Transmission overheating

[Marco waegebaert]

Hello I drive a landcruiser 100 from 1999 with a 4 speed auto. The problem is that it keeps overheating. After only 1 - 2 hours of highway driving my transmission is already at 120°C. The oil that's comming out of my transmission cooler is just warm (like 40 degrees or something. Just warm on my hand when I pull the hose of ). Is there a chance there is something just making to much heat in my transmission? Or what else could be the problem?

 

[AARONTLC]

Hello I drive a landcruiser 100 from 1999 with a 4 speed auto. The problem is that it keeps overheating. After only 1 - 2 hours of highway driving my transmission is already at 120°C. The oil that's comming out of my transmission cooler is just warm (like 40 degrees or something. Just warm on my hand when I pull the hose of ). Is there a chance there is something just making to much heat in my transmission? Or what else could be the problem?

Hello, 120° didn't sound bad until I saw it was Celsius LOL! If you have access to a temp gun, I would want to get readings from all around your transmission to make sure that you are not getting false information. If you have 40°C return fluid then I would think it is hard for you to be overheating unless the internal pump of the transmission is some how bad. I would think some readings from a temp gun could get you headed in the right direction. Good luck!

Edit: You said the fluid was warm on your hand. With the engine running that fluid should ha have been shooting out pretty good. Did you have good flow? Or did you pull the hose off with the engine off? That would be a good test to make sure your pump is running healthy.

 

[SteveH]

Is your torque converter locked during this highway driving when the trans gets hot? Cool transmissions happen during lockup, not during non-locked torque converter operation.

 

[Marco waegebaert]

Hello, 120° didn't sound bad until I saw it was Celsius LOL! If you have access to a temp gun, I would want to get readings from all around your transmission to make sure that you are not getting false information. If you have 40°C return fluid then I would think it is hard for you to be overheating unless the internal pump of the transmission is some how bad. I would think some readings from a temp gun could get you headed in the right direction. Good luck!

Edit: You said the fluid was warm on your hand. With the engine running that fluid should ha have been shooting out pretty good. Did you have good flow? Or did you pull the hose off with the engine off? That would be a good test to make sure your pump is running healthy.

The temperature I measure is in the line going to the radiator. And I pulled the hose off when the car was idling. The oild didn't shoot out bit is was just a steady stream.

 

[Marco waegebaert]

Is your torque converter locked during this highway driving when the trans gets hot? Cool transmissions happen during lockup, not during non-locked torque converter operation.

Yes torque converter is locked up

 

[AARONTLC]

The temperature I measure is in the line going to the radiator. And I pulled the hose off when the car was idling. The oild didn't shoot out bit is was just a steady stream.

Ok, yes “Steady Stream” sounds good.

 

[2001LC]

I'd wash fins of all three radiator first.

I'd complete a full 12 qt. flush, from cooler return pipe niple. That is the return pipe, next to and near top side of radiator on right side in engine bay, in USA left hand drive.

You'll see a steady stream of ATF at cooler return hard line/pipe while engine running. ATF will, come out, faster than you can add through dipstick. So you'll need to shut off engine periodically, so AT pan doesn't run dry.

By flush from last point before returning (after cooler) to AT, you be assured no restrictions to, in or out oil cooler. You'll also be flushing oil cooler.

You can add ATF into return hose that was removed from return pipe niple. It should flow in hose easily, with a syringe or fluid transfer/hand pump tank. Which, would also be indication, of no restriction in the last ~3 ' of pipe, before entering AT.

I'd use Mobil1 full synthetic multi vehicle ATF.

I'd monitor ECT & ATF temp through tech stream, while on your same HWY drive. You should see ~ 88c ECT and ~75C ATF.

If flow good during flush. ECT correct range and you continue to see 120C ATF. You'll need to rebuild or replace AT (auto transmission).

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