ATF Temp gauge lights up

[DaveB]

Some months back I went to Ilfracombe to bring my sisters caravan back. While towing the atf temp light came and at roughly the same moment we overheated.
I stopped, had a look (we were on a hill so I couldnt check the atf level), couldnt see anything wrong.
Didnt want to chance it so called out the breakdown. Guy came and stuck a glass unit on the rad and proclaimed the head gasket had gone.????
Now I know the idiot was talking crap cos the liquid should of changed colour and didnt.
Upshot was we came home on the back of recovery truck many hours later.
Next day I topped up the water level, started her up & no probs even at normal runnig temp. No lights no nothing. While hot set handbrake, ran thru the gears and put her in drive. (Didnt go anywhere cos handbreak worked)!
Checked atf and no nothing not even on the dipstick!!! She was dry.
Spoke to a mechanic friend and we both concluded that was the original cause of the over heat.
Towing my own caravan the other day when atf temp light came on again. Pulled over immeadiatly, switched off engine and checked atf again. On the mark for hot this time. Got back in, started her up no atf temp light for rest of journey. Bugger did it again two days ago. Stopped, restarted no light!!!
Has anybody got a clue as to what is going on?
PS others might like to remember to check the atf cos that can easily be the cause of overheating.

[BUSHWHACKER]

The AFT gets very hot when towing and the cooler at the bottom of the radiator can't cope. As a consequence the engine coolant heats up too resulting in overheating.
There's a temperature sensor on the transmission which activates the warning light..

If you regularly tow then you may want to invest in a seperate transmission cooler as a back-up to the standard cooler.

http://toyotasurf.asn.au/techsite/trannycooler.htm

[DaveB]

Thanks, but that doesn't explain why the light comes on but goes off and stays off when I turn off the ignition and switch it back on again. I think I could probably ignore the light in safety but we all know sods law.

[BUSHWHACKER]

Thanks, but that doesn't explain why the light comes on but goes off and stays off when I turn off the ignition and switch it back on again. I think I could probably ignore the light in safety but we all know sods law.

It does, as I explained, the ATF is getting too hot and then the light comes on!
It's just a warning light not a temperature gauge.

did you check the fluid level with the engine idling?
Is the fluid red and NOT brown?

[DaveB]

The atf is red and as I said in my original post the engine was on and the surf in gear when I tested the atf.

The point I am trying to make is: if we assume the light comes on at 100 degrees or higher, when the light comes on I immeadiatly pull over, switch off, restart and drive away again. The light stays off for the rest of the journey. The atf will not have had time to cool in the short time that I stopped for, nor does it usually come on again throughout the rest of the journey. For the light to show atf temp warning it must have a temp sensor in it otherwise it would not be temp operated.

What concerns me is that it comes on but doesn't return when the engine is restarted.

[Darren]

It does sound like the ATF sensor isn't working right but works abit. I would agree with adding an ATF cooler, I tow a caravan reguarly and although I didn't get as far as the ATF light coming on I would frequently see the temp guage rising when towing which I put down to heat from the transmission, I often had to back off the revs and slow right down to let it cool especially for hills. I added an ATF cooler exactly as the write up above for about 25 quid and it solved it completely I can push on as hard as I want uphill towing now and the temp hardly moves. IMHO The ATF sensor might not be quite right but a cooler would solve the real problem.

[DaveB]

I agree with what you are saying Darren and with Bushwacker, but at the end of the day I dont know that the atf is overheating because the light comes on intermittantly and doesn't stay on. The main temperature gauge stays slap in the middle with no indication of any change. Having had a 2.4 blow, I now watch it like a hawk. I can fit a cooler and will but that might not stop the light coming on which is the real problem. And as I said before if I fit the cooler and it still happens and I ignore the light sods law comes into play.

Does any body know where the sensor is and how hard it is ti replace?

[michael sa]

...
The point I am trying to make is: if we assume the light comes on at 100 degrees or higher,
...

It's a lot hotter than that when it comes on:

Section AT-195
http://personal.utulsa.edu/~nathan-b...48electron.pdf

12. INSPECT TRANSMISSION FLUID TEMPERATURE SWITCH:
Check that there is continuity at the temperature of
145*C–155*C (325*F–343*F).
If continuity is not as specified, replace the switch.

I'm pretty sure the A343F is similar.
Why not change over the temperature switch to eliminate it from being the problem?
It's located on the transmission cooler outlet pipe close to the transmission - you can't miss it. (Online EPC for mine says part # 89429-34010)
http://www.toyodiy.com/parts/p_J_199...KPQT_8410.html (yours may be different)

More interesting reading here:
http://personal.utulsa.edu/~nathan-b...autotrans.html
-edit-
Dave on a side note, I fitted one of these a while back and I'm very happy with it:
http://www.toyotasurf.asn.au/forum/v...911&highlight=

[DaveB]

Well thanks for all the advice, I will be replacing the temp sensor as Michael suggests. And I will be getting the cooler. Its £19 + £26 p&p through ebay.
Once again thanks for your help.
Daveb

[GRASSMAN]

Hi Dave,

Where on ebay are you getting the tranny
cooler from. I need one for my 2.4 as i do a
lot of towing, cheers.

Gman.

[MattF]

Google or search on Ebay for Mocal.

[DaveB]

Hi GRASSMAN,
this link should take you to the dealer. I copied it direct while on his page.
http://cgi.ebay.com/ebaymotors/ws/eB...3AIT&viewitem=

Its the stateside of ebay.

[DaveB]

The cooler I am going for looks the same as the one shown by Bushwacker earier in this topic. I have looked at the Mocal ones and they seem to start at about £70 new.

I'm not buying secomdhand cos you don't know why its being sold.

Anyway we'll see how it goes.

[dieselboy]

The cooler I am going for looks the same as the one shown by Bushwacker earier in this topic. I have looked at the Mocal ones and they seem to start at about £70 new.

I'm not buying secomdhand cos you don't know why its being sold.

Anyway we'll see how it goes.

How did it go?

[TonyN]

How did it go?

I don't think he's listening...

Last Activity: 24th November 2009 14:38