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Just did a compression test...

Started by Agentlongwood, December 31, 2019, 03:49:58 PM

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Agentlongwood

I've never done one before, and wanted to double check my work here with yall.  I got really consistent readings, between about 180 and 190 on all 6 cylinders.  I actually thought it was supposed to be like 120, so I wanted to check with some folks who know more than I do  (you guys, lol).  I pulled all 6 spark plugs, and the intake so I could wedge the throttle body wide open.  Then I put the compression tester in, put the throttle pedal to the floor and pushed the start button.  I let it turn over about 5 times and stopped it manually.  If I let it go, it would try to turn over for what felt like too many turns.  I got out checked the gauge, reset it, and moved on to the next cylinder.  Does all that sound accurate, and seem correct?
2014 Lincoln MKS - Sold... And I still miss it sometimes

ZSHO

#1
Compression Test

Make sure the oil in the crankcase is of the correct viscosity and at the correct level and that the battery is correctly charged. Operate the vehicle until the engine is at normal operating temperature. Turn the ignition switch to the OFF position, then remove all the spark plugs.
Set the throttle plates in the wide-open position.
Install a compression gauge in the No. 1 cylinder.

Install an auxiliary starter switch in the starting circuit. With the ignition switch in the OFF position, and using the auxiliary starter switch, crank the engine a minimum of 5 compression strokes and record the highest reading. Note the approximate number of compression strokes necessary to obtain the highest reading.
Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.

If one or more cylinders reads low, squirt approximately one tablespoon of engine oil meeting Ford specification on top of the pistons in the low-reading cylinders. Repeat the compression pressure check on these cylinders.

Compression Test — Interpreting Compression Readings

If compression improves considerably, piston rings are worn or damaged.
If compression does not improve, valves are sticking or not seating correctly.
If 2 adjacent cylinders indicate low compression pressures and squirting oil on each piston does not increase compression, the head gasket may be leaking between cylinders. Engine oil or coolant in cylinders could result from this condition.

Cylinder Leakage Detection

When a cylinder produces a low reading, use of a cylinder leakage tester will be helpful in pinpointing the exact cause.

The leakage tester is inserted in the spark plug hole, the piston is brought up to Top Dead Center (TDC) on the compression stroke, and compressed air is admitted.

Once the combustion chamber is pressurized, the leakage tester gauge will read the percentage of leakage. Leakage exceeding 20% is excessive.

While the air pressure is retained in the cylinder, listen for the hiss of escaping air. A leak at the intake valve will be heard in the Throttle Body (TB) . A leak at the exhaust valve can be heard at the tailpipe. Leakage past the piston rings will be audible at the PCV connection. If air is passing through a blown head gasket to an adjacent cylinder, the noise will be evident at the spark plug hole of the cylinder into which the air is leaking. Cracks in the cylinder block or gasket leakage into the cooling system may be detected by a stream of bubbles in the radiator. Z


2013 Performance Package SHO| Livernois Custom Methanol Tune|3-Bar Map|Reische-170-Stat|Full Race Tial-10psi BOV in Black|PPE-Gloss Black Hot Pipes|EPP Dual Intake in Gloss Black|PPE Catted DP|Corsa Sport Cat Back Exhaust|H&R Sport-Springs|CFM Performance Billet Valve Cover Breather In Gloss Black|Llumar 20%Ceramic window Tint|MSD Ignition Coils in Black|Extreme Roof Spoiler|Redline Fluids all around|Gearhead Intercooler|First-SHO With Direct Port Alky-VP-M1-100%-Methanol Injection|LMS-Custom-Dyno-Tuned @ 415whp-465wtq| Best Trap Speed of 115.54 mph|

Agentlongwood

Thanks.  That's pretty much what I did.  Dang close anyway.  I really want to know about the readings.  Is 180 abnormally high?  I got a pretty basic tester, and would hate to fin out it was giving wildly inaccurate readings.
2014 Lincoln MKS - Sold... And I still miss it sometimes

ZSHO

#3
Quote from: Agentlongwood on December 31, 2019, 04:49:07 PM
Thanks.  That's pretty much what I did.  Dang close anyway.  I really want to know about the readings.  Is 180 abnormally high?  I got a pretty basic tester, and would hate to fin out it was giving wildly inaccurate readings.
NP buddy! 180 psi should be desired threshold.. Post updated ^^^ Z   :)


2013 Performance Package SHO| Livernois Custom Methanol Tune|3-Bar Map|Reische-170-Stat|Full Race Tial-10psi BOV in Black|PPE-Gloss Black Hot Pipes|EPP Dual Intake in Gloss Black|PPE Catted DP|Corsa Sport Cat Back Exhaust|H&R Sport-Springs|CFM Performance Billet Valve Cover Breather In Gloss Black|Llumar 20%Ceramic window Tint|MSD Ignition Coils in Black|Extreme Roof Spoiler|Redline Fluids all around|Gearhead Intercooler|First-SHO With Direct Port Alky-VP-M1-100%-Methanol Injection|LMS-Custom-Dyno-Tuned @ 415whp-465wtq| Best Trap Speed of 115.54 mph|