Toyota Sienna overheating problems

Filed Jul 17, 2026 · Engine · NJ

I am submitting this complaint to request that the federal safety agency document and evaluate what may be a broader defect affecting certain Toyota Sienna vehicles and determine whether it presents a potential safety-related defect trend. My 2015 Toyota Sienna was diagnosed by an authorized Toyota dealership with an external rear-bank head gasket leak. A head gasket is a critical engine component, and failure can result in coolant loss, engine overheating, reduced engine performance, stalling, or complete vehicle disablement. These conditions may create a safety risk, particularly if they occur while driving in traffic or at highway speeds. An authorized Toyota dealership confirmed the diagnosis and submitted a goodwill assistance request to Toyota. The dealership noted my history as a repeat Toyota customer and recommended that assistance be provided. Toyota denied the goodwill request based on the vehicle's age and mileage. I subsequently appealed through Toyota's customer relations process, and the denial was upheld. I understand that the federal safety agency does not resolve individual warranty or customer-assistance disputes. My purpose in submitting this complaint is to request that the federal safety agency determine whether similar reports exist involving premature head gasket failures in this model year or related vehicles and, if warranted, evaluate whether a broader defect trend exists that could present a safety concern. Potential safety consequences include engine overheating, loss of power, stalling, and unexpected vehicle disablement. The vehicle has been maintained in accordance with manufacturer recommendations and has not experienced any overheating event that would reasonably explain a premature head gasket failure. Thank you for your consideration and for documenting this complaint as part of the federal safety agency's review of potential vehicle safety issues. Respectfully, Vehicle Owner

Filed Feb 6, 2026 · Engine · NJ

i am having repeated issue with Toyota sienna engine 1. Engine oil leaks through timing chain cover 2. Engine coolant leak Engine oil leak keep repating even I fixed earlier and leaks again due poor engine design same issue fixed on Nov/22/20 - 59k

Filed Oct 7, 2025 · Engine · IN

Coolant leaking from rear of the engine through the head gasket. Vehicle struggles to accelerate beyond 55mph or 80kmph. A quick search on the internet shows that this is a frequent occurrence in this 3.5L V6 engine from Toyota model years 2011 through 2017.

Filed Aug 12, 2025 · Transmission · IL

A catastrophic failed automatic transmission; UA80E of Toyota Sienna 2020 at 85,000 miles. It occurred while I've been driving downhill. No warning lights, not overheating, no diagnostic ODB code, no other indications prior to the failure. Failure created a substantial safety risk for myself, my four passengers and other road users. Sudden loss of transmission function could lead to potential dangerous situation. Minivan was towed to the nearest Toyota dealer where transmission assembly was confirmed for replacement.

Filed Mar 31, 2023 · Engine, Transmission · OH

As a result of the transmission cooler being a part of the radiator system, the transmission cooler ruptured while driving causing immediate loss of power and the engine to overheat. This malfunction also caused coolant and transmission oil to contaminate the engine compartment as well as the transmission. This is a major iengineering flaw and safety issue as I was on the interstate when it happened and was stranded on the side of the highway until help could be obtained.

Filed Jan 13, 2018 · NJ

My sienna is 3.5 years old and only has 33,178 miles on it, which means it is out of warranty for years, and it needs a new radiator due to engine coolant leak. Oil changes and maintenance has been normally done at our local dealership. Seems odd for a radiator to go to soon so money is out of pocket to fix.

Filed Oct 23, 2017 · Brakes · 97,402 miles · SC

Re: tsb # t-sb-0045-14 rev2 september 19, 2017 front brake vibration we have been having a front brake vibration problem since june of 2016. We have spent money on new brakes, rotors, calipers, and tires, all to try to stop the problem. Just a couple weeks ago the tsp referenced above was brought to our attention. We have been to our local toyota dealer and have been in contact with toyota and are not satisfied with the response. They say it it not a safety issue, but how can overheating brakes not be a safety issue? We would appreciate your looking into the problem. We are facing paying hundreds of dollars to fix the problem that they should be resolving.

Filed Nov 13, 2015 · Electrical · 126,123 miles · FL

Driver's side power window stopped working. Mileage approx. 126,123. Toyota dealer said window regulator assembly and motor needed to be replaced. I specifically asked if the master power window switch was involved, because toyota just sent out recall 15v689000 saying the master power window switch in some toyota vehicles could melt or overheat. Toyota assured me that no, the switch was not involved. I took the van to another shop for repair. They replaced the window regulator assembly and motor, as per toyota diagnosis. The window still did not work! And when the master switch was depressed, the control panel began to visibly smoke! To further test, the shop supplied separate power to my original window regulator assembly and motor - and they worked fine. The shop then re-installed my original window regulator assembly and motor, and replaced the master switch. The window now works. Toyota clearly missed the boat on this one. The switch failed and the fact that it visibly smoked means that it does, indeed, fall under the recall. This repair should be covered or reimbursed under the toyota recall. And yes, the sienna is affected.

Filed Apr 25, 2015 · Engine, Transmission · 121,482 miles · NJ

Radiator failure resulting in coolant leakage in the transmission fluid and transmission is failing. I noticed my 2004 toyota sienna had some belt noise that got worse. The van was due for a water pump/timing belt change. Later the engine temperature gauge read high and after checking the fluids noticed the antifreeze level to be low and topped it up. A week later while driving on the highway steam started coming out of the hood. I noticed the pink fluid had also leaked out of a tube (looked like a relief tube) on the driver side. Radiator level was low. The transmission fuel looked pinkish and read about six inches above the max level on the dipstick. Trans fluid was milky pink, thick, and had grainy deposit. Took the van to the autoland dealer in springfield, nj to diagnose the problem and to have the water pump and timing belt change at the same time. Had to leave the van overnight. I picked up the vehicle with a nearly $2000 bill for repairs (brakes, tire rotation, timing belt and water pump) other than changing the trans. Fluid or telling me what was wrong. Dealer said someone put additive to the fluid???. Note that only autoland had been servicing the vehicle. They refused to change the trans fluid. "I am not touching that." the dealer said. I now know from a local trans repair shop that the radiator was leaking coolant into the trans fluid. A known problem with radiators on toyota vehicles that had a recall. I never received notice of the recall. I now have an estimated $4,000 problem to replace the radiator and transmission that could have been prevented if autoland had done its job properly and not refused to change the trans. Fluid. I am very disappointed with toyota and with autoland's service.

Filed Mar 30, 2015 · Engine · 66,860 miles · MI

I believe the product to be defective because of the issue that I had faced with this vehicle 2 weeks back while driving in the freeway. Two weeks back while I was driving with my family (wife and 2 kids) the vehicle on 275 s freeway @ 70mph on 8th march 2015 1:00 am, the engine check light turned on and I noticed the engine heat indicator fluctuate like a fuel indicator. I tried to slow down, but by that time I lost the power of the vehicle , which made it really hard for me to steer the vehicle between the lanes and take it out of freeway to a shoulder, the brakes were not functioning either. It was one of my scariest ride I had in my life (you can imagine yourself, engine loosing power while driving in a freeway, I was with my entire family, and not having control on the vehicle), it put me and my family at such a big risk. Glad I was able to some how take the vehicle out of the freeway and used the parking brake to bring the vehicle to a stop at a freeway shoulder @ 8 mile road exit. The next day, I took the vehicle to victory toyota of canton, a toyota dealer for diagnosis. After thorough diagnosis from the dealer, he figured out the engine water pump failed, which lead to the engine getting overheated and engine got damaged, which needs to be replaced. They came back with the cost of 10,000 usd for fixing the vehicle. The vehicle has only 66,860 miles on the odometer.