Poor compression

Hi.

I have a dodge shadow 1991 with 186000kms, been experiencing rough idle
and very poor mileage. Took the car to the garage and measured cylinder
compression...results
1 - 135
2 - 70
3 - 85
4 - 130

What can I do?

Alberto Mirarchi

 

Check the head gasket. I'll bet its blown between #2 and #3. While the
head is off, have it and the block surface checked for straightness. Has
the engine ever been overheated?

 

Hi.

The engine has never overheated yet, but I'm also losing prestone which
can be another bad indicator. I am thinking of performing this work my self.
Keep in mind I have no experience and don't really know how big or difficult
of a task this maybe. Any advice?

Alberto

 

I've never done a head gasket on a 2.2/2.5, but I've done a number of
other engines and talked to people who have done 2.2/2.5s. Its pretty
straightforward. Use a Fel-Pro replacement gasket, use new head bolts
(these engines use "torque-to-yield" bolts that stretch, and while you
can re-use them if they pass a "straightedge" test, its generally best
to get new ones) and keep everything clean. Take the head to a machine
shop for examination and smoothing if needed, and check the block with a
steel straightedge.

When re-installing the head, follow the bolt torquing procedures
EXACTLY. This normally means using a torque wrench to bring them to a
specified torque, and THEN using a breaker bar to turn them a fixed
amount (something like 1/4 or 1/2 turn) to properly stretch the
torque-to-yield bolts.

 

It's not a small job, but if you have a book to help you with doing things in
the right sequence not that hard really.
I've done 3 or 4 2.2 head gaskets and haven't had any problems yet.
I did find that cleaning the engine FIRST makes things go a little smoother.
After taking the first head off and fumbling around with the timing belt, I
realized it was a perfect time to replace it anyway. The next few I just cut
the old one off and replaced it.
You will need some half inch drive sockets (15mm for the head bolts, and 18mm
for the engine mount to replace the timing belt), a GOOD torque wrench, and a
breaker bar.
With the head off check it for any warping, and cracks ( usually in the small
space between the valves, and everyone I've seen was cracked) You may want to
consider replacing the head, I got my last one from Clearwater Cylinder Heads
in FL and was amazed by how much heavier the new replacement was than the
factory head. Shipping core charge and all was less than $300 and it's new not
rebuilt.
Bumper to Bumper sells a head gasket kit that includes ALL the gaskets and new
head bolts ( don't try to reuse the old ones)
I still think the toughest part was disconnecting the exhaust pipe, and I would
recommend removing the head with the exhaust and intake manifolds attached, if
you're not going to replace the head just leave them on, if you do replace the
head they're easier to get off when it's on the bench.
Sorry if this makes it sound more complicated than it really is,
Jude