PDX88IROC

How to replace the thermostat on a 1988 Camaro with a 305 TPI
(and do the throttle body coolant bypass while you're at it...)

My Camaro started taking forever to warm up and running abnormally cool on the highway, the common signs of a stuck open thermostat. After getting a shop quote for $160 and having changed a bunch of thermostats in my time, I decided to do it myself. The Haynes manual thoroughly failed me, giving fairly generic instructions on how to change most thermostats, but not how it has to be done on a 305 with TPI so here are my notes with pictures for those who also want to try to do this themselves. Turned out not to be so bad as a Honda Civic, but definitely not as easy as I would have expected on a Chevy V8 either! Do you really have to remove the throttle body? There is probably someone out there who has managed to do it without, but it certainly must be easier if not required to do so.

Here is a picture of it finished:


First I removed the air duct connecting the MAF to the throttle body, and left the MAF in place for the whole procedure. Then disconnected the throttle cables and these two 10mm bolts.


Also, carefully unplugged the vacuum line from the bottom as the tubing can become brittle.


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PDX88IROC

On the other side, disconnected the two larger vacuum lines, the TPS electrical connector, another electrical connector under that, and the other two 10mm bolts. Then removed the throttle body.


I used a couple of 5/8” bypass caps to plug off the fittings on the throttle body as I will be doing the coolant bypass mod. It looks nice and will keep junk from getting up in there if I ever decide to put it back (doubtful). I cleaned up th carbon build up and noticed one of the throttle butterfly blades was loose so tightened those little screws too. Would hate to find out what would happen if one of those little screws fell out and got sucked into the intake!


Here is the throttle body removed with the fittings that need to be connected to do the bypass.


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PDX88IROC

I used the AutoZone molded heater hose Part #D87658 referenced in this thread: https://www.thirdgen.org/forums/tpi/...nt-bypass.html, but laying the hose in there, I didn't see how it was supposed to be such a good fit?


But cutting an inch off the elbow end and a few inches off the other end like they said....


And it does fit pretty good!


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PDX88IROC

On to the thermostat, not only was it stuck open but the housing had a failed gasket and was quite an ugly mess. I easily removed the 14mm bolt from the front of the housing, but mine had this stud/nut combo on the back (???) so it required a deepwell socket which I did not have and had to break to go to the hardware store. So probably a good idea to look first and see if yours is like that and get such a socket if you don't have one. A long socket extension was the key to getting to that bolt also.


Here is the new thermostat and housing gasket. My shop guy strongly recommended getting the GM “self sealing” gasket, and after going to all the auto parts stores having them look at me funny and try to sell me universal gaskets, I went by the Chevy dealer and got it for like $2.54. I didn't get a part # as it didn't come in a little bag, the parts guy just handed it to me. Apparently you don't use any other sealant...we'll see!


Removed the housing, cleaned off the old gasket the best I could with a scraper and emory cloth, and dropped in the new 195 degree thermostat. Again, my shop guy strongly recommended sticking with the 195 and not going cooler since my computer hasn't been chipped for it.


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PDX88IROC

Here is the “self sealing” gasket in place. I should have sopped up that coolant out of the bolt holes because it started oozing out when tightening down the bolts (duh).


Here is the housing reinstalled. I put the stud/nut combo on the front this time so it would be easier to get to with the deepwell socket than when it is under the intake plenum.


And here it is with the throttle body reinstalled and thermostat and throttle body coolant bypass done!


Hope others find this post useful, it's my first one! Sorry for all the continuations, but it would only let me attach 3 pics at a time and I really wanted them to be attached vs. linked because I hate it when linked images are broken!

Blue1990camaro

iTrader: (1)

this is a freaking great write up

peterc005

Great post.

88camaroscv6

iTrader: (1)

i changed my thermostat and i didnt have to remove any part of my tpi intake, just squeezed a wrench in there... good write up anyways though

hydrolic144

iTrader: (2)

Good write up. A lot of good points. Especially that vacuum line. By now they are extremely brittle. Good pic on the coolant bypass as well.

88I-ROC

It's an old post, but just wanted to drop a line for a fellow IROC owner from the Portland area. Just so happen, I own a 1988 red IROC with the 305 5 speed as well.

Regarding the lower temp stat I will have to disagree. I've been running 180' stat and 180' fan switch in PDX for 2 years and it was the best thing I ever did to the car, the guage doesn't show over the 1/4 even on hot summer days and I didn't changed the ECM chip. The only downside was I think I lost couple mpg's thats about it.

PhoenixFirebird

iTrader: (2)

I've swapped to a 180 thermostat in my 89 TPI, no computer changes were necessary other than the fans, but I didn't even mess with them, no real need to. I also had a nut-bolt combination, I was scratching my head when I saw that aswell lol. I did the same when I put mine back on, moved it to easier access. When I was doing mine, I didn't have to unhook any vac lines or cables, I just unbolted the 4 10mm bolts, and the throttle body moved enough for me to get a socket on the thermostat bolts. I agree, I expected it to be easier being a V8 and all lol. I've been meaning to do the throttle body bypass, thanks for reminding me Great post!

snipzors

Great write up exactly what i want to do, since my bypass hose split on me last night and poured coolant everywhere lol... just that i dont have an autozone here, is there any other part numbers with different companies that will have the same bends?

PDX88IROC

Yes, there is another part number GOODYEAR Part # 63069 mentioned in the following thread that has even better looking bends in my opinion (Just based on the pics, I have not actually used that one).

https://www.thirdgen.org/forums/cool...nt-bypass.html

I was unable to find it locally and didn't want to wait to have it shipped, so went ahead and used the AutoZone hose. RockAuto has them for like $4 + ship if you can wait to have it shipped.

PDX88IROC

Hey! We'll have to get in touch sometime. I just got my Oregon plates "88 IROC" so you'll know if you spot me!

88I-ROC

Thats cool!! where are you located in Portland? I live around Tigard. We should go to the PIR sometimes.

majobis

iTrader: (3)

(quote)

Hope others find this post useful, it's my first one! Sorry for all the continuations, but it would only let me attach 3 pics at a time and I really wanted them to be attached vs. linked because I hate it when linked images are broken![/QUOTE]

Very clear instructions and photos. Most helpful was the inclusion of circled bolt areas, part numbers & socket sizes.

ChevyTom

Could you show a picture from a different angle so I can understand where the thermostat is located? I only want to change it, but from your pictures I don't quite understand where it is located

paulo57509

ChevyTom

Thanks mate! You are awesome! I will look at it today. But it seems I might have to remove that throttle thing to get a better grab at it

James Sutton

iTrader: (2)

Important not to use sealant INSTEAD of gasket, as sealant can bleed, esp. if there's too much of it, and cover the thermostat valve, causing a boil over, which can require a new head gasket & engine tear down, all for lack of a $2.54 part. I wouldn't use any sealant in there.

Much discussion on boards here about best thermostat; I compromised & used 190 degree unit. But where you live matters.

ChevyTom

I haven't been able to do it yet, because on sunday I took out all my tools but found out I needed a 10 mm wrench for the job, and guess what...that was the only one I had lost. So I bought me a 10 mm wrench today and will start on it.
My local US Car shop didn't have a gasket that fitted my thermostat, but he gave me this big block of gasket so I can just cut it out and make my own (put the old one over, and draw a line where I will cut). So that should do the trick. it's a high heat gasket, but somewhat thicker than the original. So we will see if it will work.
But I heard something that if the change of thermostat doesn't fix my problem, he mentioned it could be the "feeler arm" that can be the problem.
Anyone knows where that is located? (picture appreciated)

ChevyTom

I got only to the part where I was about to remove the fuel injection, but I couldn't do it because I don't know how to remove this throttle part.
It's not like on your pictures, since yours has a screw on, but mine is more different. I tried pulling it, and pushing it but I couldn't that round thing off.

Any ideas?

paulo57509

You pry the little arm of the clip that's covering the pin UP so it clears the top of the pin and at the same time you push the whole clip to the rear (as it's oriented in your first photo).

Once you get the clip off you'll see how it's made and will be able to figure out how to re-install it.

ChevyTom

I did it Changed thermostate and it worked. Now engine runs at 200 farenheit all the time.
But it was very difficult.
I started first early, and I managed to take off the clips as the guy in the previous post told me...

ChevyTom

...then I got the port injection off to get the thermostat easier off...

ChevyTom

...then I got the port injection off to get the thermostat easier off.
But I got really problem getting the right screw off. I tried all my strength with a wrench but it was stuck shut. So I had to use this special tool u see in the last pic...

ChevyTom

...the left screw was so old and with full of rust it got stuck in my tool haha.
I had to ply it off later with a grabbing tool.
And for the right screw I had to use the special tool with a bent angle to manage to screw it off. Then later I had to apply the wrench to finish the job

ChevyTom

...and this is how my thermostat looked. It got this red plastic / rubber thing around. Don't know if this was a sealant or special gasket. But underneat it was a gasket.
I peeled off the red rubber and cleaned it so it was only metal left.
Then I made my own gasket by cutting it out and using the old gasket as a model. It worked great!

ChevyTom

...I finished very late. The whole thing took me maybe 3 hours in total.
Thanks for the help guys! Saved me a lot of money!