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Discussion Starter · #1 ·
Greetings!
I went out to my '06 HD this morning and found a small puddle of coolant on the pavement. And the reservoir was nearly empty. The leak is dripping off the trans bellhousing flange, on to the crossmember, and then down to the street. Also, yesterday when the truck wasn't quite warmed up, I saw some whitish smoke from the exhaust. It wasn't steam, definitely oil smoke. It only lasted a few seconds and hasn't repeated today. Could the two be related? I'm considering that the leak could be from the coolant line to the turbo, or a heater line fitting. If they are related, blown head gasket? I hope not! I have no place to work on it if that's the case. I'll be forced to have a mechanic do it. $$$$$$$ which right now I don't have a lot of. Just started a new job and the pay isn't great, yet. Overall the truck runs fine, does not smoke when warm, and does not leak when warm either. Oil pressure is +/- 32 psi when fully warmed up, and up to 120 psi when cold. Fuel mileage is around 18 mpg in mixed driving. Fuel mileage has slightly increased during my time of ownership; I bought it in April.
Any general advice would be greatly appreciated! :)
 

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Is the top radiator hose hard like a tennis ball after it sits over night? If so probably a head gasket. Theres a plate on the bell housing on the passenger side kinda behind the down pipe. Check that its been known to leak. Also a pressure tester will help you locate a leak a lot easier.
 

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Discussion Starter · #3 ·
Thanks! I'll check the upper hose in the morning. Leak seems to be more on the driver's side of the bellhousing.
 

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Discussion Starter · #4 ·
Checked the top radiator hose this morning. It's soft. Leak is getting worse. It's definitely coming off the driver's side of the bellhousing. Possibly the change in the weather. I'll try to get down there with a mirror & flashlight and get a look.
 

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.....Leak is getting worse. It's definitely coming off the driver's side of the bellhousing.
You'll want to look in this area, Small length hose, feed to the turbo.
Extended length needle nose pliers straight & bent will ease your pain in accessing...it's down under a lot of things, but can be seen.

 
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I had to replace that little hose he's pointing to. Its a little bit of a pain. But Id get ahold of a pressure tester and use it to find the leak.
 

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Discussion Starter · #8 ·
Thanks again folks for the suggestions.
Still leaking. Had a mechanic friend go in with a flashlight & mirror. Coolant line to turbo: No leak. Cover plate on bellhousing: No leak. Nothing visible at head gasket area on either bank. No coolant smell from exhaust, and no steam. Just a puff of white/blue smoke very rarely when warming up.. We pressurized the cooling system to 25 psi and it held for hours. So far the coolant loss is appropriate with what is leaking out onto the ground, but I still can't find the leak. No unusual coolant temps, and the truck continues to run great. Coolant warning showed up on the dash display today, but as soon as the truck cools down, coolant reservoir level goes back to normal minus what leaked onto the ground. Thermostats seem to be functioning normally. Only consistent behavior is the leak when the cooling system reaches whatever the ambient night-time temp is, and the colder it gets at night, the worse it gets. Today I did find that the turbo's inlet tubing clamp was loose, but I doubt there's any coincidence with that. Blown head gasket?
 

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What color is your coolant. Duramax will not eat coolant when the head gasket blows it will push it out of the reservoir. . How high on the bellhousing? Oil cooler is back that way. I have never not been able to find a leak with a tester very strange.
 

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Discussion Starter · #10 ·
What color is your coolant. Duramax will not eat coolant when the head gasket blows it will push it out of the reservoir. . How high on the bellhousing? Oil cooler is back that way. I have never not been able to find a leak with a tester very strange.
As I mentioned in my previous reply, the cooling system was pressurized to 25 psi and it held for hours, and no leaks found. Coolant is the normal Dex-Cool orange. No color change there. I had a little dribble of coolant out of the overflow this morning, but I believe I over-filled the previous day. I'll keep an eye on it. Rad hoses are firm, but not rock-hard from an overnight cool-down. With res cap off and fully warm, no bubbles are coming out. I believe that wherever the leak is at, air is also getting in there. It's high up on the back of the engine. That's all I can say right now.
 

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The only other thing I can think of up top would be the egr cooler itself. Not sure if they leak on the outside though.
 

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Discussion Starter · #12 ·
No leaks in two days. I'm not naive enough to believe that it's fixed itself. I have a bad feeling that the previous owner might have thrown some stop-leak into the coolant to "fix" the issue the easy way. My instinct keeps going back to a head gasket. I hope not. When I have time I'll start pulling stuff off the top of the engine to get a better look at places I can't see. One of my mechanic friends has a bore scope. That should help if I can borrow it. Might get a better look that way.
 

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Discussion Starter · #13 ·
Forgot to ask...... how difficult is a head gasket job on the Duramax? If that's the path I'm forced to take, It would be really helpful. I may have a friend do the job with my help.
 

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Discussion Starter · #15 ·
Not difficult, just time consuming. I personally wouldn't have some one "help" me, too many things to get misplaced and wonder where does this go?
Understood. But I'm a mechanic too, and he'd be okay with my help. Main issues for me are time and a place to do it. If I had both in my favor, I'd go it alone.
If I take the plunge I hope the heads are okay. I'd get a stud kit too. I don't trust those torque-to-yield bolts one bit. Seen them fail from new.
 

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Discussion Starter · #16 ·
Finally the suspected blown head gasket really blew yesterday. Took it to a friend's shop and the process will begin once we replace the front wheel bearings, axles & ball joints. Going to lift the cab off the chassis so we have easier access. ARP head studs and heavy-duty head gaskets will go in. Will I need to skim the heads? And what's a good brand of head gasket, besides factory? Thanks in advance. :)
 

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Most will say GM Grade C are fine. I went with the Victor Reinz Grade C. The Grade C (1.05 thickness) seems to be the key. I have zero miles on the Victors, but Mike Diesel has been running them for quite some time, I believe. He just did an engine build and has those in his build.
 

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Finally the suspected blown head gasket really blew yesterday. Took it to a friend's shop and the process will begin once we replace the front wheel bearings, axles & ball joints. Going to lift the cab off the chassis so we have easier access. ARP head studs and heavy-duty head gaskets will go in. Will I need to skim the heads? And what's a good brand of head gasket, besides factory? Thanks in advance. :)
You should have the heads checked for sure, May or May not need it. Stick with the gm grade c gaskets.
 

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Discussion Starter · #19 ·
Thanks again everybody for the advice!
Once my mechanic friend got a closer look at everything, it turns out the head gasket is not blown, but a gasket/o-ring failure near or at the oil filter adapter and the cover plate at the bellhousing were leaking badly. One was spraying coolant up to the head/block joint, making it seem like a head gasket went bad. Now that both leaks are fixed, there is no leakage visible. No puddles on the ground in the morning. I'm still getting a little air out of the system. But I have a question: How much does the level in the coolant reservoir vary between hot & cold? When warmed up the level drops about 3" but comes back when it cools down. Is this normal for a Duramax? None of my passenger cars do this. Could a thermostat be stuck? I bought a new cap for it too. No change.
 

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Mine seems to have more in the overflow when it is a bit warm (warm fluid expands), and as it cools and draws a vacuum on the cap, and expansion ceases, the level lowers in the evening.
 
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