Question about 1998 Ford Mustang

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Compression for 1998 Mustang

How many pounds of compression should I have on a 1998 3.8 liter Mustang engine. I may have blown a head gasket as it got hot and there is water in the oil pan.

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  • otto13 Jun 24, 2008

    I tested the pressure today and one head's cylinders were 165,165,165. The other was 172.5, 172.5, 175. Based your your advice I need to look for another problem. What would be your thought. The engine has 101,000 miles.



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You may also want to do a simple check to see it the cooling system is holding pressure. You can use a tool or have a mechanic pressure up your system to check it it holds presure. Also after reaching operating temp, check the radiator cap after 20-30 minutes to see if it is holding pressure. I have also seen in the past a failed water pump. If the weep hole is plugged and the seals are out of the pump, coolant could leak into the crank case.

Posted on Jun 27, 2008

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Depends on condition of engine.What you want to look for is a large difference between related cyls. If all are with in 10-15 percent of each other your problem may be some where else.

Posted on Jun 23, 2008


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How can you tell if you have a blown head gasket in a 2003 Ford Explorer if no water is in the oil

Water in the oil is not the only symptom of a blown head gasket. You can have a blown gasket where the cylinder gasses are being injected into the the water jacket only. This will overpressurize and overheat the engine. There is a test that can detect this using a coolant sample from the radiator to test for hydrocarbons present in exhaust. Lastly, the gasket can blow to the exterior of the engine, allowing compression gasses to escape the engine block. The quickest DIY test to determine the possibility of a blown gasket is a cylinder compression test. The compression should be approximately the same in all cylinders and should not leak down quickly. If it does, this indicates either a blown head gasket or possible valve issues.

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How many pounds should the compression tester read?

There is no set amount of compression that is correct as it depends on atmospheric conditions, engine wear, etc. The important thing is that each cylinder tests within 10% of all others. Readings should be taken with throttle held wide open, and for most modern engines 120 to 150 PSI is ok. 90 psi or less usually indicates a problem. Crank engine over 4 or 5 times for reach test, with full battery and all plugs removed.

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What is a compression check?

Checking the compression amounts to using a pressure measuring device either held and sealed by rubber gasket against the cylinder spark plug orfice, or could be threaded the same as your specific plug is. It is a measure of the compression pressure within your cylinder when it is on the compression stroke....meaning all valves closed and the cylinder going up toward the cylinder head resulting in compression. Reasons for low compression are worn piston rings, burnt or mis-adjusted valves, or could be a cracked cylinder wall, blown head gasket or a hole in a piston. Gasoline engines run much lower compression than diesels. For your compression pressure norm, Google in your engine or buy a service manual and it will have the specs in pounds per Sq. in.or PSI. Good Luck

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1998 camaro 3.8 not firing on # 6

Pull plug #6 out and inspect the color of the plug.
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Head gasket will cause low to NO compression

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Compare compression to other cylinders.


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98 honda accord v6 only has 90 psi compression

90 psi compression is the minumun for gas engine to ignite, you have low compression what is the compression next to it? The compression on Honda V6 is 200psi. you can have a valve problem a blown head gasket, Also make sure your compression gauge is accurate by using another compression gauge

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One cylinder is low in my 1998 Volvo s90 and the repair shops says the engine needs to be replaced. Is this true>

Not necessarily. I assume you mean that the compression on one cylinder is low? This is generally either the rings/cylinder, or valves. Sometimes a blown headgasket can drop compression, but will generally have other symptoms, ie., blown between one cylinder and another, blown between the cylinder and a cooling or oil passage, etc.

A GOOD shop will check more than compression, to determine where the exact problem is.

*A head gasket blown between 2 cylinders will have low compression on bothe affected cylinders.
*A head gasket blown into an oil or cooling passage will blow bubbles (gasses) into the affected area.
*To check the rings/cylinder, after running the first compression check, put a few ounces of oil into the cylinder through the spark plug hole. Re-run the compression check on that cylinder, and if the compression improves dramatically, you have bad rings on that cylinder.
*To check the valves, you need what is called a pressure differential guage. You place the affected cylinder at TDC (Top Dead Center) on the compression stroke. You then attach the guage, and apply a set amount of air pressure to the cylinder, usually about 100psi. One dial on the gauge reads input pressure (100psi), and the other reads how much the cylinder is actually holding. A drop of more than 10-15% generally indicates a bad valve in the head (as long as the prevoius checks came out OK). To determine which valve is bad, remove the intake ducting and listen for escaping air (Intake Valve) and listen at the tailpipe for the same (exhaust valve).

These are general procedures for tests so that you can see if your mechanic has actually performed them or not. If you want to run the tests yourself, I can give you more specific instructions.

Head Gasket - need to remove the head and check the head and block for cracks. Then replace the gasket and reinstall the head.
Bad Valve(s) - need to remove the head and have the bad valves reground or replaced by a machine shop and then reinstall the head.
Bad Rings/Cylinder - the engine will need to be removed and either machined and rebuilt or replaced.

Again, if you want any more specifics, please ask.

Hope this was helpful!

Sep 17, 2011 | 1998 Volvo S90

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I have Ecort 1.8 td from 2000 Y of production, and have white smoke on pipetail and idles very roughly, engine coolent is OK, oil level is OK, what can it be the problem?.

Even though coolant level is OK, it does not rule out a blown head gasket-has the engine recently been overheated? You should get engine compression checked, to see if you have low compression in 2 adjacent cylinders, to rule out the possibility. White smoke and very rough engine performance point to a blown head gasket, however.

Jan 05, 2011 | 1998 Ford Escort

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I got a 1998 dodge 5.9 liter,it got hot so i changed water pump,thermostate,fan clutch,cleaned radiator out,still gets hot......why

hi this sounds like you might have a blown head gasket, what you will have to do is get it compression tested to see if you have a leak you have changed all the normal parts that would normally cause overheating, so looking at the information you have given i would say its a blown head gasket...hope this helps

Sep 07, 2010 | 1998 Dodge Ram 1500 4WD

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What's the difference between a blown head gasket and a blown intake gasket?

The head gasket goes between the block and the head, and seals the combustion process, and cooling water, and (if oil is pumped obove the heads to valve components) oil pressure.

Intake gaskets seal between the intake manifold and the head, and seal against intake vacuum, and in many cases, coolant.

A badly blown head gasket will so destroy compression in the cylinder that you can hear uneven cranking as that cylinder comes up on compression, kind of a “whir, whir, WHIR, whir, whir, WHIR, whir” with the capitalized whir being the engine spinning much faster due to no compression holding the starter back.

You will never be able to hear a problem with an intake manifold gasket until the engine actually starts to fire and/or run.

Aug 10, 2010 | 1994 Pontiac Grand Am

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28 Solutions for ''HOw can I tell if I have a cracked head blown head gasket or cracked blown like how can I see it''

Often (but not always), a blown head gasket will also cause deposit of water on a piece of cardboard held an inch from the tailpipe output while the engine is running (when this is happening, it is likely that the catalytic converter has been ruined and the muffler will corrode in short order as well).

Sometimes drops of water will be seen dropping from the end of the tailpipe. Another clue: turn on the heater; often when the head gasket is blown an odor of antifreeze and synthetic rubber will emanate from the heater vents.
Many of the symptoms of blown head gasket can be caused by some other problem in the cooling system, without the head gasket being damaged. Conversely, other problems with the cooling system can cause a blown head gasket and/or warped head.

When checking for a blown head gasket, one of the most common tell-tale signs is a milky-gray ring around your oil cap. When coolant enters the engine oil through a crack in the head or through a blown gasket, it evaporates and leaves a milky ring around the oil cap. Another easy way to tell is to check your oil dipstick. Change your oil and pull out the dipstick. Make sure that you take note of how far up the dipstick the oil is. Top off your cooling system and fill your cooling reservoir to the top. Screw radiator cap back on and start engine. Run engine for about 20-30 mins. or until it reaches normal operating temperature. Allow engine to cool (engine must cool completely to get accurate oil reading!!). Check oil dipstick again. If the oil has a watery appearance and has risen noticeably up the dipstick, the you probably have a blown head gasket or a warped head. Also look for a dripping, sweet-smelling liquid coming out of your tailpipe. Any of the above symptoms could be the result of a blown head gasket. The easiest way to tell is with a compression meter. This replaces the spark plug and lets you know what compression each cylinder is running at. If your compression is abnormally low, then you have a blown head gasket or a warped head. (note: consult repair manual for appropriate compression of each cylinder.)

Dec 12, 2009 | 2005 Dodge Grand Caravan

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