Iron 6.0 cooling system over-pressurizing VID inside
01-29-2019, 10:08 AM
#1
Iron 6.0 cooling system over-pressurizing VID inside Alright so from what I can tell, I've had this issue ever since this engine was built. There are combustion gasses entering the cooling system from somewhere.
A little back story/info....iron 6.0, ls3 heads, got shortblock used and heads were some cores that a friend had laying around which he ported for me after I bought the cores.
So got the engine in the car everything seems ok but every time it went under high load/RPM I would get some coolant on the windshield. Found it was coming from coolant crossover where it bolts to the heads.
Replaced the O-rings and used a little dab of engine sealant and no more issues from there. But then at WOT it would sometimes blow the coolant level sensor out of the radiator.
Did it once racing in mexico, popped sensor back in radiator filled it back up with water and raced it 3 times right after that with no issues. Second time it did it was same situation but I eased it home afterwards.
It does not overheat but after just a couple/few minutes of running the upper hose gets STIFF and builds up 20+psi of pressure.
I replaced the head gaskets a few months ago with no change. Removed the heads about a week ago and sent them to machine shop. They pressure tested good and they say heads are flat.
So now I'm wondering if maybe the crack in the head (if any) only shows once heated. So I'm debating on slapping on another set of heads real quick just to rule that out before I pull the engine and find another block
Posting here just to see if anyone has had a similar issue and maybe has some pointers/recommendations on what the next step would be. See vid below, that's cold start!
A little back story/info....iron 6.0, ls3 heads, got shortblock used and heads were some cores that a friend had laying around which he ported for me after I bought the cores.
So got the engine in the car everything seems ok but every time it went under high load/RPM I would get some coolant on the windshield. Found it was coming from coolant crossover where it bolts to the heads.
Replaced the O-rings and used a little dab of engine sealant and no more issues from there. But then at WOT it would sometimes blow the coolant level sensor out of the radiator.
Did it once racing in mexico, popped sensor back in radiator filled it back up with water and raced it 3 times right after that with no issues. Second time it did it was same situation but I eased it home afterwards.
It does not overheat but after just a couple/few minutes of running the upper hose gets STIFF and builds up 20+psi of pressure.
I replaced the head gaskets a few months ago with no change. Removed the heads about a week ago and sent them to machine shop. They pressure tested good and they say heads are flat.
So now I'm wondering if maybe the crack in the head (if any) only shows once heated. So I'm debating on slapping on another set of heads real quick just to rule that out before I pull the engine and find another block
Posting here just to see if anyone has had a similar issue and maybe has some pointers/recommendations on what the next step would be. See vid below, that's cold start!
01-29-2019, 12:49 PM
#3
So the exhaust valves on cylinders 6 and 8 were very clean. 6 and 8 spark plugs had a clean side to them and the pistons pretty much looked the same with #8 being maybe slightly cleaner than the others. Nothing really looked steam cleaned though.
01-29-2019, 04:09 PM
#4
What head gaskets, bolts and torque procedure are you using?
How has the block surface been cleaned/prepped? Has someone taken a wizz wheel to it?
Not that this helps now because the heads are off but you can do a leak down test on the cylinders, take the radiator cap off and see if bubbles appear in the coolant.
Have you looked at all the cylinder walls really close to see if one of the liners has a small crack in it?
If the heads test out good it really can be only a few things.
How has the block surface been cleaned/prepped? Has someone taken a wizz wheel to it?
Not that this helps now because the heads are off but you can do a leak down test on the cylinders, take the radiator cap off and see if bubbles appear in the coolant.
Have you looked at all the cylinder walls really close to see if one of the liners has a small crack in it?
If the heads test out good it really can be only a few things.
01-29-2019, 05:58 PM
#5
What head gaskets, bolts and torque procedure are you using?
How has the block surface been cleaned/prepped? Has someone taken a wizz wheel to it?
Not that this helps now because the heads are off but you can do a leak down test on the cylinders, take the radiator cap off and see if bubbles appear in the coolant.
Have you looked at all the cylinder walls really close to see if one of the liners has a small crack in it?
If the heads test out good it really can be only a few things.
How has the block surface been cleaned/prepped? Has someone taken a wizz wheel to it?
Not that this helps now because the heads are off but you can do a leak down test on the cylinders, take the radiator cap off and see if bubbles appear in the coolant.
Have you looked at all the cylinder walls really close to see if one of the liners has a small crack in it?
If the heads test out good it really can be only a few things.
Block was cleaned and prepped before I installed the heads last go around. no wiz wheel marks.
I did a lazy man's leakdown before I pulled it apart, left valvetrain all together and just forced engine over to where valves were closed on cylinder, did not see any bubbles out of radiator with shop air in the plug hole.
Have not looked very closely at cylinder walls just yet, I have looked at them but not close enough.
According to machine shop, heads are flat and no cracks showed. A friend of mine has another method to check the heads so i'll be getting his opinion as well soon.
01-29-2019, 08:24 PM
#6
TECH Enthusiast
Have you tried a chemical leakage test?
You use a tool like this https://www.summitracing.com/parts/o...iABEgKmPvD_BwE
with a special liquid that changes color when combustion gasses are present.
The only problem with this kit (although it can be very effective) is that there are some cases where it can't detect the leak until the engine is already overheating. The problem is that you have to use this tester with the cooling system open, and by the time the engine starts overheating (or even getting close to it), the coolant is going to be pushing into the tester.
Lastly, what is a "wizz wheel?" I have an idea of what you're talking about, but I want to be specific about the product/ materials.
You use a tool like this https://www.summitracing.com/parts/o...iABEgKmPvD_BwE
with a special liquid that changes color when combustion gasses are present.
The only problem with this kit (although it can be very effective) is that there are some cases where it can't detect the leak until the engine is already overheating. The problem is that you have to use this tester with the cooling system open, and by the time the engine starts overheating (or even getting close to it), the coolant is going to be pushing into the tester.
Lastly, what is a "wizz wheel?" I have an idea of what you're talking about, but I want to be specific about the product/ materials.
01-29-2019, 08:40 PM
#7
Lastly, what is a "wizz wheel?" I have an idea of what you're talking about, but I want to be specific about the product/ materials.[/QUOTE]
The small red 2in abrasive discs you put on an angle air grinder to take off gasket material.
They work great on cast iron stuff but I've seen some people wreck aluminum parts with them even being careful.
The small red 2in abrasive discs you put on an angle air grinder to take off gasket material.
They work great on cast iron stuff but I've seen some people wreck aluminum parts with them even being careful.
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01-30-2019, 12:59 PM
#9
Have you tried a chemical leakage test?
You use a tool like this https://www.summitracing.com/parts/o...iABEgKmPvD_BwE
with a special liquid that changes color when combustion gasses are present.
The only problem with this kit (although it can be very effective) is that there are some cases where it can't detect the leak until the engine is already overheating. The problem is that you have to use this tester with the cooling system open, and by the time the engine starts overheating (or even getting close to it), the coolant is going to be pushing into the tester.
Lastly, what is a "wizz wheel?" I have an idea of what you're talking about, but I want to be specific about the product/ materials.
You use a tool like this https://www.summitracing.com/parts/o...iABEgKmPvD_BwE
with a special liquid that changes color when combustion gasses are present.
The only problem with this kit (although it can be very effective) is that there are some cases where it can't detect the leak until the engine is already overheating. The problem is that you have to use this tester with the cooling system open, and by the time the engine starts overheating (or even getting close to it), the coolant is going to be pushing into the tester.
Lastly, what is a "wizz wheel?" I have an idea of what you're talking about, but I want to be specific about the product/ materials.
01-30-2019, 07:20 PM
#10
TECH Enthusiast
I borrowed a block tester from orielly and used that but the liquid never did change color. Didn't make sense to me. My only thought was that the leak is too small for the fluid to change in a short amount of time. There were bubbles coming up into the tester/fluid from the extra pressure but fluid never changed. Only had it on for a few minutes though.
Of course, I've also seen some that pass this test, and a compression test, but still had bad head gaskets. That's what makes bad head gaskets such a pain to track down some times.
01-30-2019, 07:58 PM
#11
I had a radiator cap make me chase my *** one time. I checked everything 10 times. Did a new head gasket, checked surfaces and everything. Turned out the radiator cap wasn't venting pressure and I kept blowing up radiators and popping hoses. Found my original 10 year old cap laying in the parking lot near the dumpster, put it on and never had a problem again.
It was a small import radiator cap on an Integra. Nobody in town had a radiator cap tester that would work for that cap so I just never knew it was the cap.
You can't use your cooling system pressure tester to test pressure in the system and diagnose it unless you put it in somewhere other than where the cap goes, if you have the cap off there is nothing to vent pressure and it will go up over 20. The cap purges pressure at 15-16 or so depending on which cap you're running but most OEM's have a 15-16 psi cap on them.
Using the block test fluid is tricky. If you get the engine up to operating temp with the cap off the coolant will boil over because it's above boiling temp. And if you have a bad headgasket a lot of time it doesn't show at idle because you aren't making much pressure in the cylinders. So I have someone sit in the car with the motor cold and put it in gear and give it gas to build pressure in the cylinders. However sometimes it's hard to catch a leak with the motor cold so sometimes you have to walk that fine line of getting heat in the motor but not enough to boil the coolant and contaminate your test.
On that car I originally mentioned, I ended up figuring out the cap was the problem by running the radiator a little low on coolant so when the coolant expanded it had a place to expand into. Once I ran it a little low I never blew another radiator or hose so I knew my cap was just sealing the radiator. You can try that as a test step and see how it goes.
If you have flat surfaces, new headgaskets and the same issues then it could be a funny crack in the head, block, or cylinder liner. Will be hard to find but if you can load the motor with it cold up to warming up under load and test it then that may work. You can also put a funnel or coolant fill adapter on the radiator as you test and hold the tester near the opening of the radiator and test, that way when the water surges up it doesn't fill your tester. It's hard to smash the tester into the rad cap hole and not get coolant in the tester.
It was a small import radiator cap on an Integra. Nobody in town had a radiator cap tester that would work for that cap so I just never knew it was the cap.
You can't use your cooling system pressure tester to test pressure in the system and diagnose it unless you put it in somewhere other than where the cap goes, if you have the cap off there is nothing to vent pressure and it will go up over 20. The cap purges pressure at 15-16 or so depending on which cap you're running but most OEM's have a 15-16 psi cap on them.
Using the block test fluid is tricky. If you get the engine up to operating temp with the cap off the coolant will boil over because it's above boiling temp. And if you have a bad headgasket a lot of time it doesn't show at idle because you aren't making much pressure in the cylinders. So I have someone sit in the car with the motor cold and put it in gear and give it gas to build pressure in the cylinders. However sometimes it's hard to catch a leak with the motor cold so sometimes you have to walk that fine line of getting heat in the motor but not enough to boil the coolant and contaminate your test.
On that car I originally mentioned, I ended up figuring out the cap was the problem by running the radiator a little low on coolant so when the coolant expanded it had a place to expand into. Once I ran it a little low I never blew another radiator or hose so I knew my cap was just sealing the radiator. You can try that as a test step and see how it goes.
If you have flat surfaces, new headgaskets and the same issues then it could be a funny crack in the head, block, or cylinder liner. Will be hard to find but if you can load the motor with it cold up to warming up under load and test it then that may work. You can also put a funnel or coolant fill adapter on the radiator as you test and hold the tester near the opening of the radiator and test, that way when the water surges up it doesn't fill your tester. It's hard to smash the tester into the rad cap hole and not get coolant in the tester.
Last edited by 00pooterSS; 01-30-2019 at 08:06 PM.
01-30-2019, 08:13 PM
#12
You should try it longer than that. I've seen some engines take about ten minutes or so to start leaking exhaust gasses.
Of course, I've also seen some that pass this test, and a compression test, but still had bad head gaskets. That's what makes bad head gaskets such a pain to track down some times.
Of course, I've also seen some that pass this test, and a compression test, but still had bad head gaskets. That's what makes bad head gaskets such a pain to track down some times.
I go through this all the time with the block test fluid and tester. It's a pain in the ***
OP I wasn't able to see the vid at first and I don't have sound on the computer at home at the moment so I can't hear your video. If you started that from dead cold it's building pressure way too fast and you have a combustion leak into the cooling system.
I'd try to put at least 100 pounds of shop air to each cylinder and watch the pressure tester or watch for it to push coolant out the radiator
01-30-2019, 09:07 PM
#13
TECH Fanatic
I 've seen bad radiator caps do that befor as 00pooterSS said. What pressure is the cap you are using? I'd go purchase a quality 15-16 psi relief radiator cap. Try that before all the "hard" work 
01-31-2019, 09:53 AM
#15
00pooterSS, I did use shop air ~100psi into each plug hole with the cap off and watched for bubbles to find none after testing all 8 cylinders. That's what made me think it was maybe a crack that opened up with just the slightest amount of heat.
It might just be me, but in the video I posted the first time I give it some RPM, the pressure doesn't climb all that fast. But the 2nd time it shoots up pretty quick. Possibly because the crack opens up/shows itself that much more with a little heat. Again I'm just throwing around options/possibilities here.
Before I pulled it apart I had just got done installing my used be-cool aluminum radiator and a brand new GM 18lb cap. Ran engine and sure enough after a few minutes it started pushing pressure passed the cap and to the overflow tank. Only reason I noticed is because the nipple for the radiator where the overflow hose attaches wasn't sealed 100% and it was leaking coolant.
It might just be me, but in the video I posted the first time I give it some RPM, the pressure doesn't climb all that fast. But the 2nd time it shoots up pretty quick. Possibly because the crack opens up/shows itself that much more with a little heat. Again I'm just throwing around options/possibilities here.
Before I pulled it apart I had just got done installing my used be-cool aluminum radiator and a brand new GM 18lb cap. Ran engine and sure enough after a few minutes it started pushing pressure passed the cap and to the overflow tank. Only reason I noticed is because the nipple for the radiator where the overflow hose attaches wasn't sealed 100% and it was leaking coolant.
01-31-2019, 10:11 AM
#16
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Did you try leaving the pressure tester on with the engine off to see if the pressure bleeds out overnight? You could try that and look for signs of coolant getting into a combustion chamber with a bore scope. Kind of a pain since it sounds like you have the heads off already.
01-31-2019, 05:45 PM
#17
Did you try leaving the pressure tester on with the engine off to see if the pressure bleeds out overnight? You could try that and look for signs of coolant getting into a combustion chamber with a bore scope. Kind of a pain since it sounds like you have the heads off already.
01-31-2019, 05:52 PM
#18
This sounds like a bitch. I'd suspect the heads before a cylinder liner crack though. Inspect the cylinders super close and the water jackets and see if you find anything. Also check the block surface closely, someone posted pics recently of a crack that ran length wise down the block along cylinders 2-6 ish. It was on the outer side (exh man side not intake side). Clean the block up with light sand paper or whatever your preferred method is and then take a peek. If there is a crack it may be hard to see with head gasket goo still on the block
01-31-2019, 07:37 PM
#19
This sounds like a bitch. I'd suspect the heads before a cylinder liner crack though. Inspect the cylinders super close and the water jackets and see if you find anything. Also check the block surface closely, someone posted pics recently of a crack that ran length wise down the block along cylinders 2-6 ish. It was on the outer side (exh man side not intake side). Clean the block up with light sand paper or whatever your preferred method is and then take a peek. If there is a crack it may be hard to see with head gasket goo still on the block