adamb

1992 SC-300
104k miles

I bought this car at 98k miles with a full history from the Lexus dealer (excellent first owner, it's been a great car) but lately it has been overheating. The radiator cap had come apart so I replaced that. I cannot see any obvious leaks and though the fluid looks a little dirty it is surprising that it would make it near-redline after maybe 6-8 minutes of highway driving.

Replacing the cap helped a lot, but it is still running very hot. And the records show that this thing got a flush and fill @ 91k miles.

I am going to flush and fill myself when I get off work, but would wild fluctuations in temp (without actually overheating) indicate something more sinister?

Lost and confused, need help.

TeeDub

Ait bubbles trapped in the radiator... Or thermostat.

PERRYinLA

Air bubble in the system (bleed it)
Stuck themostat (test it)
Debris/deposits in the coolant (replacing it tonight should help)

adamb

I have opened the cap a number of times, so the air bubbles issue seems the most logical. I will burp it tonight after work.

Will idling it with the cap off for 5ish minutes also flush the air out of the thermostat or will that take a different procedure?

(Thank God for car owners who keep detailed car records.)

adamb

Also, is a flush and fill 13K after the last one overkill?

VSsc400

iTrader: (1)

i'd say it's the thermostat also. If not the rubber seal on the thermostat has become deteriorated and pieces of it are floating around the system.

adamb

I am liking all of these thoughts a lot more than the horrific idea of a blown gasket.

But I'm not running rough and my oil looks fine. I need to get this taken care of before it goes that far.

You guys are awesome.

I will update with the results of the flush & fill.

Now I just have to get up the nerve to remove the bottom panel to get at the bottom radiator plug. I hate doing things like that. (I've never done anything under the car on a Lexus, so I'm assuming that panel covers it.)

teke52

I just completely replaced my radiator...got a good deal on a new metal one locally for $160, probably could've gotten it a little cheaper online but when you need a part you need a part...time is of the essence and all...lol. Anyway, after me and my dad ripped it apart and put in the raplacement I had air in the system and pretty much the only ill effect of the air was that the heat wouldn't come out hot until you brought up the RPM...to push the air out of the sytem or because of the added pressure in the system...but the car NEVER overheated, not with the air bubble issues, not even with the old leaky radiator and I know it was really low on antifreeze before we yanked it out. So I don't think it's an air issue.

It really sounds like a thermostat and it's right up front on the engine, easy to get to, a few bolts to remove and costs less than $20...even from a stealer...oops I mean dealer. just my .02.

audi2nr

iTrader: (1)

hey just a suggestion, dont over look the fanclutch, i have a buddy who has a chev. blazer and he had an overheating problem so we replaced the fan clutch and that did it, no more overheating. also the thermostat could have taken a dump, u can test it in pot you dont need anymore. just boil water and put the thermostat in, also use a thermometer to see the temp, if it opens at the right temp, then obvously its ok. another thing about the fan clutch is that it can help out your a/c system if your current clutch doesnt engage..... just my 2 pennies!

mikeloc24

That was my thought as well. I was experiencing something similiar (do a search for my "weird thermostat happenings" and you'l see) and someone suggested it was my fan clutch or "fluid coupling assembly" If it's that the part costs $120 from Carson Toyota and you can swap it out in under 15 minutes (held in by 8 screws, no need to remove the fan shroud). The way to tell is when the fan is spinning you can grab it and stop it very easily, I wouldn't necessarily reccommend doing this, but in my case it was the only way to know for sure. I grabbed my fan and was able to stop it immediately. Ordered the part and swapped it out all within 3 days, no sweat. Hope this helps.

PERRYinLA

Believe it or not, I went for years without any fan at all on my BMW 3.0cs!

I'm not recommending that, since whenever I hit traffic, I could see the temp gauge start creeping up, but the point is that the fan or fan clutch is not a factor on a car that overheats on the highway, as adamb has mentioned.

mikeloc24

No, not on the highway. Even though I did experience it myself while on the highway, but who's to know if it wasn't a combo of issues. I at first thought I had a stuck thermostat, then a bad radiator (even though I had just replaced y radiator about 3 months ago), and finally the fan clutch.

Check them all out Adam, just make sure all those components are working properly. Even though there's no real way to "check the thermostat." Those things aren't too accurate anyway. From my research your engine temp can sway up or down 70 degrees before your thermo even notices anything, not good. If in doubt swap it out as it's a cheapie part that's easily obtained.

Perry, check your pm.

adamb

Well fellas, perhaps I have some photographic evidence of a problem here.



My SC-300 is urinating.

Is it supposed to be urinating? If it is, then that's not right.

And why is it green? The last people to put stuff in the radiator was Lexus and shouldn't they be using Reddish coolant (official Toyota)?

I am confused and unhappy.

Did little pixies come drill a hole in my radiator or is that some kind of release hole.

What sucks about cars is that you can't learn without asking stupid questions.



p.s. - I promise the outside of my car is kept very clean. But under the hood it is a mess.

SC400Dude

Whoa,
this sucks dude.....

At least you know what the problem is visually.
I run the green stuff in my car currently. My friend has the red stuff in his Tundra.....but both work the same in my opinion.....

vredniykot

looks like you gonna need a new radiator, that aint no vent or release valve
when thermostat opens and lets coolant to circulate that's when it will leak but when thermostat closes it will suck in air and when next time thermostat opens it will circulate that air trough the system and trap bubles in thermostat and cause it not to open/open late and overheat