BURP.......er, excuse me....

[AZNomad]

My 2007 "King Ranch" exhibits this disgusting habit of Burping on a cold start. Here's the sequence of events that playout the same every single time:

First start after sitting for 2 days
1. Start truck
2. Leave @ idle
3. 4 seconds later ~ BURP

On-going starts the rest of day
1. Start truck
2. Leave @ idle
3. 4 seconds later ~ SILENCE

I thought at first it was the A/C clutch engaging and the sound was the belt grabbing the drive pulley, so I made sure the Climate Control was off the next time I started the truck (after 2 days) and sure enough BURP

So, here is where I am at with this....... I am either dealing with a BURP or some issue that engages about 4 seconds after start.......
Any (and all) feedback is appreciated.....

The Nomad

[Dave]

I have not heard of this issue. hopefully someone will be able to help you out

[jfines@cox.net]

I have no clue.

But if you live near Scottsdale you can give Nate at Strictly Diesel - Diesel Repair, Diesel Engines a call. Around here, he's the man.

[npccpartsman]

The only thing I can think of that occurs about that time interval is the turbo veins moving when the engine oil pressure comes up. Usually only happens after the truck sits for a few hours.

[mschn99]

describe the noise better.....if its a "thump" its normal.... The wording of describing a noise can do a lot for us. Does it sound motor related...trans related...body related?? Anything that will lead us down the right road. Does the idle fluctuate...etc...etc...

[AZNomad]

This noise is not a vibration, it is a timed issue that activates every single time at the exact same time under the exact same circumstance. Idle remains steady and constant when it happens. Nothing changes on the gauges, no electrical fluctuation. It is not moisture related. I live in Flagstaff where the relative humidity is generally around 10% but it also did the same thing when I was in Ohio last month and the humidity was 99%.

It does occur when something is activated ~ and it happens about 4 seconds after start. If I shut the engine off and immediately do a re-start ~ it doesn't happen, and it won't do it again all day long regardless of how many times I start. If I let it sit for 2 days it will do it again ~ every single time. I can honestly say it isn't resonance, vibration, squeek, squeel, etc. It is like a burp ~ or a flutter type of sound. Like a medium pitched burp.

Sorry ~ that is the best way I can describe it......

[mschn99]

my best guess from what your describing is that its the heater blend door. Vacume bleed off over a few days lets it relax into its off position, and when you fire the truck it will shut, maybe causing your noise. If your temp controll is set to the appropriate temperature setting it will close even with the unit off. If i remember right it closes when in "warmer air" or "fresh air" mode and is open in A/C mode....but i could be backwards on that...

[BIGGER]

I have the exact same issue, however mine make the noise about 2 seconds after I turn the key on, but haven't yet started the motor. Kind of a SHHUUNG sound, coming from the turbo area.

The turbo veins/oil pressure suggestion above makes sense to me. It only seems to do it on mornings when the temperature is below 70 deg. Perhaps the oil is thick enough to turn the turbo when it is cold. I have always wondered what it was.

[late_99_PSD]

Make a video of it and post it up. Otherwise we're guessing blindly.