90 Accord, low compression on 3rd cylinder??
 

90 Accord, 196k on original motor, runs but obviously low on power...I was expecting to put in another motor but I checked compression first...#s are about 190 on 1,2, and 4, but 3 is down at about 55. I added oil into the plug hole and tested again with no change. I suspect the valve stem seals, and I wonder if I can get away with just putting on a good head. However, I don't want to do this to find out the compression rings are bad or that another problems pops up. Does this sound like valve seals? Is there another test to verify this or to rule out rings. I would love to get this running again for less than $200.
Thanks in advance
Gene

RE: 90 Accord, low compression on 3rd cylinder??
 

Nope, it's most likely a leaking valve. A leakdown test will narrow down the problem.

RE: 90 Accord, low compression on 3rd cylinder??
 

I would just buy a rebuilt head if the milage was lower but you might want to consider a rebuild on it.

RE: 90 Accord, low compression on 3rd cylinder??
 

Just to explain the reason... When you check compression, the valves are closed, so there's no pressure across the valve stem seals. Bad compression can only go a few places:

Leaky valves (not stem seals). A leakdown test will let you hear whether it's leaking into the intake manifold vs. the exhaust manifold.

Leaky piston rings. A leakdown test will let you hear it leaking into the crankcase.

Leaky head gasket. A leakdown test will let you know if it's leaking into the water jackets.

RE: 90 Accord, low compression on 3rd cylinder??
 

Thanks for explaining that to me...It makes sense now where before I didn't quite understand.

RE: 90 Accord, low compression on 3rd cylinder??
 

Very Good Information here Jim Blake..Thanks to you good members who know the "Right Stuff" our other members are recepients of your Good Information..
WheelBrokerAng [sm=americanasmiley.gif]

RE: 90 Accord, low compression on 3rd cylinder??
 

Also, have you been the only owner of this vehicle. A previuosly broken timing belt could have caused this as well. Believe me I know someone who found out the hard way. People will regularly just slap another belt on as long as the motor still runs. It seems that only one cylinder is affected as long as the engine was not revving high when the belt broke.


Just a thought...

RE: 90 Accord, low compression on 3rd cylinder??
 

yeai agree. its only speculation until you get it leak tested but i think its a busted timing belt that bent a valve.