BenAmr2turbo Posted October 3, 2024 Report Posted October 3, 2024 Hi there, sorry to start a new topic for this but I just wanted to check before I blow a headgasket or overheat.. I have an Link Coolant NCT12 on a 3sgte in the factory coolant sensor position on the engine outlet tree. I see 91ºc before the stat even opens and the radiator return is cold. My question is - what is normal temperature for this sensor being on the cylinder head outlet? I will get to 96ºc at which point I turn the car off, then it rises to over 100ºc. Would anybody be able to tell me if this would be considered overheating or am I being too cautious? Thanks, Ben. Quote
Blackbandt Posted October 3, 2024 Report Posted October 3, 2024 So in my opinion, the temperature at the cylinder head, the heat is higher than with the thermostat housing or at the radiator. What temperature is displayed when the car is cold? About the same temperature as the outside temperature? Ps: When you turn off your car. Is it normal that the temperature goes up for a short time. Since my water pump runs more. BenAmr2turbo 1 Quote
BenAmr2turbo Posted October 3, 2024 Author Report Posted October 3, 2024 Thanks, the cold temperature is indeed the same as ambient temperature. When warm - the interior fans blow hot, this can keep the NCT12 showing 88-89. The thermostat doesn't seem to open or allow flow to the radiator until the NCT12 shows around 96 degrees, when the fans are already on (set to 95) Should I.... back the fans off to only kick in at for example 98 degrees to allow the thermostat to open and flow through the radiator? I think my instincts are telling me because the fans are blowing through a cold radiator that its overheating, but it may be that the thermostat is just not open Would fans ON at 98 degrees using a cylinder head mounted sensor sound acceptable? Any other suggestions? Thanks Ben Quote
David Ferguson Posted October 3, 2024 Report Posted October 3, 2024 Sounds like you need a thermostat that opens earlier (like 80 - 85c). What is the expected opening temperature of you current thermostat? BenAmr2turbo 1 Quote
Blackbandt Posted October 3, 2024 Report Posted October 3, 2024 Why did you install the temperature sensor on the cylinder head? Where is it actually installed? I would try to measure the temperature to another place. BenAmr2turbo 1 Quote
BenAmr2turbo Posted October 3, 2024 Author Report Posted October 3, 2024 Well, when I say cylinder head, It's on the outlet housing as per pic..... The link sensor is the same as the OE sensor which sits here. The original radiator switch is broken and no longer available, and it had twin aftermarket fans/alloy radiator. Can I not control the fans and monitor the temps with this sensor? Thanks Ben. Quote
Laminar Posted October 3, 2024 Report Posted October 3, 2024 It's not unheard of to have a thermostat stuck closed. I think the stock 3SGTE unit should start opening at 180F/83C and be fully open by 203F/95C. If you're getting no flow into the radiator by then I'd suspect the thermostat. BenAmr2turbo 1 Quote
David Ferguson Posted October 3, 2024 Report Posted October 3, 2024 If the thermostat was opening at 83c -95c, you would expect the sensor trace to flatten out in that range (and the radiator would heat up). Then the fan would be coming on at the right time. Make sure your coolant system is fully bled (no air pockets), since this sounds like a new engine installation into the car. BenAmr2turbo 1 Quote
Dean Posted October 4, 2024 Report Posted October 4, 2024 I’ve often had to pump the rubber radiator hose that connects to the thermostat (if you have access to one) to get the warm water from the top of the engine flowing enough to open the thermostat. This would then release the massive air pocket that’s in the system. It’ll keep overheating until you bleed the system properly. BenAmr2turbo 1 Quote
BenAmr2turbo Posted October 4, 2024 Author Report Posted October 4, 2024 Okay thanks for all the suggestions, the MR2 turbo can be a pain to bleed properly especially from empty. I will keep going through the bleeding process, as the thermostat is a brand new toyota part, along with the complete water pump and housing. I suspect an air lock in the return up to the thermostat. What would people recommend as a shut off temp using this sensor to protect my build? Thank you Ben Quote
David Ferguson Posted October 4, 2024 Report Posted October 4, 2024 probably 105 to 110c, with a good 1.5bar (22psi) pressure cap. I don't know about your thermostat specifically, but many have a small hole to allow air pockets to bleed through the thermostat. The hole needs to be oriented to the top of the thermostat -- installing upside down may prevent proper bleeding and trap air in the head. BenAmr2turbo 1 Quote
koracing Posted November 17, 2024 Report Posted November 17, 2024 Non-OEM thermostats are the bane of my existence with the 3SGTE - just throw them right in the garbage. I've recently had a few issues even with OEM thermostats don't seem to open as well as they should. It's not uncommon to just drill a 1/4" hole through the thermostat to help with bleeding and getting *some* flow to the other side of the thermostat to help stabilize coolant temp quicker. As I work almost exclusively on MR2s I've invested in a vacuum filling system that eliminates the issues with air pockets on a traditional fill/burp for coolant on mid-engined cars. Quote
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