When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I was snooping under my hood yesterday and notice it looks like I have two coolant tanks. The one on the left was almost empty so I filled it to just under “Max”
What’s up with two tanks. ?
Last edited by Amigo; Oct 8, 2024 at 08:00 AM.
Reason: Spelling
The Lexus NX Turbo has two coolant tanks to manage the cooling system more effectively1. One tank is for the engine coolant, which helps keep the engine at the right temperature, and the other is for the turbocharger coolant, which cools down the turbocharger to prevent overheating2. This dual system ensures both the engine and the turbocharger operate efficiently and within their optimal temperature ranges.
Microsoft's AI is reasonably correct in this case. Impressive . I've actually seen an AI pull out an old explanation I did on one of these forum threads on a different topic, I laughed, I hope I was right!
But just for completeness, the left side tank is the engine coolant which is circulated by a mechanical engine driven water pump and directed via a computer controlled multi-way valve. Its normal to see more variation in the coolant level depending on how long / how hot it was when the car was last driven, but yea, keep it topped up as needed. The coolant tank on the right is indeed the turbocharger coolant but also services the intercooler (removes heat from the intake air after being compressed by the turbo). The coolant is circulated by an electric pump. On some turbocharged cars, the coolant pump can continue to cool the turbo even after the engine is shut down, not sure if this happens on a Lexus though. I've found the level to be very consistent over time, I assume a lot less variation in temp on this system.
The Lexus NX Turbo has two coolant tanks to manage the cooling system more effectively1. One tank is for the engine coolant, which helps keep the engine at the right temperature, and the other is for the turbocharger coolant, which cools down the turbocharger to prevent overheating2. This dual system ensures both the engine and the turbocharger operate efficiently and within their optimal temperature ranges.
I would make a plan to take your car to your dealership soon. Engine coolant in both cases for the turbo cooling circuit or engine should not lose coolant under normal circumstances. Maybe after several years of use due to evaporation. Please take the time to at least call them to discuss. I haven't heard of low reservoirs coming up on these models. I have a '22 350h with almost 30 k miles on it and all reservoirs are still sitting at full. A pressure test will confirm if you have a leak. Should be covered under warranty I would think too. Best to be safe. And always use Toyota recommended coolant it's specific for Toyotas / Lexus.
I would make a plan to take your car to your dealership soon. Engine coolant in both cases for the turbo cooling circuit or engine should not lose coolant under normal circumstances. Maybe after several years of use due to evaporation. Please take the time to at least call them to discuss. I haven't heard of low reservoirs coming up on these models. I have a '22 350h with almost 30 k miles on it and all reservoirs are still sitting at full. A pressure test will confirm if you have a leak. Should be covered under warranty I would think too. Best to be safe. And always use Toyota recommended coolant it's specific for Toyotas / Lexus.
@TheCDN I agree , @Amigo should not be having to refill these and he should take his NX immediately to Lexus dealer.
It was my left radiator expansion tank that was closer to the min level, I brought it up to the max level and will keep an 👁️ on it.
I’ll hold off on the dealer trip for awhile, it is a 3 hour round trip for us not including appointment the time.
It was my left radiator expansion tank that was closer to the min level, I brought it up to the max level and will keep an 👁️ on it.
I’ll hold off on the dealer trip for awhile, it is a 3 hour round trip for us not including appointment the time.
Mine was a bit low right from the factory too. I splashed in a bit to top it up a couple times during the first few months, I haven't had to touch it again in over a year. So far I've attributed it to a new coolant fill getting the last bit of the air out. Sometimes I check it, its at max. Other times its a bit below. Coolant system pressure/temp will probably change a bit from one day to the next how much coolant is pushed into the overflow and then pulled back. Obviously as others have pointed out a continuous need to add coolant is not a good sign.
Mine was a bit low right from the factory too. I splashed in a bit to top it up a couple times during the first few months, I haven't had to touch it again in over a year. So far I've attributed it to a new coolant fill getting the last bit of the air out. Sometimes I check it, it’s at max. Other times it’s a bit below. Coolant system pressure/temp will probably change a bit from one day to the next how much coolant is pushed into the overflow and then pulled back. Obviously as others have pointed out a continuous need to add coolant is not a good sign.
l wasn’t overly concerned either. Could have been just replacing a little air in a new system like you had to do. Also temps have dropped from the 90’s & 80’s to the 40’s lately causing some volume contraction.
l’ll keep an eye on it.
Same here your see my prior post I have 2023 RX350 ICE with the same engine, after my first months I was just looking and noticed it when cold it was at min radiator one, also intercooler was little low as well. Last Nov filled them both to max line, checked today radiator one was half way filled from Max-Min, it had definitely lost some from year ago, The intercooler one was fine at Max. I think it has something to do with this Turbo engine as I have zero leaks, I also do oil analysis so I know it not ending up in engine. If you look at dealership new cars your see a lot of new ones are at low line. Again speaking about ICE new Turbo set up not hybrid as that has different engine.
Coolant Tank (s) ?
. I've actually seen an AI pull out an old explanation I did on one of these forum threads on a different topic, I laughed, I hope I was right! 
Power Control Unit Coolant Reservoir & Engine Coolant Reservoir
