my 83 tr4 thermostat replace

[florykitty]

its time to replace my thermostat on my tr4 since cold weather coming,and my temp gage stay most time when i drive the car at cold,so pretty much no heat ,if the car just stay at idle it will go up so heat coming but when i drive the car it goes all way to cold and stay there so i decide first think replace the thermostat ,so i have a new oem one comes with a gasket also.i decide do it my self if you guys tell me what to do step by step,i apreciate ,thanks ted,so after that incident happnt i only have left one tr4 ,83 with sunroof ac pretty nice shape ,and a 81 old school hatchback ,

[dlb]

replacing the t-stat is really straight forward. raise the front end of the car a bit, or just park it facing uphill a bit -- this will help make it easier to get air pockets out of the coolant when you refill it. drain the coolant from both the bottom of the rad and the side of the block, just by the oil filter. if the coolant is over 2 years old, replace it with fresh stuff. remove the upper rad hose. undo the two 10 mm nuts and remove the thermostat housing from the block. replace the t-stat with the rivet (if the new t-stat has it) at the top. i use high temp silicone sealant on the t-stat housing but you can probably use the paper gaskets fine too. don't overtighten the 10 mm nuts on the housing, you will warp it. put hose back on, refill the rad with coolant, squeezing the lower hose occasionally to 'burp' the system. make sure the overflow reservoir is all filled to the 'full' line. start the car, check for leaks. let it idle till the rad fan comes on, continually checking for leaks. continue to check the coolant level while the vehicle is cold for the next few days or week, as some air pockets may work their way out over this time and allow the coolant level to drop.

[ARCHINSTL]

For lessening the mess of draining the block, see: https://tercel4wd.com/forums/viewtopic.php?f=10&t=10493
Tom M.

[florykitty]

got it thank you thank you much,i am not a very handy person but my tr4 make me to become,i have no choice ,once in a while they need something to fix ,they are about 30 years old so we expect those problems but in this days they dont make cars to last 30 years cause everthing become busnees ,

[Petros]

buy only a good quality thermostat (made in USA or Japan preferable), they cost in the $14 to $18 range, the cheap ones are junk (under ten bucks) and not worth buying at all.

You will need a new gasket as well, and I would use Permatex form-a-gasket (gasket sealer) on the thermostat to hold it in place, it is easy for it to fall out of position when installing and cause a bad leak if it does not stay all the way in its seat in the housing.

there is a funny thread on this topic, but I could not find it in the achieves.

[simon84]

I am considering changing the t-stat in my 87 tercel. It is running cold and no heat which sucks as it just got f***ing cold here. I recently did a flush and new antifreeze in an effort to make sure the heating would work as it has always been lacking. In fact, my 84 tercel heating was also always pretty crappy too. I plan to check and try to eliminate possible airlocks first though.
I suspect a stuck open t-stat or airlock but I am wondering if there is anything else that I could check?
I have already changed the t-stat in this car about 4 times and getting sick of it. It has run cold before, then it was back and forth running hot and cold. Last year it was running hot so I got a used t-stat from a forum member in the Kootenays. So I guess I should not consider that to be too reliable.
I am fine with paying a bit more for better quality but it's funny how I have never had these issues with cheap t-stats in other cars.
FYI it has a 4AC and I put a larger radiator from a Camry into it.

Much appreciated if anyone has any other tips.
I am told that these cars can produce lots of heat but this is my second one with terrible heater performance.
Should I get a higher temp t-stat?

[jimcrazy]

I had the same problem,temp gauge was in the middle were it should be but after 2o min drive to work the heater was blowing luke warm not enough to clear the windshield. did some searching on here and found a post on checking the trap door in the heater box, take out the grove box 2 screws, 2 heat ducts 2 more screws, then the white connecter box that the fan blows through to the heater 4-5 nuts, then I found the door flap, all of the foam gasket was rotted off of it with a big air gap when closed. I rolled up a couple of rags stuffed them in the door hole just to try, back together and now the best heat ever of the 7 tercels I had over the years. trying to find some nice soft foam to replace the gasket and take the rags out

[dlb]

welcome back, simone.

i want to confirm that in addition to not blowing hot air, the temp gauge is reading well below halfway. is that correct? in that case, the first thing i would think of is a failed open t-stat. but if you've changed it 4 times, i think it's really unlikely that all 4 of those have been bad out of the box. the bigger camry rad might be the problem. it might be fine in hot weather but in sub zero temps, i don't think the increased cooling capacity is your friend.

when i lived in edmonton one winter and drove a 3rd gen tercel, i zip-tied a cardboard air shield in front of the grill to help it stay warm on the long highway drives at -20 C. worked great. so i'd try that first. cheap and easy, and hella styling. put some jiffy marker flames on it for extra style points.

but if your temp gauge is reading about halfway and it's still not blowing hot air, a badly corroded heater core would be my guess. my pal has this with the 86 sr5 i fixed up several years ago. i've never replaced one but by all accounts, it's a rather large, crappy job.

[ARCHINSTL]

simon84 -
IF you have to replace the heater core - member sdoan produced an EXCELLENT post on this, with photos. It is a sticky in the Repair Guides Forum.
https://tercel4wd.com/forums/viewtopic.php? ... eater+core+
The flap you mention is visible in one of the early photos.
Tom M.

[jimcrazy]

well curiosity got the best of me, when I was running my 88 wagon it also had no heat, swap out 3 heater cores 1 of which was a new alum one same result no heat, just went out and pulled apart the blower duct work to find the foam on its door flap missing altogether. good side I have good core if ever needed

[simon84]

Thanks for the quick responses.
Just to confirm, the temp gauge is reading low so the thermostat is suspect. Not sure if an airlock could mess with the temp reading though. I will check coolant level and airlock first as that is the simplest stuff to do.
I have removed the AC from this vehicle and so I have taken some of the heating ducts apart for that. I will definitely recheck the flap.
Is it right near the fan or closer to the heater core?

[jimcrazy]

it is closer to the heater core, the cable from your hot to cold lever hooks on to the white lever to shut the door tight and to put the air from the fan to go to the top level

[simon84]

So here's what I found.
I have one of those garden hose fittings on the heater hose under the hood near the firewall. I opened that up and it looked dry. Opened the rad cap and there's fluid in the rad. I started it and revved it to see if that would get things moving. I also made sure that the heater control valve was open. after a couple of minutes the antifreeze frothed up to the top of the rad.
So I poured some antifreeze right into the fitting on the heater hose and when it was full I replaced the cap.

So it looked like there was some kind of airlock in the heater core.

But I did not stop there thanks to the tips from jimcrazy.
I opened up the heater box behind the glove box as he did and found that the condition of the flap at the heater core looked good. There are actually two flaps here. One is above and one is below and they are both linked. When the heat is on they are both open and send air through the heater core. When the heat is off they lie parallel right next to the core and the air bypasses the core.

There was another problem there. The heater control for hot & cold is not working well. It only just works the coolant pipe valve under the hood and only moves the flaps next to the heater core about half way. So I disconnected the cable that connects to the flaps and made a coat hanger controller that comes down just below the glove box. It allows me to fully open or close the two flaps. I am happy to have full heat or no heat and just use the fan level to modulate the hot or cold air delivery.

This did the trick. Went for a grocery trip and the temp gauge came up, only to about 1/4 though. The amount of heat was quite good. Better than I have ever had in a tercel. I am convinced that is was the same problem on my last tercel. I am rather happy with the fact that I will not freeze my ass off this winter. When it gets colder, I may try dlb's cardboard trick and see if it bumps the temp gauge up a bit.
So I am not planning to replace the t-stat yet. I think it is probably working after all. Is there a simple test for that?

I can try to post some photos of the fix tomorrow if anyone is interested.
I think I may try to install a choke cable to control the coolant valve under the hood. Unless anyone has a way to free up the cables so that they run smooth again. The other problem is that the levers inside the heater controls get bent and misshaped when the cable are sticky and then nothing seems to work. Overall, I think that the tercel heat controls were not built to last this long.

[dlb]

well done, simone. so industrious.

the heater control cables are easy to free up. just disconnect them from the end that moves something and dribble some kind of lube down the inside of the sheath. i have used light household oil but someone on here mentioned something better that will not trap so much dirt over time. i'll search and see if i can find that recommendation. anyway, after doing that for 5 minutes you should find the heat level lever slides nice and smooth. i find the long cable that goes to the coolant valve on the firewall is usually the only one causing any problems. luckily it's also the easiest to access.

you're right that the levers tend to get bent when they get sticky. i've had some success removing the controls, straightening them, lubing them, and reinstalling them, but it's a bit of a chore. an ounce of prevention, pound of cure or whatever the saying is.

[dlb]

found the thread i was thinking of, simon. here it is.

https://tercel4wd.com/forums/viewtopic.php?f=7&t=9549