Low Compression ? Help~!
Thread Starter
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HCF Member
Joined: Aug 2009
Posts: 888
From: San Diego County, CA
If one, or more, cylinders read low, squirt approximately one (1) tablespoon of engine oil on top of the pistons in the low reading cylinders. Repeat compression pressure check on these cylinders.
1. If compression improves considerably, the piston rings are at fault.
2. If compression does not improve, valves are sticking or seating poorly.
Chubby Chaser
Joined: Dec 2007
Posts: 4,681
From: whitwell,Tn 37397
well do the test to find out. a port n polish is for if the valve isnt getting a good seal the machine shop grinds it and polishes the port to make a sure seal.
deffinitly do the test i posted then post results. if not piston rings then valve and a valve adj could (slight) possibility fix your prob.
deffinitly do the test i posted then post results. if not piston rings then valve and a valve adj could (slight) possibility fix your prob.
Thread Starter
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HCF Member
Joined: Aug 2009
Posts: 888
From: San Diego County, CA
The indicated compression pressures are considered normal if the lowest reading cylinder is within 75% of the highest.
Seventy-five percent of 131 is 98 , the highest cylinder reading is 131. Therefore, cylinder No. 3 being 60 which is less than 75% of cylinder No. 4 indicates an improperly seated valve or worn or broken piston rings.
If one, or more, cylinders read low, squirt approximately one (1) tablespoon of engine oil on top of the pistons in the low reading cylinders. Repeat compression pressure check on these cylinders.
1. If compression improves considerably, the piston rings are at fault.
2. If compression does not improve, valves are sticking or seating poorly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on the pistons does not increase the compression, the cause may be a cylinder head gasket leak between the cylinders. Engine oil and/or coolant in the cylinders could result from this problem.
Seventy-five percent of 131 is 98 , the highest cylinder reading is 131. Therefore, cylinder No. 3 being 60 which is less than 75% of cylinder No. 4 indicates an improperly seated valve or worn or broken piston rings.
If one, or more, cylinders read low, squirt approximately one (1) tablespoon of engine oil on top of the pistons in the low reading cylinders. Repeat compression pressure check on these cylinders.
1. If compression improves considerably, the piston rings are at fault.
2. If compression does not improve, valves are sticking or seating poorly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on the pistons does not increase the compression, the cause may be a cylinder head gasket leak between the cylinders. Engine oil and/or coolant in the cylinders could result from this problem.
Moderator
Joined: May 2007
Posts: 11,417
From: FL
The indicated compression pressures are considered normal if the lowest reading cylinder is at least 75% of the highest.
Seventy-five percent of 131 is 98 , the highest cylinder reading is 131. Therefore, cylinder No. 3 being 60 which is less than 75% of cylinder No. 4 indicates an improperly seated valve or worn or broken piston rings.
If one, or more, cylinders read low, squirt approximately one (1) tablespoon of engine oil on top of the pistons in the low reading cylinders. Repeat compression pressure check on these cylinders.
1. If compression improves considerably, the piston rings are at fault.
2. If compression does not improve, valves are sticking or seating poorly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on the pistons does not increase the compression, the cause may be a cylinder head gasket leak between the cylinders. Engine oil and/or coolant in the cylinders could result from this problem.
Seventy-five percent of 131 is 98 , the highest cylinder reading is 131. Therefore, cylinder No. 3 being 60 which is less than 75% of cylinder No. 4 indicates an improperly seated valve or worn or broken piston rings.
If one, or more, cylinders read low, squirt approximately one (1) tablespoon of engine oil on top of the pistons in the low reading cylinders. Repeat compression pressure check on these cylinders.
1. If compression improves considerably, the piston rings are at fault.
2. If compression does not improve, valves are sticking or seating poorly.
3. If two adjacent cylinders indicate low compression pressures and squirting oil on the pistons does not increase the compression, the cause may be a cylinder head gasket leak between the cylinders. Engine oil and/or coolant in the cylinders could result from this problem.
Chubby Chaser
Joined: Dec 2007
Posts: 4,681
From: whitwell,Tn 37397
when they do the compression test the bad cyl they need to put a little oil in the spark plug hole then compression test it again, its called a leak down test. if you have bad rings the compression will rise. if it stays the same then its a valve
Thread Starter
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HCF Member
Joined: Aug 2009
Posts: 888
From: San Diego County, CA
Well I really appreciate the help you guys have given me, but my mom's friend is a mechanic and he actually troubleshooted the car.
The only problem was the bad cylinder needed a valve adjustment, and he did it pretty cheap.
nonetheless, problem solved. !
thanks guys!
The only problem was the bad cylinder needed a valve adjustment, and he did it pretty cheap.
nonetheless, problem solved. !
thanks guys!
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