Question: What would cause this heat damage to air diverter valve?

[jotto]

Whilst checking out the engine bay, I notice a hose with disconnected and with what looked like heat damage. Further investigation found this...

THe bottom of the valve looks as though it has suffered some serious heat damage.
Is the base of the valve simply a 90 degree union where the two rubber hoses meet from either side of the engine? If it is, my thought was to cut off the burnt section and fit a 90 degree copper bend, open to the valve and then secured in place with either epoxy or chemical metal. It wont look pretty but will be unseen and hopefully do the job.

My main worry is what caused it and what other damage will have occurred.

I did notice the hose on the passenger side has suffered heat damage and cracked at the engine end as well. My first thought was possibly a stuck riser valve in the exhaust causing over heating?

The corrugated hose from the air filter to the air pump is also split but I can possibly salvage that.

 

[bill81vette]

I would have to look under mine,but as far as I know,
it is OK....haven't seen that before though.....

 

[jotto]

I would have to look under mine,but as far as I know,
it is OK....haven't seen that before though.....

Hey Bill,
Thanks for the reply but Im not sure I understand. When you say it is OK, what is OK? lol. From what I can tell, the bottom of the vlave should have 2 outlets to which the rubber hoses connect to. I have a partial spout of one and a hole where the other should be. I think the other bit might still be in the end of the hose!
Im guessing it should look like this?

 

[Peer81]

On one (not very clear) picture it shows three black vacuum connections. But to be sure I can look at it for you this weekend

Groeten Peter

 

[Hib Halverson]

What would cause heat damage/rotting to a 31-year old, plastic diverter valve.

Hmmm...let's see. What COULD it be?

 

[jotto]

On one (not very clear) picture it shows three black vacuum connections. But to be sure I can look at it for you this weekend

Groeten Peter

Thanks Peter, appreciate that.
From what I can see the only pipe that was disconnected was the large black one coming from the drivers side of the engine. The one from the passenger side was still, but only just, connected.

I have nothing to lose so will try to repair it. Wish me luck!

 

[jotto]

What would cause heat damage/rotting to a 31-year old, plastic diverter valve.

Hmmm...let's see. What COULD it be?

Lol, OK OK....I guess I was wondering if there would be something wrong like a stuck check vlave or something. Im guessing not all 81 diverter valves look like this......

 

[Hib Halverson]

Lol, OK OK....I guess I was wondering if there would be something wrong like a stuck check vlave or something. Im guessing not all 81 diverter valves look like this......

I'll guess that some of them do. Considering the age, heat under the hood and other atmospheric conditions, the plastic might be just "rotting".

Problem may be that it's difficult to find a replacement. Both of the sources I'd use for diverter valves (some call them "secondary air injection switch valves") do not list one for an 81 Corvette. I have an old ACDelco part number of 214-39, but a Google search comes up with nothing...which doesn't surprise me as it looks like that particular valve may have only been used on 81 Vettes.

Keep in mind that hot exhaust does not flow through the diverter unless the air check valves are bad, so if both your check valves were bad I suppose the valve could end up like that. Are the check valves functioning properly?

Airflow is from the AIR pump, through the diverter valve and, if the diverter is closed, then to the atmosphere, or if the diverter is open, then to the AIR manifolds.

 

[GerryLP]

....Keep in mind that hot exhaust does not flow through the diverter unless the air check valves are bad, so if both your check valves were bad I suppose the valve could end up like that. Are the check valves functioning properly?....

My suspicions exactly. Those check valves can look even new on the outside, but on the inside, they corrode from heat oxydation and condensation makes matters worse.

The original check valves in my L81 were shot, but looked their radiant best on the outside. L