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misterp

HOW-TO: Replacing Your Thermostat

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Installing a colder thermostat is an easy performance-minded modification for your engine. The reason for installing a colder thermostat is to safely allow more ignition advance in the Powertrain Control Module's (PCM) programming. A cooler running engine can safely use more ignition advance; by installing an aftermarket 160-degree thermostat the engine cylinder heads run cooler, and this in turn will reduce the tendency for detonation and allow you to safely reprogram your vehicle's PCM to add more spark advance. With more advance you will see a more efficient engine: more power, crisper throttle response, and better mileage.

 

On the other hand - installing a colder thermostat by itself *without* reprogramming your PCM will make the engine loose efficiency. It is common for vehicles to suffer a 1-2 mpg drop in highway mileage using a colder aftermarket thermostat with the factory PCM tune.

 

Replacing a thermostat is a very good learning experience if you have never worked on a vehicle before, no auto repair training is required to follow this How-To guide. If you can loosen and tighten a bolt and have access to a couple common tools you can do this. Before you begin you will need a replacement thermostat, a flat-head screwdriver, a 10mm socket wrench, pliers, catch pans or buckets (some shade-tree mechanics forgo the catch pans), a funnel if you are clumbsy :D and 2 gallons of new Dex-Cool anti-freeze from the parts store (you will be draining and refilling the cooling system); THE COOLANT MUST BE DEX-COOL (ORANGE), if you mix ordinary (green) anti-freeze with Dex-Cool (orange) you will DESTROY your cooling system.

 

WARNING - anti-freeze is a potentially lethal chemical, do not drink it. With its sweet smell, sweet taste, and bright color it may attract your pets or children; do not let them drink it. Ingesting anti-freeze is a serious medical accident - call poison control immediately.

 

This will take 30 to 90 minutes, depending on your experience; let's begin!

 

01%20-%20FillTankCap.jpg

 

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07%20-%20Pull-1.jpg

 

08%20-%20Pull-2.jpg

 

09%20-%20Housing.jpg

 

(continued...)

Edited by Mr. P.

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10%20-%20RadHoseClamp.jpg

 

11%20-%20Unbolt.jpg

 

12%20-%20PryHose.jpg

 

13%20-%20OEMTstat.jpg

 

14%20-%20CleanHousing.jpg

 

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16%20-%20HoseInstall.jpg

 

Reinstall the air duct by backtracking the steps you used to remove it from the vehicle. Tighten the band clamps 'firmly', cinching them down will not improve their seal.

 

OK, you can now put the tools down, it's time to refill your cooling system.

 

1. Close the radiator drain valve (under the front bumper, driver's side);

 

2. Refill the engine with coolant - the SS cooling system refil capacity is 12 to 15-quarts (3 to 3.75-gals), and as a general rule you want at least a 50/50 mix of anti-freeze and water in the engine, if you live in colder climates you will want less water and more anti-freeze, the correct amounts will be charted on the back of the anti-freeze bottle; the chemistry doesn't have to be exact, give-or-take a half-pint is close-enough. Do not fill beyond the "FILL COLD" mark on the fill/overflow tank. (In my SS, I ended-up adding 5 quarts of anti-freeze plus 5 quarts of water.)

 

*Optional Step* - add a product to your anti-freeze called 'Water Wetter', highly recommended in ALL cooling systems, not too expensive and drastically improves the efficiency of the coolant. You will find this at speed shops or mail order houses (Summit Racing, Jeg's and the like).

 

THE FOLLOWING COOLING SYSTEM PURGE PROCESS IS CRITICAL, if you do not purge all the air from inside the engine you will have 'hot spots' or uncooled areas caused by these trapped air pockets in your engine heads, and aluminum heads will not tolerate this localized overheating, they will warp.

 

3. Start the engine and let it idle, immediately inspect for leaks (if you think you spot a leak, turn off the engine before it gets too hot to work on!) After one minute of idling, put the cap back on the fill/overflow tank;

 

4. Get the new thermostat to open by warming it to operating temperature; you will know that the thermostat has opened because the lower radiator hose (and radiator) will suddenly go from room temperature to almost scalding hot, and you can check for this by touch as the engine warms up. You can help the process along by gently increasing the RPM from idle to 3000-RPM over 30-second intervals. AFTER the new thermostat has opened turn off the engine (the lower hose will be hot to the touch, check it with your hand to be sure but don't burn yourself).

 

NOTE: During first warm-up you may notice that the temperature guage on your dash rockets well above the 220-degree mark - this is not a cause for immediate alarm, it happens because there is an air pocket blocking the hot coolant from reaching/heating the coil on the new thermostat and opening it. If this happens go ahead and let the engine continue to idle for an additional 3-4 minutes (no more) giving the thermostat its chance to open provided that the dash guage needle does not 'go into the red'. If the thermostat still fails to open after a few minutes OR the engine does begin to overheat (guage begins creeping into the red), turn off the engine and let it sit - after a few minutes of 'heat soak' the thermostat will eventually open on its own (even with the engine off) and then you can continue to the next step in the refill instructions.

 

5. SLOWLY remove the fill/overflow tank cap, BE CAREFUL IT MAY BE UNDER PRESSURE, if so it will try to spray coolant onto you; let the pressure bleed off before completely removing the cap;

 

6. Restart the engine and let idle again for at least one minute with the fill cap OFF; this burps the trapped air out of the cooling system.

 

7. Refill the fill/overflow tank to 1/2-inch above the "FILL COLD" mark and screw the cap back onto the fill/overflow tank.

 

8. Drive the vehicle a few minutes (to the store and back? :cheers: ) and check the coolant level in the fill/overflow tank when you return.

Edited by Mr. P.

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:thumbs: Thanks for the instructions, a couple of questions. One, do you need to purchase a new o rig gasket? and two where are the purge instructions?

 

Thanks again. :yellow_loser:

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:thumbs:  Thanks for the instructions, a couple of questions. One, do you need to purchase a new o rig gasket? and two where are the purge instructions?

 

Thanks again.  :yellow_loser:

Manufacturers always package a fresh gasket with a thermostat, look for it in the box. And you read the post while I was still composing, go back now!

 

Take care, happy wrenching...

Mr. P. :)

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Mr P. Awesome post ! :cheers:

 

What do you do for a living ?

 

You seem pretty dam orginized !

 

George

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We have a star!!!! your left hand is bound for glory ... its going places ... it is the most popular left hand on the entire site! hehe lol .... Nice write up ... good job.

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Since I see you have an 03, isn't the one for an 04 different. Just asking because I heard the two years were different.

 

Late- Alex

Edited by r8rs4lf

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great job Mr. P. :cheers: This is exactly what this site needs. This stuff helps newbie's learn how to mod their own SS. Great write up :thumbs:

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Since I see you have an 03, isn't the one for an 04 different. Just asking because I heard the two years were different.

 

Late-  Alex

Yes. The 2004 and newer models just require the themostat to be replaced. In the 2003 models the thermostat and housing needs to be replaced. Anybody with a 2004 or newer model what to do a write up on this? Super job Mr.P. :thumbs: You should write a do-it-yourself book on SS mods. I would buy one. :cheers:

Edited by SSThunder

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Good info.. Thanks again P. Since a tune is required to get the most out of the new, cooler stat, Should I get it tuned first, and then replace it? Or get it replaced, and then get it tuned? I ask this because I'll have to wait for shipping from Canada (Westers) to get a newly tuned PCM..

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great job Mr. P.  :cheers: This is exactly what this site needs. This stuff helps newbie's learn how to mod their own SS. Great write up :thumbs:

Thanks, I appreciate it. I myself enjoy wrenching and all-around car crafting, it's my first (of many) hobbies. After all the wonder help I've received here on SilveradoSS.com I thought the least I could do was contribute back, and help/encourage other SS enthusiasts that want to be more involved with their truck.

 

Mr. P. :)

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Good info.. Thanks again P.  Since a tune is required to get the most out of the new, cooler stat, Should I get it tuned first, and then replace it?  Or get it replaced, and then get it tuned?  I ask this because I'll have to wait for shipping from Canada (Westers) to get a newly tuned PCM..

Install both at the same time; if that is not possible, put the colder thermostat in first even though it will cost you a couple bucks in lost highway mileage. Do not run a PCM tune having more advance on a high-temp thermostat, you'll have a lot of detonation/knock retard.

 

Mr. P. :)

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