Miata know it alls..: Off-topic discussion forum: Grassroots Motorsports Magazine

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July 18, 2011 7:21 p.m. hotchocolate New Reader

Could you please explain to me why i have oil--yes oil--in the tailpipe of my '93 miata? I noticed it last week, but it was not enough so i though it was condensation. Anyway, today, I saw a more of it. It seems to "condensate" within about two inches of the exhaust tip. It is clean around the muffler. I don't know what to think or where t start.

I have heard everything from cracked rings to cracked block to PCV valve to blown head gasket. It was 100* here today and it drove fine. It did not overheat did not feel down on power, no oil in coolant, no milky residue on oil filler cap. Any ideas?
July 18, 2011 8:11 p.m. Curmudgeon SuperDork

Are you sure it's not carbon mixed with water? If it's really oil, you need to yank the plugs and look at them. The only way I know of for oil to get in the exhaust is via the combustion chamber. It would coat the whole inside of the exhaust.

Try this: put a friend in the car and have them drive it while you follow. Have them accelerate, decelerate, etc and look for blue smoke. No blue smoke = not likely it's oil.
July 18, 2011 10:10 p.m. Keith SuperDork

If there's enough oil to puddle at the tailpipe, it'll also drip out the flanges and lay a serious smokescreen in your wake. You won't need a friend to follow you, your rear view mirror should tell the tale clearly. I'm leaning towards the carbon idea myself.
July 18, 2011 10:55 p.m. hotchocolate New Reader

Thanks for the tips guys. I will double check. I am more than 90% sure that it is oil. However, there is no blue smoke and it doesn't seem like it is losing any extra oil. I only notice this after i have driven long enough that water should evaporate. I will try and take pictures. Could overfilling the crank case do this? It is possible that I did this--but i am usually pretty careful about stuff like that.

One other thing i will add is that i am getting a check engine light and symptoms for the water thermistor. Could it be related? Could it be the humidity? We will get to the bottom of this--I know that
July 18, 2011 10:57 p.m. hotchocolate New Reader

on a side note, i posted this in the wrong place. Sorry guys. Feel free to move it.
July 19, 2011 12:45 a.m. spnx New Reader

Overheat lately? My car looked like that when I burned the rings out of it.
July 19, 2011 7:52 a.m. ppddppdd Reader

The only two cars I've had that burned significant oil also COVERED the bumper with black slime and blew clouds of smoke you couldn't miss, and they never had puddles in the exhaust.

Are you driving the car far enough to really evaporate out any condensation?
July 19, 2011 10:40 a.m. Keith SuperDork

What's the check engine light for?
July 19, 2011 10:58 a.m. hotchocolate New Reader

Good question about the overheat. i know it has not overheated, but it ran hot about a month and a half ago at a test and tune. It has been fine since.

The check engine light is for the water thermistor. I checked about a couple weeks ago.

Also i added about half a quart of oil about 500 miles ago. it has not lost any significant amount. It is still at the full mark on one side of the dipstick and a smidgen over full on the other side.
July 19, 2011 4:37 p.m. hotchocolate New Reader

Okay, nobody laugh:(. i found out after further investigation that during one of my spirited drives my spare jug of oil got "wedged" between the battery and the taillight. Problem was I thought it was shut tight. I guess it was not. It very slowly leaked in that shallow recess where the battery vent tube exits the trunk. Guess what is underneath that on the other side? The exhaust. It was leaking on the pipe and somehow getting slowly sucked into the first two inches or so of it.

Thank you all for your advice and patience. That's why i love this place. Take home lesson is check the easy stuff first. Thanks again guys.
July 19, 2011 5:44 p.m. Keith SuperDork

I had a similar leak in my Land Rover years ago. One of the spare jugs of transmission fluid got punctured by something else in the cargo area, and the truck started leaking transmission fluid out the tailgate. It leaks from a lot of places, but that's the first time the tailgate has leaked. Out, anyhow.

Before anyone makes any rude comments, the fluid was in case of field repairs! A Disco holed his front diff on that trip, and once we'd patched the hole, guess who had the fluid he needed? Ha!

Glad you found it.
July 19, 2011 6:00 p.m. spnx New Reader

Whew! That's a relief!
July 19, 2011 7:17 p.m. Curmudgeon SuperDork

Well. Now I know of ANOTHER way to get oil in the exhaust. Glad it was no worse than that.

War story: had a car (FWD LeSabre) brought in at the Buick place for a transmission leaking fluid leaving spots on the owner's driveway. Tech inspected the car, dry as a chip, nothin'. Customer was PISSED but took the car. It got towed back in the next day for a transmission leak, we were all mystified and put the car on a lift, we were all gathered at the front of the car with flashlights and the owner stomps into the shop. 'NO WONDER YOU DUMBASSES CAN'T FIND IT! HERE'S THE DAMN LEAK!' But he's at the BACK of the car. So we all walk back, sure enough there's a drop of some kind of red nasty on the bottom of the spare tire well. But it ain't transmission fluid.

So we open the trunk... it's a bag of tomatoes that went bad and the juice is dripping through a body plug. Urrrppp...