How To: Replace 4.3 Thermostat

[xambitionx]

If you notice your 4.3 seems to take a while to warm up, you may have a sticking thermostat. There are many reasons why you may need to replace your thermostat. Here, we will focus on the remove/install procedure.


First, lift the hood. Make sure your motor is cooled.

Remove the air intake and coolant overflow cap.

Remove the bracket holding the throttle cables and the ac wiring using a 10mm deepwell socket.

Pull the hose out of the bracket that goes from the water pump to the heater core and twist and pull up on the retaining bracket for the hose, it will pop right off.

Using a 13mm deepwell socket, remove the 2 stud bolts holding the thermostat housing to the intake.

Pull easily up on the thermostat housing, easily pull it aside.

Using a needle nose plier, for it may still be warm, remove the thermostat.

Now, clean the seat where you will install your new thermostat. You can use a q-tip, if its not got build up.

Install your new thermostat in its new gasket.

Now, insert the stat into the seat in the intake.

Replace the housing onto the intake over the new thermostat.

Tighten the bolts to torque specs, using a 13mm deepwell socket.

Re-install the bracket for the hose that feeds the heater core from the water pump, by pushing it on and spinning.

Re-install the bracket that holds the throttle cables and a/c wiring, with a 10mm deepwell socket.

Re-install the air intake to the throttle body.

Re-install the overflow cap.


Start the engine, allow to warm up. If no leaks, you're done.

If you have leaks, find the location and re-inspect the torque tightness, gasket(replace if needed).

[Crew Cab Sonoma]

also, make sure the bolt holes for the thermostat
housing are cleaned and dry of any spillled coolant,
or the next time you remove them, you may
tear up the threads in the manifold, due to corrosion,
or even break a siezed bolt off in the manifold.
i've seen it happen many times...

you can use compressed air, q-tips, rags,
or even WD40 to get the coolant out of the bolt holes.

i put studs into my manifold to solve the problem...

[klurejr]

Thanks for the write up, I am gonna do this soon.

[CatDaddy52]

Always use anti-seize compound on any/all bolts......

[lesterl]

What year/ engine model is this for?

[rhygin]

All the vortec 4.3s are like that Vin W or whatever they are called... 96-04?

[S15vortecpwr]

someone was searching.

great thread bump.

[klurejr]

Quote: Originally Posted by S15vortecpwr

someone was searching.

great thread bump.

yep, I have become a master at searching forum threads for the info I need.


I just did this about an hour ago on my wifes 2000 S-10 Blazer with the 4.3.

A few things of note, the OP only mentions to re-connect the brackets that hold the throttle cable, but you do need to remove them first

Also, the OP does not mention why he pulls off the cap to the overflow. I was not planning on a flush of the coolant, and thus ended up with coolant all over the top of the motor when I pulled the cover of the Thermostat off.

Any suggestions on how to drain enough coolant so you don't spill? I just hosed off the motor afterward, but I would rather not lose coolant, now I need to put some back in.

From what I read the factory thermostat should be a 195 degree one, but on the way home from getting it smogged it was about 207, just under the 210 mark on the gauge. I did not drive it all that far, I am hoping it was just hot from the smog test and not a bad thermostat stuck in the closed position right from the factory.... but I guess anything is possible.

[rhygin]

Usually people drain the radiator a little but your always gonna get at least a hose full... I mean you can be surgical about it and shit if you want drain 6 inches out of the radiator, remove the upper hose at the radiator slowy and carefully, drain it into a coffee can or something by bending it over then you might only have about a cup of fluid or so left when you pop the Tstat housing end off... Up to you I just make a mess...

[klurejr]

yeah, the mess was not anything a little water could not fix.

[joyride]

not to be a dick, but if people don't know how to replace their thermostat without needing directions....uhhhhhhh.....i guess in a nice way i worry about them.

[rhygin]

Quote: Originally Posted by joyride

not to be a dick, but if people don't know how to replace their thermostat without needing directions....uhhhhhhh.....i guess in a nice way i worry about them.

I thought the same thing but some people just dont get brought up that way... Alot of people have no idea where their spare tire is or even that they have one...

[dj00140]

Quote: Originally Posted by joyride

not to be a dick, but if people don't know how to replace their thermostat without needing directions....uhhhhhhh.....i guess in a nice way i worry about them.

Everyone has to start somewhere, not everyone is big into auto repair and just wants to save a buck in this economy... Some people may just want to read over a guide to be sure not to make a costly mistake, these forums are here to help right?

[joyride]

Great first post. You are exactly correct on everything you just wrote.

[rhygin]

Oh and just because Ive seen people do this... Thermostats can go in backwards lol... Seriously be careful and put it back in the way you took it out or you might be looking at a headgasket depending on how badly you fail.

[What?]

Re-do the post to be more clear and easier reading, this will go into the sticky.

[klurejr]

Quote: Originally Posted by joyride

not to be a dick, but if people don't know how to replace their thermostat without needing directions....uhhhhhhh.....i guess in a nice way i worry about them.

The first thermostat I replaced was on my 2004 Subaru STI. The thermo is located at the bottom of the motor, you have to drain all the coolant first, jack the car up and it is a real pain to replace.

So, I made no assumptions coming into this job and made sure I looked everything up beforehand.

Being careful and methodical is not a problem in my opinion.

[rhygin]

Quote: Originally Posted by klurejr

The first thermostat I replaced was on my 2004 Subaru STI. The thermo is located at the bottom of the motor, you have to drain all the coolant first, jack the car up and it is a real pain to replace.

So, I made no assumptions coming into this job and made sure I looked everything up beforehand.

Being careful and methodical is not a problem in my opinion.

I just looked up a how to on that to see what it was like and thats ****in stupid lol, that whole setup, that timing belt is scary... Bad ass cars tho...

[lesterl]

My 1999 Sierra had the thermostat on the bottom of the block (5.3l).....

[lessersivad]

Quote: Originally Posted by rhygin

All the vortec 4.3s are like that Vin W or whatever they are called... 96-04?

My '94 Jimmy has a vin "W" vortec and the stat is on the front of the intake, not the top.

Just a simple FYI.

[gnasty]

in the picture after you removed the housing the thermostat seems to be sitting right there in the open. I tried to replace mine today but my thermostat seems to be stuck inside the housing.

[sfhellwig]

I knew how to do the t-stat but still appreciated the write-up. I watched someone do my 2.8 t-stat once. Same position in the manifold but he had to scrape it down and silicone it in. I would have assumed the same for this one had I not read it before doing it a while back. Now, since mine still has a trickle from it, anyone know what that torque spec is? Maybe a few of them depending on year? I have a torque wrench but thought I could do this by hand, guess not.

As for the t-stat stuck in the housing, give it a gentle pry or tug with pliers. My stocker was stuck pretty good but it was just the gasket being compressed for so long. Slight sideways pressure from a screwdriver popped it right up.

[bricooper78]

the "W" 4.3's suck! i lost the socket, broke an extension, geesh lol

but I have a question-- I stuck my thermostat in (spring side into the motor) and let it warm up, and it's doing exactly what the old thermo is doing. letting the needle get to the 2nd mark past 100. I think i have a 180 thermostat, it's not marked, and I can't remember what my guy told me (i frequent the parts store, we get to talking...)

so my question is, since the 1st thermo was easily moved by my hands, and this one is in (i believe, hope) the correct way, aaaand all of my other gauges work.....

what the hell is wrong with this thing??? can that one gauge go bad or is there a temp sensor that i don't know about?

something may have been plugged, the overflow looked like a greyish mudpit, but the rad and hoses were all green and clean. i am stumped. any ideas?

[rhygin]

The second mark past 100 like 140? thats not bad?

[bricooper78]

i just checked again, i'm thinking 125. it was 82 here yesterday when i did this though. when i bought this thing, it was 34 outside, and i ran it 2 hours home on the highway, so i figured that was just that. kept it decent in the cabin, and it's old, i'm not expecting miracles lol

but is that a normal temp? the needle is still sitting where it was when i shut it off. there is 100, then a hash, then my needle directly centered between that hash and the 2nd hash, then there is the bigger mark (i'm guessing 155) then the next hashes and then 210. would have gotten a pic, the cell has no flash, and the camera just gave me one wicked reflection.

[rhygin]

Mine runs at about 160. Might try for a picture cause the lines are kinda ****y.

[bricooper78]

yea i was planning on taking one, i realized how dumb i sound while typing the last message

my 3.4 runs about 210, my 3.8 runs about 200, i have never driven anything that stays this cool.

but, i guess at least it's running lol

[fastmark1993]

mine gets half way to 100... and the heat sucks d*ck

[bricooper78]

i cleaned the overflow res, changed the thermo again (seemed to be fine but oh well), and i can climb to i'm guessing about 160ish.... i think i got a 180*

[rhygin]

160 is better than 210 lol.

[Crew Cab Sonoma]

glad he mentioned step one: "lift the hood".
boy, that was a time saver!
sure beats going through the wheelwell opening
to get at it...

[bricooper78]

rhygin--> my car is a grand am, it runs 210 from the factory!!!! no wonder the LIM gaskets fail every 40K miles, stoopid emissions and whatnots!!

[lesterl]

I ended up getting a Stant Superstat at Advance Auto, tried many other brands from other parts warehouses and they felt like they opened a tad too easy, was worried that the new superstat wouldnt open, but it works like mad, always had trouble getting the engine warmed up (had to run it on the road to open it up.)

[deadclown]

speaking of his ass temps get this i have a 1993 saturn sw2 and when i idled for a little bit at a light or somthing in the heat of the summer my car would heat up bad itd get up to 3/4 on the temp gauge and it always scared me cause the fan never came on well apparently saturn figured right b4 the temp gauge redlines is when the fan should come on i changed the temp sensor and everything but the fan never cuts on till its about red line heat thank god for the old air condition trick where you turn on the ac and it builds up a lot of pressure and kicks on the fan

[rhygin]

Quote: Originally Posted by deadclown

speaking of his ass temps get this i have a 1993 saturn sw2 and when i idled for a little bit at a light or somthing in the heat of the summer my car would heat up bad itd get up to 3/4 on the temp gauge and it always scared me cause the fan never came on well apparently saturn figured right b4 the temp gauge redlines is when the fan should come on i changed the temp sensor and everything but the fan never cuts on till its about red line heat thank god for the old air condition trick where you turn on the ac and it builds up a lot of pressure and kicks on the fan

The fan turns on with the a/c to cool the condenser so your a/c wont be hot. Maybe your fan controller or relay is bad.

[mycamaros]

Quote: Originally Posted by lessersivad

My '94 Jimmy has a vin "W" vortec and the stat is on the front of the intake, not the top.

Just a simple FYI.

Also the "W" or CPI 4.3 use a 44 mm Thermostat not a 54 mm like the "Z" or TBI use

[aminus21]

What's the correct thermostats to get for our 4.3's? The guy at the parts store gave me a few options. I'm in Socal and I don't do any towing, just daily driving.

[ranman]

Not meaning to step on anyone, but why would low engine temperatures be a good thing? I read a lot of 'less is better' on the internet.
Heat is what makes the oil perform it's job and allow moisture and contaminates to boil off. If the temps never get slightly close to that point, what's good about it?
I'd think higher engine temps (190-200ish) would be a win win when combined with cold air intake. Cool oil isn't a power benefit, tho cold intake air is.

[ranman]

One theory.
http://www.importtuner.com/tech/impp...r/viewall.html

[Crew Cab Sonoma]

Quote: Originally Posted by ranman

One theory.
http://www.importtuner.com/tech/impp...r/viewall.html

FAIL...
I love how their " warm" vs. "cool" engine test with cold components
test only had a coolant temp change of less than 3 degrees...
190.5 vs. 187.6 deg.

[Crew Cab Sonoma]

I'm a proponent of cooler engines, but not just because of power reasons.
it also reduces overall cooling system stress.
cooler operating temps allow lower system pressures, which can reduce
pressure failures in hoses, freeze plugs, radiators, ect.
it also greatly reduces the tendency for plastic components like
such as our intake gaskets, and external parts such as wire loom
and such from getting brittle and crumbling with age.

also, the coolant itself tends to be less "corrosive" at lower temps.
especially if your coolant is a bit old and its PH isn't ideal anymore.

and while it doesn't apply to our engines, ones with iron blocks and
aluminum heads tend to go through less thermal expansion variation
between the two components, which reduces "sliding" friction on the
gaskets.
the gaskets get a twofold advantage from lower temps.

[Crew Cab Sonoma]

as for the power and fuel economy effects, I haven't seen
much significant difference in either.
though my truck has seemed to run its best at the track
when I was using a 140 deg. marine thermostat.

also, oil temps tend to not be influenced a lot by
coolant temps. they pretty much have their own curve
which is only minimally altered by coolant temp.

[leppard614]

Quote: Originally Posted by joyride

not to be a dick, but if people don't know how to replace their thermostat without needing directions....uhhhhhhh.....i guess in a nice way i worry about them.

Well some of us aren't greaseballs and actually have a real job. ****en jerkoff

[t01blaze]

Are you saying a real job is detailing cars? What's with the attachment?

Thermostat replacement is one of the easiest jobs I can think of.

[leppard614]

Quote: Originally Posted by t01blaze

Are you saying a real job is detailing cars? What's with the attachment?

Thermostat replacement is one of the easiest jobs I can think of.

That's me going through the car wash you dumb redneck. I pay the ****** to put some good ol' tire shine and dry 'er up Get 'r done baby.

[Crew Cab Sonoma]

Quote: Originally Posted by leppard614

Well some of us aren't greaseballs and actually have a real job. ****en jerkoff

I see... so, someone who can work on his/her own vehicle is a
"greaseball", who can't possibly have a "real job"???

does that also include people work on cars and trucks for a living?

[leppard614]

No it doesn't, but some people are what is comonly referred to as a "Do-it-yourselfer", meaning that I use this site to learn how to perform certain repairs but apparently the jerk up there thinks that is something to "worry about." I work for a very well-know after-market parts company and a lot of the people there are ASE certified mechanics but they make more money sitting on a computer in a cubicle as opposed to turning wrenches. I have no problem with people who are highly knowledgeable with fixing cars, I just don't think those people should talk bad about those of us who don't know how to do every possible repair.

[Crew Cab Sonoma]

well thanks for the clarification.
it sure sounded like you had a very low opinion of people
who know how to do something you apparently didn't...

now if you don't know how to do something as basic as a
thermostat replacement no one of these engines, that's fine
I guess, but it is about as simple as it gets.
so if you don't know how, don't come on here and start hurling
insults at those who do, for pointing out the obvious...
most of us have had "real jobs", and still learned how to work on cars
in our spare time.
just sayin...

[leppard614]

That's my point. To YOU it's a basic job but for someone who has never done the job before of course I'm gonna research it cause the Haynes manual isn't the greatest sometimes. NOW that I followed the directions and replaced the thermostat, yes it is a very simple job. Your little S-10 pickup is disgusting by the way. Good talking with you. Leave me alone and don't reply, thanks have a good life you blue-collar pussy.

[Crew Cab Sonoma]

I don't think that really is your point.
looks like you have considerable disdain
for "blue collar" people, "greaseballs" who,
in your opinion, don't have "real jobs"....

you're thin-skinned, shallow, and like to think you're
somehow better than others, because of you're job.

quite pathetic, really...