LLY Thermostats

Hansen.lucas

New member
Mar 25, 2020
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I’m thinking I need a set of thermostats in my truck. I just replaced my block heater maybe 2,000 miles ago, so my coolant is rather new. My question is can I get away with not draining the whole system for this job? If so does anyone know the minimum amount needed to drain to not make a mess? Also any recommendations on thermostat brand?
 

SoCalMike

Member
Dec 11, 2010
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SoCal
There is a bleed screw on top of the thermostat housing. I use a shopvac and straw to suck out the coolant through the bleed screw. Once you stop getting coolant out with the vacuum, pop the thermostat housing off and replace the thermostats. I would get a replacement thermostat housing oring gm# 94011604 or you can get FEL-PRO 35759 like I did. also get the oil tube oring part# 94007612 Stick with OEM tstats. 1.5 to 2 gallons of coolant sound about right.

Merchant has a kit with part numbers if you want to source your own parts.

Source: https://www.youtube.com/watch?v=qjXDifpGGrs&list=PLut56oFdvdG4HsrVHtxCGocHNtuNH8SKj&index=4
 

jbay

New member
Feb 26, 2021
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I’m thinking I need a set of thermostats in my truck. I just replaced my block heater maybe 2,000 miles ago, so my coolant is rather new. My question is can I get away with not draining the whole system for this job? If so does anyone know the minimum amount needed to drain to not make a mess? Also any recommendations on thermostat brand?
I recently changed my thermostats. My truck was running at 150degrees. I bought mine through Merchant Automotive ( Engine Coolant Thermostat Kit | 2001-2010 (merchant-automotive.com) . They also provide a new O-ring for the housing and they have a very good how to video. I read that coolant draining wasn't necessary. I tried to change mine without draining and found out that makes a mess! I needed to drain mine. I also removed my reservoir cap first before opening the drain valve at the bottom of my rad. I wouldn't recommend that either...it comes out fast! Keep the system sealed when you open the drain and it will create a vacuum so the coolant does not rush out. Some say you also do not need to remove the AC compressor. I needed to move mine out of the way to get the housing over the thermostats and out of the hard pipe.
 

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