Hearing a "boinnngg" sound when turning off key

[jfnall]

Not sure how to search for this one.

'07 stock FJC. 104,000 miles. When I turn off the key, I hear a boing sound coming from the back of the vehicle. Sounds like a spring being sprung. Not sure how long it's been going on because my wife drives it. But it will make the sound every time. I can turn the key to on but not start it and when turned to off it will still make the sound. It's not very loud, but definitely audible.

It makes this sound after doing some running around and making stops here and there. After getting home and letting truck sit in garage for 30 min..... No being sound now.

Any ideas where to start?

 

[speedrye]

I'd start trying to isolate where the sound is coming from, but I'd look at the evap equipment under the rear of the truck. I think it's supposed to vent the gas tank when the truck is shut off for emissions purposes. It's the black box mounted under the cargo area and it's pretty easy to spot if you climb under the truck and look up.

That's the only item in the rear that I can think of that's active when the truck is shut off.

 

[jfnall]

I will check it tomorrow. It is a single short sound right at the moment the key hits the off position.

 

[speedrye]

Usually it's supposed to make a quiet buzzing sound for a few seconds. It sounds like it's opening a valve or something, so if it broke, I'd imagine there's a spring in there that could be making a boing noise.

 

[BMThiker]

I think these suggestions are on the right track... crawl under the truck and have your wife turn the key on/off until you can isolate the location. Black box about the size of a cigar box is mounted under the floor of the cargo area, aft of the rear axle. This is your evap/charcoal canister filter. I've heard they only expire prematurely if you have a tendency to "top off" the tank when you fill up. The excess back splash filters down into this unit.

 

[1911]

This is your evap/charcoal canister filter. I've heard they only expire prematurely if you have a tendency to "top off" the tank when you fill up. The excess back splash filters down into this unit.

Admittedly only a single data point, but I've been filling mine up to the tippy-top of the neck every fill-up for the last 135,000 miles, with no problems whatsoever. There is a one-way valve in the evap system that keeps raw fuel from entering the canister and evap system. I suppose it's possible for this simple valve to malfunction (like any other mechanical device), but in my experience the odds are low and the valve is perfectly reliable.

 

[BMThiker]

I had asked my mechanic why he was replacing the canister on another truck in the shop (4R iirc). He said they usually last forever, but topping off the tank is what usually kills them. I used to top mine off, to get an extra 1/4 to 1/3 gallon in it, but now I don't. I didn't ask any more questions, and I don't know the intimate details of how it works, but I believe him. I probably topped off my tank for the first 80-90K miles and no harm done (as far as I know).

 

[jfnall]

This sound I'm hearing doesn't do it all the time. Usually when it's been driven for a bit. I will start paying attention to what the fuel level in the tank is when the sound happens

 

[LuigiHodges]

It is a single short sound right at the moment the key hits the off position.

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[jfnall]

It is a single short sound right at the moment the key hits the off position.

So you have the same sound happening too?