ledelgado

06 GX470 muffler exhaling white smoke for a while, now the smoke disappeared, however, a new hissing engine noise is evident. The noise increases with the revolutions of the engine and it never stops. Please help!!!

cssnms

White smoke and a hissing engine,,, that doesn't sound good!

SIERRAGX

I would have the car checked out by auto professional asap at the first sign of tail smoke.
How's the level and condition of engine oil and coolant ?, sounds like coolant leaks into the oil. Stop driving until it's fixed, hopefully not too late.

gsobol

White smoke, generally coolant getting into the cylinders. Check coolant level ( !!! do it when engine is cold) Also, check your oil, see if there is brown,yellow sludge on the dipstick. Water and oil don't mix, when mixed inside the block the normal engine operation will cause frothing to occur hence sludge. Hissing may mean blown head gasket (that could also explain white smoke), air is being sucked in (or out - but the sound would be closer to farting :-)) through the breach in the gasket. Also, check your air supply hoses, and the air box for leaks. There could also be a leak between the intake manifold and the heads (that also could generate the hissing sound).

*** cssnms said: "that doesn't sound good!"

ledelgado

Took the GX to the dealer, they said that the cause of the smoke was an oil "overfill". Regarding the engine noise...of course..it was not evident at the time of the inspection...NO codes came back from the computer...

snhrph

Possible... Smoke from burning oil is usually light blue.

White smoke, as gsobol mentioned, is typically from coolant getting into the cylinder(s). The easiest way to check is to pressure test the cooling system. The more accurate process is to pressure test each individual cylinder.

mann777

I have had this hissing or rushing sound or air rushing out or whatever !!! (sounds like wsssssssssp) between 2500 to 3000 RPM while accelerating, and then it dissappears. And this happens only on "d" mode and not on "P" mode. makes a hissing noise when I accelerate(not at idle). When I let my foot off the gas a little the noise will go away and come back when I accelerate again.Tried all option. I have exhausted all ideas of troubleshooting methods on the source of the sound, Done a lot of research, still unable to solve. Lately I even had a pipe run to Engine bays and other end to hear the source while driving. Still cant figure out, Checked the Manifolds, Air Intakes, Vacuum Lines, PCV valve, Head Gasket,Steering Pumps ( leaks etc) All absolutely clean, no areas showing any signs of discoloration due smoke or leaks. I will glad to hear from other members if they had this experience and how they have solved it. I have almost gone to 10 dealers and almost all of them are dumbstruck ( where the hell is the air gushing noise coming from) Yep no answer, Now it has been 6 months and kinda got used to the low decibel noise.

Turbinator

Wait.. you're the local GX expert, and if YOU can't figure it out, then no one can...!!

Good luck..

Turby

gsobol

Does that happen in every gear? Can it be an intake noise? Full or partial throttle? Duration of the noise - split second / few seconds? Can you maintain the noise if you feather the throttle?

mann777

been there, done that, Replaced the hose, Intake rubber plasticky Hose connecting the Air filter, Butterfly Clamps, everthing you can think of, Still no luck, As I said at 2500-3000 RPM, that would be when the Gears are shifting from 2nd to 3rd I believe on roll, the noise is just for 3-4 seconds at that stage, and dissappears, otherwise it is just normal, no compression leak, I have stripped the entire unit around the Engine and refitted it, still no luck, I have given up. Now I beginning to think if it could be Torque Convertor, which is right behind the AT.

gsobol

You may be right, especially if it happens during shifting. That would be indicative of transmission or converter as the source of the noise. I'm surprised though that transmission or converter sounds would be heard over the engine noise. Weird.

Unclebob9

I am having a sililiar problem with my 92 LS400; It started when I was passing, excellerated to 90mph, heard a "Pop" noise, then hissing sound from behind the A/C vents. Pulled the dash apart, nothing there. It will not make the noise while in Park and reving the engine. Only does it while driving on the freeway and the faster I go the louder it gets. All fluid levels are good and clean. can find no vacuum leaks.
The "pop" sounded like a pressure hose popping off its fitting.
Anyone else had this problem and were you able to find the cause?

Jafch1

OIl overfill will definitely cause white smoke to occur during start ups and drives around town.

The hissing noise you hear is more than likely a vacuum leak. Try taking a squirt bottle with soapy water and spray it on all the hoses and intake manifolds. If you start to see air bubbles you've found the issue. If nothing arrises, then use a can of throttle body cleaner and spray around all the hoses. If you hear the idle rise, you've found your leak.

Unclebob9

Problem solved, My Catalytic convertor was blocked, the pop I heard was apinhole in the exhaust as it plew out a weld spot, the hissing was resonating from that tiny leak (just in front of the rear cat) all the way up through the dash vents. My lack of power was due to the back pressure from the clogged CAT.
Replaced the CAT and no more hissing, power is back to where it should be.

Bob