Do I need to rebuild?

[LittleRed4wd]

Hello again,

I'm wondering if any of you guys could help me out. My dad and I have an 86 4wd that smokes like crazy. We bought it back in August, and it was fine (we weren't looking to buy a project) but after a week it would throw out blueish- whiteish smoke. We figured the previous owner had used no-smoke or something similar. Anyways, the car has sat since then while we figure out what to do with it. From what I've read, white smoke means head gasket, and blue means oil burning. With the amount of blue smoke coming out I've figured we'd need a rebuild. Heres the thing though: The engine runs super smooth, way better than out other terc that I drive almost daily. Does an engine with worn out rings still run smooth? Or could it just need a head gasket? Valve seals?

So to sum up: The engine idles quiet and revs very smoothly, but throws out huge amounts of blueish- whiteish smoke. (So much that it fogs up the whole road). Is there a chance I won't have to rebuild/ replace? Or are these just the normal symptoms for that?

Thanks in advance--

[xirdneh]

i 'd start by pulling the spark plugs and looking at the ends to see if one plug looks different from the others.
then look in the spark plug hole after rotating the crank till the piston is visible to check for differences.
get a book that has pictures of various used spark plug ends (or use the internet) and tells why they look the way they do.
next i would compression check each cylinder on at least a slightly warmed engine.

[4wdchico]

Good chance that it is the valve stem seals. If the car has sat for very long they get hard. My '85 smoked a bunch before I changed them & now it is totally smoke free. Very easy to change on the 3ac, not a whole lot harder than adjusting the valves.

[LittleRed4wd]

I'll have to see about valve seals. All plugs look the same, a bit of oil and carbon on them. Once I finish fixing tvsv stuff I'll fire it up and do a compression test. For now, is there anything else I can check?

[Petros]

check the PVC system, if it puts oil into your air cleaner it will smoke. Make sure you have not overfilled the crank case with oil, that will also cause it to smoke. You really need to do a compression check (Autozone will lend you the compression gauge at no charge). really worn rings can run smooth, but still have low compression and allow a lot of oil past the rings, they wear out evenly so it still runs smooth. Also, sometimes a ring can break causing lot of oil to get past one piston only.

If your compression is good and even (130 psi or better), likely the problem is valve stem seals or the PVC system, bother are relatively easy fixes.

A rebuild is a major job, but it will be less expensive to buy a replacement import engine. Usually about $400 for a long block, and you swap over the external parts and install it. These are great buys and there is no reason to rebuild the engine unless you want to tweak it to improve power or performance. You can swap out an engine in one afternoon, a stock rebuild will cost you $700 or more, and many days to get all the parts and machine shop work done.

I would not recommend just replacing the rings. I have done that, but the problem is the bores wear and you get piston slop and eventual piston damage on your rebuild. So you have to rebore the cylinders (done in an automotive machine shop) and used new over sized pistons. Most wrecking yard engines will be just as old as yours, so the low mile import engine is the way to go.

[LittleRed4wd]

How do I go about checking the pcv system? I have a new valve I can put in. I have a compression tester, but how long do I need to run the engine for? It's leaking lots of coolant so I don't think I can run it for more than 5 minutes or so. Will that be enough warm up time for accurate readings?

[Petros]

Yes, that would work fine. IT can also be done cold. Take all the spark plugs out and than have someone crank the engine for you. Test each cylinder in tern, only about 5 or 6 compression strokes should do it each. Test "dry", and squirt some oil in the hole and test again. If it goes from say 95 to 135, worn rings, if it only changes a bit, but it still very low, than it is bad valves. IF less than 10 psi change and are all high and even, than your engine is in good condition.

Test the PVC my jiggling the valve, if you hear it loose, it is good. You can clean it out with solvent if gummed up, also check the hoses for being clear and everything is connected properly.

[splatterdog]

One way to tell which way the oil is coming from is to mark the plugs before removal, so you know which way they sit when installed.

If the oil residue/crust is coming from below-rings, above-valve seals/guides, or if you are lucky just a PCV malfunction. Not a 100% test, but gives you a good idea. Note- every car will show some residue from the intake valve's direction

If compression is good but the oil rings are stuck/sticking I would do some chemical flushing before tearing down. Sometimes bad rings can leave fresh oil streaks on the cylinder walls. Easily checked with our spark plug hole location. Also-cross hatch scratches should be observed on the cylinder walls.

[LittleRed4wd]

Okay, warmed it up a bit and did compression. 120psi on each cylinder. I checked our other car and it was the same. I ran out of daylight so I never got to the wet test. Does this mean the rings are good? I'll check out the pcv and do the wet test tomorrow.

[Petros]

They are worn, but not too bad. let see the wet test. Cars can run good to well under 100 psi, but they are really worn out and be down on power. Good compression would be 135 psi and above. In my high compression engine (11.2:1 compression ratio) I get 185-195, wet it will be over 200 psi.

The fact they are all even is a good sign. it may burn oil at that lever of wear, but not enough to cause large billowing clouds of smoke. So the smoke could be coming from something else beside the rings. In my experience bad valve seals will also not cause bad oil burning, but a damaged valve guide can. So it is possible a single bad valve guide is causing all the oil burning. If you can determine it is all coming from one cylinder, than likely it is somewhere in the head. If the guide is bad, the only option is to remove the head and replace it, and perhaps the valve itself.

Some claim a treatment of Restore, or Seafoam will help the rings seal. might try that before replacing the engine.

good luck

[LittleRed4wd]

How can I narrow it down to one cylinder, and find if the valve guide is bad?

Also, I've heard alot about the import engines, how might I find one? Is there a web site?
Thanks for all of your help--

[Petros]

if any of the spark plugs look more sooty than the others, or when you look at the piston top, the one with the most carbon/oil build-up. It is much easier and less expensive to rebuild the head than replace the whole engine, so make sure the problem is in the head first.

Go to your local Craig's list and search for Japanese engines, or import engines. Also do a local yellow pages search. Most major cities have suppliers of imported engines. Most include delivery to our house in their price, so there might be some in nearby states that will ship one to you.

[takza]

You COULD replace the valve stem seals without removing the head. And there are various methods to clean the ring packs...solvents or water which might help some there.

[gotama]

id like to reply to 4wdchico 's post..and revive an old thread i found re:valve seals..ill start a new post also..i have a 84 4wd s/w thats in baja mexico all year and she sits for 6 of those 12 months for 10 years now..car just started blowing blue before i left this year and im sure its just what 4wdchico said..valve seals harden up and crack..this motor has only 125k miles and only leaks oil and has great power and so so mileage bout 25 mpg..im gonna take down some new valve seals..ill need a valve spring compressor. compressed air? or not?..il do a comp test too..ive got an adapter to hold up the valves with compressed air while i change the seals if its nessasary..anything else i should have or be prepared for?

[celtglen]

... wrecking yard engines will be just as old as yours, so the low mile import engine is the way to go.

Hi Petros...where do you find these? I Googled for them but none have the 3AC.
thanks
CG