I have a 1968 Toronado.

Last Friday I took a ride while it was quite warm out there - about 91 DegF. And I passed a hill of some 1000 feet high difference... but not too quick.

It was to check if engine cooling system leaks - but it was okay and engine didn't show a sign of really getting too hot.

BUT the transmission boiled over! The fluid boiled over the ventilation opening at the rear top of the trans and over the filling tube - mass of fluid! BIG MESS! It stopped boiling when switching the engine off.

Could let it cool down by just waiting 30 minutes and then drive home carefully - it didn't do it again.

Is that something I have to expect with this car? Just too hot weather and too high hill to climb at?

 

I've seen transmissions boil over if they are overfilled. The fluid level should be checked after the car has been driven at least 25 miles, in park with the engine running. If it was filled to the mark on the dipstick when cold, it would be too full. I would check that first.

 

My 69 would do that until I put a transmission cooler on it. It would not only vent out of the vent tube, it would blow it out of the fill tube right down on the LH exhaust pipe.

Trouble is the grille and bumper just about have to be off the car to make a neat installation. I suppose you could mount it low, down behind the valance panel. Just make sure all the air dams and seals are in place down there.

Just realised you're in Switzerland. Mountainous territory for sure. Maybe you're lucky enough it was just slightly overfilled and it won't do this again.

 

Think you guys are right - there might be to much fluid in the case. My shop (that I rarely allow to touch my car ) changed filter some time ago and I think, yes, that person filled it just up over the mark.

Then it will boil over without being much to hot - right? I always assumed that the engine would boil over first. Since transmission fluid should not get much hotter than engine coolant when "cooled" in the same radiator?

(And YES, fluid was blown out of the fill tube to the LH cylinder head - making IMPRESSING smoke coming from under the hood...)

 

NEVER overfill an automatic transmission, even by just a small amount, because this (or blown seals) can happen.

As mentioned above: Transmission fluid should be checked fully warmed up, at idle, on a level surface, in Park or Neutral, after running the selector through all the gears.

- Eric