Toyota says the transmission needs replacing to fix the coolant leak!

About a month ago I noticed the hybrid cooling system overflow tank level had dropped about half an inch. There was some pink crusty dried coolant buildup visible on the front side of the transmission housing behind a small black bracket. The dealer hybrid tech could not identify where the leak was coming from, and a pressure test was ok. He cleaned up the dried coolant, and asked me to drive it for a week or so and come back.

The level did not drop for about two weeks. Over the past two weeks it dropped about 1/4 inch, and the pink crusty buildup was starting to come back. Off to the dealer I go on Monday. About a few hours later they tell me I need a new transmission.

The district service and parts manager had to approve the transmission replacement. He approved it yesterday. I'm waiting for a call back from service to see when the transmission will be put in, and if the hybrid warranty covers it. I do have the Toyota extended warranty for 100K miles. The car has 98,910 miles on it.

I'm rather surprised that a slow coolant leak resulted in Toyota saying I need a transmission. The hybrid tech did say the leak is not due to the pump, hoses or clamps. I'll update as I find out more.

 

That sure is cutting it close. Was the coolant ever changed or was it original?

I am curious as to where the leak actually is. If it did pass a "pressure test"... Where is it going and how is it getting out?

I also wonder how many transmissions they have changed on these cars? I'm sure it is not routine. That would scare me a little.

 

The coolant is the original factory fill. The service tech said he left it on the pressure test quite a while. This leak is very slow. I drive around 500 miles a week. So it took about 2000 miles for the level to drop less than 1/2 inch. It was just luck I found the dried antifreeze build up. The tech said it was not ATF, but antifreeze.

Toyota called today and said the new transmission arrived and the install should be finished tomorrow. I'll try and get more info on what actually failed.

I did not take a photo of the leak. If you open the hood, and look under the air intake at about a 45 degree angle to the front of the transmission, you will see a black bracket with one bolt holding it in place. This is about half way down the front of the transmission, roughly below the electric water pump. The leakage was around that bracket.

 

Sorry, I'm confused, are you talking about TCH?
1. TCH has no transmission per se, are they replacing whole transaxle?
2. as far as I know there is no cooling of transaxle which performs transmission function in TCH, or is there?
3. There are 2 cooling systems in TCH: one for engine, another one for inverter - I'm assuming this is the one leaking, correct?
Funny, I'm at 98k something myself, need to take it to the dealer before my 100k expire to check for problems.
Please keep us posted, especially why to replace "transaxle?", did coolant got inside and damaged electric motors? is there TSB about it since they linked the leak to transaxle from the beginning, which wouldn't be obvious at the first look.

 

Just picked up the TCH. Pete, you are correct, the transmission is the transaxle. The HV coolant circulates through the inverter and the transaxle to help cool the electric motors. That is the coolant that was leaking. As I understand it, the coolant cools the transmission oil, which cools the electric motors.

Keep an eye on the coolant level! I had no symptoms or warnings. The TCH ran great. The only reason I noticed is in the 5 years I've had the TCH, the HV coolant level never changed until last month. Suddenly I was seeing a drop in level. A very small drop, but definitely lower levels on the overflow tank. You could have knocked me over with a feather when they said the transaxle needed replacing. I would have never guessed the seal between the transaxle halves was leaking.

Dang they want a lot for the transaxle. I had a brief look at the tech's repair sheet, showing $4,395 for the transaxle and 7.9 hours to R&R it. Total bill was about $5400. Toyota covered it under the Hybrid Warranty. My cost was nothing. My copy of the invoice shows

Concern: Cust state coolant leaking from HV system coolant on to transaxle - transaxle cleaned on last visit - see history - recheck

Cause: Coolant leak at case half seem

Correction: Remove and replace HV transaxle

 

So, is the new trans-axle going to be warrantied for 100,000 again?

This is scary. I am rapidly approaching those miles. Probably next month.

I marked both of the tanks with a black sharpie pen when I bought the car. They have not moved (thank god).

Imagine this happening at 110,000 miles...

 

According to the service writer, the new transaxle is warrantied for 12,000 miles or 1 year. However, the Hybrid Warranty is still in effect and covers the replaced transaxle until it expires. I'm in California, and the Hybrid Warranty is 150,000 miles or 10 years, which ever comes first. Currently CARB states are California, Connecticut, Maine, Massachusetts, New Jersey, New Mexico, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington. CARB states have the longer warranty period if the car was originally purchased and is operated in a CARB state.

I was surprised the coolant flows between the transaxle case halves. Does the Prius transaxle do the same? I'm curious as I've never heard of a coolant leak with a Prius transaxle.

 

This is actually not as bad as it sounds:
1. every single car I ever owned (6 total), no exceptions, developed serious transmission problems between 60k -150k.
2. my second car I own, 01 Honda Accord has tranny problems since about 110k and dealer wanted somewhere around 4.5k-5k for replacement, so the price is just about on the higher side what typical transmission replacement cost, no big surprise here.
3. some states, mine including has 150k warranty covering transaxle, I'm not aware of any non hybrid car with such extended warranty and yes my Honda repair would be out of my pocket, that's why I haven't done it yet, so TCH has nice advantage here.
4. Now this is pure speculation on my part, but I don't think small amount of coolant leaking into transaxle would create major problems, if caught early. Coolant shouldn't be too corrosive and if the car was out of warranty, just repairing the leak by taking apart and resealing transaxle should fix the problem for less money. Of course dealer won't do it, since all they do is replace whole part, but there are some independent shops that could do it. I know one specializes in Prius and has website, where they show repairs done to Prius transaxle. Number of shops capable of doing such repair should grow as the hybrids become more common and they begin to age, so this could be another, cheaper option, to fix such a problem.
Hopefully this is not going to be a major issue with most cars. I know for the fact that I lost some coolant in both engine and inverter system, now I need to take a closer look.

 

Root cause could be either case porosity (unlikely, given the mileage), case crack(possible, even likely in case of a previous accident), case erosion (scary, it implies coolant failure leading to metal corrosion)
or failure of gasket/sealing material (most likely).

Kudos to Toyota for stepping up and replacing the unit - could be that they simply didn't consider it 'field-serviceable', or that they didn't want to risk a field repair (and related $$$) that would ultimately need a replacement. Could also be that they considered a risk of coolant entering case and contaminating lube, which would have created a high risk of catastrophic failure. Remember, lubed for life really means that the component lives as long as the lubricant can continue to do a good job.

 

nash, can you provide source for that warranty statement, please? i did some research yesterday, and everywhere i found that it is the hybrid battery that is under extended warranty of 150K. nothing about HSD componentry.
i am very glad you had yours covered, but am curious, in case life happens.
thank you.