93 oil loss?

[Kevin Evans]

My friend has an 93 4.0 Ranger. He seems to ignore the oil light when it comes on, so I always end up having to add a quart when I drive it.


Anyway, I've noticed that his 4.0 has a fairly high oil consumption rate. Doesn't appear to be any drips, so I'm guessing it's being burned. I'm wondering what steps should I do to diagnose it. Should I check compression and all that?

I know on my 84 2.8, a fairly common issue is with the valve seals getting crispy and leaking oil into the chamber. Is that an issue on the 4.0 too?

 

[RonD]

Not an issue, 4.0l didn't have "hot spots" like the 2.8l did, but valve guide seals wear out on any engine.

Pull out a few spark plugs and have a look at the tips, light tan is a good clean burn
Darker is rich burn
Blackish is Rich or oil

Also try this test
Drive down a hill with truck in lower gear and foot off the gas pedal, this increases the vacuum in the intake so will suck in extra oil from leaking valve guide seals
At the bottom of hill give it some gas and watch for puff of bluish smoke out the tail pipe, that's the extra oil being burn and shows valve guide seal issues

Yes, lower compression and then a dry and wet test may show rings are older and leaking a bit more.
4.0l runs 9.0:1 compression ratio so at seal level to 2,000ft elevation you should see about 155-165psi in each cylinder, all spark plugs removed for good crank speed

Older rings cause more "Blow-by"
Blow-by is the very hot gases that "blow-by" the piston and rings when a cylinder fires, some is normal, but it increases with miles on the rings.
The hot gases vaporize some of the oil coating on the rings, pistons and cylinder walls, thats were oil vapor in an engine comes from, bearings and valve train squirts oil they can't vaporize it
Cheaper oil vaporizes more, just FYI

The PCV(positive crankcase ventilation) system was added to prevent Blow-by oil vapor from polluting the ground and air
Prior to PCV systems there was a tube on upper oil pan or lower block that pointed down at the ground, Blow-by oil vapor exited via that tube, so it dripped oil when ever engine was running
PCV system sucks that oil vapor out and burns it in the engine
PCV Valve and hoses need to be in good condition because this actually creates a lower pressure in the valve covers which slows and valve guide seal leaks
It also pulls the oil vapor from lower engine to upper engine which allows most of it to condense on engine parts so less vapor.
Check and clean hoses and replace PCV valve every 2 or 3 oil changes

Common test for too much blow-by is to pull out dipstick, start engine
Use a paper towel over the dipstick hole, it should not blow it out of the way, should just sit there
Obviously if you see oil vapor blowing out the dipstick hole with engine running PCV system is not working, lol.

If Blow-by is high, then you can install a Catch Can on the PCV system, not hard to do, this allows more oil vapor to condense in the Catch Can before it is sucked into the intake to be burned, you empty the Catch Can as needed.
You are still using the oil but not burning it so better for spark plugs and Cat converters