06 LBZ Coolant Leak? - Chevy and GMC Duramax Diesel Forum
06-07 LBZ & LLY Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #1 of 5 (permalink) Old 09-04-2019, 01:09 PM Thread Starter
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06 LBZ Coolant Leak?

OK Im baffled...
06 LBZ, Stock,185K miles. Got a low coolant notice on the dash, level was just below the seam on overflow tank. Let it cool for 2 - 3 hours, topped off to fill line. Drove it about 100 miles next day, no problems. Checked when I got home, coolant level was 1/2 above seam on tank. Checked it next morning, level was same, opened top of tank an a small bit of pressure bled off and level went to where I had filled it to. Drove to work the next morning then home again (about a 15 mile round trip), when I checked it again the level was at the seam. This morning I checked it, level was back to where I had filled it, when I got to work it was down to 1/2 over the seam. Drove it about 4 miles then checked, level was back up to where I had filled it.
Truck has not overheated (200 max), coolant level never below middle of over flow tank, upper radiator hose not hard when running at temp, no coolant in oil I can see, no smell.
Im baffled, any ideas?
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post #2 of 5 (permalink) Old 01-12-2020, 04:40 PM
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Did you ever get this resolved?

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post #3 of 5 (permalink) Old 02-04-2020, 05:40 PM
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My guess is water pump. I’ve been chasing this for awhile and finally saw a leak and it’s from the weep hole, hard to find with no huge puddles in the driveway coolants in the truck and Friday is the day. Just ticked because I just put idlers, belt tensioner, belt on last January. I should have bit the bullet then
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2006 SIERRA CC SB 2500HD 6.6 LBZ 179,000 and ticking
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post #4 of 5 (permalink) Old 02-06-2020, 07:25 AM
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I had coolant loss that took me a bit to figure out, no puddles or drips, turned out to be the EGR cooler cracked internally. Luckily my EGR fell off, so I haven't had to worry about that since.
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post #5 of 5 (permalink) Old Today, 03:02 PM
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I had a leak similar to yours, i could not figure it out for the longest time. Turned out my leak was from the heater hose connection off the firewall, it was leaking while it was running just a few drips at a time. Its about a $6 part and a good 15 minutes to change, havent had any issues again so far.
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