New to me LMM

jamespjackson

Member
Jun 24, 2016
32
0
6
Hey guys, today I picked up a 2008 Silverado crew cab 4x4 3500 LMM.
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It was a work truck and the company took it to a shop after the low coolant light popped up. They told him they thought the passenger side head gasket was the cause and only slowly leaking externally.
There is no coolant in the oil, no coolant leaking on the ground, and does not smell sweet like it's leaking into the exhaust/combustion chamber.
Anyways I bought the truck today and it did not appear to lose any coolant on a 6 hour trip home. It's actually a very powerful truck. I parked the truck and about an hour or two later went and checked the upper radiator hose and it's squishy. Also when the truck is ran there is no pressure in the degas bottle. The cap always comes off with no pressure. No bubbling either, even at idle. I crawled under the truck and can see signs that there had been in the past a coolant leak onto the down pipe, but nothing is wet currently. I've been doing a lot of research and a lot of people seem to find this gasket to be a cause of a leak in that area.
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Does the LMM have this gasket and would that make sense for my issues?
The coolant level did not drop any today but I will continue to monitor it this week.


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Tothemax

xgmtech
Oct 16, 2014
607
8
18
new york
my lbz did that at 69k and fixed itself by 75k. I never lost any measurable coolant but when changing oil would see the wet streak and a droplet on the bell housing. it was def coming from that gasket under that plate. I used a mirror to verify. it stopped leaking before I had a chance to repair it and it never leaked again.
 

minerigger

Active member
Dec 24, 2013
2,660
1
38
Casper, WY
Another spot to look is the plastic heater core fittings at the firewall. If your worried you could rent or purchase a coolant pressure testing kit and pressure the system up and look for leaks
 

jamespjackson

Member
Jun 24, 2016
32
0
6
Okay guys overnight the system lost maybe an inch. No signs on the ground, or oil... started up and ran fine. Exhaust smelled normal.


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jamespjackson

Member
Jun 24, 2016
32
0
6
Do you guys think I should rule out a head gasket?
No pressure in system
After driving upper radiator hose is soft
Heat and air both work perfectly
Truck reaches operating temp idling normally.


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jamespjackson

Member
Jun 24, 2016
32
0
6
I'm gonna try to pressure test it today and see what i get. How much pressure and how long should it hold?


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