By on May 13, 2013

(photo courtesy:

Stephen writes:


My wife has a ’99 Camry (4-cyl) that smokes like a chimney. While I think it’s fun to see other people’s reactions while sitting in traffic on the 405, she’s getting tired of the constant smell of noxious gases and embarrassing looks in the office parking lot.

I’ve narrowed the origin of the smoke down to the exhaust flex coupling right under the oil pan, which is covered in baked on oil residue. It looks like when the engine is running, oil is dripping out of that basket-weaved coupling and causing the smoke. I can’t see anything dripping down onto it from above, however, and it doesn’t seem to consume too much oil, maybe 1/2 qt. over ~ 2 months. This may be due to my wife’s short commute – only about 4 miles a day, on city streets, so it doesn’t have too much time to burn off a lot. Apparently it doesn’t take too much oil to create a large amount of smoke, though.

The forums haven’t been too much help on this one so far, and so I’m stuck on how to proceed. Other than replacing that flex coupling, where’s the next place to look? I’m suspecting it’s a combination of head gasket replacement and a valve job, but I’d rather have a little more confidence in that solution before spending the weekend rebuilding the top end.

Looking forward to your expert opinion.

Sajeev answers:

Dude, I seriously doubt you have a head gasket problem. You’d have far more issues on the 405 if that was the case.

Usually an oil leak (on an otherwise fully functioning engine) dripping on the exhaust comes from leaky valve cover (cam cover to be exact) and that’s not a big deal at all.  I know that 4-cyl Camrys from this era did have bad valve stem seals, but that only causes a little blue-ish smoke at start-up.

Unfortunately I don’t have a Camry around to eyeball me a diagnosis.  So my guess is you have a bad valve cover gasket, loose valve cover bolts or a combination of both.  Do two things, right off the bat.

1. Re-torque the valve cover bolts to spec.

2. Wash the engine with a can of degreaser ($3) and a garden hose. Or a coin-operated car wash. Since you have a drip all the way to the flex tube, spray the degreaser down there too before hosing everything down.

Now what?  Monitor the valve cover gasket for leaks.  Hell, check every single place oil can leak, as you now have that luxury.  Odds are you will find the source, and odds are it is a very cheap gasket that needs attention.

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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16 Comments on “Piston Slap: A Flexible Burn?...”

  • avatar

    What Sahjeev said ~

    This is a very common thing , minor oil leaks onto the hot exhaust making terrible stink and smoking .

    I’d replace the suspect gasket once it is discerned .


  • avatar
    Gardiner Westbound

    Be careful “shampooing” the engine. Plastic bag everything you can.

    Water and electricity don’t play nice together. An engine compartment contains an alternator, sensors and dozens of electrical connectors. Water will corrode them creating uncorrectable problems. Warm or cold water on a hot engine may cool it too quickly, stress the metal and cause cracks. It can also contaminate drive belts promoting slippage and squeaks.

  • avatar

    It doesn’t take much. Also automatic transmission leaks are good for James Bond smokescreens. A friend of mine caught a truck on fire when the transmission puked ATF onto the exhaust. I think Sajeev is right on here though with the cam cover gasket being the culprit. I would go so far as to say go ahead and order one if you haven’t done it. The gasket on mine had hardened and cracked and broke into about 6 pieces when I removed it. It is an easy fix and I think around 20 bucks at the dealer.

    • 0 avatar

      A friend of mine years ago had a ’91 Chevy Beretta 6cyl and three speed automatic. A school bus had massed up nicely the right front fender of the car, which he refused to fix until the city paid up for the damage. This made driving in it as a passenger extremely exciting as the accident caused an opening through the wheel well and had bent in a power steering hose coupling. The hilarious result of this was the tendancy everytime he made a hard left, PS fluid would shoot onto the hot block and send a flaming ball of fire nearly six feet out the passenger side front wheel well. On two lanes streets in a small college town many a bike rider and dog walker was surprised and singed by the rolling Molotav.

  • avatar
    DC Bruce

    Unless its been replaced before that gasket is overdue for replacement. Seems like it would be suspect number one, and not much oil makes lotsa smoke.

  • avatar

    Clean it well with engine degreaser, figure out where the drip is coming from. Unless I am misunderstanding the author (entirely possible) I doubt the flex connector has anything to do with it other than being in the path of the drip.

  • avatar

    When I’ve cleaned engine bays due to the issues of damaging electronics I use Simple Green, it’s a great degreaser. I run the engine until warm, 5 to 10 minutes. Then I mist the engine bay until damp. Stress, mist. Then I spray it down with Simple Green. I leave the engine running while I do this. I then lower the hood, but don’t latch closed for about five minutes. The engine basically steam cleans itself. Then I open the hood, mist the engine again until the bubbles no longer run, and then shut it down. I’ve never hurt an alternator, sensor, or electrical item. The object is to mist, because the engine is designed to get lightly wet, just not inundated with a hose.

    • 0 avatar

      that’s such a simple, effective process I can’t believe I’ve never heard of doing that. can’t wait until I have a chance to do this on my next Craigslist beater.

      as this relates to the post, a valve cover seal leak is a really obvious suspect for this issue. don’t know if the valve cover also includes spark plug seals on this motor, but those would likely be degraded as well. if that’s the case this is an excellent time for a tune up.

      a Subaru I got from CL had this issue. the oil had entirely coated the underside of the front end with oil. I emptied two cans of brake clean at it and it took care of the clean up.

      • 0 avatar

        One word of caution. It will leave a white ring on the hood blanket/insulator. You can re-dye it black after if it is that important. Once the engine cools wipe down, use straight Simple Green to get any tough spots.

  • avatar

    The best way I’ve found for tracking down the origins of leaks is with UV dye. For those who don’t know, you basically put a small amount of dye where you put in your oil, wait a few days, then take a UV light in the dark and you can see the trail of oil leaks. You can buy a kit at an auto parts store for around $30 that comes with a light. Dye refills are about $5 a piece. Far less than what it takes to have a shop diagnose just one time.

    But the flex pipe has nothing to do with it, and my stab in the dark is also that its a leaky valve cover which is very common. You also might want to replace you PCV valve, it could be plugged up and causing pressure.

    But I’d always recommend finding out exactly where the leak is coming from rather than shotgunning gaskets at the problem.

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