I just put in a brand new oem thermostat for my 92 sc400, and I drained only the radiator prior. I never filled the filler hole on top. of the water inlet . I only filled the reservoir and started burping it though there. my car doesn’t overheat nearly as fast as it did with the old thermostat, but it’s still overheating gradually.

months prior, I never had any overheating problems while driving, but while in a drive thru, or sitting for a while the needle would gradually move up. I searched through forums and figured out my lower radiator hose was boo boo so I ordered a new one along with the thermostat and coolant temp sensor (the one that goes to the gauge). and I replaced them all at once and now I can’t even drive 5 minutes down the road😭

now as previously stated, when I burped the car (reservoir only) my car doesn’t overheat as fast but still overheats.

any suggestions? do I need to fill the filler hole? I cracked it open and coolant was coming out of it. do I have a clogged radiator? Is the water pump done? current mileage - 216k, timing belt done @175k.

 

I've read on the SC400's you do need to have the filler hole above the thermostat open; and fill it with coolant to the very top. When the car is cold, you should be able to start with this removed and add coolant to both your reservoir and the filler hole as the thermostat opens and allows coolant to flow through the radiator. When your thermostat is open and the car is warm, top off this filler hole to the top before capping it again; then make sure your side reservoir is at the correct level.

 

do I need a funnel for the filler hole? because when I filled just the reservoir, I started the car for like 7 seconds then turned it off and I checked the filler hole and coolant was at the top already.

 

Here's what the instructions for the car says, it sounds like you should have the engine off when initially filling the filler hole; then fill reservoir to correct level, start the car with heater on max hot and add coolant to your reservoir as needed.

 

I would jack up the car slightly since that point in the engine is the highest point, If you need a funnel then use a funnel unless you have a steady hand to pour the coolant in that small hole. I bled mine through the reservoir, I cracked it open so I could see the fluid bubbles come through the cap. I tried bleeding the system with the cap off and that wasn't happening so I put it back on and gave it a 1/4 turn to release pressure. I cracked the top bolt as well, since I wasn't sure if it needed to be cracked as well, but nothing came out of there, so I torqued it back down. TBH it was pretty quick to bleed it in comparison to my Tundra and it was double the time with my Celica.

 

is it possible that i’m doing everything wrong? I just installed a new radiator today hoping everything would work fine again but its still gradually overheating. while the engine was cold I filled the filler hole with the radiator cap unscrewed. and I filled it until the reservoir began to overflow, then I capped the the filler hole and stuck the funnel in the reservoir to begin bleeding. off intial start there was no bubbles that came up at all, and it idled nice and. the idle dropped like regular. once it was at operating temperature I held the rpms to about 2k, and let go and the coolant in the funnel would jump up. it took about 5-7 minutes for the temp gauge to start creeping up slowly. and I shut it off immediately. I still think im doing it wrong somehow but i don’t know😪. my next bet is replacing the radiator cap. my fan is constantly spinning so I don’t think its that. I also think maybe the funnel i’m using isn’t the best for bleeding, idk, I just want my car to stop overheating 😪

 

No need to fear a step at a time. Did you replace the thermostat? If you did did you install it correctly?
When it overheats, do you hear it gargling? or boiling?

Come to think of it, close the expansion tank, crack open the radiator. Pressure will release from there. If you need to add any coolant it will be through the expansion tank as it's already vented. Turn it on heater on full blast with defrost too. Make sure your front end is raised.

 

no boiling or gurgling, but both hoses are hot, lower is a little less hot then the upper. and I believe I installed the thermostat correctly. I had the nipple at the top facing the filler neck. but ill try leaving the cap cracked. I saw bubbles coming up through the filler neck funnel when I did that but I took the cap off because I couldn’t tell if coolant was going down or not.

 

You were on the right track, just have to let it bleed all the bubble out. Only fill it up if it gets really low, or if you could see the low line once it reaches that line then add more. You may want to shut it off and let it cool down before you open anything in the coolant department. Once you add the coolant to the full line, or all the way to the neck do the same process again, until it stops bubbling out. At that point you will know it's bleed thoroughly. If you're overheating, or your heater stops working, that means there is still air in the system.

 

Tally is right - these cars are notoriously hard to bleed and sometimes it can take a few attempts. Throw the front end up on ramps, proceed with the method you've been using, and make sure the heat is turned on high to make sure coolant is circulating through the heater core as well. Give it one more shot and report back!

 

ok will do, im gonna go out in a few hours and try again. the car was on ramps everytime i’ve done the process and the heat always gradually got hotter. so i’ll wait until all the bubble come out of the filler neck, cut the car on with the radiator cap vented to release air correct?

 

Do you have one of those caps with a red latch?? If so close the radiator cap all the way and lift that tab up, when it overheats shut it off, let it cool add more coolant and restart the process... TBH took me 3 days on my Celica had to remove the expansion tank and hang it from the hood, until then it bled thoroughly.
something like this cap here.

 

I don’t, and add more coolant from where?

 

radiator/reservoir cap vented car still cold. now do I start the car just like this and keep adding coolant to the filler neck?

little bubbles coming out while the car is cold

 

just a quick update, I’d really like to get a step by step in depth with what I need to be doing exactly. everyone has their own methods it seems, I just need one that I can follow and do straightforwardly. I just went out again and I posted pictures as to what I was doing and I need to know if I’m doing it correctly.
while the car was cold, I inserted my funnel into the filler hole and I opened the reservoir cap. these cars (atleast my year) only have an expansion tank that goes directly to the radiator. I don’t have a physical cap that goes straight into the radiator. as I was filling the filler hole, the reservoir was being filled also. I waited until the reservoir was at the top and then capped it. from there I poured a little more coolant into the funnel going into the filler hole and then I started the car. I didn’t see many bubbles coming up from the funnel, and when it got to operating temp I held the rpms from 2-2.5k for a few seconds. I noticed when I did that the coolant in the funnel would drop down, but when I let go it came back up. I feel as if i’m getting close to doing it right. there maybe a last step I’m missing. after a few minutes I cut the car off and check the reservoir, it was low so I released the reservoir cap and the coolant in the funnel from the filler hole filled it back up. I restarted the car and after a few more minutes the temp began to creep up so I shut it off. at this point the system is pretty hot so i’m letting it cool down but there was some gunk that came up in the funnel ill insert the picture below. you guys have been nothing but helpful and i’m greatly appreciative for how far i’ve come. the temp is still rising gradually but I have hopes that when I go back out the second or third time ill have gotten all the air bubbles out. LMAO my bad for this damn essay I can’t help it I wanna be as clear as possible .