Wierd brief noise???

[RT]

Hello All,
My work truck, the one in my sig, had been parked for almost two weeks. When I started it, all was normal for the first few seconds then it started making a popping/blowing sound. Sounded exactly like an intake valve was hung up/stuck slightly open and the compression stroke was blowing back through the intake. I shut it down and then restarted it. This noise went on for 8-10 seconds and then it went away. That was yesterday and since then I have stopped and started many times with no drama.

Truck runs great like it always has. My biggest fear is that one of those little plastic rocker keepers has failed but AFAIK when this happens it then very quickly drops a valve and you know about that in a hurry. 247K and the valve covers have never been off. Truck is very well loved/maintained. Any ideas? Thanks, RT

[gmctd]

At 247kmi, it's way passed due for those 16 keepers, particularly those on the turbo-side, and timing chainset, injectors, and Inj Pump - you'll be surprised at the cured driveability issues you didn't know you had, once the timing is back on the mark.

Oops - never mind on the timing chainset, just noticed your DSG set.

Prolly time for a waterpump, and check the harmonic balancer and accessory drive pulley for rubber deterioration, incl dry-rot - wouldn't hurt to replace the serp belt and tensioner(s).

Also time for the annual clean-out of the detritus-trap between the radiator and the ac-condenser and oil cooler.

[RT]

Truck is well maintained. Already have replaced all you have mentioned, some twice. Except the IP. There are no driveability issues. Truck runs great and still gets 18.5-19.5mpg. Yes the plastic clips are original and need to replaced. What I am asking is if the clips can cause an intermittent noises like what I experienced. Thanks, RT

[Robyn]

What you had happen is an intake lifter bleed off and it took a few seconds to pump up.

My 94 will do this once in a while and the engine is fresh a year ago.

Unless it gets chronic and does it a lot its no biggy.

You really notice it when you open the intake air box up to let the sucker breathe. :eek:

What GMCTD says is good advice though.
The plastic rocker guide buttons do get hard and can go away and when this happens many bad things can result.

Usually the result is a dropped valve if the rocker pops the keepers loose.
Then its game over. :(

Robyn