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Transmission cooling lines? Other catastrophic items?

I heard that a failure in the transmission coolant line could be catastrophic. Are these in all cars or just high performance ones?

I have a 95 corolla with 255K miles.

I am committed to basic maintenance items to keep my car going for the long term, but a ruined transmission or blown head gasket / cracked head would be the end of the car.

Are there any other items I need to check which would be very expensive or catastrophic?

Losing ANY of the fluids will cause major breakdown.
But getting to that point is not real easy in the first place.
Just be careful where you drive so as not to bottom out or ‘‘snow plow’’ the under carriage.
Out here on the rez we see a lot of snow plowing of cars after the more common pickups make ruts the cars can’t negotiate.
A/C condensers,
Coolers for steering, engine oil, and transmissions are some of the first things down there to get damaged from being too low.

Stop immediately if you feel you’ve hit something and look for leaks.
Leaking out the fluid doesn’t cause the damage…operating the unit ( be it transmission , engine , axle , or steeing ) without its fluid does.

I’ve see city cars lose fluids after parking over one of the parking space stop curb thingys.

Transmission cooler lines, usually going from an automatic transmission to the bottom ofa cooler located inside the bottom of the radiator, commonly fail from rust in our area, along with brake and fuel lines.
You may notice drops of transmission fluid under the car or a good sized puddle of it if the line breaks.
If it breaks while you are driving you may smell hot transmission fluid. followed by a slipping transmission if you don’t stop. Do not attempt to drive the car anywhere, have it towed.
Repair of the line is fairly easy, just cut out the leaking part and put in a gas and oil proof section of fuel line with hose clamps. Brake lines would have to be replaced with new steel lines Gas lines would be replaced with new steel lines or a short section and be fixed with high pressure fuel line and high pressure clamps. With fuel systems pressures today I always double clamp both ends.

Are these in all cars or just high performance ones?

They’re on every automatic vehicle I’ve owned built since the mid 60’s.

I am committed to basic maintenance items to keep my car going for the long term, but a ruined transmission or blown head gasket / cracked head would be the end of the car.

You can say that about ANY car. Is this the first car you’ve ever owned?

Tranny line failure are so rare - I’ve never seen one. I’d be more concerned with a failure of a radiator hose since they do fail every once in a while.

Just keep up with normal maintenance as outlined in your owners manual.

Like so many seemingly insignificant parts that might fail and result in further catastrophic failures occasional inspection would likely result in spotting a problem in the early stages. Look under and around the car on a regular basis and become familiar with its operation. If you have kept that car running reliably for 255,000 miles you must be doing something right already. Congratulations.

do they ever simply fail? Should you get them changed preemptively?

The metal lines can rust through and cause a leak or you can hit something and cause a leak or the line rubbing against something can cause a leak. Had one of each over the last 50 years. Also I’ve had the rubber hose on an aftermarket cooler pop off. So that’s three times in 50 years of driving. So it does happen but not very often. I’d worry about tires more.

. Also I've had the rubber hose on an aftermarket cooler pop off.

I forgot about the rubber hoses. I’ve had a vehicle where the last 4" was rubber hose. Never saw if fail though.

The OP’s Toyota should have rubber transmission lines to connect to the trans cooler in the radiator. At almost 20 yrs, I would go ahead and replace them when you have the fluid serviced. I used to own a 15 yo Buick that had rubber transmission lines that had gotten old, cracked, and seeping. I had to replace them. I currently have a 14 yo Ford Explorer with an external trans cooler with rubber lines. It was in an accident 2years ago where the trans cooler got punched. The lines looked Ok, but were pretty stiff. I just went ahead and replaced them, too. After all, why take the risk?

It is only catastrophic if you drive low on fluid. My daughter hit a branch in the road, busted out a radiator and condenser connection. It was bleeding coolant profusely, fixed up no problem, same for trans. tow it or blow it!

And on that issue please be aware that black rubber fuel line, emission hose and vacuum hose will not withstand hot transmission fluid. A good parts house will have the correct hose and a counter man who knows the difference.

I replace trans cooler lines all the time

Cooler lines . . . oil, transmission fluid, power steering fluid . . . are some of the most common failures

Transmission cooler lines do fail. On the way home from an orchestra rehearsal, I found our clarinet player stopped in the middle of the street in her 1996 Taurus. The car was probably 12 years old at the time. A couple of the fellows and I got out of my van and pushed the Taurus to the side of the street and I gave our clarinet player my cell phone to call a wrecker. The problem turned out to be a broken transmission line. It was a cold night and she hadn’t driven very far. Apparently no damage was done to the transmission as she still has the car and has had no transmission problems since that time…

Most have mentioned the external lines so far. Those should just be inspected regularly. It’s one of the reasons I change my own oil - to look at stuff like that. The issues have been covered - the steel ones can rust through. The rubber ones are like any other rubber hose on a car. They are often cheap to replace - though sometimes not.

But these are the easy leaks to avoid and detect. The bad ones are the ones you can’t see inside of the radiator. If those get to leaking and coolant gets mixed in with the transmission fluid, then forget about it. By the time you figure it out, your transmission will be toast. The question on that one is really a question of cooling system history. If the cooling system has been well-maintained according to the manual (change intervals + coolant type + competent servicing) then there is unlikely to be an issue. If the cooling system has been neglected, then the resulting corrosion will lead to issues.

Yeah, when my cooler line popped off I was about 6 blocks from home and lost my trans fluid. I walked home and the wife either pushed me or pulled me home with our other car where I put the line back on and filled the trans again. We were young then and no transmission problem. Thing is I had just had the thing overhauled not long before that where they put the aftermarket cooler on because of debris in the internal radiator one. They either didn’t get the clamp tight enough or something but I double clamped them after that and no problems.