my 2003 Is with the 2JZ is overheating. Just replaced the thermostat. Have done it twice now, put a new one in that had a “fail safe” device to keep it from closing shut. Funnily enough it did open at all in my car (or maybe so I thought) and after doing the Tstat job my car was still over heating. But only when the heat was off. When it was fully cranked the car was able to hold its self at optimum temp. Bought another Tstat, tested it and it opened at 82°C so I put it in. Again the car was overheating. I figured I was doing it wrong and getting air in the system so I bought a no spill, funnel kit and bleed the air out of the system, took it for another drive and it’s the same problem. No leaks in the system, it is dumping coolant out of the overfill though as it’s overfilling and expanding when it reaches to hot. Honestly am pretty stumped, car drove fine and never had this problem before the Tstat went. Drove it around for a month or so with a Tstat that was stuck open and finally got to it, and now it’s overheating everytime I lay on it without the heat on. Any ideas? Let’s what cha got?
only overheats when thrashing it with the heat on full or with the heat off and just driving it. Fans turn on and work fine. Car burns oil but not like crazy, so could be headgasket but doubt it as it only just happened when the Tstat was replaced. Isn’t the water pump as the heat wouldn’t be reaching the heater core and I wouldn’t be getting heat to the inside of my car (Which I am). I’m going to pressure test the radiator but I have found no leaks or anything suspicious. I believe the Tstat is in properly as the air bleed hole is aligned in the right spot. Only thing I can really think is the Tstat is still not opening all the way, but seems like that is the corporate as I tested it out of the car. Any other ideas?
If the head gasket blows between the cylinder and the water jacket it isn't going to burn more or less oil, I mention it as an option as if the thermostat went in the first place and it overheated then it may have blown the gasket. The compression from the cylinder can then pressurize the coolant system and blow it out the reservoir like it would overheating.
I have seen a water pump with, believe it or not, worn impellor blades. The seals and bearings were fine and it still circulated some coolant so the heater would work but the car would eventually overheat as soon as you drove it.
Radiator doesn't have to leak to be bad, its more about the thermal efficiency or ability to pass the heat on to the air going through it. If the fins are rusted out, beaten up or knackered it wont cool the water enough, but if that were happening you would probably hear the fans going hard. I assume the fans are going when it is overheating? I have seen some people have to hose them out to blow all the grime and gunk from the fins.
Radiator cap could be no good, not able to seal or hold pressure any more.
When you bleed the air out did you raise the front of the car up, remove the radiator cap then start and let it warm up? That's how you normally would bleed the air out of these cars, not sure how a funnel kit works as I've never had to use one.
Could still be a faulty thermostat or perhaps a faulty temperature sender.
Personally I would bleed the system as mentioned. Then start a process of elimination like try starting the car and let it idle, paying attention to when/if the fans come on. Watch what happens on the temp gauge as it warms up, the fans should come on as it goes over half way. If not then check the relays for the fans and start looking at that side. If that all goes ok and it doesn't overheat then it must be something not letting it cool when you start driving and putting heat energy in, so start looking at the other things like blockages in the radiator and condition, maybe try a different brand thermostat. Or it is something like the blown gasket pushing air into the system and looking like its hot, do a compression check.
this is all really good info. As I was checking through all of those things, trying to diagnose my problem. I realized I had only done my bleeding with the heater core engaged and the fans on low. This was causing my fans to both be on while doing testing. Today I realized without the heat on the fans do not turn on at all, even when the car is overheating. The bottom coolant hose remained much cooler then the top. Telling me it is infact another faulty thermostat. This is the second one I have had in. The fact that I also tested this in boiling water before putting it in my car also tells me something else is wrong. Any ideas. Maybe a faulty coolant temp sensor? I wouldn’t say it’s that as I ran my OBDll scanner and was able to read my coolant temp at 115°C and my car was about 3 lines from the danger zone. Pretty stumped. I feel confident the thermostat is in properly and I don’t think there’s much evidence of blockage as everytime I have drained the coolant it has appeared pretty clean. Any other ideas on why these thermostats are not working and does anyone have any recommendations for a Tstat they have used and know works? Thanks
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Lexus IS Forum
5.5M posts
129.7K members
Since 2000
Community dedicated to Lexus IS Enthusiasts. Come in and enjoy our articles, galleries and information on aftermarket parts for the IS300, IS250, IS350.