Using too much oil? Easy fix!

[nujac]

My used trooper that I pick up 3 months ago was using 1 to 2 quarts of oil every 3000 miles. The motor was covered with alot of oily dirt and grime. This is usally the sign of a major vacuum leak. The new engines that are made now days have less room for air movement under the pistons. If you do not have real good vacuum oil will start leaking out of seals and gaskets because the crankcase develops too much pressure as the pistons go up and down. The best fix for this is to go to the autoparts start and pick up about 10 feet of every size vacuum hose they stock. Vacuum hose is cheap and it is always good to have some extra hose for future repairs. Pick a day or place that has lots of good lighting. You will need the extra light to see where each of the vacuum hoses start and finish. It took me about 3 hours to change every vacuum hose on the car. My 94 trooper is over ten years old so I changed every hose on the car because if the hose was not bad now it would be soon. Never try changing more than one hose at a time. It is far to confusining to try to remember where more than one hose goes. There is a good chance you will find a hose that has gotten hard and simply broken off. In mose cases you can find the other broken hose or follow the natural cure of the hose to see where it once was. Some vacuum hose are molded and can cost $20 just for a 6" length. You can save that $20 if you take a little extra time and make a longer hose. The longer hose may need a new path so the hose does not kink or get melted on something hot. Be sure to change every hose even if you think that it is good and also make sure that you do not have too short of a bend in the hose and kink it. The last thing to do is install a new PCV valve. On the 94 3.2 DOHC it is located under the drivers side intake mainfold. I would have changed the PCV valve rubber groment but do not know how to get in such a tight place to do it.
I can now go 3000 miles between oil changes without having to add any oil. Looking at the stick I use or lose about 1/3 of quart of oil between oil changes.
Also another reason for oil to leak from the engine is using the wrong weight for the temperature that the engine is operated in. In the summer I use 20-50 because in south Texas the temperatures can reach over 100F. And durning our very short cool months I use 10-40. You can look in the owners manual for the correct weight for your temperature. And if you live in the mountains where temperatures stay below 32f for months on end do not forget to change back to your summer oil as soon as the weather warms up. Some folks run 5-10 when the temperature is below 32f and it runs like water out of the seals and gaskets when the weather warms up.

[trooperbc]

i was real excited to read that you had the cure for excessive oil usage in isuzu's by simply replacing old leaking vacuum hoses. but when i started to reread and follow exactly what you were saying. . .it sounds like you're confusing crankcase pressure with vacuum. they are two totally different, in fact opposite, things.

Originally Posted by nujac

My used trooper that I pick up 3 months ago was using 1 to 2 quarts of oil every 3000 miles. The motor was covered with alot of oily dirt and grime. This is usally the sign of a major vacuum leak.

The new engines that are made now days have less room for air movement under the pistons. If you do not have real good vacuum, oil will start leaking out of seals and gaskets because the crankcase develops too much pressure as the pistons go up and down.

basically, i think your premise is wrong. vacuum in an internal combustion engine has nothing to do with the crankcase "room" below the pistons. vacuum is created within the intake manifold system side of the operation as the piston and valves and combustion do their things.

you will, however, add to a better running engine by finding and repairing any vacuum leaks, as the engine, and the computer, won't be misreading the fuel/air ratio.

Originally Posted by nujac

The last thing to do is install a new PCV valve. ...I can now go 3000 miles between oil changes without having to add any oil. Looking at the stick I use or lose about 1/3 of quart of oil between oil changes. ...

i think you hit the nail on the head with the PCV valve. a stuck (closed) PositiveCrankcaseVentilation valve will cause excessive pressure in the crankcase (the area below the pistons). this pressure is from the blowby that gets by the piston rings that 'seal' the cylinders/pistons. and this pressure, if bottled up, will tend to cause oil leaks as the pressure looks for ways to escape through seals and gaskets. so changing out a defective pcv valve could very well account for a marked decrease in oil seapage and usage. and you might want to make it your first thing to do.

your dramatic change from 1-2 quarts of oil every 3k miles to 1/3 qt is remarkeable.

your writeup on replacing the vacuum hoses is spot on, except for the connection to oil usage.

//bc

[nujac]

The crankcase is very much connected to the the top of the engine. When you change your engine oil you can hear the oil making its way to the bottom of the engine. If you take the ID of all of the oil return holes from the top of the head to the crankcase you will see that what ever vacuum you have in the valve cover you have in the crank case because they are connected. One of the old tricks to see if you had bad rings was simply remove the PVC valve hose and feel the exhaust gas coming up through the valve cover hose. On some of the older V8s, one valve cover had a PVC hose to the intake below the carb and the other valve cover went straight to the air cleaner. When the rings went bad you would notice black motor oil on the air filter where the hose from the valve cover lined up. On engines with high mileage that have some exhaust blow pass the rings it is very important to have very good vacuum to keep the pressure down in the crankcase so that it doesn't push oil past the main front seal.

[trooperbc]

Originally Posted by nujac

The crankcase is very much connected to the the top of the engine.

*true

When you change your engine oil you can hear the oil making its way to the bottom of the engine. If you take the ID of all of the oil return holes from the top of the head to the crankcase you will see that what ever vacuum you have in the valve cover you have in the crank case because they are connected.

*also true. but there is no vacuum in the valve cover

One of the old tricks to see if you had bad rings was simply remove the PVC valve hose and feel the exhaust gas coming up through the valve cover hose. On some of the older V8s, one valve cover had a PVC hose to the intake below the carb and the other valve cover went straight to the air cleaner. When the rings went bad you would notice black motor oil on the air filter where the hose from the valve cover lined up.

*true. no argument.

On engines with high mileage that have some exhaust blow pass the rings it is very important to have very good vacuum to keep the pressure down in the crankcase so that it doesn't push oil past the main front seal.

*not true. the hose, with or without the pcv valve, vents the crankcase to the intake for combustion. you could vent it to the air, but that's not good for the air. it's the venting that keeps the pressure in the crankcase down so it doesn't look for escape through the seals and gaskets (this venting also, btw, removes harmful contaminants from the crankcase).

so, you are making the same mistake on this nujac. all your arguments are sound, except when you say there is vacuum in the valve cover. vacuum in an internal combustion engine is created on the intake side of the combustion process(es). there is no vacuum in the valve cover or in the crankcase.

you are absolutely right on all that stuff about the pcv and blowby and oil usage etc. but, when you say
""On engines with high mileage that have some exhaust blow pass the rings it is very important to have very good vacuum to keep the pressure down in the crankcase so that it doesn't push oil past the main front seal.""
this is the very argument for why you want to have an operating pcv, so that this pressure is directed up to the intake and not out the seals. a plugged pcv will cause the pressure to build up in the crankcase and look for an escape route. pressure is not vacuum. the vacuum of the engine has nothing to do with it.

if you want to hold onto this theory of yours, so be it. there really is nothing more i can contribute. perhaps someone else can chime in...

i will try to locate a good explanation on the net. i've seen a couple of internal combustion engine articles with animated video that might be of help...

good luck

//bc

{{{ edit add #1: here's a link to a wikipedia article on the pcv valve components and how they work -- including how manifold vacuum "sucks" the crankcase cases to be combusted:
http://en.wikipedia.org/wiki/PCV_valve }}}
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{{{ edit add #2:here's one on the crankcase (there are lots of other articles on the auto engine you might find useful)
http://en.wikipedia.org/wiki/Crankcase }}}
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[rodeo02]

Right on the money trooperbc. The only part of the 'vacuum system' that has anything to do with sweeping the crankcase and keeping crankcase press low is the PCV system. Keep the vac side and breather side of the PCV system free and clear and you are good to go.

Nujack, that is some serious good work to replumb everything you can get at! On a soon to be 13yr old vehicle, hoses are going to let loose sooner or later.

Joel

[nujac]

I am no expect on using the right terms for vacuum or pressure inside a motor. But how about this for a theory: Pressure will build up inside an engine due to things just getting hot and expanding, exhaust gases pass the piston rings, worn valve guide and seals and who knows what else. That pressure has got to go somewhere. The top and the bottom of the engine is connected with the oil return passages. Pressure or vacuum will find the path of least resistance. And hopefuly the path of least resistance will be out the PCV valve however it can find its way to it and not the oil seals or gaskets. On a new engine very little if any air, gases, vacuum, pressure, or what every you would like to call it goes backwards through thoses oil return holes. This is because the engine is tight is everything is staying where it belongs. For the average person to keep an older car running he does not need to understand the theory of air movment inside an engine. The only thing he need to remember is that all of thoses vacuum hoses on a car need to be in good shape and not leak for his car to operator correctly.

Thanks for your time
Nujac

[Rmasters3]

My Isuzu dealer's shop foreman told me there are two things that can help: cleaning the EGR valve and tube and a new PCV valve. Neither is a "Fix" but it helps moderate the condition.

[Ramblin Fever]

Rmasters3 - you can also try a thicker oil; Rotella 5w-40 is excellent for year-round use.

[AmysTrooper]

We started with thye Shell rotella synthetic 5 w 40 and with about 1500 miles on the oil change it seams to be working. I did add some oil at 1000 miles on oil change but much less that with convemtial oils ( 1/2 qt ). I think once the oil has been in there a while I will see more improvement, atleast I hope.

[Ramblin Fever]

Great - you can run that Rotella for at least 4k miles; I wouldn't go above 5k though - these engines like clean oil constantly.

[nujac]

To follow up on the orginal thread. I am still using less than 1/2 quart every 4000 miles using 10-40w. The motor has over 180,000 miles and I no longer have oil dripping on the floor or that oily covering on the motor.

[LEM]

Forgive my lack of knowledge and experience, but how does one identify a vacuum hose versus any other type hose in the Trooper engine? I've been using Rotella and getting about 600-700 miles per quart; believe it or not this is an improvement from the lighter oil.

Also, will the local Advance Auto PVC valve work as well as the OEM valve? What's the best route?

Thanks for any tips.

LEM

[Ramblin Fever]

I've tried the PCV of local parts stores; don't fit as snug. Personally, just get the OEM, it's only like $9-10.