By February 27, 2013 6 Comments Read More →

Blue Smoke from Exhaust Pipe

Reader Question

I recently broke the timing belt in my car. After having a new timing belt and the heads replaced there is now blue smoke coming out of the exhaust and runs terrible. Can you please tell me what is wrong with my vehicle and the solution to my problem.

Thank You


Hello there!

Blue smoke is not good, means there is motor oil getting inside the cylinder somewhere.  And with your recent repairs I can only ASSUME that there is a problem with the head.  Did they do a valve job on the head, is it a used head etc. etc.??

The best thing to have done would be to get a machine shop to resurface the head, check for cracks, then do a complete valve job on it before installing. They should have also replaced the valve stems seals, which usually leak oil when at idle and when sitting up overnight.

I would do a compression test on all cylinders, then check ignition timing on the timing marks and recheck the timing belt installation.

The running bad complaint could be due to oil getting on the spark plugs OR the timing belt was installed incorrectly.  Even the best of mechanics can get a timing belt off a tooth which makes the car run real bad, or not at all. I have a feeling you will be doing the job over again.
Keep me posted.

Austin Davis


About the Author:

Austin Davis, consumer car repair advocate. "Hi there! I love to help people solve their car repair problems and I hope my site was helpful to you today. Thank you for stopping by."
  • Austin Davis

    Hi there,

    Hummmmmm, using higher oil weight can help SLOW down oil consumption going on inside the engine. if you have blue smoke you have oil burning inside the cylinders, and you shouldn’t. Don’t get to thick or you will cause other problems, so maybe just a straight 40 weight would be the max I would use, or use 10-30W BUT also use an oil additive called “Engine Restore” which I have had good success with in the past….do this instead of heavy oil.

    IF you had this starting issue immediately after the timing belt installation, I would assume the belt was installed incorrectly, or the base ignition timing is slightly off and he needs to recheck his work. A lot of parts had to come off to get to the belt, so anything could have been unplugged and overlooked.

    I would probably also have him do a compression test on all cylinders, you might have some internal wear causing both issues and the test will show that. If compression is low on 1 or more cylinders, its new engine time….or new vehicle time.

    You might have BLACK smoke or dark smoke, which would mean you have too much fuel inside the cylinders that can not be completely burned off…and a timing belt that is “off a tooth” can cause this fuel rich condition. So, as I am typing I think or HOPE this is what has happened and not internal wear or oil burning.

    Let me know what he comes up with, but lets hope this is his problem.

  • Steve

    okay so here’s my story Austin… similar to the person with the 03 neon, my timing belt went so I had to replace the heads and the timing belt… I didn’t want to go through this again so I recently had my mechanic put in a new timing belt after another 60,000 miles. after that when id start it up it would run rough for a minute or two and then idle normally… now I just got an oil change and it started blowing blue smoke… so I brought it to my mechanic who put in the timing belt and he is going to put in heavier weight oil to see if this will stop the blue smoke.

    so my questions are:
    1. can it be as simple as putting in heavier weight oil to solve the problem?

    3. what if the heavier weight oil doesn’t fix it, what then?

    2. also should he check the timing belt to make sure he installed it correctly?

  • Austin Davis

    I hear ya Mark, and you definitely sound like you are experienced and knowledgeable. I really don’t know what else to suggest to you though, sorry.

    I would love to find out what the problem was…if you can ever figure it out please let us know what the outcome was.

  • Mark Danico

    I had the heads off and checked them over and as I said i removed the valves and cleaned them,checked for valve guide wear and checked for trueness with a machinists straight edge no light shining anywhere under the straight edge,it did not do this before tear down and I did check the cylinders very closely while it was opened up,the only thing I can think of is a crack in the intake manifold and it’s sucking oil mist from the valley but I even did a home magnaflux on the intake last week when I had it off,the compression is at or above factory specs 150 lbs is what they call for and a leak down test shows no unexpected loss of compression even dry,this is the first engine I have torn down in 40 years that has given me trouble,thankfully it’s mine so I don’t have anyone breathing down my neck…LOL

  • Austin Davis

    Hummm, you did not mention having this newly excessive smoke issue before you replaced the seals (just minor smoke). I think you still have a valve type problem…from what you told me anyway, and if it were me I would remove the cylinder head and take it to a machine shop for inspection. Then do a complete valve job and resurface once we know the head is in good shape.

    The head should be pretty easy to remove, and the machine shop might charge you $200 or so plus a new headgasket. Also make sure to check each cylinder for scratches or excessive wear, even though the compression seems pretty ok.

    I think I would do that before I gave up. You could also probably get away with using a very thick engine oil weight, like Castrol Straight 50 to help reduce consumption.

  • Mark Danico

    Hi,I have a 1967 283 with 25,576 original miles on it when I got the car it had the standard valve seal smoke so I tore it down to the block removed the valves cleaned the lead of them reinstalled them with new seals,put Fel-pro top end gasket set into it and it smoked for a bit thought it was from washing everything and soaking it plus putting oil on everything as I put it together.
    Compression test is between 150 and 155 on all cylinders,it smokes bad under full throtle and holding back going down hill very lightly at idle I removed the intake and found what appeared to be a leak in the intake gasket thought case closed took it for a 200 mile ride yesterday and it took 4 quarts of oil and smoked like hell going down every hill so I put it in nutral to stop that,I am stumped I looked the intake all over it appeared to be all dry in the runners so I didn’t think it was cracked etc. I have tried running it with the PVC system unhooked I’m ready to give up!!