4.0 slight burning oil heads or rings?

stranger96 · Nov 17, 2014

So I have 96 super cab 4.0 5 speed 488s 35s 225k

When I first fire it up in the morning everythings fine no smoke nothing runs great.
But once its warmed up I notice a smell of smoke I cant see smoke physically under load but when coming to a stop light from driving I can smell it go by me.

Also is I start the truck after it is warmed up and been sitting for 15ish minutes it puffs a bit of smoke but goes right away.

I haven't run a full compression test yet i've only gotten to one cylinder which was 150 cold

Input would be great the truck feels slower than it should be and i'm wondering if its the top end or rings before I start spending the money.

stranger96 · Nov 17, 2014

also just feels low on power

bf750 · Nov 17, 2014

time for some rings

stranger96 · Nov 18, 2014

ive also heard it could be the valve seals or a cracked head?

Hitchner2009 · Nov 18, 2014

you can tell if they are valve seals by watching your exhaust fumes. Blue smoke is burning oil. It wont be like super blue like a smurf. But you will see a blue tint to the smoke. Cracked heads will not be the cause for this situation. Your most logical ones are piston rings or valve seals. There are tests you can perform to verify this.

To verify your piston rings need replacement:
Perform a compression test(Static and Dynamic) For rangers i believes all the numbers have to be within 10-20% of each other. Look this up do not quote me on this specification.
Perform a cylinder leak down test. Your values should all be lower than 10% leakdown on the INTAKE stroke. Performing a leak down test on the exhaust stroke will show VERY HIGH leakdown ratings and could result to a false reading.

Good luck!! Any questions just ask!

stranger96 · Nov 19, 2014

Compression results

1-165
2-175
3-155
4-155
5-165
6-170

I looked up the maximum difference allowed by for and it was 25%

I am close but not horrible to that tolerance with about max 20%

These numbers seem pretty good to me. I'm thinking more valve seals because I smell the oil more when I am down shifting and coming to a stop.

RonD · Nov 20, 2014

If you go down a hill with foot off the gas but in gear, then give it a little gas at the bottom of the hill and you get that puff of blue smoke it is valve guides.

With the throttle plate closed and RPMs up it causes a higher vacuum in the intake, if guides are leaking that will pull more oil down the stems.
Same as slowing down in general, the down hill just makes it more pronounced.

Lucas oil treatment can soften seals and swell them a bit.

My '94 4.0l compression numbers close to yours and with 300K a few more miles, I have new guides but bottom end, bearing and rings, is original.
So I would say guides as well.

adsm08 · Nov 20, 2014

Or some external leak dripping on the exhaust. I see many more concerns like yours, where the most noticeable symptom is the smell, caused by oil on the exhaust than any other issue.

stranger96 · Nov 20, 2014

I am leaning more towards guides and seals as well there are no oil leaks on the truck other than on the oil pan and the oil I can physically see a puff from the exhaust pipe on a hot day with the engine warm when starting it up

cp2295 · Nov 22, 2014

Yeah check that y pipe, my rms was leaking and burning on the y pipe. Those numbers are good I wouldn't be worried about rings or guides.

Are you sure it's blue, not white?

4.0 slight burning oil heads or rings?

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