I want to service the cooling system by swapping out the thermostat,
and changing over to normal prestone green antifreeze.
Any noob advice appreciated..no experience with LS motors.
Thanks.

 

I am about to do the same thing, here is a link to what I found. Also, the pcm must be retuned if you lower the thermostat for the new operating temp. Good luck.

http://www.ls1.com/forums/f6/diy-coo...-flush-157898/

 

If you are going 'green' you either have to unscrew the block drains (under the exhaust manifold/headers, near the front of the block), OR REALLY REALLY flush out the system MULTIPLE times if you leave the drains in.
This involves a maximized flush. Then a fill with just distilled water, run for 15-20 minutes, and then dump this, and finally a refill with 50% green and 50% distilled water.

I personally think NOTHING is wrong with the so called "Death Cool", as long as one keeps up on it, does not let ANY; air/oil/power steering fluid/Red Line Water Wetter into the system, and uses a GREAT Dex Cool product like Zerex with distilled water 50/50.

 

I recommend you stick with the stock 'stat. There is
nothing to gain on any car that's not up against the
dieseling limit. If you have a cooling issue the 'stat is
not it.

 

I'm going Green on my new iron 390ci, as soon as I get home this Friday from a trip. It has Dexcool in it now......it's getting the swap.

I waited on this change for like 10 years. Now after seeing about 10 LSx owners do this over the years.......and seeing over-all temp drops for EVERY SINGLE one of them......I'm doing it.

I'm just adding 3/4 of a jug of Green and a bottle of Hyper Lube. The rest will be hose water. My city water is perfectly fine so no need for distilled. I've been using hose water for 15 years with no issues of any kind.

XCELERATIONRULES,

As mentioned......FLUSH it 100% clean. My Flush write-up will show you how. I'm on this crappy iPad or I'd find it for you. Just search it.......under my name.

.

 

Here ya go.

My write up. Looks like allot, but its easy. Read through it, then go do it. I would do the degreaser part if I were you.


Best/easiest way to flush and get every drop of old coolant out.

****My power steering fluid leaked into my block, so it was bad, but this flush process works for normal maintenance flushes too. You might just want to skip the degreaser stages.****
-Cold engine.
-Remove radiator fill cap.
-Remove the t-stat from the housing. ((Buy a new t-stat housing gasket, they're like $3.00)) Leave the housing attached to the rubber radiator hose, just remove the 2 housing bolts and pull it away from the water pump to get to the t-stat. (2-3 minute job). ***The t-stat itself can be removed from the so-called one piece t-stats just like we can remove the t-stat from the newer two-piece t-stats. And the housings will bolt right back to the water pump.***
-Put t-stat housing back on. (1 minute) Just put one bolt in, no need to put them both in, there’s no pressure in the system during the flush.
-Take the entire radiator drain valve (petcock) "off" and let it drain, don't just open the valve itself. It'll drain faster with it off and that’s what you want. ((Buy a new petcock valve before starting this flush process, sometimes they break when you remove them all the way just because they're cheap plastic and they get briddle over time, they're like $2.00))
-Take a hose and stick it in the radiator fill cap, running medium to high.
-Start the engine when the radiator looks like its full again.
-Turn heat on full blast
-Let it run for about 15-20 minutes or until the water is running out the drain CLEAR.
-((If you want to, you can wait till it runs clear, "close" the drain valve, add some degreaser (I use ½ gallon of Formula 88 to clean mine) and let it run for 15 minutes, then let it sit for 15 minutes, then run it for 5 minutes, then drain it all again. Then open the drain and put the hose in for about 5 more minutes and run it all out till its CLEAR. The degreaser will help break up the crap thats stuck DEEP in the BLOCK that sits and swirls and doesn't like to come out.)) ***NO…degreaser will not hurt anything. Just make sure its ok for aluminum.***
-When it runs clear your entire system is clean.
-Remove the overflow reservoir from the car and clean it out real good. (I had to use gasoline to clean mine out because the sludge and grime was so thick inside. The gas broke it all down and then it flushed right out. I filled it about 1/3 up with gasoline and shook the hell out of it real vigorously, the black stuff kept coming out. I did that like 4 separate times with gasoline till no more chunks of black crap came out. Make sure the lines that go to the reservoir are also cleaned out. Or just buy a new piece of 3/8” heater hose and replace that line, 3 feet will do, then cut to fit. My sludge came from my power steering fluid leaking into my coolant system.)
-Put the t-stat back in.
-Put the overflow reservoir back in.
-Put the drain valve back in. Use the new one, what the hell.
-Put half a jug of Dexcool in the radiator. (Or if you live in very cold places, 1 to 1 ½ jugs of Dexcool)
-Fill the rest with water.
***You do not need to use distilled water, clean hose water is just fine, just make sure your city water is clean and not total crap quality.

**Bleeding the system of air:
Take the radiator cap off when its COLD, top it off, start it up and let it idle, and let it warm up till the t-stat opens. I rapidly squeeze the upper and lower radiator hose like 20 times each while its warming up to help move any air bubbles through the system and by the t-stat on the engine side. When the t-stat opens you’ll see the level drop as you squeeze the hoses, its sucking the coolant through the system. You will also see the coolant start to flow in the radiator fill neck, once it starts to flow the level should drop down a lot, IMMEDIATELY top it off with coolant/water. Then the flow will stop when the t-stat closes. Wait one more time for the t-stat to open again and start to flow, if it drops down again top it off again. Do it a 3rd time if you want to make sure. When the level does NOT drop down when the t-stat opens and coolant is flowing....you're system is free of air bubbles. I always squeeze the upper hose during the whole process to keep any air bubbles moving through. Always works like a charm. Just keep checking your temp gauge until the t-stat opens for the first time to make sure it’s not sitting there overheating from a trapped bubble. May take 10-15 minutes for the t-stat to open the first time.
If you do start to get hot while sitting there and the t-stat will not open…..you have an air bubble on the engine side of the t-stat. Shut the engine off and rapidly squeeze the upper and lower radiator hoses again. Then start the engine again and see if the t-stat will open. Sometimes you just have to work those hoses to move the air through. Even after it seems topped off after a couple cycles…check it the next time you have a cold engine…top off if needed.

.

 

 

The cross-contamination is caused by a leaking factory power steering cooler which is located in the radiator hose that connects to the driver's side tank. You will need to delete this cooler as part of your clean-up process, otherwise the PS fluid will simply continue to leak into the coolant. You can do this by ordering a radiator hose for an earlier model, from before the PS cooler was standard, such as a '98-'99 non-WS6/SS car. Here's a link to our massive sticky thread about this exact problem:

https://ls1tech.com/forums/general-m...g-success.html

Some folks choose to install an aftermarket cooler, but most applications don't require this. I deleted mine and drove it around for thousands of miles afterward without any issues. I posted a bunch of data on post-delete fluid temps somewhere in the thread above.

You'll also want to check the PS system for any coolant contamination.