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Soldering: Aluminum to steel?

wheels87k5

wheels87k5

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I didn't want to hijack Zims thread where soldering is being discussed on a Relay subject so:

I've been chasing a mild idle issue. There isn't a large jump in the tach or anything, but when the idle doesn't hold steady then there is a problem. I found one of the problems while working on the throttle body.

The port for the MAP sensor had a crack in the stem at the entry point to the throttle body. I'll post pics in a few. I tried to see how far around the crack went and put too much pressure on it that it broke completely off. I drilled out the broken off part and reinserted the stem. Of course it will not stay in it's place so I was wondering since the throttle body is aluminum and the port stem is steel, can it be soldered? I've been told it can be done but would require a lot of heat that could melt the throttle body. Some say to use JB weld.

What say yee?

Fordum, I know from reading that you've done a lot of soldering. What works best?
 
Soldering clean copper with good solder is reasonably easy. Soldering aluminum to steel would be the exact opposite. :)

Is this a TBI? A new throttle body from the wrecking yard would be what I went for.
 
Actually I have heard of a system that will solder aluminum to steel. I actually saw an ad for the stuff somewhere, never tried it. Copper to steel is easy, aluminum not so much.
The only thing I can think of instead of soldering, would be threading. I would have to see the parts, but if there is enough metal in the aluminum, you might be able to thread it to a standard pipe thread.
Then thread the stem to a standard size and use a bushing between the two.

I will see if I can find the solder info.
 
OK, found something. I have no experience with this outfit, but they claim that their stuff can do what you want. If you find out anything, let us know.

http://www.breckocorp.com/
 
Thanks for the link.

Here's the crack on the stem.



Broken off





I was able to drill, using the next size up routine, the broken piece out of the throttle body with no damage. And smoothed the edges of the left over piece of stem. There was enough of the stem to insert into the port but it would not stay in place so I used a tack hammer and tapped it in further into the port and it got a good hold and seal. But I know for a fact that it's going to come out sometime down the road and I was curious as to weather it could be soldered for a permanent seal.
The throttle body is aluminum and the stem is steel? The stem sticks to a magnet but the magnet doesn't stick to the throttle body. Right now it has JB weld on it. And so far the blazer has run better than it has in a long time.

I've been chasing a very mild up and down rev issue for a couple of years and this was the cause. I have also found other things that were not up to spec like the new IAC I bought. It's only 3 months old and is bad already. I replaced it with my backup and now it will hold the RPM setting instead of climbing back up 400 rpm more after shutting it off and then restarting it 2 minutes later. I've been scratching my head on this thing that I'm now completely bald. Well, there's still a couple of strands but I'll save on shampoo. :rolleyes:

I was also fighting a bad injector issue as well. I finally got that taken care of in the midst of the above.

I thought the EGR might be causing some of the problem so I burned a new chip that deletes the EGR and everything is blocked on the TB and manifold. I get no SES light and it runs very good. It still needs the chip tuned for the mild upgrades but I'm still in the learning phase of that.

And get this. My spare stock throttle body had the same thing happen. The MAP stem is also broken. I'll check that link out and see what they have to offer as for a permanent repair just in case the JB weld fails.

Sorry, no pics of the repair with the JB weld but I will get pics if I need to remove it again.

Thanks for all the help
 
I think if its just a vacuum port barb fitting,I'd try to thread the hole and use a barb fitting with pipe thread,if its large enough size to use say,a 1/8" npt tap on it..if not you could use a bolt,drilled for a vacuum passage,tap the throttle body for whatever size bolt will fit,you can also grind the head of the bolt down to a barb shape to help hold the hose on..

You may be surprised what J-B Weld or similar epoxy sticks like "Quicksteel" can hold up too...properly done,the bond is probably as strong as the base metal is..
 
Aluminum can't be soldered with any normal solder - it's like scotch taping grease to water. There are aluminum brazing rods designed to repair aluminum radiators, A/C lines and such. Don't know how well they work, but when I looked into it a while back, by the time you had the equipment to do the repair, it was cheaper to replace the part.

I think by drilling the old piece out and fitting the left-over tube in there, the repair will be fine. I would just add JB-Weld or something like that when inserting it, with a little piled up on the outside. It just has to hold vacuum and not fall out. They are probably just press-fit from the factory anyway.

You might try radiator repair epoxy instead of JB? http://www.amazon.com/Mastercool-90934-Alum-Repair-Epoxy/dp/B00AZJTEAS

Pipe thread is tapered, so tightening a pipe into that hole could crack that part of the throttle body. I wouldn't go there unless it fails again or something.
 
So far the JB weld is holding up. I let it cure for 36 ours before running it. I went to the link provided by Fordum. They have a solder that will do aluminum to almost any metal but I haven't heard from them yet. Sent an email asking more about the product and how to get it. I'm not sure they sell in small quantities. Might hear something early this week.
 
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