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Diagnosing Headgaskets
Lots of threads for overheating, thermostats, radiator caps, and overflow tanks now that the summer is upon us. Before you go out and buy a bunch of parts that don't need to be replaced, then spend countless hours replacing them, only to find out they didn't correct the condition you're concerned with, your time and money might be better spent learning how the system actually works and diagnosing the problem correctly the first time.

Some members are under the impression that when a headgasket blows, it BLOWS!! That isn't always the case. The problem generally starts long before the gasket finally gives up. It looses integrity and starts bypassing compression from the combustion chamber into the water jacket. Not only are the hot gases forced into the coolant, they also cut into the composition portion of the gasket causing the material to be sheared off. From there, the fiber can end up in any number of places in the water jacket. The head, the waterpump, the thermostat, the radiator, etc.
I recently had to replace mine. The bike would run warm, the cooling fan would run continuosly. However, it took nearly 100 miles of riding before the symptoms would appear. At first, I thought it was bits of sealant I had used. After filling the cooling system, I could go another hundred or so miles, then the overheating would reoccur. It wasn't the sealant.
[Image: gasket.jpg]
Headgaskets are not as difficult to diagnose as most make them out to be. There are "tell tale" signs that can only be caused by a blown headgasket or a headgasket that is failing.

Before testing, verify that your radiator cap and recovery system are in good working order. It is imperative that the radiator cap is working correctly.

Overflow tanks: They are not overflow tanks. They are storage for the coolant "recovery" system. Inspect your radiator cap and you'll see TWO seals. One for the top of the radiator neck, and one for the lower portion. The area in the neck between these two seals is the "operating chamber" that allows the recovery system to work. As the coolant increases in temperature, the pressure increases, because it is a closed system. To allow for expansion, the radiator cap (lower seal) vents coolant to the recovery bottle. As the coolant decreases in temperature, it creates a low pressure area in the radiator and the coolant is then drawn back in to the radiator, past the same seal, thus keeping the cooling system "full" at all times. The seal at the top ensures that the system stays tight. If coolant can leak out, air can leak in. If air can leak in, the coolant will NOT be drawn back into the system.
If your seals are badly worn, or cracked, replace the cap. If the seals appear good, have the cap tested to ensure it is operating correctly.
Inspect the sealing surface of the radiator neck for both seals. Make sure there are no "nicks" or low spots that would affect the operation of the system.
Commonly overlooked is the upper portion of the neck where the radiator cap "locks" into position. This is a double step. Once the cap is snug, you must PUSH DOWN and TURN the cap for proper seal. Unfortunately, some owners lack "finesse" and jamb the cap opening it or securing it, which causes the tangs on the neck to be deformed. This will result in no seal or poor seal and negatively affect the operation of the recovery system.


Remove the faux tank.
Fill the radiator to the proper level. If it's low, there's a reason.
Remove the hose from the radiator neck to the recovery bottle "AT" the recovery bottle.
Place the hose into a funnel/bottle to catch any coolant that may be expelled.
Bring the bike up to operating temperature, watching for coolant discharge at the hose. A small amount of coolant is normal due to heat expansion
After the bike has reached operating temperature, and the cooling fan has cycled (twice), the system temperature AND pressure should now be stabilized.
Since it's cycled the fan twice, this is a good indication that the thermostat is functioning correctly, the water pump is circulating coolant and obviously the cooling fan and thermostatic switch are working as well.
Rev the engine a few times, watching the recovery hose, and see if the cap is still venting coolant due to excess pressure.
Since the pressure due to engine temperature has already been accounted for, there is only one other place the pressure can be coming
#1 07-26-2009, 05:22 PM,

Messages In This Thread
Diagnosing Headgaskets - by Guest - 07-26-2009, 05:22 PM
Re: Diagnosing Headgaskets - by SIR tricky - 07-26-2009, 06:37 PM
Re: Diagnosing Headgaskets - by 85GL1200I - 08-10-2009, 05:35 AM
Re: Diagnosing Headgaskets - by Guest - 08-10-2009, 07:15 AM
Re: Diagnosing Headgaskets - by 85GL1200I - 08-10-2009, 09:25 AM
Re: Diagnosing Headgaskets - by Guest - 12-22-2009, 12:57 PM
Re: Diagnosing Headgaskets - by Guest - 12-22-2009, 02:26 PM
Re: Diagnosing Headgaskets - by Guest - 12-22-2009, 04:41 PM
Re: Diagnosing Headgaskets - by rrboomer - 12-22-2009, 08:47 PM
Re: Diagnosing Headgaskets - by Roleketu - 06-20-2010, 12:03 PM
Re: Diagnosing Headgaskets - by SIR tricky - 06-20-2010, 02:03 PM
Re: Diagnosing Headgaskets - by Guest - 06-20-2010, 02:16 PM
Re: Diagnosing Headgaskets - by SIR tricky - 06-21-2010, 08:48 AM
Re: Diagnosing Headgaskets - by Roleketu - 06-26-2010, 12:06 AM
Re: Diagnosing Headgaskets - by joe turner - 06-26-2010, 05:00 AM

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