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Repair: Ruptured Auto Radiator with Adhesive

06/02/2010 9:38 PM

I chose to repair my radiator instead of replacing it when the bottom header (or tank or manifold) separated from the core.

I cannot fault the manufacturer for this because it occurred during a head gasket failure. Combustion gases filled the cooling system faster than the radiator cap could vent liquid coolant. However, considering cost and time to repair, I would prefer if the failure occurred elsewhere instead. In addition, I was trying to repair the head gasket with a ceramic engine sealer and needed a robust radiator during the interim.

With this in mind, I decided to eliminate the failure mechanism which was O-ring migration. (The flattened O-ring was pushed out of the channel, around an edge and up to the crimp tabs.) I replaced the O-ring with two-part epoxy resin. I had to make two modifications to the radiator to accommodate an adhesive.

I etched and anodized the aluminum core where it comes in contact with the nylon header (or tank or manifold). In fact, I etched and anodized the crimp tabs and inward almost to the tubes. Both etching and anodizing was done with a single application of phosphoric acid gel. This created a nano-structure to hold the adhesive. I immediately rinsed with distilled water, although deionized water would suffice.

The second modification was to chemically activate the glass-reinforced nylon header with a propane torch flame. This is done by moving the center (fuel-rich) part of the flame quickly along the edge of the nylon header. It is not necessary nor desirable to melt the nylon. I made a pass along each of the three surfaces at the squared edge.

I spread a thin layer of epoxy on the activated nylon and anodized aluminum surfaces (including the tabs) and a generous bead in the gasket channel. While pressing the header against the core, I used a rubber mallet to bend the tabs against the header. I followed up by using a vise-grip to bend each tab end to fit in the retaining groove. Almost every tab was back-filled with epoxy squeezed from the gasket channel.

This radiator repair exceeds factory strength by a very large margin. Not only are the original tabs now held in place with epoxy, the header is bonded with epoxy. As I found during testing, hoses became the new failure mode. The steps used in this repair are certainly difficult to justify in manufacturing most radiators, but in high-stakes situations where you want a robust radiator that cannot disassemble (spontaneously or otherwise) it is great.

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#1

Re: Repair: Ruptured Auto Radiator with Adhesive

06/02/2010 10:51 PM

Hello avid0g, It sounds like a good fix. BUT what about thermal expansion difference in the aluminum and plastic tank? With the holding tabs backed filed with epoxy holding the tank in place and the two surfaces etched to hold the epoxy. Would it not be likely fatigue somewhere in joining the two together developed somewhere in time and allow a leak?

It was just a thought I had.

Although I has a radiator several years ago repaired with epoxy where the tubes joined the plate at the tank. The two sections were aluminum on aluminum. No problem for the several years after that.

Charles

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#4
In reply to #1

Re: Repair: Ruptured Auto Radiator with Adhesive

06/03/2010 11:48 PM

Charles, I will certainly update this thread whether the car outlasts this radiator repair or vice-versa.

The fiberglass reinforced nylon tanks have a coefficient of expansion closer to glass than to raw nylon, but I don't know if that is relevant to your concern.

The tank fits quite tightly into the aluminum channel in the first place, so there was little room for shear along the perimeter of the join. I think that most shear will occur at right angles to the perimeter.

Even if the epoxy delaminates from one material in the channel, it may maintain a good seal if the delamination does not extend to the edge. Since the epoxy is relatively flexible and it extends well away from the stressed areas, I expect it to maintain a good seal unless it cracks.

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#7
In reply to #4

Re: Repair: Ruptured Auto Radiator with Adhesive

06/04/2010 1:33 AM

Hello avid0g, That was all I was thinking about was the epoxy coming un-glued from one surface or the other. As I would think the Aluminum would have one rate from the reinforced nylon tank. The original design with the o-ring would allow for some movement between the two and keep the seal. As to the epoxy if it can "flex" some, say somewhere between the thermal expansion of the Al and the tank. I would think it will work. And the only other thing I was thinking about was the "swelling" effect of the working pressure once everything heats up when the engine is running. But with the two surfaces etched and cleaned. It seem unlikely the epoxy to come loose. But I just had to ask the questions just to get a discussion going of the odds where or if a failure could occur.

For what parts cost to replace on autos today even used parts "which could be questionable at best". I do think what/how you repaired the radiator IS a good repair. "Now I've probably just jinxed it"

Good luck with the repair and DO KEEP US UPDATED.

Charles

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#8
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Re: Repair: Ruptured Auto Radiator with Adhesive

06/04/2010 2:16 AM

"But with the two surfaces etched and cleaned..."

I want to emphasize that etched aluminum is not a great bonding surface for epoxy that is exposed to hot water. The bond fails within days.

That is why I anodized the etched aluminum. In fact, I allowed the etch to go on for much longer than normally necessary. This allowed time for the aluminum surface to develop nanostructures from the aluminum-saturated acid. (This creates a dull instead of shiny surface that has an intriguing texture under a magnifying lens.)

I also ramped up the current quite slowly to allow the aluminum-in-solution to contribute to the nanostructures instead of coating them. The full-current anodizing created a very deep aluminum oxide layer below the nano-textured surface.

What I love about this project was that insight and technique far outweighed cost and overhead. It was just aluminum jelly, wet paper towel strips, stainless wire, a battery charger and a couple light bulbs. I worked on the radiator in the laundry slop sink.

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#9
In reply to #8

Re: Repair: Ruptured Auto Radiator with Adhesive

06/04/2010 3:30 AM

Sorry, I did not include anodize in my replies. BUT I do understand if Al is not anodize it will form it's own powdery oxidation which is not good for bonding anything.

I like the idea of using aluminum jelly.

So I take it one side of the charger was attached to the radiator, then a layer of Al jelly then wet paper towels then the SS wire laid on top (maybe weighted down for better contact?) What voltage/wattage of light bulbs I "assume" to control current? Last was the battery charger a stander 12vdc auto battery charger. Was it hi/lo type or did it have variable adjuster. And what amount of time did it take to get the anodize you wanted?

Your method sounds a (little/a lot less) involved than a full blown tank setup. Which sounds like it would work for some small parts/ideas I'm planing on in the future project or two.

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#10
In reply to #9

Re: Repair: Ruptured Auto Radiator with Adhesive

07/01/2010 3:13 AM

The manual charger has a high/low switch for 6/2 Amps at 12 Volts. I used my dome light bulb for 20 minutes. I can only hope this was conservative (slow) enough to add to the nano-structures instead of covering them.

I assumed that when I noticed foam/bubbles, it was safe to increase the current, so I did. Next time I will have to measure the specific gravity of some A.J. samples to see if the suspended aluminum is removed.

The current never reached 5 amps. Since it was so low, I anodized for another 40 minutes. The low current levels may be caused by the foaming gel and/or by the charger resistance.

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#2

Re: Repair: Ruptured Auto Radiator with Adhesive

06/03/2010 11:04 AM

Depending on what kind and model of vehicle and engine, possibly you might have attained a back-up relief for excessive cooling system pressure by just installing a lower pressure release radiator cap. Most caps have a release pressure of around 15 pounds. Lower pressure caps are available , but again depending on the car it may require a higher pressure to prevent boiling over. That was quite a fix you described on that radiator , let us know if it holds up as described in a previous post regarding expansion reactions. Good luck and thanks for the info.

h

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#5
In reply to #2

Re: Repair: Ruptured Auto Radiator with Adhesive

06/04/2010 12:22 AM

The second application of ceramic engine sealer requires a fully pressurized system and a completely degreased environment. The repaired radiator provided the former while I used a good degreaser/flush. The radiator cap was venting into the overflow tank, but once I kept the engine near an idle, it was not overwhelmed during cleaning. (Once gas was present under the cap, it could keep up.)

I am happy to say the sealant did it's job well. The new radiator cap only vents if I disable the radiator fan (removed fuse) and allow higher temperatures than normal. (This test was run durining engine flush after the second sealing, and revealed a greasy heater hose connector at the firewall, which stopped failing after cleaning.)

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#3

Re: Repair: Ruptured Auto Radiator with Adhesive

06/03/2010 12:44 PM

keep sealing it up and you will have a bomb. I hope you arent driving on roads near my home

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#6
In reply to #3

Re: Repair: Ruptured Auto Radiator with Adhesive

06/04/2010 12:41 AM

When the heater hose popped off the firewall hose nipple, it was quite a sight seeing all that steam coming from under the hood! I suppose, if I were to glue those hoses in place, it could fail more startling? Not. Don't worry if this becomes a standard way of building premium radiators. The radiator cap is the only necessary pressure relief mechanism.

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#11
In reply to #3

Re: Repair: Ruptured Auto Radiator with Adhesive

02/19/2018 7:25 PM

I resoldered the instrument panel PCB. Then, my wife and I drove this Neon for another 18 months before junking it. (It needed more work than the Blue Book value.)

Although I kept some 50/50 in the trunk, I never used it up. Radiator was still good.

Now I own a 2000 SAAB 9-5 Gary Fisher Edition Station Wagon. This requires a steady trickle of used parts, but I feel better about feeding this Swede.

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