jakenbake

So I was asked in a private message to share my experience with towing in my RX400h. It isn't a very long story since the vehicle only ever towed a couple times.

My RX didn't even have a hitch until it had 115,000 miles on it. I bought the OEM hitch and harness knowing I would be towing from Portland to Phoenix.

Before the big move I towed a small trailer around Portland to help a friend out when he was moving cross town. The car did great. Then the big move came. I loaded up my u-haul trailer and I estimate that it weighed around 5000 pounds in total. That extra 1500 pounds or so may have been what ultimately killed my car. But the car pulled the trailer rather effortlessly and I never had a problem.

Once I got to Phoenix, I took it Lexus and had a service done. They said that the coolant may have boiled over a little but that everything looked fine. I drove the car for about another 10,000 miles before I started to notice that the revs would stay high even after I let off the gas and they would continue to stay high until I would come to a complete stop. It wouldn't always do this but it did it consistently enough that I was able to show the tech at the Lexus dealership.

Initially the dealership wasn't able to figure out what was wrong since the car had thrown no trouble codes, but after a week they hooked it up to the computer and drove around so they could record the vehicle statistics as it was being driven. They determined that the hybrid system was overheating and was likely caused due to towing with the car. They didn't know exactly what needed to be fixed but they did know it was either the hybrid battery ($4000) or the inverter ($8000).

To end...I would never tow with a hybrid again. Maybe I would if it was just a little dingy behind me but I would never even come close to pulling full capacity. Especially when the potential cost of damages is $12,000. I could buy a used truck for towing with that kind of money.

HtownBlue

Jake,
The towing wasn't the cause of this issue. Now towing did indeed exacerbate an already existent issue in the engine cooling system. The entire engine / hybrid electrical cooling system designed by the gen 1,2&3 hybrids Toyota made was less than ideal in a few ways. Not to mention the heat generated by both an engine and an electrical system that is franku shoe horned I to such a small space for its size. It's no wonder that cooling this beast is and always has been a concern. Toyota engineers when interviewed on the expansion of the hybrid fleet beyond the Prius said as much. It was a huge concern when modifying the systems for different vehicles.

I would not tow unless you are sure that your coolant systems are in good shape. Especially with higher mileage vehicles where build up can occur over time and can damage the entire system.

I feel for you man. You were probably unaware that there was an already inefficient issue before towing. Just google coolant issue RX400. These engines are amazing but run on a delicate balance of certain systems. You can have an issue and not even be aware until it's too late for a few problems.

Just be cautious when towing. Have your coolant serviced at least every 40-60K at most.

thomas1

Something else the electric cooling pump on the hybrid side failed on my RX at around 100k miles...I plan to replace it every 100k...part is cheap and easy to replace.

smassey321

I just changed my radiator last weekend and I took the old one apart to see if there was blockage. It looked new inside. Now the outside was a different story. The fins had a ton of sand in them so the blockage was more external air flow than internal coolant. My coolant gauge has never moved higher than half way even with towing.

I also agree that the RX400h may not be the best vehicle for heavy duty towing. But it really depends on your situation. For hilly high speed roads it puts a big stress on the drivetrain. However if you are on flat roads it is fine. I towed my 3000 lb boat both in flat Florida and hilly California and I am speaking from first hand experience.

smassey321

I changed my hybrid coolant and used the ebay techstream tool to run the pump and remove the air. It was pretty easy. I plan to test run the pump more often to listen for signs of failure. When everything is on, it is hard to hear the pump. Techstream can run just the single pump.

jakenbake

I have to disagree. My coolant system was in great shape. The original owner changed the coolant at 50k miles and I changed it again at 105k miles. It was also changed again at 110k miles when the radiator was replaced due to a leak. So poor coolant system maintenance was definitely not the issue.

thomas1

You know the engineering of the hybrid system may only have been designed for basic vehicle weight. Sure they say you can tow, but tow on any vehicle requires service more often as it is considered severe service. I change my fluid every 15k on the transmission, yes I know quite ****, but I just don't have any good feedback on this system. The fluid when I bought the car was brown (87k miles) and so I decided once a year for a drain and fill was a no brainer. I am attempting to go a full 250k on this vehicle. The only hybrid failure I have had was the electric cooling pump at around 104k miles. so that is also on my schedule....at 100k miles change.

jakenbake

I agree thomas1...Regardless of what they say the vehicle can tow, I don't think it should be used for towing. Especially when the potential cost of something going wrong is so high.

thomas1

yup big difference between a inverter and a regular transmission cost wise. And your local tranny shop cant repair it. I believe it is a factory only thing...

smassey321

jakenbake, Is there any chance that the air vents to the batteries were blocked during the long tow? My kids like to fill the back seat area up with stuff and sometimes they block one or more of the 3 air vents under the seat.

jakenbake

No they weren't... I specifically cleared everything off the floor back there when I loaded up the car to make sure they were clear.

maseace

jakenbake, do you have the towing package with the transmission cooler visible in the lower driver side grille?
Photos

jakenbake

Yes...it did have the towing package. It is my understanding that all the hybrid versions of the RX came with the towing package. But even if that isn't true....Mine for sure had the towing package with the extra transmission cooler.

chopstickz

I find this thread funny as the towing capacity of this vehicle is only rated at 3500lbs, and it's never ever recommended to tow full capacity but yet you stated you towed a trailer that weights over 4000lbs.

rns

I don't know if there is some variation of tow weights and how they are calculated but my Eurospec Awd Rx400h maximum trailer weight is 2000 kilograms = 4409 pounds.

I've got impression that tow rules here allow tow weight to be at the maximum manufacturer allowed weight.

I have not experienced any other downside so far than the fuel economy when towing with Rx400h. Seems that towing is much bigger issue for a hybrid car than to my other diesel engined vehicle.