TheSamba.com :: View topic - Should the outer shell of heat exchanger be loose?

Wed Jul 27, 2005 8:21 am

'75 2L
The outer shell on both slide a little. Are they suppose to that way? Also, how does one check to make sure there is no exhaust leak in the exchanger? I have them off right now and wanted to check them before I install.

Wed Jul 27, 2005 9:40 am

The way that all works is that it is a "air to air" heat exchanger. No exhaust is allowed in the outer skin.

Best way is actually braze that on there, JB weld it, or even crimping is better than nothing. It will just improve the heater action by making that as air tight as possible.

Wed Jul 27, 2005 10:17 am

Rumdum wrote: '75 2L
The outer shell on both slide a little. Are they suppose to that way? Also, how does one check to make sure there is no exhaust leak in the exchanger? I have them off right now and wanted to check them before I install.
Mine are loose and rattle sometimes, for exhaust leak, you could fluid test them to see if they hold fluid...it's a very thick pipe and most likely isn't leaking exhaust from this location. (most leaks occur between joining pieces of metal- ex: elbow, header to heat exchanger, etc.)
Once installed, check the interior with a Carbon Dioxide meter- as CO is odorless and tasteless- to insure you're not leaking fumes inside. (flatulation is ok unless a female is there)

Thu Jul 28, 2005 1:36 am

Rumdum wrote: '75 2L
The outer shell on both slide a little. Are they suppose to that way?
Years of rusting has turned thick metal into what you are seeing.

Quote: Also, how does one check to make sure there is no exhaust leak in the exchanger? I have them off right now and wanted to check them before I install.
Remove the muffler, open the exhaust valve, pressurize the cylinder with compressed air and try to block the hole on the heat exchanger with a wet hand. If you can force air out another opening you've got a leak.

The exhaust pipes are encased in a radiator casting. They usually go bad at the ends.

Fri Nov 06, 2009 6:37 pm

Randy in Maine wrote: The way that all works is that it is a "air to air" heat exchanger. No exhaust is allowed in the outer skin.

Best way is actually braze that on there, JB weld it, or even crimping is better than nothing. It will just improve the heater action by making that as air tight as possible.

This is an OLD THREAD.

Randy just so I know I am getting this right. There should be NO EXHAUST getting into the outer shell. Does that mean the outer shell should be sealed at all openings (front, back, and 2 where the exhaust ports enter) Mine are loose and I want to seal them, Is JB weld strong enough, or should I have them welded closed?

Thanks

Fri Nov 06, 2009 6:54 pm

Not Randy, but...

You want these sealed. Air from your engine fan is pumped through your heat exchanger, where it picks up heat, and then travels all the way to the front of the bus before it can warm your toes.

If the heat exchangers can slide on the pipes inside them, then air is escaping too. This makes it harder for warm air to get to the front of the bus when you want heat or defrost. Sealing the heat exchangers as best you can reduces the amount of air that is lost, and will improve the airflow to your cabin.

DJ Roberts

Fri Nov 06, 2009 10:34 pm

If the shell is welded to the pipes it will crack in days or weeks, the pipes expand far faster than the shell. The shell needs to fit tight if you want good heat, I usually TIG weld or braze C shaped patches around the pipe openings and let it float on the pipes like VW did it but thicker where it touches.

The only way exhaust can get in there is if there is a crack in the pipes internally, the shell is under positive pressure when running.

Sat Nov 07, 2009 12:42 am

Thanks guys, that makes a lot of sense,

Busdaddy. do you have a picture of what you mean by the C patches?

My exchangers are off right no so easy time to do the fixes

Sat Nov 07, 2009 8:57 am

I can't get a pic of any right now as they are all installed but usually the area around the pipe is worn or rusted so there is a gap and the shell rattles around loose.

Imagine a circle of 20ga sheet steel with the ID the same as the pipe OD and the OD of the circle approx 1" larger (or more if the hole is huge), then cut the circle in half so you get 2 C shaped parts. Lay it on the shell at the pipe and tack down where it touches, then hammer it down so more touches and tack that down, more hammering, tacking, hammering, etc.......

Make sense?

Sat Nov 07, 2009 8:58 am

Yes, makes sense.

Does it have to be TIG?

Sat Nov 07, 2009 9:08 am

Nope, I've used brass rod in the past with good results, you could even do it with pop rivets or screws and muffler cement.