I wasn't having any problem with my radiator but decided to flush it because it only had water and I wanted a 50/50 mix of coolant. I unscrewed the plug at the bottom of the radiator and let all the water out. Then I screwed the plug back in and filled the radiator with coolant. To me it seemed like not enough went it but it was filled to top. I started car and let it run for a while and it started to overheat. I've double checked the coolant level and it seems fine but it overheats ever time I run the car.

What did I miss?????

 

bleed it..... air pocket most probably.

 

Turn the heat to HOT and let the motor run as you pour it in while also squeezing the rubber hose SLOWLY here and there, as gerrb said there's just air in the system that needs to be worked out.

 

^^ Everything Gerrb and Kris said. I've had the same happen before. These cars and MKIVs can retain pockets of air after a coolant flush unless it's done just right. Also, tilting the nose of the car up slightly on jack stands can also help while bleeding the system.

Getting the system vacuum flushed & filled at a shop is the absolute best way to solve it but you do not have to.

 

keeping the heater on can help also.

 

ok guys...i'm finally about to address the bleed. I had to wait to get the replacement power steering hose that was leaking (the original job) and put it on. Now I'm going to look through the coolant system posts here for some help on bleeding then try to get the car back on track.

 

Hey guys. The 97SC4 only has one radiator plug down at the bottom of the radiator, RIGHT????? Some threads for other models indicated a secondary or even third plug you need to empty to change the coolant. ?

 

A FEW threads actually mention the bleeder plug that is just above the thermostat housing and the need to remove it to complete the bleed process.

 

just make sure the overflow bottle is full and let it warm up it should clear itself out of air.
I just use the one screw on the bottom to drain, plug it back in and fill the thing back up, don't overthink it.

 

The bleeder plug or water inlet bolt ended up being very stuck. Ended up taking car to a couple very local shops and asking them to take it off for me. First guy, a smaller shop, wouldn't touch it, said he might break the thermostat housing below. Second guy, a larger very established shop, had me pull in---luckily he was in the lobby and recognized me from past visits otherwise his wife charges right away--and he took a 3foot long hollow metal pipe, hammered the correct 17mm 3inch bit over the stripped bolt, then put the pipe over the socket wrench. It took a good push but it came off. He didn't charge a dime. I had already gone to Lexus dealer to purchase the replacement bolt ($10). I will attempt to bleed the system tomorrow after i pick up ordered bolt.
Presently the car's heat is not working and it's overheating...two things it was not doing prior to me draining the water out of the radiator....so I am pretty sure I introduced an air pocket into the system. My plan is get the front end up on jacks then follow the instructions here for bleeding the coolant system even tho few of them mention the bleeder plug. Whereas most of them mention how easy it is to get an air pocket in the system.

 

did you do the suggestions above? I am guessing you didn't cause the bleeder plug if that is what it is doesn't need to be messed with at all. I just filled a radiator last night with no issues on my GX.
when the motor is cold you run it with the heater on and the cap off and let it warm up and add water as necessary, if you did that then it still overheats then that would be an issue.
The overflow jug has to be full or the radiator will pull air into it from there, defeating the purpose so fill it up and keep an eye on it they tend to go down after a fresh fill.

not having heat on a sc400 is a known indication that there is not enough coolant in the system, and/or you didnt burp it with the heater on.
the heater has to be on or the air pocket can stay in the heater core or in the piping right before and after it (coolant wont flow there with heater off but you drained it via gravity). when the sc400 is a little low on coolant, the heat stops, so you for sure have air in there and need to get it out and replace it with coolant.

Just be sure not to never open the cap after the enigne is running with it closed, then it can be pressurized, and it can cause serious burns and damage to your self/others around.

 

It looks like I got the air pocket out My heater is back on and the car is running smoothly without overheating. The bleeder plug ended up being very important. I guess when i first attempted to flush the radiator I created a fair amount of air pockets that were not allowing the water to reach the engine.

Here's a recap of what I did to fix it.
1. Put the front end on jacks.
2. opened both the reservoir and bleeder water inlet plug located above thermostat housing on 97 sc4's
3. filled up the reservoir with coolant water mix.
4. filled up the open bleeder plug with coolant water mix until i thought it was full.
5. turned heater on full blast
6. turned on car and let it warm up
7. revved it up to 3000 rpm'sj a few times as it was dark here so didn't want to be too loud.
8. added water to only bleeder plug till it was full...turned out I needed alot more water for this part and engine made crazy "im thirsty!" noises till it was full.
9. watched bubbles come up out of reservoir
10. revved again some more then watched more bubbles come up out of reservoir
11. made sure bleeder plug was full and screwed it in (will replace it with new one tomorrow)
12. waited till no bubbles were coming out of reservoir, then capped it off.
13. Let engine run for a while to make sure it wasn't overheating which seems to be the case. heater was working fine so far.
14. Thanks you guys!!!!!