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Discussion Starter #1
Hello all!! New to the forum and have a few questions. I Just purchased a 05 gmc 2500hd with the lly. Got the truck for a steal as my buddy told me he thinks the head gasket is bad. Anyway I got the truck home and noticed the radiator had a crack in it. so I changed that out along with a new coolant tank cap and then tested for exhaust gas in the coolant tank witch came back negative several times. My symptoms are the upper hose gets pretty hard but if you let the truck sit 10-20 min you can squeeze the hose completely. Also sometimes after a long drive I can kill the truck and squeeze the upper hose completely. I also have good heat from the vents. I did notice sometimes it will push coolant out the over flow of the coolant tank. Before I order a complete head gasket kit with grade c gaskets and arp studs. I would like some input as I'm pretty stumped on this. Thanks
 

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People who have tried various test kits, like for exhaust gas in the coolant tank, have said they got negative results even when they had bad head gaskets. So you really can't trust those test kits.

The #1 diagnostic is that the radiator hose is still rock hard after the engine has cooled down overnight. This assumes the cooling system can hold pressure, of course. A few have said it caused the water pump to leak, which is probably a water pump that was on its way out anyway.

Another diagnostic has been seeing a lot of bubbles in the reservoir tank, that is, exhaust bubbles.

Another diagnostic can be the mysterious loss of coolant. The level drops, but it doesn't come out anywhere (actually, it's going out the exhaust). [added on edit] But beware, the coolant leak could also be somewhere else, like the EGT cooler.

The radiator hose SHOULD get hard when the engine is hot because the cooling system is suppose to pressurize up to 15 psi. As the engine cools off, this pressure eases, even to the point of sucking a little air back through the cap (which vents to prevent a vacuum). That's the difference with the head gasket diagnostic where the cooling system stays pressurized even after the engine has cooled down.
 

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Discussion Starter #3
People who have tried various test kits, like for exhaust gas in the coolant tank, have said they got negative results even when they had bad head gaskets. So you really can't trust those test kits.

The #1 diagnostic is that the radiator hose is still rock hard after the engine has cooled down overnight. This assumes the cooling system can hold pressure, of course. A few have said it caused the water pump to leak, which is probably a water pump that was on its way out anyway.

Another diagnostic has been seeing a lot of bubbles in the reservoir tank, that is, exhaust bubbles.

Another diagnostic can be the mysterious loss of coolant. The level drops, but it doesn't come out anywhere (actually, it's going out the exhaust). [added on edit] But beware, the coolant leak could also be somewhere else, like the EGT cooler.

The radiator hose SHOULD get hard when the engine is hot because the cooling system is suppose to pressurize up to 15 psi. As the engine cools off, this pressure eases, even to the point of sucking a little air back through the cap (which vents to prevent a vacuum). That's the difference with the head gasket diagnostic where the cooling system stays pressurized even after the engine has cooled down.
That's what has me stumped as my truck can sit for 10-20 minutes and the hose is soft again. I have definitely noticed it pushing the coolant out of the over flow hose a few times.
 

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Actually, most techs that I know, myself included, use just two specific tests on a dmax to know if the head gaskets are going.

1. Check coolant for the presence of combustion gases with a block test kit.

2. Cooling system pushing coolant out for no apparent reason. If this isn’t readily apparent, increasing the engine speed to 2500+ rpms for 5+ minutes or even brake torquing the engine will usually make it reer it’s ugly head in no time flat.
 

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Discussion Starter #5
Actually, most techs that I know, myself included, use just two specific tests on a dmax to know if the head gaskets are going.

1. Check coolant for the presence of combustion gases with a block test kit.

2. Cooling system pushing coolant out for no apparent reason. If this isn’t readily apparent, increasing the engine speed to 2500+ rpms for 5+ minutes or even brake torquing the engine will usually make it reer it’s ugly head in no time flat.
I did the combustion block check and the test came back negative every time (tested it about 7 different times) I'll give it the brake boost check when I get home from work in the morning and let you know how that turns out.
 

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Discussion Starter #6
Well I got it to spit coolant out of the over flow hose and so i let the truck cool down for about 6 hours and noticed the upper hose was flat. I started the truck let it run about 5 minutes and noticed bubbles in the coolant tank. Ill be replacing head gaskets soon as possible.
 

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Well I got it to spit coolant out of the over flow hose and so i let the truck cool down for about 6 hours and noticed the upper hose was flat. I started the truck let it run about 5 minutes and noticed bubbles in the coolant tank. Ill be replacing head gaskets soon as possible.
That's why I don't always go by the rad hose deal. Bubbles in the coolant tank while it's running and blowing coolant out of the overflow are both SURE signs where you are heading though.
 
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