joints, lack toughness, and are not suitable for dissimilar material bonding. Current trends for environmental safety have led industry away from solvents." [ADHESIVES for Nylon]

 

[Henro]

That's an interesting question, which I should have included in my list of possibilities. Plumbing cement (like for PVC or CPVC, I assume you mean?) is actually not an adhesive -- it's a solvent. It chemically dissolves, or "melts", the PVC so the two parts are in fact welded. So it is a form of welding.

However, I too wondered about solvents for Nylon, and here is the low down. Bottom line -- not practical for normal folks unless playing with formic acid is your thing.

"At room temperature, bonding using conventional solvents will not provide effective bonds on nylon. Some non-conventional solvent cements are sometimes used. Nylon dissolved in formic acid forms a high strength bond, but the cement is very toxic and highly corrosive, which makes it unfavorable for most modern manufacturing environments. A solution of resorcinol or calcium chloride and ethanol offers a less toxic formulation--the bonds are best when cured with heat. The other major issue is the solvent adhesives tend to form brittle joints, lack toughness, and are not suitable for dissimilar material bonding. Current trends for environmental safety have led industry away from solvents." [ADHESIVES for Nylon]

I skipped the last three pages of what I assume was reasons why anything you might try would not work.

Looks like you came up with a solution, but I did not have the energy to try to understand your long post (maybe only long at my age and short attention span) explaining the solution!

Glad it seems to be working for you though...