How to troubleshoot Head Gasket and Head issues
#11
10-19-2010, 06:40 PM
The usual symptoms are white "smoke" that smells like antifreeze from the tailpipe, misfiring in one or more cylinders, and one or more spark plugs discolored (unusually clean due to the steam-cleaning action of leaking water).
A simple test you can do at home is to get the radiator completely full and start the engine (cold) with the radiator cap off. Look for bubbles in the radiator when you rev the engine up. A severe case will blow coolant out like a geyser. If you only see a few bubbles it could just be trapped air, or it could indeed be a leak in the engine. There is a device garages use to analyze the gas and see if it contains CO2, which comes from combustion in the cylinders.
If you have a leak the next thing would be to take the head off and check the head and block for flatness. If the block is no longer flat the engine is very likely beyond repair. You can try having the head machined flat ("shaved") if necessary. Reassemble with a new gasket and hope for the best.
A simple test you can do at home is to get the radiator completely full and start the engine (cold) with the radiator cap off. Look for bubbles in the radiator when you rev the engine up. A severe case will blow coolant out like a geyser. If you only see a few bubbles it could just be trapped air, or it could indeed be a leak in the engine. There is a device garages use to analyze the gas and see if it contains CO2, which comes from combustion in the cylinders.
If you have a leak the next thing would be to take the head off and check the head and block for flatness. If the block is no longer flat the engine is very likely beyond repair. You can try having the head machined flat ("shaved") if necessary. Reassemble with a new gasket and hope for the best.
I am repeating this question to you, since I did not receive any other replies, and your reply seemed the most complete. My last statement read:
OK, so the weekend is here, and so I pulled all the plugs, removed the fuel pump fuse, floored the gas pedal, cranked the engine for about fives seconds each time, and measured the compression in each cylinder, and my readings for each cylinder from left to right are as follows: 190,185,190,187. These do not sound like numbers for a blown head gasket, or a cracked head. My mechanic had reported readings of 70,90,80,80. How could I have screwed my measurements so bad that I am getting more than double his measurements? Please advise. Did I totally screw up the readings, or did the mechanic lie? What do you think? From what I have described about what I did, could I have made a mistake to more than double the results?
#12
10-20-2010, 01:27 AM
Small gasket leaks won't affect the cylinder compression readings. Your readings seem correct. An engine with compression below 100 typically won't start or run very well. For finding leakage to the cooling system, a leakdown test like the other guy suggested is much better. Most compression testers can be connected to an air compressor to do leakdown tests.
Are you losing coolant from the radiator? Check it before every trip when the engine is cold. There are other reasons for "threatening to overheat". I suspect that the occasional losing power is an unrelated issue.
Are you losing coolant from the radiator? Check it before every trip when the engine is cold. There are other reasons for "threatening to overheat". I suspect that the occasional losing power is an unrelated issue.
#13
10-21-2010, 05:41 AM
Small gasket leaks won't affect the cylinder compression readings. Your readings seem correct. An engine with compression below 100 typically won't start or run very well. For finding leakage to the cooling system, a leakdown test like the other guy suggested is much better. Most compression testers can be connected to an air compressor to do leakdown tests.
Are you losing coolant from the radiator? Check it before every trip when the engine is cold. There are other reasons for "threatening to overheat". I suspect that the occasional losing power is an unrelated issue.
Are you losing coolant from the radiator? Check it before every trip when the engine is cold. There are other reasons for "threatening to overheat". I suspect that the occasional losing power is an unrelated issue.
#14
10-21-2010, 06:46 AM
Let's back up. Your main concern is that the coolant is getting pushed out or otherwise lost from the radiator, leading to overheating, right?
Assuming there are no external leaks, the major cause of that is a head gasket leak.
The leakdown test is to force air into the cylinders (one at a time) with the engine stopped. If the air leaks out of the combustion chamber into the cooling system, bubbles of air will appear in the radiator. That shows that the head gasket is bad or there is a crack or other internal leak in the engine.
Assuming there are no external leaks, the major cause of that is a head gasket leak.
The leakdown test is to force air into the cylinders (one at a time) with the engine stopped. If the air leaks out of the combustion chamber into the cooling system, bubbles of air will appear in the radiator. That shows that the head gasket is bad or there is a crack or other internal leak in the engine.
#15
10-21-2010, 06:10 PM
Let's back up. Your main concern is that the coolant is getting pushed out or otherwise lost from the radiator, leading to overheating, right?
Assuming there are no external leaks, the major cause of that is a head gasket leak.
The leakdown test is to force air into the cylinders (one at a time) with the engine stopped. If the air leaks out of the combustion chamber into the cooling system, bubbles of air will appear in the radiator. That shows that the head gasket is bad or there is a crack or other internal leak in the engine.
Assuming there are no external leaks, the major cause of that is a head gasket leak.
The leakdown test is to force air into the cylinders (one at a time) with the engine stopped. If the air leaks out of the combustion chamber into the cooling system, bubbles of air will appear in the radiator. That shows that the head gasket is bad or there is a crack or other internal leak in the engine.
First of all, I want to thank you for sticking with me. Actually, originally the car had overheated. After replacing the clogged radiator, the radiator fan, and the thermostat. I took the car to a mechanic to do the compression test, and he reported 80, 90, 80, 90. I shopped around for a motor, but before I commited so much money into one, I decided to start this post thread. With some instructions from this forum and another one, I took measurements myself, and got 185,190,187,190. And this is where I am at. I am trying to establish if those readings are good enough to rule out a blown gasket. So, now, back to the leakdown test. I have to be honest, I don't understand how that works, and I don't know how to do it. Can you explain how it is done, or point me to a link where it is explained? Thanks, again, for being there.
#16
10-22-2010, 06:23 AM
You can't be sure that a head gasket is good because the compression readings are normal. It could have a slow leak.
To test leakdown, instead of measuring the pressure coming out of a cylinder, you remove the gauge from a compression tester and use the hose to force air in to the spark plug hole instead. Most testers have a quick disconnect that fits a standard garage air hose.
To test leakdown, instead of measuring the pressure coming out of a cylinder, you remove the gauge from a compression tester and use the hose to force air in to the spark plug hole instead. Most testers have a quick disconnect that fits a standard garage air hose.
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