how to change my thermostat?

**getcha01** · 03-21-2009, 05:03 PM

Alright I know how to change it, but after I drain my coolant, what do I need to refill it?...just get a gallon of red dextron and then fill it rest of way with water or what?....I want a serious answer, most of you will tell me to fill it with power steering fluid or something, but I need a serious answer, what do I put back in the system? how much? I want 50/50 mix...so how much coolant and what brand or find?....thanks for the answers

**egod** · 03-21-2009, 05:20 PM

I don't know the name of it but its the red coolant type. You won't look too much maybe a gallon or so, you should buy it already 50/50 though its just easier when you don't need much. After you get everything hooked back up run it with the cap off the radiator and slowly add till it stays up towards the top.

**Orcus79** · 03-21-2009, 05:25 PM

Are you draining it out fully? Might as well since it will be 90% empty any ways, and re fill it with a 50/50 mix of Dexcool, Dexron is tranny fluid. two gallons should be plenty for the system. THen follow what the guy above said to burp the system.

**pajeff02** · 03-21-2009, 05:47 PM

Just did the same to our car last weekend. If you are changing the thermostat, you may as well drop all the coolant and flush the system, unless this has already been done within the last 2 years or so.

The best way to do it is to drain the radiator, and then remove both block drains. The left side drain is a 17mm allen plug located just behind the alternator. You can purchase the correct tool from Autozone for around $10 -- it comes in a three socket set. The only thing I had to remove to access the plug was the splash shield which is clipped to the mid-rail and steering rack. Use a 1/2" swivel with a long extension and it is not too bad.

The passenger side is also an allen plug located above the starter. Although it may be metric, a 5/16" fits it perfect. Using a 3/8" ratchet and a long extension it is pretty easy to access. When re-installing both plugs, I utilized a small amount of thread sealant.

For the flush, the easiest thing to do is remove the thermostat from the old housing by simply bending the tabs a little. Re-install the OLD housing to the engine, fill the system with distilled water and run the car for a few minutes to circulate the water. I always turn the heater on when I do this -- not sure if it is necessary, but that way the water has to circulate through the heater core.

Allow the engine to cool, and the drain the radiator and block again. I did this a coupe of times just to flush everything out of the cooling system. Once this is done, remove the old thermostat housing, put in your new one (you may have to put a dab of sealant on it to retain the new O-ring). Make sure both block drains are in and the raditator petcock is closed. An A-4 equipped car has around an 11.8 quarts capacity -- I think the M-6 actually holds a little more.

Pour just about 6 quarts of DEXCOOL, or equivalent, into the radiator and let it settle. The air bleed from the top of the engine allows the air to escape as you fill the system. It takes a while as you can add about a fourth of a quart at a time after it tops out the radiator. After the DEXCOOL is in, switch to distilled water to top it off. At some point, you will just need to start the car and let it fill the heater core and work the air out of the system. Keep adding distilled water -- you will see air bubbles coming out of the hose that attaches just below the filler neck from the throttle body as the air is purged.

Carefully run the engine and keep an eye on the temerature gauge to ensure that the new thermostat opens and coolant circulates. You should feel your hoses as the engine comes up to temparature -- once they start to warm up you know the thermostat is opening. Make sure to check for leaks and also that you have sufficient fluid in your overflow reservoir. After the engine is shut off and cools down, you may need to top both off as air is worked out of the system.

**getcha01** · 03-22-2009, 01:11 PM

Thanks for all the info, I got a lot of tools, so that shouldnt be a problem I went to tech school for auto maintnence and got about $2000 in snap on tools and snap on tool bin...I may not mess with flushing it, unless the fluid is nasty...I will prolly just drain the radiator and then get that 50/50 mix stuff and after I install the new thermo i'll put the 50/50 in and then top off rest of way with water....yea I couldnt think of the name from the above statement I did say dextron which is what I put in my tranny dextron III, but dexcool is what I was thinking.....thanks guys I just like to know if theres anything hidden I need to know about, sounds like its not too bad....

**pajeff02** · 03-22-2009, 03:39 PM

I kept track of how much coolant came out of the radiator petcock and engine (removing the thermostat only) and it was right around 6 quarts. That leaves almost half the total coolant still in the engine. Just an FYI as a total flush really isn't that much more work.

**2001ws6** · 03-24-2009, 07:30 PM

Originally Posted by getcha01

Thanks for all the info, I got a lot of tools, so that shouldnt be a problem I went to tech school for auto maintnence and got about $2000 in snap on tools and snap on tool bin...I may not mess with flushing it, unless the fluid is nasty...I will prolly just drain the radiator and then get that 50/50 mix stuff and after I install the new thermo i'll put the 50/50 in and then top off rest of way with water....yea I couldnt think of the name from the above statement I did say dextron which is what I put in my tranny dextron III, but dexcool is what I was thinking.....thanks guys I just like to know if theres anything hidden I need to know about, sounds like its not too bad....

50/50 means no mixing it is already mixed no topping with water

**Smittro** · 03-24-2009, 07:59 PM

Just some friendly advise. Pick yourself up an antifreeze tester at the auto parts. This is a good way to make sure what your mix is. So when winter rolls around again you can be sure what temps your mix will support.

**zmg00camaross** · 03-24-2009, 08:14 PM

Originally Posted by getcha01

Thanks for all the info, I got a lot of tools, so that shouldnt be a problem I went to tech school for auto maintnence and got about $2000 in snap on tools and snap on tool bin...I may not mess with flushing it, unless the fluid is nasty...I will prolly just drain the radiator and then get that 50/50 mix stuff and after I install the new thermo i'll put the 50/50 in and then top off rest of way with water....yea I couldnt think of the name from the above statement I did say dextron which is what I put in my tranny dextron III, but dexcool is what I was thinking.....thanks guys I just like to know if theres anything hidden I need to know about, sounds like its not too bad....

your ranken material am I right

**denegrader** · 06-27-2011, 09:14 PM

Great write up i've been dealing with mistankenly drained radiator and threw 1 gallon of green i figure the dexcool was 10 yrs old so i figured it would be ok.
Well i then drained and flushed radiator 6 times till it ran damm clear.
I now want to drain block also if i can otherwise i will have to add water drive to 210 degrees then drai 6 more times till i see no more evidence of green or mixture , dexcool, when i m sure ill put dexcool.
Do you get these 17mm and 5/16 block plugs from underneath car with it jacked way up right?
I believe after i filled the radiator with green i was either low a little or had air in system and or the mixing dexcool and antifreze caused the mixture to boil into overflow tank filled it and bubbled out of overflow tank.
If the clean water w no air and filled doesnt keep car from overheating i will suspect cap may be t stat.
Ill do wat i got to to fix it.

Originally Posted by pajeff02

Just did the same to our car last weekend. If you are changing the thermostat, you may as well drop all the coolant and flush the system, unless this has already been done within the last 2 years or so.

The best way to do it is to drain the radiator, and then remove both block drains. The left side drain is a 17mm allen plug located just behind the alternator. You can purchase the correct tool from Autozone for around $10 -- it comes in a three socket set. The only thing I had to remove to access the plug was the splash shield which is clipped to the mid-rail and steering rack. Use a 1/2" swivel with a long extension and it is not too bad.

The passenger side is also an allen plug located above the starter. Although it may be metric, a 5/16" fits it perfect. Using a 3/8" ratchet and a long extension it is pretty easy to access. When re-installing both plugs, I utilized a small amount of thread sealant.

For the flush, the easiest thing to do is remove the thermostat from the old housing by simply bending the tabs a little. Re-install the OLD housing to the engine, fill the system with distilled water and run the car for a few minutes to circulate the water. I always turn the heater on when I do this -- not sure if it is necessary, but that way the water has to circulate through the heater core.

Allow the engine to cool, and the drain the radiator and block again. I did this a coupe of times just to flush everything out of the cooling system. Once this is done, remove the old thermostat housing, put in your new one (you may have to put a dab of sealant on it to retain the new O-ring). Make sure both block drains are in and the raditator petcock is closed. An A-4 equipped car has around an 11.8 quarts capacity -- I think the M-6 actually holds a little more.

Pour just about 6 quarts of DEXCOOL, or equivalent, into the radiator and let it settle. The air bleed from the top of the engine allows the air to escape as you fill the system. It takes a while as you can add about a fourth of a quart at a time after it tops out the radiator. After the DEXCOOL is in, switch to distilled water to top it off. At some point, you will just need to start the car and let it fill the heater core and work the air out of the system. Keep adding distilled water -- you will see air bubbles coming out of the hose that attaches just below the filler neck from the throttle body as the air is purged.

Carefully run the engine and keep an eye on the temerature gauge to ensure that the new thermostat opens and coolant circulates. You should feel your hoses as the engine comes up to temparature -- once they start to warm up you know the thermostat is opening. Make sure to check for leaks and also that you have sufficient fluid in your overflow reservoir. After the engine is shut off and cools down, you may need to top both off as air is worked out of the system.

**0rion** · 06-27-2011, 10:21 PM

Originally Posted by denegrader

Great write up i've been dealing with mistankenly drained radiator and threw 1 gallon of green i figure the dexcool was 10 yrs old so i figured it would be ok.
Well i then drained and flushed radiator 6 times till it ran damm clear.
I now want to drain block also if i can otherwise i will have to add water drive to 210 degrees then drai 6 more times till i see no more evidence of green or mixture , dexcool, when i m sure ill put dexcool.
Do you get these 17mm and 5/16 block plugs from underneath car with it jacked way up right?
I believe after i filled the radiator with green i was either low a little or had air in system and or the mixing dexcool and antifreze caused the mixture to boil into overflow tank filled it and bubbled out of overflow tank.
If the clean water w no air and filled doesnt keep car from overheating i will suspect cap may be t stat.
Ill do wat i got to to fix it.

you could save yourself some time and hassle by taking it to a shop and having it power flushed. It'll get all that crap out of there. The main thing I would worry about really is your heater core. You didn't say how long you ran the 2 mixed but it will definitely plug your heater core if it was in there for a while.

**denegrader** · 06-27-2011, 10:37 PM

Well was only in there for few days and the dexcools probably 10 years old.
i never turned the heater on with the mixture.
Well yeah they powerflush if you can trust emm i guess that wuould be good idea.
Probably 10 yr old dex cool in the heater core.

Originally Posted by 0rion

you could save yourself some time and hassle by taking it to a shop and having it power flushed. It'll get all that crap out of there. The main thing I would worry about really is your heater core. You didn't say how long you ran the 2 mixed but it will definitely plug your heater core if it was in there for a while.

**Too Fast** · 06-28-2011, 02:44 AM

Originally Posted by 0rion

you could save yourself some time and hassle by taking it to a shop and having it power flushed. It'll get all that crap out of there. The main thing I would worry about really is your heater core. You didn't say how long you ran the 2 mixed but it will definitely plug your heater core if it was in there for a while.

Plug the heater core with a green/dexcool mix? I've never heard or seen that happen. AFAIK, there is no heater control valve so the coolant always circulates thru the heater core. Main advantage of Dexcool is extended flush intervals. The old school green stuff always recommended a flush, or at least a drain and fill, every two years.

A coolant flush is on my list this summer, it will be the 4th time for this car. Always looks/tests great so far. (don't wanna put a hex on it!)

**JayTA98** · 06-28-2011, 03:11 AM

Check this write up i just did it yesterday. I included some pics. It might help you out some more. But its pretty much what Pajeff02 said. I agree with doing the whole system flush.

http://www.ls1.com/forums/showthread.php?t=157898

**0rion** · 06-28-2011, 04:30 AM

Originally Posted by Too Fast

Plug the heater core with a green/dexcool mix? I've never heard or seen that happen. AFAIK, there is no heater control valve so the coolant always circulates thru the heater core. Main advantage of Dexcool is extended flush intervals. The old school green stuff always recommended a flush, or at least a drain and fill, every two years.

A coolant flush is on my list this summer, it will be the 4th time for this car. Always looks/tests great so far. (don't wanna put a hex on it!)

Been there and done that.....had some mixed on my old truck. Fought the heater core for years before I finally replaced it due to it leaking. I back flushed that thing more times than I care to mention. Also, when doing the lower intake gasket I found some shit that was the consistency of crayon in the water passages. If it's clean there's nothing wrong with dexcool but if you contaminate it or mix it with regular glycol you're in for a ride.

To the OP......no longer than it was in there I wouldn't worry about it too much. Just flush the hell out of it and call it done.

**Too Fast** · 06-28-2011, 02:03 PM

That truck wasn't a 4.3L engine was it? They had lots of problems with heater cores plugging, mostly starting with low coolant. Then the air caused problems.

And I agree, just do a thorough flush and OP should be fine.

**denegrader** · 06-28-2011, 11:01 PM

just a few days never turned the heater on

Originally Posted by 0rion

you could save yourself some time and hassle by taking it to a shop and having it power flushed. It'll get all that crap out of there. The main thing I would worry about really is your heater core. You didn't say how long you ran the 2 mixed but it will definitely plug your heater core if it was in there for a while.

**denegrader** · 06-28-2011, 11:02 PM

just a few days never turned the heater on

Originally Posted by 0rion

you could save yourself some time and hassle by taking it to a shop and having it power flushed. It'll get all that crap out of there. The main thing I would worry about really is your heater core. You didn't say how long you ran the 2 mixed but it will definitely plug your heater core if it was in there for a while.

**denegrader** · 06-28-2011, 11:03 PM

just a few days never turned the heater on

Originally Posted by 0rion

you could save yourself some time and hassle by taking it to a shop and having it power flushed. It'll get all that crap out of there. The main thing I would worry about really is your heater core. You didn't say how long you ran the 2 mixed but it will definitely plug your heater core if it was in there for a while.