Signs of a cracked head??
09-22-2003, 11:10 AM
#1
Signs of a cracked head?? I have been fighting issues of the motor mysteriously consuming coolant. This weekend a buddy brought over his coolant pressure tester and we pressurised the coolant system to see if we could get the leak to show itself.
So we pressurized the system and began removing one spark plug at a time. Nothing, the pressure tester didnt move from 18psi. Upon inspection of each plug, you could tell that all cylinders were a little fat except #3. that plug was clean. With an odd residue on it.
The one thing we did notice though was the the radiator cap that is supposed to be rated at 18psi would only hit 13psi and then start dropping.
I doubt the cap is causing the problem. What concerns me is that the nice (and expensive) MTI Stage 2 LS6 heads may have developed a crack. OR a couple hairline cracks in the block. I would rather have the block go than the heads.
anyone have some insight as to a possible head problem?
So we pressurized the system and began removing one spark plug at a time. Nothing, the pressure tester didnt move from 18psi. Upon inspection of each plug, you could tell that all cylinders were a little fat except #3. that plug was clean. With an odd residue on it.
The one thing we did notice though was the the radiator cap that is supposed to be rated at 18psi would only hit 13psi and then start dropping.
I doubt the cap is causing the problem. What concerns me is that the nice (and expensive) MTI Stage 2 LS6 heads may have developed a crack. OR a couple hairline cracks in the block. I would rather have the block go than the heads.
anyone have some insight as to a possible head problem?
09-22-2003, 12:34 PM
#3
Re: Signs of a cracked head?? thats the problem. I dont know. There are no leaks of any kind. And I am not blowing any white smoke.
I am going to hook the pressure tester to the radiator tonight and fire it up and see if the pressure goes through the roof. That would indicate a bad block. But I dont know if it would do the same for a bad head.
I am going to hook the pressure tester to the radiator tonight and fire it up and see if the pressure goes through the roof. That would indicate a bad block. But I dont know if it would do the same for a bad head.
09-22-2003, 12:39 PM
#4
Re: Signs of a cracked head?? First off if you suspect a head problem do a compression check to eliminate the head gaskets. The only way that I know of to check on cracks and such is to magnaflux the heads and block. If somebody has a better idea then by all means express it but I would tend to think it could be something else. If the motor were eatting it you could smell the coolant in the exhaust I'm sure. Also make sure you don't have a bad waterpump or a leaking thermostat gasket. If a seal were to go out of the waterpump you should see the water weeping out of the weep hole, (it should have one) in the back of the waterpump. Also make sure the passenger floor of the car isn't wet. Might be a leaking heater core perhaps. Good luck whatever it is. I hope it is something stupid and simple
09-22-2003, 12:49 PM
#5
Re: Signs of a cracked head?? The motor is showing no signs of leaking. I dont have any interior so I would spot a bad heater core pretty quick. Unless the water pump weep hole is leaking into the k member and staying there I cant find anything coming out of that.
As far as a compression test. What would be the ideal numbers to see when doing that?
As far as a compression test. What would be the ideal numbers to see when doing that?
09-22-2003, 12:52 PM
#6
Re: Signs of a cracked head?? from what I hear 10-15 percent variation between cylinders is normal. Can't give you a PSI number. I know it should but up above 100 PSI more than likely being our old 8N tractor puts out 90 some PSI with a 6.X:1 compression ratio LOL
Another thing I just thought of, have you checked the engine oil lately??? Perhaps the coolant is getting passed into the crankcase from a bad crossover pipe or something??? I haven't had a look at the insides of a LS1 before so I'm kinda taking a stab at is that I know on all the older V8 motors have coolant passages in the heads and intake manifold and such. If the crossover pipe is leaking someplace perhaps the coolant could bleed into the crankcase. Again these are just ideas. Hopefully like I said before it is just something stupid.
Another thing I just thought of, have you checked the engine oil lately??? Perhaps the coolant is getting passed into the crankcase from a bad crossover pipe or something??? I haven't had a look at the insides of a LS1 before so I'm kinda taking a stab at is that I know on all the older V8 motors have coolant passages in the heads and intake manifold and such. If the crossover pipe is leaking someplace perhaps the coolant could bleed into the crankcase. Again these are just ideas. Hopefully like I said before it is just something stupid.
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09-22-2003, 05:51 PM
#8
Re: Signs of a cracked head?? Hmm, I have given my best guess. My suggestion would be to pull the plugs and leave it under pressure for a few hours and see if and where it bleeds off too. How long have you had the motor together??? Perhaps maybe it is just finally getting air pockets pulled out of it??? Just another guess, but I doubt that. Sorry couldn't be anymore help man.
09-22-2003, 06:16 PM
#9
Re: Signs of a cracked head?? We left pressure on it for quite a while and it never dropped a bit.
Speaking of air pockets. Just about 1 week prior to the problem I replaced my knock sensors. And in doing that you have to take off the intake. do you think that I could have got a pocket big enough when I unattached the TB lines to have caused this problem? But that still wouldnt exlain why I could smell coolant in the exausht. But after I put water in the radiator the smell went away and never came back
Speaking of air pockets. Just about 1 week prior to the problem I replaced my knock sensors. And in doing that you have to take off the intake. do you think that I could have got a pocket big enough when I unattached the TB lines to have caused this problem? But that still wouldnt exlain why I could smell coolant in the exausht. But after I put water in the radiator the smell went away and never came back
09-22-2003, 06:19 PM
#10
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Re: Signs of a cracked head?? Another simple test is to check for CO in the coolant to see if combustion is getting into the cooling system, there are testers that can perform this or if you can find someone with a five gas analizer hold the snifer over the radiator neck and see if ANY co is present. Hopes this helps
09-22-2003, 06:21 PM
#11
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Re: Signs of a cracked head?? If you top it up cold a few days in a row, and you are consistently down say a quart it's GOING somewhere.
Now before you go nuts, check the obvious. I know at least one guy who thought he had blown a headgasket when he just had a leaky/ bad hose.
Now if you smell it in the exhaust, maybe you are smelling it dripping on your exhaust and it is burning on the primaries... You have to check.
When I had some blown head gaskets, it would start out very minor, I would lose a pint or so. After two weeks it would be up to 2 quarts. But by then you would see and smell the coolant burning in the exhaust.
Now before you go nuts, check the obvious. I know at least one guy who thought he had blown a headgasket when he just had a leaky/ bad hose.
Now if you smell it in the exhaust, maybe you are smelling it dripping on your exhaust and it is burning on the primaries... You have to check.
When I had some blown head gaskets, it would start out very minor, I would lose a pint or so. After two weeks it would be up to 2 quarts. But by then you would see and smell the coolant burning in the exhaust.
09-22-2003, 07:05 PM
#12
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Re: Signs of a cracked head?? Other odd things to check include:
Replace the radiator cap if it looks like the plunger is getting gunked up. It might be sticking open.
Look for dexcool blowing out the res ventilation cap too. This could be caused by a head gasket problem with the exhaust gas getting in the coolant system which can over pressurize and defeat the radiator cap too. Exess fluid will blow out of the res containter top. You'll be looking for wet spot marks on the battery and the shock mount area. It will typically dry up at speed so look for mark and not neccessarily wet spots. A quick test for this is to top off the fluid. Start her up get her to temp and make a few WOT runs. Then pull over and check for fluid around the res container area.
Take off the Oil cap... do you see any moisture on it? Does it have a greenish milky slime? Again, coolant getting loose from a head gasket leak.
Pull the head cover to TB hose. Shake it... does milky oil slime come out of there?
The white smoke that you would normally expect may not show in areas that are warm enough and dry enough when you first start the car.
As strange as some of these may sound, I've seen all of them in my previous three sets of head gaskets which include fel pro and cometics.
Rick
Replace the radiator cap if it looks like the plunger is getting gunked up. It might be sticking open.
Look for dexcool blowing out the res ventilation cap too. This could be caused by a head gasket problem with the exhaust gas getting in the coolant system which can over pressurize and defeat the radiator cap too. Exess fluid will blow out of the res containter top. You'll be looking for wet spot marks on the battery and the shock mount area. It will typically dry up at speed so look for mark and not neccessarily wet spots. A quick test for this is to top off the fluid. Start her up get her to temp and make a few WOT runs. Then pull over and check for fluid around the res container area.
Take off the Oil cap... do you see any moisture on it? Does it have a greenish milky slime? Again, coolant getting loose from a head gasket leak.
Pull the head cover to TB hose. Shake it... does milky oil slime come out of there?
The white smoke that you would normally expect may not show in areas that are warm enough and dry enough when you first start the car.
As strange as some of these may sound, I've seen all of them in my previous three sets of head gaskets which include fel pro and cometics.
Rick
09-22-2003, 09:29 PM
#13
Re: Signs of a cracked head?? I have checked the oil cap, clean.
The res tank is full when the night before the incedent it was empty. But it never got to the point where it was blowing out of the top of the cap. But it is FULL there even might be enough in there to make up for the amount that is missing in the radiator itself. But looking at the coolant that is in the radiator, its clean as a whistle.
I am going to trty blowing compressed air into the cylinder and see if I get any bubbles in the radiator.
The res tank is full when the night before the incedent it was empty. But it never got to the point where it was blowing out of the top of the cap. But it is FULL there even might be enough in there to make up for the amount that is missing in the radiator itself. But looking at the coolant that is in the radiator, its clean as a whistle.
I am going to trty blowing compressed air into the cylinder and see if I get any bubbles in the radiator.
09-22-2003, 11:23 PM
#14
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Re: Signs of a cracked head?? Couldn't the problem be a leaky radiator. I had an '85 Z28 that had a cracked radiator (deer and speed do not mesh). Anyhow it would only start leaking when the system heated up and started to pressurize. Maybe your problem is heat and pressure related and that is why it is hard for you to identify.
09-23-2003, 10:54 AM
#17
Re: Signs of a cracked head??
I had the same problem on my "very expensive"LS6 Heads.Ended up being a crack in #3 intake port.
I pulled the intake and saw that intake port very clean.On the valve there was a puddle of coolant.
I pulled the intake and saw that intake port very clean.On the valve there was a puddle of coolant.
09-23-2003, 11:36 AM
#18
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Re: Signs of a cracked head?? This may have nothing to do with your problem, but I once forgot to fully tighten the coolant plug in the back of a passenger side head. It made for a very nice, slow, difficult to find dribble.
I could smell the coolant burning off, I could see the level was dropping, and feared it was the head gasket. However, just like you, the dipstick was clean etc. It might be worth a look.
I could smell the coolant burning off, I could see the level was dropping, and feared it was the head gasket. However, just like you, the dipstick was clean etc. It might be worth a look.
09-23-2003, 04:08 PM
#19
Re: Signs of a cracked head??
I had the same problem on my "very expensive"LS6 Heads.Ended up being a crack in #3 intake port.
I pulled the intake and saw that intake port very clean.On the valve there was a puddle of coolant.
I pulled the intake and saw that intake port very clean.On the valve there was a puddle of coolant.
