A343F Trans & ScanGauge II what are your temp readings? (2 Viewers)

[flintknapper]

Just installed a ScanGauge II on the 99 LX470 (205K miles) and entered an Xcode for it to read transmission temperatures.

Drove the vehicle today about 45 miles (one way) mostly highway commute 60-70 mph.

Had temp reading of about 180° F. (ambient temp around 80 degrees), coolant temp 188° F.

My 80 Series Land Cruiser (same transmission) making the same highway trip (45 miles) never got over 140° F.

Wife drove into town later in the day (city traffic) and reports the temp at one point was just over 200° F.......!

Notes: LX470 reflects the transmission temperature as provided by the ECU.
My Land Cruiser has a digital Auber Gauge and a temperature sender/probe
in the transmission pan.

Questions:

Does anyone know where the temperature is taken from on the LX470 and if you have a Scangauge and the 4 speed transmission (A343F) what kind of temps are you seeing?

^^^^^ Those temperature readings seem rather high....depending upon where the factory temperature sensor is located.

 

[LuisJr]

My 2000 stays around 140-145 in stop and go traffic. Just installed my guage yesterday morning though. No highway stuff

 

[flintknapper]

My 2000 stays around 140-145 in stop and go traffic. Just installed my guage yesterday morning though. No highway stuff

Pretty much what my 80 series does under the same conditions (depending on ambient). That is why I am concerned about the LX.

I just finished letting it idle for awhile (coolant temp 186° F and transmission temp 154° F).

I got my IR gun out and shot the pan, it showed within 2 degrees of the ScanGauge reading, which would imply the temperature shown on the ScanGauge display is pretty accurate.

So...tomorrow I will check the fluid level while doing a drain and fill. The fluid in it now is only several months old, but it won't hurt to change it.

Something is not right. Need to find out what it is. Got a 500 mile trip planned at the end of the week.

Wouldn't want to break down with the Wifey and two Dachshunds on board.

 

[LuisJr]

I totally agree on being cautious before a trip. Off work at 3am, but I'll try and keep an eye on the temp better. Any specific speed you'd like a reading of. If I still have enough energy I'll try and hit the freeway. Tomorrow afternoon I can for sure.

 

[flintknapper]

I totally agree on being cautious before a trip. Off work at 3am, but I'll try and keep an eye on the temp better. Any specific speed you'd like a reading of. If I still have enough energy I'll try and hit the freeway. Tomorrow afternoon I can for sure.

Most of the trip will be highway speeds 55-70 mph (probably average 65 mph).

Where I will likely see the highest temps though are at lower speeds (going through towns....stop and go).

Without benefit of air (at highway speeds) moving through the transmission tunnel and at times not having torque converter lock up....temps will naturally rise under those conditions.

Anything you can provide is more than I have at present and will be much appreciated. I'm thinking I shouldn't be seeing over 160-175° F. at most.

 

[abuck99]

180 is high for normal driving on a 100 series but that temp isn't quite high enough to be detrimental to the fluid in the short run. That is interesting the sensors are different between the LX and the LC.

If you have tech stream, I think you can monitor trans temp from there as a secondary check.

Inspect return lines, inlet/outlet from radiator, maybe a hose is kinked, your cooler is blocked, plugged .....? Use your IR gun to take temps of all these areas.

 

[geanes]

My engine temps on my 98 LX run in the high 180s routinely and tip into the 190 range periodically on my Scangauge II. Our real TX heat hasn't hit yet. Is that anything to be worried about? Not sure. I do drive a ton of stop-and-go traffic. My intake temps hover between 190-201. Hoping the raised air intake/snorkel will cool that down a bit. My radiator isn't "brown" by the way and my coolant was flushed and replaced with Toyota Red this past August. Going to try the X-code thing tomorrow to get the AT temp.

 

[flintknapper]

180 is high for normal driving on a 100 series but that temp isn't quite high enough to be detrimental to the fluid in the short run. That is interesting the sensors are different between the LX and the LC.

If you have tech stream, I think you can monitor trans temp from there as a secondary check.

Inspect return lines, inlet/outlet from radiator, maybe a hose is kinked, your cooler is blocked, plugged .....? Use your IR gun to take temps of all these areas.

I will check all lines, etc...tomorrow (good suggestion). I did check the trans cooler when I was out there earlier and surprisingly it read only 82° F. ??? So that might be the issue right there come to think of it, that was basically ambient temperature as if nothing were flowing through it. Hmmmmm!

Don't yet have techstream.

The only reason there are different sensors between the LX and my LC (I might not have been clear) is that I installed a temp sensor in the transmission pan and use it to display the temp on a dash mounted gauge. I don't know where the LX gets it temperature reading from (return line, oil pan, supply line)? It might be normal for the reading to be higher to IF it taken from fluid fresh out of the torque converter. I don't know.

 

[flintknapper]

My engine temps on my 98 LX run in the high 180s routinely and tip into the 190 range periodically on my Scangauge II. Our real TX heat hasn't hit yet. Is that anything to be worried about? Not sure. I do drive a ton of stop-and-go traffic. My intake temps hover between 190-201. Hoping the raised air intake/snorkel will cool that down a bit. My radiator isn't "brown" by the way and my coolant was flushed and replaced with Toyota Red this past August. Going to try the X-code thing tomorrow to get the AT temp.

Yes, my 'coolant' temps run between 186 and 191...not a problem. Its my transmission temps I am concerned about. Of course all of that might soon change when we get our Texas heat...as you say.

 

[abuck99]

Another thought; how is your truck shifting? Any flare? BTW- You can monitor Trans Slip from the SCII. Just wondering if there is some slippage causing your heat?

I read an interesting thread on adjusting the A343 line pressure in the 80 Section. Very simple and effective adjustment. Not sure it applies to the 100series A343 trans however. Might be something for your 80 though: Improving Transmission Shifting

 

[flintknapper]

Another thought; how is your truck shifting? Any flare? BTW- You can monitor Trans Slip from the SCII. Just wondering if there is some slippage causing your heat?

I read an interesting thread on adjusting the A343 line pressure in the 80 Section. Very simple and effective adjustment. Not sure it applies to the 100series A343 trans however. Might be something for your 80 though: Improving Transmission Shifting

No slipping that I can tell. Yes the 343 in the 100 series can have the line pressure adjusted. Did that on my 80 series in the past.

Going to do a drain and fill this morning and check all lines. Check tranny cooler for obstruction. Double check fluid level. Drive it and see if my ScanGauge reading matches IR temp at the pan and take it from there.

 

[abuck99]

No slipping that I can tell. Yes the 343 in the 100 series can have the line pressure adjusted. Did that on my 80 series in the past.

Going to do a drain and fill this morning and check all lines. Check tranny cooler for obstruction. Double check fluid level. Drive it and see if my ScanGauge reading matches IR temp at the pan and take it from there.

Good luck- will be interested to know what you figure out.

 

[flintknapper]

Just got back to the house with the LX, my wife had driven it to town, I went and picked it up...so it had time to heat soak a little with the engine being off.

On my way back (highway speed 65 mph, ambient 74° F) the coolant temp varied between 188-190 and the transmission temp was steady at 165° F. When I parked it at my shop at home within minutes the trans temp had climbed to 176 but seemed to level off there.

I popped the hood and felt the trans cooler and felt cold to the touch (maybe 70-ish). Neither line leading into or out of it felt very warm either.

 

[abuck99]

Recapping:

1.) Pan temp you measured with IR and found to be close to accurate with SCII trans temps-
2.) Return lines rubber & fixed metal are cool to touch-
3.) Trans Cooler is cool to touch.

Seems plausible to be a restricted flow to the cooler. or somewhere in line.

I think I recall you have the Spectra rad in your truck right? The Inlet & outlet fittings to the in tank radiator cooler: hot or cool?

 

[flintknapper]

180 is high for normal driving on a 100 series but that temp isn't quite high enough to be detrimental to the fluid in the short run. That is interesting the sensors are different between the LX and the LC.

If you have tech stream, I think you can monitor trans temp from there as a secondary check.

Inspect return lines, inlet/outlet from radiator, maybe a hose is kinked, your cooler is blocked, plugged .....? Use your IR gun to take temps of all these areas.

^^^^^^ You called it Partner!

Update: So....considering the extraordinarily cool temp at the trans cooler yesterday it was collectively determined there might be blockage somewhere in the system or in the cooling unit itself.

I first inspected ALL lines from the transmission to the radiator and to the trans cooler. All looked good.

I pulled the Trans Cooler and flushed it out, then blew low pressure compressed air through it. No restriction found.

Next I blew air through the cooler/exchanger at the bottom of the radiator. It was even more free flowing than the Trans cooler. OK....so that leaves the soft lines and the hard lines. I blew out the first line (low pressure) and as expected got transmission fluid and air commensurate with what was being applied.

Second line...NOPE! I increased the air pressure and suddenly I heard a 'Whoosh' and then a 'Kerplunk' in the catch pan. I looked down and there was a small black object laying in the pan.

I picked it up and examined it. It looked like a 'shipping plug' of some type. My guess is... it was the one for the dipstick (before it is installed). It is not unusual for manufacturers to just 'punch' these into the transmission pan and leave them there.

How the hell it found its way into one of the lines I couldn't tell you.

I buttoned everything back up, did a drain and fill and let it idle for a bit. Getting ready to go test drive it now.

But for comparison. This morning (at idle, engine warm) the trans temp was 150° F. TOO HIGH!

Now (at idle) it is 116° F. Right in line with the trans temp on my 80 Series.

So...I'll report back later with the 'highway'/extended drive temps, but I believe we have found our problem.

Many thanks to my MUD FAMILY. You guys did it again.



P.S. I count myself lucky I decided to install a ScanGuage before going on my trip. I would never have known about the elevated transmission temps without it.

 

[abuck99]

Glad you sorted it out. Was it the return line: soft or hard line? Very odd that after all the years, that plug found its way into the line now.

 

[flintknapper]

Glad you sorted it out. Was it the return line: soft or hard line? Very odd that after all the years, that plug found its way into the line now.

Soft line, the one that goes to the Driver's side radiator connection. It would have had to of 'turned' just right (tapered end first) to even get into the line. Then.... it is a darn near perfect fit.

Just got back from my test drive. 20 mile trip, 65 mph, ambient 80°F.

Coolant temp 188°F.
Trans temp 125° F. (steady)......My wife takes a shower hotter than that.

In town went up to 132°F.

My 80 Series made the same route back at 135°F. So the LX was 10 degrees cooler. But it has 100K miles less on it and probably better airflow around the engine and transmission tunnel.

In either case...the A343F transmission is generally known to run cool.

So....one little piece of plastic just about cost me my vacation plans and possibly a transmission. What are the odds?

 

[abuck99]

Sounds like proper operating temps. My A750F runs similar: 1 hour drive today 46 miles combo of hwy and city traffic: ambient temps 81deg f, engine temps 186-190, trans temp range 132-138, & 125f idling in the driveway after I returned while I was taking IR readings of the same components to help you compare against ( but alas you found your “plug”)

Have a good trip

 

[flintknapper]

Sounds like proper operating temps. My A750F runs similar: 1 hour drive today 46 miles combo of hwy and city traffic: ambient temps 81deg f, engine temps 186-190, trans temp range 132-138, & 125f idling in the driveway after I returned while I was taking IR readings of the same components to help you compare against ( but alas you found your “plug”)

Have a good trip

Thanks, appreciate everyone's contributions and help. Great to have such a helpful bunch of guys as here on MUD.

 

[Kofoed]

If you watch the scan guage temp, the trans temp goes way up if you a running a steep hill in too hgih of a gear (even when in drive) or in high range. You'll also notive the factory coolant temp guage sucks. It won't budge between 175-215