Brazing water injection spigot on exhaust. yes/no

[Sinbad1]

Have had the exhaust riser welded at exhaust manifold takeoff and its now operating perfectly BUT I now have a tiny leak from the weld around the salt water injection spigot on the exhaust. There is no cracking and must be a slight weakness or internal corrosion.

The question is whether brazing the hole (which I can do in situ) will run the risk of electrolysis even tho I suspect the brazing would only be external and not go through to the salt water mix.

Ideas gratefully received.

 

[vyv_cox]

What do you have to lose? If the braze corrodes preferentially you will be back in the same situation you are in now. If it doesn't you have solved the problem.

 

[ccscott49]

SIF bronze, (brazing) would be an ideal way of doing it, bronze should not corrode in sea water.

 

[jollyjacktar]

I endorse Vyv's remarks, ie you will solve the problem. Nothing lasts forever. Problem with brazing is through case hardening and metal fatigue [different expansion coefficients for different metals]. I found this out the hard way in my youth with home made go fast exhaust systems on my hotted up special cars. But when that happens and it will take time, just repair it again.

 

[ccscott49]

Case hardening? Anyway it should be OK for ages, it will never get as hot as an exhaust system on a car (I did that aswell, parallel technology? or just cheap) Its the water injection pipe, so will stay at reasonable temperatures. Probably last longer than us!

 

[Sinbad1]

Thanks guys for the info.....will be getting the torch out tomorrow and brazing. Haven't done it since I was a kid and my brother bought a wrecked car. After my welding whenever he went around a corner the doors on the opposite side of the car flew open!!!...Hope my skill has improved.

 

[ccscott49]

Make sure its spotless before you start and use a good flux and proper SIF bronze rod! Siver soldering will do the job aswell, with less heat and its more flexible, forgot to mention that!

 

[mtb]

Re: Hang on !!

What material is the manifold, if cast your taking a risk re shattering it because of localised heat and shrinkage / expansion then cooling down
Re Brazing do you have enough heat to get the metal hot enough .
oxy acetylene bottles will be needed in which case gas weld it

I would consider using Loctight or other chemical to seal the pipe .
I think from memory Loctight 1601 is the one to get as its impervious to heat fuels and oil present in bronze, then paint it with epoxy cold tar paint .
Mick

http://homepage.ntlworld.com/boats
I want a big steel ex trawler / tug v / cheap or swap for tug

 

[pwfl]

One other idea: the little spigot come loose on my exhaust &, looking at it, the brazing didn't look that strong a method of attachment. I tapped some threads into the pipe it was brazed onto instead, & screwed in a small threaded hosetail. Much more secure.

 

[vyv_cox]

You need to be certain that you don't reduce the bore of the water hose fitting. Back pressure generated here will cause very rapid seal wear in the pump and in some designs you can fill your engine with water.