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1988 Volvo 740 Turbo - Please Help

 
Carlos
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      25-07-2003
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
 
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TWC
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      31-07-2003
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


 
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Carlos
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Posts: n/a
 
      31-07-2003
Date: Thu, 31 Jul 2003 21:07:55 +0800
From: TWC <(E-Mail Removed)>
Newsgroups: alt.autos.volvo
Subject: Re: 1988 Volvo 740 Turbo -Voltage Regulator vs. Voltage
Rectifier

>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


Are you sure? I got from this homepage:
http://www.swedishbricks.net/700900F...nator%20Diodes

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
 
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Peter Milnes
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      01-08-2003
Try replacing the suppression capacitor on the back of the alternator which
should get rid of excess AC sitting on the DC.

Cheers, Peter.

"TWC" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
: 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
:

 
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James Sweet
Guest
Posts: n/a
 
      02-08-2003
Don't measure AC, measure DC, unless you have a true RMS meter it can only
accurately measure 50-60 hz sinewaves.

"Carlos" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> 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



 
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Arnold Perez
Guest
Posts: n/a
 
      08-08-2003
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
Carlos <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> Ok, here is an update, the problem is turning weirder by the day
>
> Today morning, I decided to make a last measurement before taking the
> car to the mechanic (since I couldn't find the capacitor to replace it
> and I don't think I have the tools to replace the diode assembly).
>
> With the car off completely, I measure DC voltage at the battery and
> got about 13V (DC), then switch the voltmeter to AC and got 27 V
> (AC)!!?? Ok, this is new, I don't understand what can be wrong. I
> don't think the alternator is brocken now, since I can't see why my
> battery should be giving me AC voltage with the car off. Where AC can
> be coming from in a turned off car?? I don't have an oscilloscope,
> but let's assume it is not voltage but noise. Where can 30V noise can
> be coming from in my car if the car is off? The only thing powered in
> the car I believe is the clock, maybe the radio but I think the radio
> is not the problem since I had it disconnected before and the problem
> was still there.
>
> Any ideas? Thank you very much.
>
> Carlos Henry
>
>
>
>
>
>
>
>
>
> (E-Mail Removed) (Carlos) wrote in message

news:<(E-Mail Removed). com>...
> > Date: Thu, 31 Jul 2003 21:07:55 +0800
> > From: TWC <(E-Mail Removed)>
> > Newsgroups: alt.autos.volvo
> > Subject: Re: 1988 Volvo 740 Turbo -Voltage Regulator vs. Voltage
> > Rectifier
> >
> > >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

> >
> > Are you sure? I got from this homepage:
> >

http://www.swedishbricks.net/700900F...ml#Checking%20
Alternator%20Diodes
> >
> > 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

>



 
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