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Advice Wanted on Repairing a Brass Radiator

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I am after some advice on repairing the brass radiator on my 1914 Humberette. I have searched the past posts and found some information.

When I bought the car from the son of the last restorer, who died, he said his father had spent £1,000 having the radiator repaired. If this was so, in my opinion, he didn't do a wonderful job!

I decided to test the rad for leaks, made some plugs to block the hoses and poured in some water.




There appears to be quite a big leak from where the overflow pipe exits the header tank.




I am concerned that if I try and melt the solder around this area I may cause more leaks that will be more difficult to repair. After cleaning the area of the leak, Is it best to put wet cloth around the area of the leak before resoldering the joint? Or, should I use something else? I remember from my days in the bodyshop we used something, I think, was called 'Cold Front'.




Another area for concern is on the right hand side of the radiator shell. The hood side (bonnet) must have been rubbing on the rear edge of the brass and has worn the corner away. as I have tried to show in the above photo. The outer shell of the radiator appears to be soldered to the radiator, therefore I don't want to disturb this soldering.


I have thought of two ways to repair this.


  1. Make a strip of brass to solder in to replace the missing area with some tags at the back to give it more strength to solder to each side of the joint.
  2. Cut out the return flange on the left side of the photo. Then make a new right angle part in brass to solder in place. Make another flat piece of brass to strengthen the joint behind the joint. Then try and solder the parts in place.


Your thoughts would be appreciated on these ideas, or can you suggest a better option?


There are dents to the radiator shell, which I think, if I try to remove them may prove difficult and may cause cracking to the brass shell. Perhaps I should leave the dents. Your thoughts would be appreciated.




LH top.




To the side on of the top on the LH side.


and just to amuse you here is a photo of the last restorers idea of a front hood hinge pin location.




A new use for a wing nut!


I am looking forward to reading your comments.









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Soft solder is made and sold with different percentages of the constituents of the alloy;  and these have significantly different melting temperatures.     For instance, David Dryden had to make new horizontal gill tubes to fit and solder into  the new replica side tanks that came from USA with his 1904 Ford restoration project.   He tinned the length of each tube with the solder with highest melting temperature.  Suppliers of copper sheet will supply the correct gauge in a roll slit to the required width.  One edge of the strip he heavily tinned along the edge on the side that was to be joined to the tinned tube.   The strip was then crinkled by rolling it between a pair of gears.   I cannot remember asking or checking what the diametral pitch of the gears was.    David was then able to spiral- wind the strip around a tinned tube, with correct spacing;  then fix the ends so they would not shift.  The strip was joined to the tube by heating with a propane gas torch .  The solder to fit and fix the ends of the new gill tubes was a much lower melting temperature so the radiative strip did not unravel.   You do not have a gill tube radiator;  but I give you this example so you can use different solders to repair your radiator as you decide.      First tour for the restored 04 Ford was a one and two cylinder event at Parkes in central NSW,  in a season when overnight frosts are frequent.  With really good trembler coils, and fuel float level properly set, the engine would start with a couple of compressions, and could idle indefinitely without boiling.     Similar cars  required great effort and persistence with their "Armstrong starters", and boiled if standing idle for a few minutes.

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Mike I agree with you that who ever did the radiator did a lousy job and I would be worried about other solder points.  I see that you are missing the webbing that goes around the edge of the shell.  When install it should keep the hood from bouncing on the radiator.  As Ivan mentioned there are different melt points for solder and I have had success using a small butane "not propane" torch and low melting point solder.  I have not had success trying to repair a solder joint without taking it loose and starting over.  That is a very creative way to hold the end if the hood.

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I worked in a radiator shop for a few years after I left school. I know the repairs look very simple, but they’re only simple for someone with the right gear and knowledge. (We made a lot of money from fixing badly done amateur repairs.) So, if there is a repair shop near you, it would be a good idea to take it there and talk through the problems—they might be able to fix it relatively cheaply.

I could not find a YouTube video that you could follow so I will try to explain what to do.

If you do decide to have a go, you need to get some bar solder. We used 18-inch lengths of a ¼ inch by 1/8 inch solder, not the stuff you use for electronics. For flux, we used a liquid flux, not the paste flux plumbers use. The liquid flux is important because it’s used to cool things down if anything gets too hot and to wash away dirt. 

The torches we used were very controllable, from a very thin pencil flame for fine work like fixing tubes in the core, up to a wide flame to run the solder out of the joint between core and tanks. And they were not that hot.   

The first repair I would do would be the pipe going into the header, as it’s the easiest. First, clean the area with a wire brush, be careful not to hit the tubes in the core.

The next tool you will need is a piece of stiff wire with a flattened end. You could use a bike spoke--cut off the threaded end and flatten the last 1/8 to ¼ inch with a hammer. This tool is used to help melting solder flow, cleaning around the area to be repaired when hot, holding fittings in place when you run solder around them and a multitude of other uses.

With the blow torch add heat, just enough to melt the solder you want to remove and nothing else. Slowly heat the area around where the pipe goes into the header tank, using the wire (bike spoke) to help the solder on its way and to clean out any small bits of paint, rust, etc. The cleaner the repair area, the better.

If anything starts to get too hot, remove the flame and douse with the liquid flux. Use a small paintbrush, but put the flux in an old coffee cup and keep it close by. I would hold the paintbrush and the torch in the same hand so I could hit the repair with the flux instantly if needed.

Once cleaned, tin around the hole in the tank and the outside of the pipe. To tin means to use the smallest amount of solder to make a very thin film over the areas to be joined.

Once the area is tinned, heat the area again, then add the flux and start adding new solder. Use the smallest amount of solder, add flux, then add more solder until you have made the joint. With soldering, you do not need a big lump around the joint. Cool using the flux.  

Rinse with clean water when cold to remove the remaining flux as this can corrode the copper over time.   

To fix the core tubes: first, be careful, because it’s really easy to mess this bit up! Warm the area of the leak, using a pencil flame and as little heat as possible. While heating with the torch, clean the area with wire, add flux, clean with wire again, add more flux. The flux will help wash away any dirt you missed with the wire. If things get out of hand remember to use the flux to cool things down.


Add the smallest amount possible of solder to tin the metal, add more flux, and allow the solder to run over the hole, then remove the heat. This all should take 5 – 6 seconds per hole.  Cool, then rinse with fresh water.


Pressure test the radiator to just above the working pressure. So, if the cap is 15lbs pressure, test at 17lbs. We did this with a compressor with a regulator, some rubber bungs/stoppers, and a tank of water.  


The other way to fix a hole in a core tube or when a tube is too rotten to repair is cut through the tube at the bottom and the top and solder up the holes where the tubes go into the top and bottom tanks.  This is skilled work and I would not recommend doing it unless you were a pro as you can quickly destroy a radiator core if you get this wrong.


I would suggest you get a few copper sheets and practice before doing any of this. Drill small holes and try filling them with the least amount of solder possible, drill two holes close together, solder over one hole, then try filling the other hole without making the solder in the first one run. Try joining two pieces together, etc. Once you’re happy with your technique, start on the radiator. [I had six months of someone looking over my shoulder all day long before I was allowed to repair customer’s radiators on my own.]  


Finally, the worst thing you can do is get it all too hot, as the solder will run from the nearby joints, making the job much bigger. Also, too much heat can start damaging the copper.



Good luck!   

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Hi Mick,


I really appreciate you spending the time and effort you have on writing your reply to my post. Not only will it help me, I hope it will help many others in the future. I had forgotten about liquid flux as I have not done much solder work for many years. When the paste became available with solder in it I started using this for tinning the parts before soldering them together. I have also done lead loading on body panels back in the early 70's, although I was not that great at it, lots of solder on the floor when repairing vertical surfaces! Another tip I had forgotten about was using the stiff wire to help the solder flow. I have used this technique with aluminium repairs to help the metal flow.


Just to prove I am not a complete novice at soldering, below is a little job I did for a fellow MGBV8 owner, fitting a tap in the bottom of his radiator for him. It was the first bit of soldering I had done for a number of years. I was quite pleased with the results.




Although, I am happy to have a go at repairing the leaks on the Humberette radiator. I don't think my skills are up to dismantling the shell from the core and completely rebuilding the radiator. I have contacted this company to get an idea on the price for them to restore the rad. http://www.vintagecarradiatorcompany.co.uk/


Thanks again Mick for all your help and advice.



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I sure learn a lot from these Forum entries. 

Liquid flux is something I have not seen or heard of since the 50's in the Navy.

Thanks  for the excellent input for us "followers" of efforts.

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17 hours ago, Hans1 said:

I sure learn a lot from these Forum entries. 

I for one find this forum very useful. It's like having an friend, who is an expert, just round the corner, even though they maybe the other side of the world. I just hope that my regular posts on my 1914 Humberette restoration help some other members.


16 hours ago, MICKTHEDIG said:

The company's work looks good. I hope they can help you.

If I don't get an email back from them by Friday morning I'll give them a call. I asked them for a 'ball park' price. I just hoping they are not a company that thinks "if you ask for a price your can't afford it"!

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