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How do u do a compression test - 1998 Cadillac DeVille

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Auto parts stores sell a compression testing tool which is a gauge and hose attachment. Remove the park plugs, make sure you mark the spark plug wires so that you can replace the wires in the correct location and keep the firing order correct. You attach the tester by screwing it into the spark plug hole and then crank the motor over several times. This has to be done for each cylinder. I recommend you get the Haynes repair manual on your vehicle so you have the proper ranges for compression for the cylinders and further instructions on doing this test.

Posted on Aug 07, 2010

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Posted on Jan 02, 2017

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What should the psi compression be thanks.


It can vary between make and model of car. However, a general rule of thumb is that 135+ average is okay. Less than 85psi is pointing at something seriously amiss in the engine.

It can vary - some cars may have 125psi as 'average' compression.

Don't expect each cylinder to give the same compression reading as there will be a fluctuation. Another general rule of thumb is that there shouldn't be more than 10% variation between the readings. That is, if cylinder No1 is 135 psi, cylinder No2 shouldn't be less than '125 ish'.

If you suspect you may have compression issues, it's quite easy to do a bit of fault finding. Warm the engine first so that the pistons are expanded in the cylinders. Then do a dry compression (normal) test.

Here's some examples of compression tests on a 4 cylinder engine:
130 127 129 127

All compression readings are within 10% of each other. Fine.

Example 2:
95 95 129 127
Here, a low compression reading on cylinder 1 and 2 suggests a problem. It may be due to a faulty head gasket/cylinder head allowing compressed gases to be transferred via the defective head gasket from one cylinder to another.

Example 3:
130 80 129 127
Cylinder No2 has a problem. It's compression is way down. The other three cylinders are fine. So .. what is the cause of the low compression on cylinder 2? It could be a broken ring/cracked piston or a burnt exhaust valve.

This is where you do a second compression test - called the 'wet' test.

Squirt some light engine oil into each cylinder. Aim for the cylinder walls so that the oil can find its way down the walls and around the piston rings. Place a rag over each spark plug hole and spin the engine to expel excess oil.

The oil that you have sprayed into each cylinder will form a 'seal' around the piston ring. Do another compression test and note down the readings. Here's example 3 again:
Example 3:
130 80 129 127
.. with the low compression on cylinder 2.

If after carrying out the 'wet' compression test you have a reading along the lines of
130 100 129 127
suggests that the bore/piston rings in cylinder 2 are at fault. The compression has increased on No2 cylinder because of the oil forming a seal around the rings.

If there is no increase in psi on the wet test i.e
130 80 129 127
This suggests a burnt exhaust valve.

May 17, 2016 | Cars & Trucks

3 Answers

2002 3.7 litre jeep. How can I ck to see if a valve is fully closing? There is no lash adj. Springs look o.K. no compression #2 cyl. All others o.K.


You put compressed air into the cylinder an listen for the air escaping , if coming out of the throttle plate ,burnt intake valve . If you hear air coming out of exhaust pipe , burnt exhaust valve . If you hear air coming out dip stick tube bad rings or piston damage. How To Perform Leak Down Test EricTheCarGuy

Mar 02, 2016 | Cars & Trucks

2 Answers

Hi I'm getting low compression pressure on cylinder 2 on my Renault Clio 1.4 16v 2003 model 1,3&4 are OK I have changed head gasket,valves,rings but still the compression is low can anyone help please


I wonder did you check your work as you progressed?
Pressure testing the valve seats for instance or even just a paraffin test? A good valve seat is difficult to obtain with the hardened steel seats used for unleaded fuel, especially when using a coarse grade of carborundum paste.

In order to discover where the compression leak is it will be necessary to set the cylinder at the top of the compression stroke, lock the engine and then inject compressed air into the cylinder using either a propriety or home-made adapter in the spark plug hole. It will soon be obvious where the air is leaking from indicating the fault.

Valve clearances are important and in the case of hydraulic self-adjusting valve lifters it is possible for them to stick and hold the valve slightly open. I generally squeeze each one in a vice several times until all the oil has been evacuated.
If the valve spring is weak or the oil pressure relief valve is stuck closed tappet jacking is possible.
Good luck!

Nov 02, 2015 | Renault Cars & Trucks

2 Answers

I have no compression in the 7 cylinder


Failed Valves

Head Gasket

Maybe other issues as well

Why not do some testing & find out

Forget the compression test

Cylinder Balance,Cylinder Leak Down Test
Do those

Aug 27, 2014 | 2012 Chevrolet Camaro

1 Answer

Correct engine compression test results


There are no "correct" numbers for compression tests, as actual compression depends on many variables. The important thing is that it is not crazy low (less than 110 psi approx) and that all cylinders measure within 10% of each other (approx). Tests should be done with throttle held wide open and all plugs removed. Crank engine about 5 revolutions for each test. Comprssion should slowly build to max reading.

Dec 24, 2013 | 2001 Toyota Altezza

3 Answers

2003 cavalier missing on cylinder 2


possibly wiring harness fault,sesor wheel installed backwards or an even fire/odd fire engine mismatched components

Nov 20, 2017 | 2003 Chevrolet Cavalier

1 Answer

What should the compression level be for a 1998 toyota camry?


compression should be about 150-180 psi with maximum deviation of about 20 psi between all cylinders. A compression test is not a very reliable way to test for headgasket leaks. It should be tested for headgasket leaks by using a chemical test caled a block test or checked with a device that can check for hydrocarbons in the coolant.

Apr 22, 2012 | 1998 Toyota Camry

1 Answer

My 1998 saturn has low compression in number three cylinder could it be stuck and if so what can i do to free it up


Low compression is not a "stuck" issue, usually there is a valve leak or compression ring issue. Both are fairly involved to repair. The next step is a wet compression test. If the compression goes up when wet, rings are suspect, if not valve is suspect. The next test is leak down test.... BUT compression loss is not a simple fix.

Apr 22, 2011 | 1993 Saturn SL2

2 Answers

Loss compression


How to Test Engine CompressionAn engine depends on an equal compression reading in each cylinder to run smoothly. If poor compression exits in one or more cylinders it can cause a rough idle condition and low power. A compression test can be performed to check wear or internal damage. To start a engine compression test gauge is needed. There are two types of gauge styles, one threads into the spark plug hole which is more accurate. The other style of gauge is constructed with a rubber plug that is meant to be pressed against the spark plug hole, this style of gauge is difficult to use. To perform a engine cylinder compression test follow the steps below.
  • Remove ignition coil connector or ignition system fuse to disable power to the ignition system
  • Test ignition system to ensure that the power to the system has been disabled
  • Remove #1 cylinder spark plug and insert compression gauge, most gauges have a hose attachment that is installed into the spark plug hole with the gauge connecting to the gauge hose.
compression_gauge.jpg
Engine Cylinder Compression Gauge
  • After the compression gauge has been inserted, use the starter to crank the engine over for about five seconds. Use about the same five seconds to test the remaining cylinders.
  • Record the compression reading as each cylinder is tested
  • Remove the compression gauge and reinsert the spark plug
  • Follow this procedure until all cylinders have been tested
  • Compare cylinders compression reading, all readings should be within about 5% of each other
If low compression exists a cylinder malfunction exits and further inspection is required. Possible causes for a low compression condition are: burned intake or exhaust valve, broken piston or piston ring, broken valve spring or a blown head gasket.

May 31, 2008 | 2000 Hyundai Tucson

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