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Duramax 6600 Discussion Forum for the Duramax 6600 Diesel Engine, including the LB7, LLY, LBZ, LMM & LML engine specific topics.

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Old 06-01-2010, 04:08 PM
kvfmechanic kvfmechanic is offline
Join Date: Jun 2010
Posts: 1
Default Coolant leak

I have a 2001 Silverado 2500HD with a Duramax.(255,000 kms) In the past 10 months or so I have developed a mysterious coolant leak that has gotten slowly worse. I am guessing it is internal( head gasket or injector sleeves) but am wondering about symptoms. I am not getting any noticeable white smoke or bubbles in the cooling sytem. The injectors were changed 2 years/ 70,000 kms ago by a dealer with not much duramax experience. The system seems to be holding pressure fairly well as I can go back an hour after shutting it off and still have lots of pressure when I take the cap off. ANy suggestions? Thanks
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Old 06-02-2010, 05:36 AM
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Mark Rinker Mark Rinker is offline
Join Date: Jun 2003
Posts: 5,813

Most likely head gaskets. 2001 production year is known for this failure - gaskets were improved and updated in subsequent years.

Search elsewhere on the forums '2001 head gasket' and you'll see the trendline.
2011 Chevrolet Tahoe 5.3L daily driver
  • Previous owner of two 1994 6.5L K3500s, '01, '02, and '05 6.6L K2500s, '04 C4500, '06 K3500 dually, '06 K3500 SRW, '09 K3500HD SRW, '05 Denali
  • Total GM diesel miles to date : ~950K
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Old 06-03-2010, 04:20 AM
tx dave tx dave is offline
Join Date: May 2008
Location: San Marcos, TX
Posts: 53

I agree with MR. I went through what you're going through. If the pressure is high (hard upper hose) after an hour. Pressureized system when you take the cap off, bubbles in the tank (hold a flashlite to it) and you'll see them. YOU HAVE A HEAD GASKET LEAK. Been there done that. I ended up changing my engine. I have an 2001, love it and will keep changing engines out if I have to until I die or wreck it. Love that truck. it still runs like new, looks like new and when I tell people its an 01 they can't believe it (Its still shiny and pretty). But yea, you're getting a small head gasket leak. I use to put a plastic bottle by the overflow tank to catch the anti freeze and pore it back in the engine every morning. Good luck with it.
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Old 07-25-2010, 05:24 PM
phillipokc phillipokc is offline
Join Date: Oct 2007
Posts: 2

I had a similar problem, ended up being the oil cooler gasket.
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Old 07-26-2010, 02:02 PM
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More Power More Power is offline
Join Date: Feb 2000
Location: Big Sky Country
Posts: 10,267

Under normal circumstances cooling system pressure should be practically nill when the truck sits for 12 hours or more. If there's a whoosh when you loosen the coolant surge tank cap, there's more pressure being generated than normal. Even though these caps are vented to limit cooling system pressures to 15-psi, chronic overpressure usually results in water pump seal failure. Now, you've got two problems....

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Old 08-04-2010, 06:54 AM
9365turbo 9365turbo is offline
Join Date: Jan 2007
Location: Spokane Wa.
Posts: 139

That's what my 02 gmc was doing. I replaced my water pump first and had coolant blowing out for a year. I took the plunge and replaced the head gaskets in february. No problems since then.
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