01 LB7 Big coolant leak - Chevy and GMC Duramax Diesel Forum
01-04.5 LB7 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 9 (permalink) Old 01-09-2020, 08:21 PM Thread Starter
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01 LB7 Big coolant leak

Need help big time. Walked out to my truck this morning to find that it had leaked a sizable puddle of coolant out overnight (puddle was about 1ft by 2ft). Upon inspecting it closer I found that the leak was coming from the driver side rear of the engine, and collecting on the front driveshaft u-joint before dropping down. Apart from the very bottom of the oil cooler, it is not wet at all so I feel confident enough to rule that out as a problem. I’ve been having to refill coolant every 2-3 weeks or so but I had never seen a leak until this morning. Leak looks like it may be coming from above the oil cooler/ up pipe area somewhere, but there is no tell-tale sign other than the driver side of the bell housing dripping with coolant from top to bottom and the u joint and surrounding area being coated with coolant. Need help asap, this is my only vehicle to and from work/school.
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post #2 of 9 (permalink) Old 01-16-2020, 07:23 AM
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Well, Iím guessing things have not gotten better since you posted, so heres a suggestion.

At the risk of insulting your intelligence, step one has got to be finding the source and as you may know, there are chemical kits that allow you to add a product to your coolant that will fluoresce under UV light. I believe most parts stores have turn-key items available.

Report back after you discover where coolant is coming from and Iím sure others will chip in with better guidance.

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post #3 of 9 (permalink) Old 01-16-2020, 07:36 AM
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@houghfarmer could it be a turbo coolant hose from the valley that was seeping and burning off before, but now is a bigger leak and running out of the valley? If its not coming out of the valley, but is above the oil cooler, then I would suspect head gasket or one of the plugs on the back of the cylinder head. There isn't really much else on the drivers side rear that it could be.

If it was on the passenger side, I would tell you to look at the block off plate on the rear housing, but that definitely shows up on the passenger side, not the drivers side
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post #4 of 9 (permalink) Old 01-16-2020, 07:41 AM
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A very likely source is the plastic quick connectors for your heater core. They are a known issue.

Should this be the issue the fix is to simply remove them and attach new hoses directly to the nipples sticking into the engine compartment through the firewall.

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post #5 of 9 (permalink) Old 01-17-2020, 08:44 AM
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Heater core hose leaks are usually on the passenger side.

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post #6 of 9 (permalink) Old 01-17-2020, 08:57 AM
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Quote:
Originally Posted by mray View Post
Heater core hose leaks are usually on the passenger side.
As I have said earlier Im not all that familiar with the vans, but I think the connections to the core itself are in front of the firewall, like the trucks. So a hose leak should manifest itself under the hood. The core is inside so it seems to me that would be a more likely culprit.

In either case, getting to the core will most likely disclose where the leak is coming from.

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post #7 of 9 (permalink) Old 01-17-2020, 09:15 AM
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Read the original post, not a van. The heater core on my 01 is on the passenger side and I don't think that the leak the OP is describing is from the heater core. Just putting the additional info out there.

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post #8 of 9 (permalink) Old 01-17-2020, 09:49 AM
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Tool borrow program at most parts places....I would obtain a pressure test kit and use that....before adding something to the coolant.

As DMAXff mentioned, most leaks on the Driver's side stem from a short hose failure up top, down below the main harness connection, a coolant return line from the Turbo.
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post #9 of 9 (permalink) Old 01-17-2020, 10:47 AM
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Quote:
Originally Posted by mray View Post
Read the original post, not a van. The heater core on my 01 is on the passenger side and I don't think that the leak the OP is describing is from the heater core. Just putting the additional info out there.
I goofed, thought this was a different thread

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