1988 Volvo 740 Turbo - Please Help

Discussion in 'Volvo 740' started by Carlos, Jul 25, 2003.

  1. Carlos

    Carlos Guest

    I bought a 1988 Volvo 740 turbo. I really like the car, but it has a
    few issues. And I would really appreciate some insight to know what my
    problem is.

    The first one is that once in a while it smokes through the tail pipe.
    It completely unpredictable when it will happen and it happens for
    about a minute. Thick smoke. Once it was kind of dark, lately is
    always kind of white. My friend says that it smells funny, it haven't
    happen in the last 15 days, and always stops in about a minute and the
    engine never has any trouble starting or running, it is annoying
    because it is very thick smokes that makes the car looks like it is
    burning. I don't know if this may be related but each time the turbo
    engages I detect a faint smell in the driving compartment (the turbo
    works perfectly). I am not sure but also it seems to me that when
    driving in the thruway, my car looses oil, maybe because of the turbo
    engaging. I had to add half a quarter of oil after a ~300 miles trip,
    while driving in the city I had driven about 500 miles without losing
    any oil (I was checking every day, because the seller told me the
    front seal in the motor had a leak, I am not sure, or else it only
    shows when the turbo engages a lot like in the thruway). I wonder if
    the problem is that the turbo is leaking oil somewhere and then it
    goes into the tail pipe, but the smoking anyway only happens very
    irregularly, sometimes like 2 days in a row (1 minute smoking) then
    nothing for 2 or 3 days, then again 15 days later. Everytime just for
    about a minute and then stops and the exhaust is transparent regardles
    of how I drive (turbo-no turbo). The motor runs well at all times even
    when smoking. I wonder if this is something I should worry about. Is
    there any place where the antifreeze can reach the turbo or exhaust? I
    was wondering about that when my friend told me about the funny smell,
    I had never notice any smell (I am not very good smelling stuff).

    The second problem, is electrical. After a couple of weeks with the
    car the charge in the battery seemed to start dropping and every day
    was less. It always started, soon after that, the alternator belt
    broke and I replace it so I thought it was maybe the belt, but then
    the problem still was there. Now every time I run the car on the
    alternator goes to ~14-15V, then when I stop the voltage reads about
    12-13V, and after several hours after I return to the car right before
    starting the car the voltage is between 10 and 11V. I check with an
    A-meter in series with the batery and when the car is off the current
    is only 11mA which I think shouldn't discharge the battery. Also, I
    when to an Autozone and they check the battery and said that according
    to their tester the alternator, battery and diodes where in good shape
    (the test was done accelerating to 2000rpm). I anyway changed the
    battery for a new one, but it still has the same behavior.

    Any help would be greatly appreciated, thank you very much.

    Carlos Henry
     
    Carlos, Jul 25, 2003
    #1
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  2. Carlos

    TWC Guest

    it may not be a problem because your AC meter reading is the rms of the
    pulse ,not indicate the frequency..Actually there is a lot of high ac
    frequency at battery terminal , like coming from the ignition , fan
    blower, AC clutch..etc

    Carlos ¼g¤J¡G
     
    TWC, Jul 31, 2003
    #2
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  3. Carlos

    Carlos Guest

    Date: Thu, 31 Jul 2003 21:07:55 +0800
    From: TWC <>
    Newsgroups: alt.autos.volvo
    Subject: Re: 1988 Volvo 740 Turbo -Voltage Regulator vs. Voltage
    Rectifier
    Are you sure? I got from this homepage:
    http://www.swedishbricks.net/700900FAQ/Electrical-Starting1.html#Checking Alternator Diodes

    That the AC voltage should be at most 0.5V measured at the alternator.
    I didn't found any difference in the value at the alternator nor the
    battery, both where 30VAC. The DC voltage is still about 14V, so I
    think my voltage regulator is working. Have you ever measured the VAC
    and found it to be bigger? I know that the signals sometimes change
    because a digital multimeter is not an oscilloscope so the signal is
    impossible to tell.

    Anyway what I get so far is that I need to replace the Diode Assembly
    (easier than messing with individual diodes). The diode assembly is
    sort of a disk inside the alternator. The piece itself would cost ~15
    or $20, but I don't know where to get it. Just to keep this updated. I
    am looking for the piece but I don't know how to get it.

    Carlos H
     
    Carlos, Jul 31, 2003
    #3
  4. Carlos

    Peter Milnes Guest

    Try replacing the suppression capacitor on the back of the alternator which
    should get rid of excess AC sitting on the DC.

    Cheers, Peter.

    : it may not be a problem because your AC meter reading is the rms of the
    : pulse ,not indicate the frequency..Actually there is a lot of high ac
    : frequency at battery terminal , like coming from the ignition , fan
    : blower, AC clutch..etc
    :
    : Carlos ¼g¤J¡G
    :
    : > I have a question. Today I measured the AC voltage at the battery and
    : > I got 30V !! I decided that my rectifiers or diodes are not working.
    : > Can somebody here please help me to recognize the part?
    : >
    : > I can see a black small sort of cilinder hold by 2 phillips screws, I
    : > believe the voltage regultator. And I can see a black smaller square
    : > bellow. Are the diodes in the voltage regulator, or are the diodes the
    : > little black box. Thank you.
    : >
    : > Carlos H
    :
     
    Peter Milnes, Aug 1, 2003
    #4
  5. Carlos

    James Sweet Guest

    Don't measure AC, measure DC, unless you have a true RMS meter it can only
    accurately measure 50-60 hz sinewaves.
     
    James Sweet, Aug 2, 2003
    #5
  6. Carlos

    Arnold Perez Guest

    It is clear to me that you have a faulty meter. To double check, either use
    your meter to measure another battery from a non running vehicle, or use
    another meter on the Volvo.

    Arnold
     
    Arnold Perez, Aug 9, 2003
    #6
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