kael

Was afraid I'd get here. Oh well, time to move forward, I could use some info.

Background:
1987 w/ L98, no known engine mods, though PO has made a few other changes.

Noted oil usage was high, using a quart after 800 miles, 3 quarts over the year. I changed coolant and noted a bunch of gunk in reservoir tank. Thought oil or something. I'm pretty sure it was oil.

This all happened in the last year, was fine after an oil change, wires and plug replacement fall 2015. Now, I think the problem might have started there, the new oil was synthetic but I have no idea what the former was since I let a mechanic do that (never again!). Possible gaskets/seals leak due to that?

I never noted any leaks, worst I saw was the coolant reservoir might have overflowed a little. Exhaust looked fine, though hard to track when driving. Revving didn't make smoke. Changed the oil myself last week, no water in oil. It was very black though at 4000 miles, some bits but nothing huge.

Finally, checked the plugs and POOT, very clear cylinder 2 has been burning oil, wet plug full of black gunk. Rest of the plugs looked okay.

Oil pressure was good, 60+ at start, 70+ driving on highway. Not sure what at closed idle, forgot to look last week. Possible oil sensor is bad, need to check manually sometime.

So moving forward, given the conditions mentioned, looking for opinions of the actual cause. I'd really love it to be valve lash or seals, those I can do. Something lower in the engine, owe. Having to pull the engine, owe. Get engine serviced, owe.

So, what do y'all think and how bad to my wallet? Questions?

ghoastrider1

if its burning oil and spewing smoke..best time to see it is after dark and hardlights behind you as you drive down the toad. Seems their headlights pick up the traces of smoke that's hard to see in full daylight.

VikingTrad3r

do you have the provisions for a friend who does that can do both a compression test and a leak down test on each cylinder.


stay organized and how you approach this do not jump around. That is the first thing to do.

it is entirely possible that you have dried out and cracked or completely disintegrated valve seals and, especially on number two, it's just letting the oil drip directly into the cylinder, this was the case on my 85. I did a valve stem seal job and all was good. But I New that my compression was great.

while I had the valves out of the heads i also ground valve face using a drill and if you line.

kael

I'm back and forth about oil in the coolant. The gunk stuff is uniform, I poured it into a clear container and let it sit for days, no separation. Thinking it might be rust from radiator cap..but then where does the oil go? Ack!

Do have cat converters, may be eating all the smoke.

VikingTrad3r

do you have smoke when you started up? It goes away after a minute or so

JrRifleCoach

Gunk in the coolant tank is normal for a car 26 years old as most owners don't look at it or will not clean it.
No noticeable smoke when starting, accelerating or decelerating?
No noticeable puddles of oil underneath the car?
Oil consumption of one quart per 1k miles is Ok for most older cars.
Less than that, I'd say it's time to consider an overhaul if your happy with the car.

Cruisinfanatic

really?

VikingTrad3r

i raised my eyebrows here too. might be right i have. ot had that experience on my vette of 100k miles. ut maybe that is for higher mileage?

mtwoolford

start with the cheap stuff.

when you remove the oil filler cap, does the crankcase appear to be under a slight vacuum ? A thin piece of paper placed across the oil fill hole in the valve cover should show signs of being sucked in, not blown off.

do a compression test; all okay if all within 10 - 15 psi of each other;

if everything appears okay, change the valve seals; even with worn valve guides, you should see an improvement, at least in the short term.

And finally, just how many miles on that engine? did it ever have a valve job ? even with low miles, 26 year old valve seals don't stay new forever.

JrRifleCoach

Ya gotta remember that engine is old school SBC with a roller cam.
26 years old and showing signs of its age.

Now your not going to tell me that 1 quart per 1K miles is excessive.

Or are you going to make some grand conclusion?

kael

OOPS! Missed the big bit of info, at 59071 miles.

I didn't see a hint of smoke. Unfortunately, my last check run was on jack stands, ran idle - 1500. Right after start was...well, whatever that is called when you start a car under 35 degress. Didn't smell like smoke and pretty clear it was water vapor. Likely the oil leak is at higher RPMs, neh?

I'll chase compression test, have to get something to measure. I was going to pull the valve covers and take a look, appreciate the advice! Think it will eventually be valve seals, engine ran fine when foot asked!

Ugh, thinking of checking the passenger side makes me cringe and curse!

As far as the coolant, it's rust. Easy check in case it helps someone else.
If you suspect rust in your coolant, put a strip of paper towel in, get wet with the nasty except for a little bit at the top. Clip it to something and let it dry. It that towel is oily/greasy, it's oil. If not, you'll probably see a bit of dry crud, it's likely rust.

If rust, check the radiator cap, see if it is rusty. Mine is, time to replace and flush the coolant very well, need to get all that rusty stuff out.

Joe C

personally, and no flames, but FWIW, I consider a quart per 1K miles excessive. currently, my 32 year old, 157K, flat tappet, old school SBC burns less than a quart between 3K mile oil changes, and i'm not thrilled about that - . BTW, I attribute my oil consumption to worn valve guides.

Cruisinfanatic

I agree, but you can't argue with someone that knows it all. Over 40+ years of many many cars, none of mine lost that much oil

JrRifleCoach

Your right. I can't argue with someone that knows it all with 40 years of experience......

This guy has an unknown low mileage 26 year old car that has sat, more than used, during this time. He switches to "syn" oil and now consumption is a factor.

Could be a rusted cylinder. Or maybe the car was started after sitting for years and someone didn't bother to prelube the cylinders?

So through personal experience.... JoeC nails it.

383vett

I'd start out with something really simple. It could be a bad plug or wire. Change the wire on that cylinder and put in a new plug a heat range hotter. Run it for a while and see if it might be ok. Sometimes simpler is better. If ok, r&r your cooling system.

kael

Whew, finally got all the compression from all cylinders, had to buy my meter on Xmas eve.

Much cursing was involved threading hose into #2.

All are 140 psi +/- 5.

My Lady really appreciates being called 26 years old.

Time to remove valve covers, neh?

383vett

Pulling the valve covers will show you nothing. Try changing the plug wire and plug as I suggested above. You might not have a problem.

Cruisinfanatic

I had a fouling plug(s) problem a couple times. First time was bad injectors. Second time was loose wire on distributor. Loosing oil could easily be just valve seals

kael

383vette, Cruisinfanatic:

Ah, I see now, you've been trying to focus on just the fouled plug. I will check that, didn't consider it might be a separate problem. Now that my head gasket is probably okay, that makes sense.


As far as valve seals, I recall someone recommending using intake seals for both intake and exhaust, any opinions?

Hot Rod Roy

I'm no expert in this department, but from my observations, GM used the same intake style seals on the C3 vintage SBC for both intake and exhaust, but did not use exhaust valve rotators. There is vacuum on the intake valves, but no vacuum on the exhaust valves, and the exhaust valves run hotter than the intakes, so their requirements are different. It appears that a lot of research went into the decision to use the "umbrella" seals on the C4 exhaust valves. Do the tighter intake style seals possibly degrade the performance of the exhaust valve rotators? Only a guess. I don't know.