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Frango100 08-18-2011 12:59 PM

Oil consumption
 
Already for a year or so my 4.7 is using oil, it was probably 3 Lts in 8000 Km. I changed the PCV twice and had an idea that it helped for a while, but then it came back again. Now its using around 1 Ltr in every 600 Km and i also see some smoke from the exhaust when giving gas. With 153.000 Km on it, would it be normal for the valve stem seals to cause a usage like this? Other then this or pistons oil scrapers, is there anything else to look at? Is there any way, without dismantling, to find the cause?
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01grand 08-18-2011 02:01 PM

Re: Oil consumption
 
Its using/burning oil, there is no evidence of a leak?

puf02 08-18-2011 05:31 PM

Re: Oil consumption
 
Check your spark plugs to see if all the cyl's are burning oil or just one or two also try a 30w oil.

Frango100 08-18-2011 09:01 PM

Re: Oil consumption
 
No external leaks anywhere. As soon as i have time (over a week or so) i will pull the plugs to check for oil fouling, however with the lower oil consumption i had before, i had no signs of fouling of any plug. I will put some clear plastic tube in between the PCV line to see if no large amounts of oil escape through there. Im using a 5W30 synthetic oil and tried also a 5W40, but without any difference.

2005JGC 08-19-2011 01:48 AM

Re: Oil consumption
 
did you use a mopar pcv valve?

I have seen some pcv valves (specifically wranglers with the 3.8l) have some common pcv valve failures that leave massive vacuum leaks and oil consumption. I have also seen a 4.7l (in a WK) that was puffing smoke due to a plugged pcv valve. Especially if you had success changing it in the past.

JeepMe 08-19-2011 07:59 AM

Re: Oil consumption
 
1 liter every 600km on an engine that only has 150,000 km is TERRIBLE for any modern engine. My '66 Mustang has more miles than that on the original motor and doesn't burn that much oil.

I would start by looking at the plugs. Then I would move to a leakdown test. Since you're seeing it in the exhaust, a leakdown test should let you know what cylinder it's coming from. If it passes the leakdown test, then I would say it's probably coming from the PCV or some other emissions crap.

Frango100 08-19-2011 10:01 AM

Re: Oil consumption
 
The first PCV was a mopar original, the second one not. Would it do any harm if i plug the PCV line for some days to see if that would make any change?

2005JGC 08-19-2011 04:29 PM

Re: Oil consumption
 
Leakdown isnt really going to help with oil consumption, all your oil seals are beyond the compression seals, the oil control ring on the pistion (at the bottom) and your valve stem seals, your combustion chamber is not attached to any seals that would show intrusion with a leakdown.

JForestZ34 08-20-2011 12:06 PM

Re: Oil consumption
 
Quote:

Originally Posted by 2005JGC (Post 469379)
Leakdown isnt really going to help with oil consumption, all your oil seals are beyond the compression seals, the oil control ring on the pistion (at the bottom) and your valve stem seals, your combustion chamber is not attached to any seals that would show intrusion with a leakdown.


But if you have a bad set of rings on a cylinder you will be burning oil....



James

JeepMe 08-20-2011 04:40 PM

Re: Oil consumption
 
Quote:

Originally Posted by JForestZ34 (Post 469674)
But if you have a bad set of rings on a cylinder you will be burning oil....



James

This. Plus a leak down test is free and easy to do yourself.

Frango100 08-20-2011 06:18 PM

Re: Oil consumption
 
And how do i do this leakdown test? Any special tools required?

2005JGC 08-20-2011 07:18 PM

Re: Oil consumption
 
negitory... oil control rings are not compression rings, you could theoretically have failed oil control rings and still have proper combustion or visa versa.

furthermore all the time to do a leakdown test and its only checking ONE possible cause of oil intrusion into the cylinder... Im simply stating that for how much it would "help" diagnose the problem it would take SO much time and still be a half ass pinpoint.

plus, a leakdown is only "free" when you own a leakdown tester.


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