Yesterday i dug into my truck. from start to finish only took about 6 hrs to do the plenum. and replace my radiator.

everything went really smooth, and when i go to take the belly pan off it wasnt blown! pretty bummed. turns out the oil was from a bad PCV valve that sure would have saved alot of money. i would have thought that with 199800 miles and at elast 50k of those miles being mine that it would ahve been shot. my gas mileage had gone down last year, and felt a loss of power, but the plenum was not shot.

oh well, it was bound to happen anyway. i had to replace my radiator too. when i removed it it feel and got a hole in it. but luckily it was covered under warranty and was able to get a new one.

Overall the job only took about 6 hrs. all the bolts came out smoothly everything was a breeze.

however ive also been noticing this odd sound the last few months, after my last oil change, when i turn the truck off i hear this ticking, knocking sound after its hot. i remember a suburban we used to have doing this. is it just the engine cooling? or the oil doing something? i dunno it kinda bugs me.

next project u-joints!

 

Mine started doing the same ticking after I did my plenum. Just figured the same thing as you. Would like to know what it is though..

 

Assorted metal parts cooling off. Nothing to worry about.

 

That's why I always recommend doing the vacuum test before assuming it's a blown plenum gasket. Not all plenum gaskets fail, but all PCV valves do. I replace them as part of a tune-up, every time. They're cheap and easy, and letting them go can cost you at the gas pump as well as at the parts store when your oxygen sensors and catalytic converter get fouled.

The ticking when cooling is normal enough. Sometimes you get fresh new ticks after working on the engine, other times you lose one. Most of the time no problem is indicated, as it's just the metal parts contracting as they cool.

 

thats what i assumed. i just dont like it. haha maybe they will go away after the next oil change... doubt it

 

does the PCV valve effect gas mileage that much? i dropped like 2-3 mpg

 

PCV should have little or no impact on fuel mileage. Resetting your computer will though. Needs to relearn how to run the engine. Give it a tank or two, and your mileage should come back.

 

where is the pvc valve? How do you tell if its bad?

 

Passenger side valve cover? Plastic feller with a hose going to the intake. Find him, take him out, and give him a good shake. Does he rattle? If he does, its 'good'. If you don't hear/feel anything moving in there, replace it.

 

That sound is usually the lifters losing hydraulic pressure. If it is a ticking / clacking sound that continues on after shutting the key off HOT OR COLD, that is the lifters losing hydraulic pressure. Lifter clack is what this is known as.

This is the ticking sound that many hear including myself after changing the plenum or oil. Depending on whether one is using standard dino oil (the correct oil) or full synthetics (the wrong oil), this will be much more noticeable when using synthetics. Synthetic oil is not able to hold hydraulic pressure under loading when in the OFF state. Thus, leaking and weeping out of the lifter itself thus causing that clacking racket. I recommend changing the motor oil to the proper weight and type to good old Valvoline Dino oil over synthetic oils. It will run much quieter. These Magnum engines were not designed to run with synthetics and vice versa.

To test this: simply rotate the engine by hand at the crank a slight amount when engine is cold. IF you hear tick tick tick in a random pattern, that noise is the change in hydraulic pressure causing that to resonate up the push rod until it hits the valve train. Or, simply turn it over and immediately shut it off. If you hear the noise, you've got a case of lifter clack.

Hot or cold, it will make that same continuous clicking, random tapping, clack like sounds like something is popping under neath the intake. Metallic like ping almost with a hollowness to the sound.

Now, in order to differentiate that audio noise with say, metal parts cooling down is a tough one. Usually, the cooling is a softer, gentler type of tone but, not always. The exhaust components make a lot of noise but, it's not constant like lifter clack.

Oh, one more additional note: depending on the viscosity and type of synthetic (SAE) it may not exhibit this symptom when cold but only while hot. Reason: Synthetic oil has a tendency to thin out under thermal loading. Coupled with expansion of the lifters, it weeps and looses pressure only while hot.

I was running Amsoil 0-30 and, hot or cold, it exhibited this problem vs. running 20-50 Amsoil whereas, it only exhibited the symptom when hot.

Hope that helps,

CM