Trans temp A/T Fluid over heat while idling

P

ptsailing

New member
To start off I've got a 1997 4runner auto with 308k miles on the truck. truck runs great and really haven't had any problems motor wise, except....when its fairly warm out and I need to go in the shops I leave my dogs in the truck with the AC on for 10 or 20 min. When I come out the truck is still running but will stall as soon as I put it into gear to drive away. I get a CEL and Auto Trans fluid temp light that comes on. I have a trans cooler installed in series (the cooler is down stream from the radiator as i live in a colder climate) so not sure how its a trans temp issue if I have better than stock cooling and the truck is in park. The last time this scenario occurred I hooked up my scanner and there were no codes thrown despite the CEL light on.

The first time this happened a year or so ago I took the truck to a Transmission shop and they said the fluid was good, fresh and new, and no sign of over heat. we replaced the fluid anyway. The problem only happens occasionally so not sure what effect this had on the issue.

Has anyone found the culprit. Been searching the forums for a while with no real answers to show.

Thanks in advance
 
Register to hide this ad
The factory procedure (recommended in the Owners Manual!) is to leave the truck idling in Park to cool off an overheated transmission... so, this shouldn't be happening.

A pre-'99 4Runner will not report transmission temperatures via OBD-II, so you can't check live data to see what the ECU thinks it is seeing for temps. The A/T Oil warning light comes on at 140*C/284*F, so the fluid would have clear signs of overheating if it truly was overheating to that degree. What is the exact OBD-II code reported when this happens?

I'm at a loss for what could be causing this though - I have never heard of this issue before.

-Charlie
 
Sounds like what happens when a pump is worn out or its flow is impeded, so it
only operates effectively at a higher rpm than usual. Could either or both be
happening here? It's pretty high mileage. Wouldn't be hard to pull a line and
check.
 
Yes as everyone says this is way Abnormal.

Mine has an aux cooler installed as yours and I cannot get it above 194 while towing or climbing. It can idle for hours and temps are 185 engine 165 trans (idle) so something is amiss in your situation.

Is the fan pulling enough air? Tested the fan clutch - does it have the 1 minute startup roar?
 
What is the exact OBD-II code reported when this happens?

I'm at a loss for what could be causing this though - I have never heard of this issue before.

-Charlie[/QUOTE]

It happened several times a while back last summer. I did not have my code reader on me. After the failure to start (cranking but not firing up) I let it sit for a min or so and it fired up....no CEL and A/T fluid light. Got home and ran my scanner but nothing showed up.
 
heat said:
Good point. What else- blocked air flow, condenser or radiator, blocked rad internally?
Click to expand...

The issue has happened a handful of times over 2 yrs...
I replaced the radiator in-between and the issue continues with the new radiator.
 
jgue467 said:
Yes as everyone says this is way Abnormal.

Mine has an aux cooler installed as yours and I cannot get it above 194 while towing or climbing. It can idle for hours and temps are 185 engine 165 trans (idle) so something is amiss in your situation.

Is the fan pulling enough air? Tested the fan clutch - does it have the 1 minute startup roar?
Click to expand...

That's a thought! I had not thought to check that. What exactly is the trigger for the fan clutch to engage and fire up (run time?...temp?)? I believe my fan runs all the time? I'll have to check. Is it possible for the fan clutch to lock in engaged?
 
HiluxSurf SSR-G said:
Perhaps you need something like this to verify the ATF temp:

Analogue Transmission Temperature Gauge to suit Lexus LX450 (Jan 1995 onward) with A343F 4 Speed Auto - CruiserBrothers

The A343F is very similar to the A340F transmission.
Click to expand...

Have you seen one of those in action? I'm all for supporting small import businesses in the USA, but that's a bit pricey when I have a dozen other issues needing attention. Also, since I'm here grousing already, that vague VDO gauge is only a little better than our factory temp needle and must be more useful on the Lexus/LC ATs they are geared to, given the temp range printed on the face. I'll stick with my $100 UltraGauge that displays fractions of a degree (admittedly, I have no idea where the computer gets that reading).
 

Attachments

  • TTemp.jpg
    TTemp.jpg
    55.2 KB · Views: 421
Last edited:
IIRC it gets its temp reading from the temp sensor on the passenger side of the trans next to the outlet pipe. That kit won't work on the 4runner as it has hard lines that go up to about a foot away from the radiator.
 
Endlessblockades said:
Have you seen one of those in action? I'm all for supporting small import businesses in the USA, but that's a bit pricey when I have a dozen other issues needing attention. Also, since I'm here grousing already, that vague VDO gauge is only a little better than our factory temp needle and must be more useful on the Lexus/LC ATs they are geared to, given the temp range printed on the face. I'll stick with my $100 UltraGauge that displays fractions of a degree (admittedly, I have no idea where the computer gets that reading).
Click to expand...
If you have a '99+, using the OBD-II information is easiest/best. It takes the reading from the same location as that kit, on the cooler outlet pipe.

-Charlie
 
$275 for a physical gage vs $5 for say Torque Pro makes no sense to me.

If you want a separate display the app can be put on an old phone - all it needs it BT to connect to odb2 reader. Luck all with the pesky trans temps.

I use a haydon 699 in series (doesn't open till 185) and even in stop go repeated conditions it won't go above 194 - ahhhh.
 
2TH4IST said:
Here is a link that shows you the fan clutch operation from timmy the toolman.

https://www.youtube.com/watch?si=Su2rhrI3TPiRieZP&v=A8OTtggtQnc&feature=youtu.be

Could your trans temp sensor be bad?
Click to expand...

That was kind of the only conclusion I had left to draw. If the shop says the fluid looks good and I have all the trans cooling mods applied then it would be reasonable to expect that a sensor is bad if all else is good?

How would you go about checking or replacing the trans temp sensor?

I did see a post (2yrs ago when this first happened) that someone had the same issue I had and they fixed it by replacing their Dex 2 fluid with Dex 3 ( or what ever the modern updated fluid was....I have searched every toyota forum I can think of and can not for the life of me find that post)
 
Did you check the fan clutch using the following method? Do you have a fan shroud?

How to check fan clutch

Try the following (by hand) with engine off:

Engine cold: Spins with difficulty, fan roars at start up
Engine warm: Fan spins freely by hand
Engine hot: Fan will not spin and fan roars as idle is increased
 
ptsailing said:
How would you go about checking or replacing the trans temp sensor?
Click to expand...

Finding a dead spot in a resistance type sensor is difficult. You would measure the resistance while the sensor is heating up. When the meter goes to zero or out of range that's the dead spot. If there is one or you suspect it's bad replace the sensor.

Just make sure your fan clutch is working properly like in the vid link I posted.
 
alumarine said:
Did you check the fan clutch using the following method? Do you have a fan shroud?

How to check fan clutch

Try the following (by hand) with engine off:

Engine cold: Spins with difficulty, fan roars at start up
Engine warm: Fan spins freely by hand
Engine hot: Fan will not spin and fan roars as idle is increased
Click to expand...

I did check it before driving with the engine cold and it spun only 1or 2 blades before stopping. I did the same after a 15 min drive on a warm day and applied the same test. Blades were the same only moving one or two blades before coming to a stop.

I checked the fan shroud and it is in place and intact, the fan runs at start up....I put my hand on the bumper side of the radiator and could feel plenty of air being pulled past.

From what I can tell it does not seem to be cooling is the issue.

Which leads me back to possibly an intermittently bad sensor?
 
You must log in or register to reply here.

Members online

Total: 312 (members: 2, guests: 310)

Forum statistics

Threads
278,309
Messages
3,554,075
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top