How old is this Jeep?
First thing I would do is a leakdown test on all cylinders--compression
testing doesn't tell you what going on unless it's gross failure. If they
are all holding well, then my assumption would be that the emission
control stuff was cattywumpus. On newer vehicles virtually every system
that could emit vapor or stuff feeds back into the engine for burning and
catalyzing into warm mothers milk plus CO2. It doesn't take much for all
this stuff to stop working right, and when it does, you're screwed. In a
simpler time I'd say check the PCV valve, but new motors hardly even have
them.
I consider myself a decent mechanic, which means I don't B.S, myself about
my limitations--I don't touch anything under the hood of any engine newer
than 1970. I don't even change the oil. A rebuilder will be clueless--they
are machinists and parts switchers. Here in Portland we're lucky enough to
have one garage owned by a guy who has all the equipment and understands
all this stuff. I take everything that's off warranty except the Ferrari
to him.
Find a guy like him.
-----Original Message-----
From: Brad Kahler [mailto:brad.kahler@141.com]
Sent: Wednesday, October 16, 2002 2:04 PM
To: fot@autox.team.net
Subject: generic question on compression checks
Amici,
This isn't really Triumph related (other than its a tow vehcile!) but I'm
looking for guidance on an engine problem.
We had an engine rebuild in our Jeep last spring and over the
course of the next year we had over heating problems, lack of power
and apparent blow-by.
We took it back to the rebuilder multiple times to try and get the
problem(s) corrected. Never did have much luck. However, trying
to get past the state emissions test last month this almost new motor
failed miserably.
Here are the apparent symptoms. OIl in the air cleaner coming from
the valve cover. Compression check shows approximately 140-145
across all 8 cylinders at first. However on the 3rd revolution of each
compression check (which is what the manual says to check for) the
pressure drops to 115-120 but comes back up to 140-145 on the 5th
revolution.
This doesn't sound like a piston ring problem to me. It would seem
to be more of a bad cam. The cam shaft was replaced, the heads
were given valve jobs. Basically it was a complete engine rebuild.
Any thoughts on what to look for? Should he just pull the heads and
cam on the assumption that the rings are probably ok? Or does this
sound like a ring problem AND a valve/cam problem?
Any help on this would be greatly appreciated!
Thanks
Brad
|