Burnt Valve? Volvo '95 850 oh deary me!

  • Thread starter Thread starter trish5
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T

trish5

Would like some help to determine what to do. Car was acting very balky at
startup and running rough. Has 106 thousand miles, no problems before this
(Bought used 3 years ago). Mechanic said they tested it and one of the
valves is burnt "low compression #2 cylinder") and we need to have a valve
job, probably cost us about 1000.00 Yikes!! When we called him back today
to ask what were the compression numbers
he said that they had not entered them into the computer.
So, my question is--how important is this "valve job?? Is this something
that is going to hurt the car not having it done? Don't know that I want
to spend a thou on this right now--Can we wait till after house heating
season in Vermont to do it (like the Spring, if it ever comes here?)
Anyway, all advice greatly appreciated--we really know very little about
this and definitely need to learn--fast!! Thanks
 
1000 seems awful high for just a valve job. I had an entire rebuilt head put
on my car for under 600$. Get another opinion from another mechanic.

good luck

RS
 
trish5 said:
Would like some help to determine what to do. Car was acting very balky at
startup and running rough. Has 106 thousand miles, no problems before this
(Bought used 3 years ago). Mechanic said they tested it and one of the
valves is burnt "low compression #2 cylinder") and we need to have a valve
job, probably cost us about 1000.00 Yikes!! When we called him back today
to ask what were the compression numbers
he said that they had not entered them into the computer.
So, my question is--how important is this "valve job?? Is this something
that is going to hurt the car not having it done? Don't know that I want
to spend a thou on this right now--Can we wait till after house heating
season in Vermont to do it (like the Spring, if it ever comes here?)
Anyway, all advice greatly appreciated--we really know very little about
this and definitely need to learn--fast!! Thanks
Click to expand...

Wouldn't hurt to have it checked out by someone else, or at least shop
around for a valve job but this doesn't sound too out of line if it is the
problem. The valve will likely burn worse and could damage the seat or head
itself if run like that. Also I'd be worried that whatever caused the valve
to burn (often a partially plugged fuel injector) will keep that cylinder
running hot, which can ruin the cylinder head or burn a hole in a piston.
 
You need advice from one of the gurus here, but IIRC the 850 is susceptible
to sticky valves caused by prolonged operation at relatively low engine
speeds. This will cause the symptoms your mechanic is reporting - low
compression on one or more cylinders, but the valve is not actually burnt.
The recommended fix is *much* cheaper than a valve job, and involves a few
minutes running the engine at high rpms in a fairly low gear - with an oil
change immediately before or something like that. My recollection is that
the condition can reach the point where the engine will not start without a
lot of cursing and drama.

Hang tight for one of the guys who knows what I'm trying to say ;-)

Mike
 
So should I occasionally take it out for, um, MORE high speed runs?
 
Michael said:
You need advice from one of the gurus here, but IIRC the 850 is susceptible
to sticky valves caused by prolonged operation at relatively low engine
speeds. This will cause the symptoms your mechanic is reporting - low
compression on one or more cylinders, but the valve is not actually burnt.
The recommended fix is *much* cheaper than a valve job, and involves a few
minutes running the engine at high rpms in a fairly low gear - with an oil
change immediately before or something like that. My recollection is that
the condition can reach the point where the engine will not start without a
lot of cursing and drama.

Hang tight for one of the guys who knows what I'm trying to say ;-)

Mike
Click to expand...

Actually, what you're describing is cause of the problem and the first
stage of symptoms. However, the first stage doesn't last too long, any
leakage is deadly and a chunk of the valve burns away. Eventually the
leak gets so big the cylinder stops firing, then the unburned mixture is
dumped into the catalytic convertor, possibly overheating and destroying
it. In the meantime you'll have misfiring and very poor mileage. This
is not a job that can be put off.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
 
Mike F said:
Actually, what you're describing is cause of the problem and the first
stage of symptoms. However, the first stage doesn't last too long, any
leakage is deadly and a chunk of the valve burns away. Eventually the
leak gets so big the cylinder stops firing, then the unburned mixture is
dumped into the catalytic convertor, possibly overheating and destroying
it. In the meantime you'll have misfiring and very poor mileage. This
is not a job that can be put off.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
Click to expand...

Mike F.,

Are you saying this doesn't sound like a candidate for the on-the-road
method and that it needs the actual valve job?

Mike
 
Michael said:
Are you saying this doesn't sound like a candidate for the on-the-road
method and that it needs the actual valve job?

Mike
Click to expand...

It can't hurt to try, but usually once the valve doesn't seal for any
reason, a sliver burns out of it quite quickly. I've seen several on
the 850 engine, both turbo and non turbo.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)
 
Mike F said:
It can't hurt to try, but usually once the valve doesn't seal for any
reason, a sliver burns out of it quite quickly. I've seen several on
the 850 engine, both turbo and non turbo.
Click to expand...
Ah - would a borescope tell the story (maybe the mech already did that)? It
sounds like the safe thing is the expensive thing.

Mike
 
Thanks, all--we're bitin' the bullet and having the job done--in the last
two days it has relllly had trouble starting.
Great site for information, so glad I just found it
t
 
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