See full version: How to: What I did to Diagnosis; Repair Blown head gasket Mercruiser 4 cylinder
My engine is a 1990 Mercruiser 4cylinder 3.0L carburated (gm motor)
my motor Symptoms
The motor Started running weaker as the season wore on, top speed was slowing down more and more, and some excessive oil was coming out of the breather into the spark arrestor. Seemed like alot of air was coming out of the breather when the motor was running, some is normal, but this was quite a bit, no smoke coming out though, which was interesting.
my VIDEO on youtube of doing this here
once all clean onto checking head and block flatness
the mercruiser manual calls for .008 thousandths warpage over 6" as a max warpage acceptable. I used a straight edge flatness bar (I got mine from Snap on a long time ago) and flat feeler guage set,
Laid the bar out and pushed feelers under where the head gasket was blown, max feeler I could push through on the block on my engine was .003 GOOD TO GO
I cleaned the head up using carb spray and compressed air,
Longer crank engine time is another sign of a failed gasket. Even worse, other cars that are suffering from this problem won’t even start.
Remove the cap off and insert the exhaust probe of the gas analyzer. Put your hand on top so the probe is getting enough gas to analyze. Make sure not to get any coolant in your analyzer because it’s only meant to read gas, not liquid. Be extra careful if you’re working with pressurized caps since most cars still have them. Check the readings and if the hydrocarbons go beyond 100, then it’s time to have that gasket fixed.
When you have a failed gasket, it will allow combustible gases to enter your cooling system. This will then manifest itself as bubbles of air that can be seen in your radiator or expansion tank. Remember to take extra precaution while doing this test because the coolant could erupt swiftly from the radiator. That’s the kind of exhaust gas you don’t want to be near in. here
Conduct the compression test by removing all spark plugs and thread the compression manually. Crank the engine and observe the readings on your compression tester for each cylinder. When two side-by-side cylinders result to 0 psi, then you are dealing with bad news.
Is it better to replace head gasket or engine? It is better to replace the head gasket so long as the cylinder head and engine block are undamaged. The cost of replacing an engine is far greater than a head gasket. … You’ll also learn how a mechanic diagnoses, strips down and inspects the cylinder head gasket. here
If your car is worth many thousands of dollars, fixing the head gasket probably makes sense. However, if you have an old vehicle that’s more rust than anything else, replacing the head gasket is probably a waste of money. here
Most blown head gaskets can be properly fixed without a mechanic. There is a point where the damage is too great and you will need the expertise of a professional to replace the gasket, but many leaks in a head gasket can be taken care of with one of our products.
When it’s no longer able to do its job, it’s officially considered “blown,” meaning you’ll need a new head gasket. … Ignoring it can lead to severe problems, such as a cracked engine block or warped head. These often result from the engine getting too hot due to a lack of coolant, usually stemming from a leak.
Also to know is, How long can you drive a car with a blown head gasket? You might be able to drive the car for a week, or it may last for a few months if you use a temporary fix on it. As a rule of thumb, it’s best to NOT drive if you suspect a head gasket issue. One thing is for sure: You will have to get repairs sooner than later.
If you suspect you have a blown head gasket, take your time diagnosing the problem. Dry and wet compression tests and cylinder leakdown tests might reveal the location of the leak. A block tester can help determine whether combustion gases are present in the cooling system — a sure sign of a head gasket failure. Your local NAPA AutoCare Center has the right equipment to help diagnose a blown head gasket if you have any suspicions .
In addition to electrical sensors and actuators, today’s internal combustion engine relies on liquids and gases to function: air-and-fuel, engine coolant and engine oil. Engine design keeps these liquids and gases from mixing so they can perform their specific functions. The head gasket is mounted between the engine block — where the cylinders are — and the cylinder head — where the intake, exhaust and valves are — and performs several critical functions.
The signs of a blown head gasket aren’t always obvious. Knowing exactly how the head gasket works can help steer you in the right direction when it comes to making a successful diagnosis and repair.
Engine oil performs three important functions: lubrication, cooling and hydraulics. The oil pump sends pressurized oil — up to 60 psi in most applications — throughout the engine to lubricate bearings, bushings, journals and timing chains. It also drives hydraulic actuators, such as variable valve timing. The head gasket prevents oil from entering the cylinders, between power strokes, and the coolant. [links]
Engine coolant surrounds each cylinder in order to maintain a stable operating temperature; it also needs to flow into the cylinder heads to cool the combustion chamber, valve and spark plugs. The head gasket prevents coolant from entering the cylinders between power strokes and when the engine is off, and the oil (when the engine is off). more
Upon combustion, air and fuel can generate upward of 700 psi in gasoline engines and upward of 2,000 psi in diesel engines. In order to keep that pressure in the combustion chamber, the head gasket needs to be robust and installed properly. The head gasket prevents liquids and gases from escaping into adjacent cylinders and the surrounding oil and coolant galleries.