Something burned up... how bad is this?

[Tuba-man]

I'm obviously a fool for thinking that this poor '78 Volare could just be started up after sitting nearly 20 years and driven with just an oil change and some tires. But she seemed to be running fine - the 318 was smooth and quiet and even passed California emissions. Then the other night I heard what sounded like a massive exhaust leak while coming off the highway. Below are pictures of what I believe to be the source.

I don't know much about emissions equipment as most of my experience is with pre-75 Mopar engines. Would someone please tell me what this thing even is (and how/where to replace it)? Why did it burn up?

 

[Justwondering]

If we don't have an award for 'Most Gruesome Mechanical Fail', we should -- you would have my vote.

 

[BudW]

I know what it does, how it does it and I know why it was disconnected and (will be) discarded from my vehicles – but none of that helps you any.

I have one that might work (maybe) – but it is still attached and will be for a few more months.
I’ve seen those fail before – but not like that.

Some pictures that might help.

Dodge part number is 4041397 "AIR SWITCHING DIVERTE" – which was superceded to 83506382 "AIR SWITCHING" in 2009.

 

[Tuba-man]

Yeah - it's pretty spectacular. Perhaps I can find one of these at the boneyard.
Any ideas why this might have happened? I had noticed that the junction between the front hose and the 'air switching valve' seemed a little weak - there may have been some moisture in there or something.

 

[BudW]

The part moves air under a little bit of pressure (a couple of PSI) and the valve simply moves air between the exhaust ports in exhaust manifold or downstream to catalytic converter, depending on component temperature. The part doesn’t run hot (underhood temperature).
The only thing I can think is a secondary fuel source and a heat source (propane for testing purposes, maybe) but that doesn’t explain why or how.

This part was used in most ‘70 and ‘80’s V8 cars and all worked pretty much the same way. You should be able to find something (even Ford or GM) that will work. Most of the newer ones bolted to the AIR pump (smog pump).

Finding the metal tubes and one way check valves (on the metal tubes) is the hard part (which you don't need).

 

[Aspen500]

I can almost guarantee one (or both) of the one-way check valves on the tubes failed. When they do, exhaust will go the wrong way and get to the diverter valve and,,,,,,,,,,,,,,,,,,,,melt.

I remember this happening on Ford's all the time "back in the day".

The check valves are readily available. The air switching valve,,,,,,,,,,,,,not so much.

They look similar to this:

 

[jasperjacko]

I'm pretty sure that's the blow off valve for the turbo.... must have over-boosted it!lol

 

[Tuba-man]

Thank you gentlemen!
Is there an official part name for the check valves? Definitely going to hit the junkyard for the air switching valve.

 

[Aspen500]

Can be called air inection one way check valve or aspirator valve. Not sure which term Mopar used though.

 

[Tuba-man]

Great - thanks!
Here it is:
BWD CV8 - Exhaust Air Supply Check Valve | O'Reilly Auto Parts

 

[Aspen500]

Fortunately the same valve was used on multiple makes, not Mopar only.

 

[BudW]

For whatever reason, about 50% of those Air Check Valves or Aspirator Valve (same thing) are screw on (like above) and about 50% are welded on (see picture, below).

The part are the same - so if you have a welded on valve, see if you can find a fitting that will fit the new check valve (above post) and get it welded on (the fitting, not the valve). The guts of the valve are exactly the same – so you will not have any issues in California for emissions testing.


I don’t understand why the factory didn’t make them all screw on. I also don’t understand why they didn’t use a thicker metal pipe (or out of stainless steel).
On the same note, Chrysler was having money problems in ’77-78 so maybe the bean counters had some items stretched as thin as it could go (IDK).


Note: the air check/aspirator valve is rather, correction, is quite noisy when left unhooked (air cleaner off or whatever).

BudW

 

[Aspen500]

Some also went inside the tube (like an exhaust pipe into a muffler) and used a tiny little saddle clamp to secure it (some Ford's did anyways).

 

[Tuba-man]

Alright... got the new check valves (plugged) in and, although it's not attached, something "like" an air-switching valve in place - picked up another diverter valve from a Cordoba and it's a place holder. I'm still not sure what it does but the car is running now and seems to be okay. Already passed smog so that's not going to be a problem for quite some time. Thanks for all of your help!

 

[BudW]

There are two Aspirator valves used on cars with an A.I.R. pump.

The first one is indicated by blue arrow and valve is located between the vacuum amplifier (yellow X) and engine breather (gray X) on top of the intake. Its hose attaches to bottom of air cleaner and uses filtered air – on cars without A.I.R. pump, or to the switching valve on cars with A.I.R. pump. That upstream pipe bolts to rear of both exhaust manifolds in direction of green arrows.

The downstream A.I.R. Aspirator valve (top red arrow) either attaches to exhaust manifold outlet, to Y-pipe just below the exhaust manifold or down by the cat converter (depending on year car was built).

The upstream allows for quicker exhaust heat up (the cat converters have to be at 1,000’ (or so) before they start working) and then downstream once exhaust is hot.

Cars without A.I.R. pumps, all air goes in at rear of manifolds.