Wierd Over Heating Issue's

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spdrcr771

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Ok it starts like this. The day I was starting my car from the 1.3uz build. Found out that the temp sensor in the stock radiator does not thread to the Megan supra radiator stock location spot, you can thread it but it aint right. So in desperation, (i never do this) but I DID, I used the JB weld 2 part puddy, to seal it up. NO LEAK. A few days later the temp gauge starts to go up, so I pulled over b4 it even gets close to the red. Shut it off, get out an check, no leaks, no smell, nothing. Start it up, it's sitten @ normal. I thought "thermostat". I make it to autozone, buy a thermostat for a 02 SC430
cause if you ask for a 98sc400 it dont fit. There part #'s F'd up or somthing, I think it's for a 92-97. Got it home, changed it. Filled up the radiator & no prob. 1 week later, Im driving to OK city to buy a Tacoma for my wife, & the temp gauge starts going up & then dropping back down. It would do it 3-4 times in a row then stay at normal for a while. So Im thinking that POS autozone thermostat is bad. So i make it to Norman OK Lexus dealership to buy a OEM thermostat. Get it, try to limp the car to the dealership, where the truck is @. It starts peggin & not comming down, it takes me 1.5hr to make it 8mi. I change the thermostat @ the car lot after buying the truck. When I pull the A.Z. thermostat out of the housing, theres like no fluid comming out of the housing neck. Im like its got no leaks, where did the fluid go? Then I start thinking, I didnt burp the system when I changed the thermostat the 1st time, I just added to the radiator. Stupid I know. Maybe I had a air pocket & that was causing the problem. So filled it up, burped the system, go drive it b4 heading back 230mi home, its perfect no leak, no overheating, no prob. Drive home got to IRL race. That was on 6/5/10. Tonight on the way home from INLAW's house 6/21/10, there it goes, doing the same thing it did on the way to OK. WTF, I dont get it. The only other thing that is wierd, is when Im crusin under 3K rpm it kinda feels like the motor is missing just very slightly, any type of throttle pressure & its moving w/no miss or hessitation, I also thought I might be feeling that cause of the touque converter (2800) stall, baybe it doesnt have enough throttle to fully engauge or something. I just dyno'd it, it runs great. Now @ this point Im thinking 2 things, eather Its leaking @ the JBweld temp sensor spot & im not seeing it, or its burning/loosing it some place else. It idles fine, no water comming out the exhaust, no smell of antifreeze. So its cooling down right now, Im fixing to go check it out. What do yall think. If there was something wrong with the 4.3 block dont you think it would be running like crap. I mean 15 days to lets say leak/burn enough antifreeze to make it start to overheat is a long time. Radiator/overheating problems let you know there, there asap,not 15 days later.
 
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Ok well I think if found the problem. Its me & my friend's BS jbweld around the sensor that is leaking. I pushed on the jbweld & I saw a little water squish out from under it. we made a little worm out of the puddy b4 we wrapped it around the threads, to make it like a O ring of jbweld, then he only threaded the sensor in half the way, so that in the FUTURE "now" maybe the sensor would come out with out it being a major PITA. Well looks like it didnt seal right cause he didnt tighten it all the way. So I guess its time to custom fab a new bung hole for the new sensor to fit in. Just a little FYI for anyone thinking about putting a megan supra radiator in you SC.
 
Does the coolant in the resevoir come back up when the engine is cold? If the coolant disappears, then there must be a leak somewhere. If you're sure there's no leak in the front of the engine, then the leak has to be from the back, given the heads are sealed tight. I'd check the heater hose, water bridge, and a couple of coolant hoses around the TB. Also, I'd check the oil to see is the color has changed to milky chocolate. You can also remove the thermostat and drive for a while to see how the temperature changes.
 
Ok well I fixed the issue. It was the crappy a$$ jbweld temp job that FAILED. So I had a local machine shop make me an adaptor to fit the Megan Supra radiator to fit my sensor. Check it out.

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