4.7L HO and the case of the missing oil... - JeepForum.com
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post #1 of 13 Old 11-18-2019, 01:54 PM Thread Starter
borisb
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4.7L HO and the case of the missing oil...

Hi everyone, I have a WJ 170K on it, and it has been oil thirsty since I've owned it (6 months and 15k miles). Last straw occurred yesterday as I had to top off oil after a full change done in September (600 miles ago). After I topped off the oil (added a quart), I drove 150 miles, and the oil was right back where it started (1/4 inch below the add mark on the dipstick).

I've narrowed it down to PCV valve or coolant mixing issue. It is not being burned off as there is no black residue round the tailpipe or grey/blue smoke and it is not leaking out onto pavement as I check often and there is never a puddle or spot. Anyway I could check either of these theories?

What do you think? I am a very inexperienced home mechanic so any advice on other things to check or how to replace a PCV valve would be incredibly helpful. I should, add almost every time in the last few months I have checked the oil, it has been in the "add" section. I know the key to longevity of the 4.7L is fluid changes so I want to correct this ASAP.

Thanks all for the help!

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post #2 of 13 Old 11-18-2019, 02:05 PM
sdg3205
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Are you also loosing coolant? You can always have your oil analyzed by Blackstone labs who can confirm if coolant is in the oil.

I suspect your just burning it. Valve stem seals on these engines wear out and result in a lot of burned oil.

Crawl under with a good light and look for leaks.
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post #3 of 13 Old 11-18-2019, 02:07 PM
Cirruslydakota
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Mine was eating a quart about every 2-300 miles before I rebuilt it. Valve seals were the culprit, wouldn't always smoke and only blew blue smoke when it idled for a while and i gave it throttle. 190,000 miles.

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post #4 of 13 Old 11-18-2019, 03:39 PM
Double E
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That's some significant consumption. 170 is when the valve stem seals begin to leak but I never found them to lose more than 1/2 quart all the way through 225K miles. Even then I was seeing blue smoke on startup.

Leaking only while running is how this sounds to me. It may never provide a puddle to diagnose that way but there should be some spray on the underside somewhere....or is it truly bone dry everywhere underneath?
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post #5 of 13 Old 11-19-2019, 10:30 AM Thread Starter
borisb
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You guys seem to be in favor of the "oil burned off via valve stem" theory. Why not the PCV? Do you think it's worth changing the PCV valve, as it seems to be easier and more affordable than doing the valve stems?

@Double E , I have been checking the underside of this vehicle for the last 4 months to spot an oil leak, while parked over pavement, gravel and dirt, and I have never seen anything at all.

I have also never seen or smelled any kind of smoke. I have had an oil pan drip in another vehicle that was burning off and I know what that smell is like, and there is nothing similar here.
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post #6 of 13 Old 11-19-2019, 10:37 AM
GmanWJ
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Change the PCV and see if your problem goes away. They are cheap and should be replaced anyway.
We probably think "valves" because replacing the PCV did not solve our issues.


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ok mostly just repairs, but we are closing in on a lift
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post #7 of 13 Old 11-19-2019, 11:35 AM
Double E
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Is it truly bone dry everywhere underneath?

'04 Freedom Edition HO & '04 Overland HO (previous '00 Laredo 4.7)
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post #8 of 13 Old 11-19-2019, 10:25 PM
DL44
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I had a similar oil consumption issue. It was leaking valve stem seals. I think it only really burns it while under throttle and so itís not as noticeable.


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post #9 of 13 Old 11-20-2019, 05:53 AM
griffint007
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I have an 04 4.7L HO with 117000 miles and and it is using a quart about 400-500 miles. I first replaced valve cover seals as they were leaking and changed pcv valve. I put lucas stop leak in 500 miles ago and I think it made it worse. Anyone know how much a shop typically charges to change valve seals?
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post #10 of 13 Old 11-20-2019, 04:22 PM
scott_0
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OP, if it's the valve seals, you'll have visible smoke while at idle, if there is no visible smoke, it aint the valve seals. I replaced my valve seals 3yrs ago, but I had a good bit of visible oil smoke while idling. try the pcv valve and see if it helps

Quote:
Originally Posted by griffint007 View Post
I have an 04 4.7L HO with 117000 miles and and it is using a quart about 400-500 miles. I first replaced valve cover seals as they were leaking and changed pcv valve. I put lucas stop leak in 500 miles ago and I think it made it worse. Anyone know how much a shop typically charges to change valve seals?
it will be very expensive to have a shop do, if you can work on cars at all, I'd do it myself, it's really not awful with the proper tools, I bought then Denlors tool, and used my small 1.5gal air compressor and replaced mine. word of warning the back two cylinders on the passenger side are tight to get to

the tool you'll need
https://www.ebay.com/i/202040224023?...kaAqDoEALw_wcB

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post #11 of 13 Old 11-20-2019, 08:32 PM
blueseasons
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Rather than change the PVC valve, check to see if its working. With the engine running, remove the oil filler cap. Stick your finger in the cap on the side where the PVC valve connects to it. If you get suction. Strong suction and your idle dips a bit. Its good.
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post #12 of 13 Old 11-21-2019, 05:55 PM Thread Starter
borisb
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Today's update, checked underneath and there's a moderately thick layer of oil/dirt on what I believe is the oil pan, so that is probably some gasket/seal that needs replacement. Regarding the PCV, there was black crud and oil inside the rubber hose that attaches to the valve. Does this mean that oil was getting sucked into the valve... ? Anyways that is changed, oil is topped off, and I'll check to see how long it lasts. Thanks again for everyone's advice.
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post #13 of 13 Old 11-21-2019, 07:28 PM
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Quote:
Originally Posted by scott_0 View Post
OP, if it's the valve seals, you'll have visible smoke while at idle, if there is no visible smoke, it aint the valve seals. I replaced my valve seals 3yrs ago, but I had a good bit of visible oil smoke while idling. try the pcv valve and see if it helps

it will be very expensive to have a shop do, if you can work on cars at all, I'd do it myself, it's really not awful with the proper tools, I bought then Denlors tool, and used my small 1.5gal air compressor and replaced mine. word of warning the back two cylinders on the passenger side are tight to get to

the tool you'll need
https://www.ebay.com/i/202040224023?...kaAqDoEALw_wcB

Any tips on how to use this tool? Thinking of replacing my valve seals but don't really know the procedure involved here ...


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