PAIR Reed Valve - rattle on startup (1 Viewer)

[eikelben]

I was shocked to find not a single posting about this noise – I was hoping to learn that it's a "land cruiser" sound and nothing to be worried about. I have read about people eliminating the system entirely – we do have emissions where I live so not likely a path I want to go down unless it offers some added benefit.

I encounter this noise when starting from cold. The truck typically idles at around 1600-1800 on startup and eventually settles to around 650-700 (I'll have to double check that the next time I have the truck out, but I believe that value to be accurate).

Here is video of the sound I get at startup. If I had to guess, I'd say it makes the sound for 20-30 seconds or so and then stops. The engine maintains a fairly high idle and slowly creeps down. Is this typical or something that needs attention?

A visual for those needing some context:

 

[richardlillard1]

Normal on every 93-94 I’ve seen.

 

[eikelben]

Normal on every 93-94 I’ve seen.

Good to hear. Hopefully the video will help someone in the future.

Just for my own understanding,any ideas what is actually occurring inside the unit?

 

[richardlillard1]

The reed valve is preventing back flow from the exhaust from entering the pair and intake. This becomes even more of an issue if exhaust back pressure is lessened, as you would find with some aftermarket exhausts which are less restrictive than the stock setup.

 

[richardlillard1]

Basic design of a reed valve. It’s meant to restrict in one direction, while flowing in the other as most check valves do. The rattle is the check valve petals doing their job until pressures are regulated in the system.

Also worth mentioning that removing the pair system will not have any affect on power, mileage, or anything else. It exists solely to lean out the exhaust gases and thus lowering emissions.

 

[WCBlueSky]

Normal on every 93-94 I’ve seen.

Yeah I confirm my 94 makes this noise on startup.

 

[landboozer1]

Good to hear. Hopefully the video will help someone in the future.

Just for my own understanding,any ideas what is actually occurring inside the unit?

It did, mine sounds exactly the same at cold startups only

 

[RAYJON]

Just a thought my 93 has always done this but pull the vacuum line off of it when you first start, the noise will go away and you will be able to hear if anything else is making noise