# Welding, soldering or brazing a bung to brass radiator tank



## r-mm (Aug 25, 2020)

Hello all

I'd like to add a temperature sender bung to an brass tank radiator.  From poking about the web I believe soldering / brazing is the correct method.  The radiator will be a new reproduction of a 70's unit so at least it will not have decades of gunk on it, but I have no idea what alloy of brass it will be.  

I have a TIG and a small, not totally wonderful Bernzomatic oxy/acty torch.


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## tq60 (Aug 25, 2020)

Why there?

Often in equipment or add to hose via a coupler

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## r-mm (Aug 25, 2020)

The coupler is the common solution yes, but I find it to be a bit inelegant as it adds a joint and for my application, puts the sensor on the opposite side that I'd like it.  

Here's a picture of a radiator (not mine) that has the solution I'd like: a bung on the lower driver's side facing rear.


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## ELHEAD (Aug 25, 2020)

I believe solder is what is needed. 
Dave


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## RJSakowski (Aug 25, 2020)

Soldering is the traditional way of attaching a port.  If the core tubes are soldered in, brazing would possibly cause a leak in the core.


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## r-mm (Aug 25, 2020)

Thanks guys.  For work of this scale what type and size torch would be appropriate?   I've got this Bernzo oxy/map torch.


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## Lo-Fi (Aug 25, 2020)

Yep, soft solder it on. That setup should work fine. Just be sure to submerge or wrap with wet cloth anything that's close and has a solder joint. Get in with the heat, flow the solder and get out as quickly as you can. A really small torch is not an advantage in that respect. The longer you spend, the more heat soak you'll get to places you don't want the heat. Your fit, prep and application of flux are key to success too.  Worth doing a test run if you've got some copper or brass scrap the same size as the bung and gauge of the plate. 

Good luck!


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## benmychree (Aug 25, 2020)

Or, be more cautious and let a competent radiator repair man do it; imagine being on the road far from anything and having the thing blow out, what then?


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## r-mm (Aug 25, 2020)

Ha I should have said... this is for a 10 year project where I am perpetually out of my league and like it.  Did the welding, assembly, wiring, motor, rebuilt the transmission.  I'd say a solid 85% of it I did right!  Failures welcome/encouraged.  Not a daily driver, a journey.


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## aliva (Aug 25, 2020)

Soldering would be good, silver solder is better but requires more heat. What ever method you choose, lay the rad horizontally on a bench fill the tank  with water 1" below the bung level and solder away. The water will dissipate the heat from the rest of the rad. Last step pressure test .


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## FOMOGO (Aug 25, 2020)

On brass you would be fine using regular plumbing lead free solder and paste flux, though 50/50 would be a little easier if you could find any. Make your fit up as tight as you can get it, and clamp it in place so it can't move around on you. Don't forget surface prep, wire brush, or emery cloth/sandpaper. Put most of the heat to the fitting, and as soon as it freely takes the solder, let it flow in and around and get out. Just mapp gas should be more than adequate. if you are doing it on the bench, should be a piece of cake, and clamping it in place shouldn't really be neccessary. Mike


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## r-mm (Aug 25, 2020)

Thanks guys.  I go have a regular old Bernzomatic MAP torch.  It has a reasonably fine point, nothing too precise but based on what I'm reading here it sounds like it should do?  

I'm not familiar with the solders mentioned.  What would make me pick 'plumbing lead free' vs '50/50' ?
I don't have anything on the shelf and can pick up either.


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## Old Mud (Aug 25, 2020)

IMHO pure lead or 50/50 should be much better than Lead free. All old radiators were built with pure lead. Even the 50/50 means it's 50% tin. Tin is stronger but takes more heat. As far as your designed area for your fitting, you do know that would be the coolest part of a radiator ? Most heat would be at the top where the engine return is.  A little practice and you will be fine.


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## NortonDommi (Aug 25, 2020)

A pin-point flame is not what is needed. Soft solder with a large gentle  neutral flame.  I'm 100% with you as to location. Senders in the top of the head is insane as if coolant level drops the gauge reads low usually the last thing is the gauge pegging itself from superheated steam right before  disaster.


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## westerner (Aug 25, 2020)

In real estate there are three critical points-
Location, Location, and Location

In my experience with soldering, there are also three critical points-
Clean it, Clean it, and Clean it again. 

Literally ANY contamination of nearly ANY kind in the joint will compromise the flow of solder, and thereby the integrity of the joint. 

After that, any of the tips above will get you a good joint.


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## Ulma Doctor (Aug 25, 2020)

have you considered a temperature sending unit in the block?
or was this purely radiator temp you were wishing to observe?

i cracked up when i read...


r-mm said:


> Ha I should have said... this is for a 10 year project where I am perpetually out of my league and like it.  Did the welding, assembly, wiring, motor, rebuilt the transmission.  I'd say a solid 85% of it I did right!  Failures welcome/encouraged.  Not a daily driver, a journey.


reminds me of my brother. no schoolin but has restored most of my dad's 84 F-250 6.9L Dino power Turbo,4X4. He's had a few setbacks but has seemed to take them well. i have had extensive training and real world working on a fleet of 6.9L engines, i was able to help with the beast when he didn't want the help- but the beast fired off about 6 months ago. not quite ready for daily driving, but in a few months that will likely occur.

as long as you keep up the good work, the hurdles will be surpassed one by one! 
i think you'll do just fine


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## markba633csi (Aug 25, 2020)

Biggest problem will be accidentally unsoldering nearby joints.  
Use the wet rag method mentioned by Lo-Fi in post #7.  Use some extra flux, either paste or liquid.
Electrical rosin-core solder would be ok to use.
-Mark


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## tq60 (Aug 25, 2020)

Lots of flux and "tin" it first.

Practice on loose part first.

Clean, then with paste flux on a paint brush heat the part then as it gets warm touch the flux to it and it will spread.

Grab solder and touch to item where flame is not.

When right temp it will flow easy and you want to get a coating of solder on the whole area.

Grab with pliers and shake off excess.

Stop in water to cool.

Repeat until you can get the heat just right to flow even without hearing just one spot.

Once comfortable tin the radiator and wipe off excess with dry rag.

When cool apply paste flux to surface then clamp the part in place.

Apply heat to the bung while touching solder to the joint.

The flux will transfer the heat and given both sides tinned they will bond with the heat and added solder.

When it melts apply all along the joint with heat removed and it should look like a Oreo when done.

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## Alcap (Aug 26, 2020)

My Uncle and Grandfather used to solder gas tanks with an electric iron . I did one myself on a garden tractor gas tank that has a slice in it . JB Weld didn't hold up.  Soldered a copper patch .  I would think a large electric iron with the heat applied at the bung would get it hot enough to solder if using a torch might loosen up other joints .


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## Old Mud (Aug 26, 2020)

R m, i just re read your post and saw the pic. you posted. I believe the pic. you posted is of an Aluminum radiator. Have you checked that yet ?


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## r-mm (Aug 28, 2020)

Thanks all for the advice.  Old Mud - that was an 'inspiration pic'.  My radiator is brass for sure.  

Alcap the electric torch is interesting for its safety margin you note.


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