What Can Cause White Smoke From An Exhaust After Changing Head Gaskets And Catalytic Converter

Posted in Catalytic Converters
  • What Can Cause White Smoke From an Exhaust System After Changing The Head Gaskets and Catalytic Converter and only last a few seconds and doesn’t do it again? I have a 2000 Pontiac Sunfire SE Sedan! I have a Pacesetter Monza Exhaust System, AEM Cold Air Intake, and a MagnaFlow Hi-Flow Catalytic Converter. When I had the New Hi-Flow Converter put on my car, I had the head gaskets replaced with brand new ones. I also had the oil changed at the same time since it needed it soon anyways. So recap, new gaskets, converter and oil (check). When I first started my car up after I got into it, I let it idle for a little bit to warm up before I took off. The car started to smell like something burning. Then I put the car in reverse and POOF, comes out a white cloud of smoke that only lasts a few seconds! The car ran a few marks above 195 for that day sometimes rise a few more than that. but since running the car a month since that happened, it doesnt smoke, smell, or run extremely hot. before I had this all done, the car would heat up quickly when idleing. going up in temp 6-7 marks above 195. since then it only idels 2-3 marks above 195. still a problem with overheating. Im clueless on what is the problem. new converter, gaskets and a oil change and still overheating problems. I also had the Spark plugs changed and the wires. With all the new parts, I have noticed the car idles @ or around 500-1000rpms which I think is pretty low since it should run around 1000-1500rpms right? a trained Mechanics Help would be appreciated. I want serious answers only, no uncalled for answers!!! Thanks for any help and hope this helps in diagnoseing the problem!

    There are 4 Answers for "What Can Cause White Smoke From An Exhaust After Changing Head Gaskets And Catalytic Converter"

    1. James D says:

      When a head gasket blows it will put coolant in your exhaust thus the white smoke. When repaired the coolant residue is still in the exhaust mostly in he radiator . You will get the smoke for awhile if they did the job correctly and then it will go away . You should change your thermostat and flush your radiator . Your idle problems could be your 02 sensor on your exhaust because it reads the amount of Oxygen that flows threw your exhaust and adjust your fuel when to high or to low. If it gets coolant on it the sensor is dead.This should be done anyway evan if your mechanic installed the head gasket wrong or for a better word just screwed the job up.

    2. Guitmn54 says:

      I’m not sure I understand what your saying? your car was overheating you had the head gaskets changed. It smoked white for a little and it’s fine now? or is it still overheating? it it’s fine now I would say it’s fine the white smoke was left over anti-freeze from when the gaskets were leaking and it’s now burnt off. If it’s still overheating possible bad head gasket, bad heads, or check the thermostat take it out and boil it in a pot on the stove with a thermometer to make sure it open at the correct temp.!

      your idle speed should be in an automatic tranny around 1000 rpms in park and and around 800 or 900 in drive a standard tranny should be around 900 all the time

    3. Stephen R says:

      Water in the combustion chamber caused the white cloud and if it has not done it since, it is fine, it is just reminence of anti-freeze and water buring off from the job.

      Temp is a bit high.It may be running hotter due to the thermostat having a higher opening temperature than the original one. It’s also possible that the gauge is registering higher temperature than the actual engine temperature. Does the cooling fan come on? water pump, thermostat and clogged rad can all cause what you are describing. That said, there is nothing wrong with 195.
      500 is too low, 1500 way too fast. It should idle at about 800. and it looks like you are close to the mark. Keep in mind your car is computer controled, every change you introduce without re-programing the PROM puts your calibration out slightly, and thier is a relearning process for the computer. If it is reving up and down on a slow cycle of about 200 RPM @ idle I would guess that to be not enough back pressure in the exaust system now….or a vac leak

      White smoke or semi white can be produced in several ways. One way is oil this is normally a whitish blue to blue smoke and has the apparent smell of oil being burned. Next could be antifreeze when it is being burned it has a sweet type of smell and tends to dissipate in the air rather quickly. Next is automatic transmission fluid which is normally found on automatic transmissions and its normally drawn into an engine thru a vacuum line via a defective transmission modulator valve or some other defective part. Transmission fluid is very apparent and billows out so bad that you can’t see anything behind you.

    4. Tamalekingpin says:

      For your overheating problems, try switching out the thermostat. Or it could be that the radiator is just old…or your water pump took a poopie on you.

      Your car should idle around 750 rpms. As for the white smoke, that was left overs that still in there, nothing to worry about.