mr7confused

New PCV, new PCV hose to the upper intake plenum. The valve still rattles correctly, and is seated in the valve cover nicely. However, I've got a small mess on the valve cover, as well as on the air box after the long tube from the oil fill.

I've been told to run a compression check on the engine, as well as a leak down test. I've never done one but I figure it will be easy once I get my hands on the tester. The idea in this case is to check the condition of the rings to make sure oil isn't getting by or fuel isn't getting into the crank case. How does it end up on top of the valve covers by the PCV? I know there are oil passages to the top of the heads but I didn't think there would be any air flow? Or am I just all twisted up?

Thread is subject to wander as I resolve this and other relevant issues. I'm ok with that.

bubbabud

Blowby 101 blowby is the term for the gases that leak past the rings and into the crank case all engines have some blowby as the engine wears the blowby gases increase. If the crank case were sealed the pressure from these gases would build up and blow out seals and gaskets. older engines were simply vented to the outside air through a down draft tube that went down to the underside of the car. because these gases contain condensation, water and fuel vaper as well as oil mist and carbon monoxide so there was usualy a second vent [useualy the oil cap] on top of the moter so some fresh air would circulate through the crank case to purge the gas and vapers. come the PCV valve to replace the downdraft tube it uses manifold vacume to suck the vapers into the manifold and burn them. because the PCV valve is conected to a vacume source it would cause a vavume in the crank case under light load conditions so the 2nd vent is the hose that goes to the air box this alows the engine crank case to suck clean air in. When the engine is under heavy load there is little or no vacume and more blowby so the excess is vented back into the air box. as the engine wears there is more blowby and more oil vapers and this is what is causeing oil stains on the top of the moter. sorry for the rant hope it makes it clear. as a side note for the price of a new PCV valve and hose if there is any doubt just replace them

dirtcrew51m

You can also listen to the amount of compression being leaked back into the crankcase when the crank is turned by hand, this would also tell you the rings\cylinder are wearing, the wetness is caused by the oil and gasses building up from the pressure at an air leak, same with the air box being wet, the oil\gasses are taking the least path of resistance besides being pulled in by the intake vacuum, also have to figure on a worn engine the blowby counter acts the pcv especially with a leaky engine.

sdmartin65

Make your own PCV valve. Start with the metal PCV valve grind the end off and remove the guts. Fill the end in with fast steel that they sell at Home Depot. Drill a hole through it very small to start with. At idle you want some suction through the oil filler cap but not too much. Drill the hole bigger little by little till you get it perfect. Blowby Problem solved.

mr7confused

Wouldn't valve seals going bad possibly have the same effect? valve seals/guides/whatevers?

upon an underneath inspection, it appears I have a leak between the transmission, and the engine. Pretty sure it's crankcase oil. This is my DD so hopefully that kind of operation isn't too time consuming. Just a seal replacement? (with respect to removing the oil pan and sliding the transmission back... I guess...

I also have to mention the whistling, on the off chance someone who knows what I'm talking about will understand and offer a solution. Engine whistles under acceleration, and it is not an exhaust leak. Could just be me but it seems to get louder as the gas tank(s) are consumed. When I finish one off then switch to the rear the whistling seems to subside a bit. Pumps not supplying the reg with enough pressure over the course of a tank? Injectors getting noisy with fuel supply reduction? Jordan just hearing things? I think I'm a vehicular-hypochondriac

dirtcrew51m

Worn valve seals will not put compression into the crank case, they will just suck oil through them from intake vacuum, to put it simple blowby is caused compression getting past worn rings\cylinders into the crankcase causing a build up of moisture and pressure into the crankcase which is why the oil looks milky, pushes the vapor or gasses through leaks in the system, more so in the intake hose connected from the valve cover to the air box with the help from the vacuum from the intake, this is why the small filter in the air box usually has oil on it.

mr7confused

Compression test it is. Any tips or tricks for it? Otherwise ill just google it and go from there.
If I'm not mistaken it should be about 180 with a 10psi or less margin of difference between all 8 cylinders, yes?
Now if I find a cylinder with way less, what would be the next course of action?

And if everything checks out fine?

Thanks guys,

Frank_Ford

I am with the guy who said that you should replace the PCV valve and the hose. by the by, how often do you change your oil? If you have a lot of sludge build upp in your engine, that could be causing problems. Also, see if you have just one cylinder that is going bad, you can tell this when you take out the plugs and one plug is caked with oil. While all the cylinders could be equally bad, I have never seen it as a cause of a major problem.

To clean up your engine if it is real dirty, I would try a couple of quick 500 mile oil changes. Empty the oil oil with the engine hot to better drain out the crud. I would not start taking the engine apart to fix leaks or other problems until trying all the low cost/low work options. Make sure you know everything that is wrong before you start taking things apart. That way you don't say fix the rings and then find out, after putting it back together, you have a bad valve.

Good luck. As an owner of an old truck (1998 4x4), I find it fun to work through the problems and get it back to running like a new one. I keep thinking about all the money I save by not having a new one costing $32 K and all the worry about keeping it safe from damage on the job site.

dirtcrew51m

Your compression might be between 100 and 150 depends how worn the engine is, usually the engine wears consistently. As I said you can see how worn your engine is by turning the crank dampener, I can turn mine by hand, and I can hear the compression bleeding back into the crank case.

bubbabud

This is what crysler has used for years its called a fixed orfice vent valve it will pass a little more blowby gas than a pcv valve that is closed {high vacume} but a whole lot less than the pcv when its open { low vacume} so under heavy load it just causes more blowby gas to go into the second vent {air box} if you make the orfice to large its just like a vacume leak and will cause a lean condition and due to the small orfice they are prone to plug up as the engine gets older