So my wonderful little 3.0 headache keeps being so much fun! I suspect a blown piston ring, but I'd like opinions before I go off buying more tools or renting them.

1994 Mazda B3000 with the Ford 3.0 V6. 224,000 miles

Previous owner supposedly had a mechanic replace the engine, but says he only replaced the block, not any of the internals.

Currently is burning a significant amount of oil. 2 quarts per fuel tank for about 250 to 300 miles. Losing power, sounds like one cylinder isnt firing correctly, steady trail of white smoke from the exhaust.

No oil in the antifreeze or vise versa as near as I can tell.

Seems like some oil dripping from the tailpipe when you start it. Nothing leaking underneath. Put a piece of cardboard under the truck and left it 3 days. No drips.

I know I can get a compression tester and check each cylinder which is my next step. However before I go and spend the money on one, is there anything else I could be missing that I need to check first before I go down this rabbit hole?

 

Pull out the spark plugs and have a look at the tips, oil will be obvious

"Burning oil" is more likely to be valve guide seals than a ring issue, and thats black smoke, dark grey not white

While smoke is coolant, or water and coolant, from blown head gasket or cracked head

Yes, test compression, cold engine, all spark plugs removed for the test, pull fuel pump relay or fuel pump fuse
3.0l should be about 160-165psi
Test each cylinder DRY, write it down
Then add teaspoon of oil to each cylinder thru spark plug hole and test again, WET test, number should go up a bit, by how much tells you if its rings or valves that are losing the most compression

 

Valve guide seals would be a good thing tbh since I can atleast change those without pulling the entire engine.

Just watched some videos and yeah this sounds more likely as I've been having the spray of oil coming from the tailpipe.

Picture from YouTube video

 

Question, how bad is it to drive it with a leaking valve guide? Any temp fixes to get me thru a couple weeks? Engine restore or something similar?

 

Burning oil with gasoline is bad for the O2 sensors and Cat converter, doesn't really "hurt" the engine

So, yes you can drive it

Replace PCV Valve and make sure PCV system is working

 

Already replaced it a couple months ago then again a couple weeks ago. Thanks!

 

The intake manifold has vacuum present when engine is running
The rear of the intake valves and their stems are in this vacuum, so if the valve guide/stem seals, in the valve cover area, are not tight then vacuum will suck in some of the oil thats being sprayed around to keep the rockers lubricated and cool.

At idle vacuum is high, 18-20", so more oil can be sucked in, it runs down intake valve stem and is sucked into a cylinder to be burn with air:fuel mix

So after sitting at a stop light for a minute or two and then stepping on the gas you would see a puff of smoke out the tail pipe.

Another test is to go up a hill then shift into a lower gear as you go down the hill, using the engine as a "brake", this increases the vacuum in the intake to 30+", then at bottom of the hill shift in to higher gear and step on the gas, should see a BIG smoke show, lol, as the accumulated oil gets burned all at once


You can change valve guide seals without pulling the heads, a few ways to do this
Rope or bladder/balloon
To get to the valve seals you need to remove the valve springs
If you remove the valve springs the valves can fall into the cylinder!!! a bad thing, lol

So you need some way to hold the valves in place while you remove the springs
You first remove all spark plugs and valve covers
Then remove rockers so all valves are now closed

You insert a smaller rope into #1 cylinder via spark plug hole, let it coil up inside
Rotate crank until rope is pressed against Valves, I use a bungee to hold pressure on the wrench on crank so it can't move, probably not needed
You can also use a bladder, a thicker balloon, and insert it in the spark plug hole then inflate it a bit, then rotate crank until piston pushes balloon again valves hold them in place
Remove the two valve springs, replace seals, install valve springs
Repeat 5 more times

 

Ok trying to do the compression test. Which adapter do I use? None of them are screwing in. Got the compression test kit from harbor freight with

• Adapters for a wide number of vehicles (straight, angled, M10, M12, M14, M18).

 

3.0l Vulcan uses 14mm spark plug threads, seat is "tapered"/angled

5/8" is wrench/socket size, one of the left overs from the CORRECT non-metric SAE sizes, lol.

You don't need to tighten the fitting for compression testing, just screw it down all the way, no need to snug it up.

And it should thread in easily by hand, just like a spark plug does, do NOT force it, if thats needed then the threads are WRONG and you will ruin the head's thread, a BAD THING

 

I looked closer and I don't think the threads on the tester are reaching the threads on the cylinder. I used the 14mm adapter, and also checked that the plug would screw into both the adapter and it all fits, so I just need something with longer threads

 

So the adapter is hitting the exhaust manifold?

It shouldn't

What about without adapter, usually the tester hose has the 14mm end on it, its the most common size now-a-days

Whats the part number of the kit you got from harbor freight?

 

https://www.harborfreight.com/compre...-pc-62638.html

Yeah the hose end should fit, but like I said, the threads on the hose aren't reaching the threads on the engine.

 

Picture here of 3.0l Vulcan head: http://www.alliedmotorparts.com/medi...280x851__1.jpg

So the wrench fittings on the adapters are too large to go into the holes for the spark plugs?
It looks like the adapter should be long enough, but yes, not the hose fitting

Found this one: https://actron.com/content/14mm-long-reach-adapter

Maybe harbor freight has similar