GM 3100,3400 Thermostat Replacement

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John Pritchett: As a former NAPA parts guy, I can offer some major advice before even installing the new thermostat.  This is a game changer and can help you save damaging your own car and whatever else is in the general area as well (you are welcome lol).
First thing is to "pop" the thermostat open gently by opening the center with both of your fingers/thumbs to make sure it won't stick initially closed since they sometimes do that (more than a few mechanics told me about this) and can cause your engine to overheat- and one more overheating might just be the one that warps that head!
Be sure to check the thermostat by boiling water in a small pan and put the new thermostat in the pan to observe it open properly, that way you know it actually works and not partially or not at all since sometimes they are shipped with "issues" as I've seen them come right from the factory not opening properly.  You can either leave it in the pan to cool down and watch it close properly or take it out with a pair of tongs or a fork etc. making sure not to jam something into the part that closes in the thermostat.
I personally have found 2 "brand new" thermostats that wouldn't open up right and was able to work the part open & closed to get them to work right since they apparently were misaligned from the factory, but couldn't see it right away- was on new Honda thermostats as NAPA used to get their Honda replacement ones from Honda back in the 90's.  I can say that the 1996 3.1 Monte Carlo engine is the SAME setup as the above, so yup you have a nightmare of a time changing the thermostat from 1995 to 2003 that I know of sadly... I almost want to look for one of those thermostat housings that are mid-hose (like some of the Olds & Buicks from the 90's) that just drop-in the thermostat- but not sure of the exact year & model cars to check lol!

George Letts: With regard to the GM 3100- 3400 engine thermostat replacement, could you give me the Craftsman wrench number? You mentioned that this wrench is used on the VW Beetle. I can not find this wrench anywhere.

24inchdubz: helping a friend with her malibu and just wow GM what crap. Toyota is so much easier to work on. I literally cannot do this or want to after watching this

rbarelas1: what happens if you remove the throttle body to remove the thermostat??

DDEENY: Hey, great job and thanks for the video.  The position of that thermostat/housing is daunting to say the least and reinforces my belief in capital punishment (for auto engineers).  We can reach the moon with astronauts (or used to) but can't design an engine that's mechanic-friendly with reachable components.  The best punishment for those engineers is forcing them to remove those 2 bolts (for free).  The old GM's with the thermostat sitting right atop the engine in your face were a breeze.
I have an '03 Impala that I want to remove the thermostat just for the purpose of running stop-leak through the cooling system to try to seal a blown head gasket (you may opine on that choice - the Impala has 165,000 miles and probably isn't worth the expense of a gasket replacement, and Pep Boys' pricing is always ridiculous) but now I'll need to seek tech support first to ask if it can be done without removing the thermostat, otherwise I'll probably be out of luck, especially without the unique wrench(es) necessary to reach the bolts.  Cleaning the surface of the stat housing is also probably difficult with such limited space to reach in.
I highly recommend the Lisle Spill-Free Funnel for purging the system rather than tampering with the bleeders.  I picked one up online for about $35 shipped and it was worth it because it's so fast and easy to use, and reliable.  I got it because I was having a problem with trapped air in the system affecting the heater and with fluctuating coolant temp gauge, which is how I diagnosed my blown head gasket (or other related breach) leading to my current endeavor with stop-leak, because the trapped air pocket has been recurrent and ever more frequent (but without any sign of coolant mixing with oil).  I haven't even bothered to use an exhaust gas diagnostic kit yet but would after the fact to determine the success of the stop-leak.  Wish me luck.  Thanks again.

Jason Camps: Thanks for this video.  I have no idea how you're getting your hands in some of those places, as I've struggled a great deal to get that lower housing bolt off, but I finally did it.  I also had the thermostat stuck in the housing which delayed me a bit.  Regardless, not having to remove the exhaust manifold cross-over pipe saves a lot of time and hassle.  I also appreciate the tip about the s-shaped wrench.  I had to go buy one but that did help.  Now lets hope I actually fixed the correct thing!

Michael Buendia: what the hell richpin06a you made this look sooooo easy. first off the bottom bolt IS A PAIN IN THE ASS. second the thermostat housing did not come out as easy as it did in the video, the actual thermostat was stuck to the housing instead of the engine. third putting the housing back on after putting the new thermostat in was hard i ended up having to take off the throttle body in order to re install the housing. after that everything was super easy. total time was about 5 1/2 hours. great video though really helped me to do this job. 

Joe Edwards: OK I just want to add this as I have done the knuckle busting, the skin slicing, and all the things that make you want to just beat someone that was on this design team. I ran out of expletives before I figured a way to beat this problem, and it is very easy to do once you look at what these engineers built and the limitations they give you when it comes to close quarter space
  Just take off the throttle body hose, the air filter cover and take out the air filter. the air filter box is a good place to put a big light to shine towards the thermostat housing. Remove the upper radiator hose from the thermostat housing, and bend it out of the way so you can work. take out the thermostat forward or upper bolt completely with a 13 mm socket or universal socket. if it falls, you shouldn't have a lot of difficulty finding it, but if you want to use the rag method, your choice. you can use a long 13 mm open end box wrench to access the rear bolt from behind all this mess. Shine a small flashlight that will let you see the rear bolt, you can rest it somewhere around the throttle body You will be doing a lot of turns to get this method to work, and you will be flipping the wrench to grab the bolt for each tiny turn using the open end side. Reach in with your right hand and wrench and do this from the back side of the motor right above the transaxle housing. loosen the bolt until you can pull the housing out, you may only have a couple or three thread grips inside the thermostat housing mounting surface. I found that doing this with my right hand, and leaning on my left arm with my head, I could get comfortable, and using a small flashlight shining down onto the rear bolt area, you can see what you are doing. Now wiggle that housing and get it over the thermostat, or try to get them both at the same time. your results will vary. Once you get the housing and thermostat out, clean it off, and put a thin layer of rtv on the back side of the thermostat, to help it stay in place. now go find yourself a nice sharp hacksaw, and cut off about a quarter inch off the upper slotted tang, tab, ear, whatever you want to call it, just make sure you leave enough so the bolt has enough to tighten down on, as long as you can see the old wear marks from the head of the bolt, you should be fine. Removing the upper slotted tang(?) gives you enough room with the rear bolt still in place (but only a couple or few threads inside the motor) to get the housing to go over the thermostat nose, and turn the housing into position. With the tang cut off, it gives you the clearance in the front to turn and twist the housing into place.Make Sure the thermostat is still in place, and hasn't slipped before you snug down the front bolt Get the front/upper bolt semi snug, and check your alignment, then tighten the rear bolt. tighten the bolts, and reassemble what you removed to get it out. I did this method, and the rear bolt is a slow process to tighten down, but it works, and you don't have to remove anything else that others are saying like the exhaust crossover, and the black cooling pipe. It's tight, but can be done this way. As a precaution, I will suggest you find a good sticky wide bandaid to cover the back of your right hand before you do it this way, especially if you have high veins to avoid the "red paint" from any of the sharp metal. I turned wrenches for 17 years for a living, and there is no reason for a thermostat which should be done start to finish including the refill in about an hour, to take as long as this does.  

Johnny Beem: Ohh My God . This job took me Approx. 5 hours to do. Most thermostats are usually a 10- 15 minute job I will never do this one my self again that second bolt kicked my A$$.   

My MK II: Great video! I struggled with that 2nd bolt on the thermostat, even dropped it 3 times. Thank God for a magnetic telescoping wand to retrieve it. I wish I had a curved box wrench like you used it would have made it easier to do.

Sir Pyro: Thanks for sharing this. I wonder if this is my problem. I do have a 2004 Monte and when I'm sitting with the engine running. It goes to HOT very fast. If I rev my engine to above 2500 rpms, it immediately goes back to a normal temperature. Within a few seconds. I've not seen anything like this. It will go to hot very fast when the rpm's are below 2500, and as soon as I hit the gas, the temp will go right back down. Do you have advice for this problem?

Michael Hamill: Hi, great video. I have a 1999 monte carlo, 3.1 L. Is it essentially the same process? Also did you need to disconnect the battery before starting the job?

HARRY LEE: Why are import cars much easier  to work on than GM build cars?

Ismael Griego: How did you remove the top bolt? I can't even get the top bolt to budge. They're both ok there super tight and I don't have enough leverage to get the bottom bolt 

Barbie Gifford: I found that if you remove the throttle body it make it a LOT easier to get to the bottom bolt and it also give you the opportunity to clean the EGR port in the intake while you are in there.

ada kittell: Do u have to drain coolant to change?

gocrazitalian: Watching this I am wondering if you can leave the bottom screw in place, as I noticed a slot on the housing.  I am thinking the slot would allow to leave the bottom bolt in place while removing the housing after loosening the bottom bolt to allow that.  I  have a 2005 Impala, 3.4L


Emily Woodard: uggh i hate that my engine is so tightly sqeeze with everything ,i took everything off like in the Video  but stuck with the bottom nut , im almost there ,Thanks for the Video it helped alot !!!!
GM 3100,3400 Thermostat Replacement 5 out of 5

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GM 3100,3400 Thermostat Replacement