A/T cooler but still overheating

S

stunt2

Member
Had an issues with A/T oil temps, so installed external cooler inline with oem one. It dropped about 60 degrees but the temps are still high: city driving at around 40mph - oil temp at 175-180. Highway ~60mph driving - 195-200degrees. Few minutes of driving at not so steep inclines and the temps reach 230-245 and even seen 265's at steep hills. No load, no passengers, 32" tires.

What could be the issue or what to do next ?
 
Last edited:
Register to hide this ad
I agree way hot. My stock 2017 SR5 on summer hot highways in CA driving 70mph cruise control on rolling highway where an auto downshift occurs on the small hills-I sometimes see 210 for brief periods then back under 200. I shift down to S4 on long upgrades and temps stay around 200. On flat I see 175-185.
Is your temp reading the pan ATF or the line going into the pan out of the torque converter?
I believe sensors monitor both.
 
Coolant temps are 187-190 at calm city driving and 195-200 at hills. Only once seen 210-213 when A/T oil overheated at 265.

Monitoring temps via torque app. It should be torque converter temp, no pan temp is available on third gens, as far as I know.
 
How big is the cooler?
Which cooler (OEM or aftermarket) is second in the chain?
How are your engine temperatures?

What speeds are you going when the temps get hot? At highway speeds, the torque converter unlocking and just the right amount of throttle really pumps heat into the fluid. The stock temp sensor (able to be read via OBD-II for '99-'02) is reading the HOTTEST the fluid gets, not the temp in most of the trans and/or pan. I'd try turning off OD and getting the trans to lock the converter in 3rd instead of unlocked in OD - that will REALLY help temps in those 'long slight climb' situations.

-Charlie
 
Can you verify the torque converter lock up actually works? Or are you always partially unlocked, sometimes more unlocked - sometimes almost locked?
Eventually the lock up clutch system friction material is worn away.
There are solenoids and valves in tranny valve body that control the TC lock up clutch. If these are not working correctly they can affect longevity of the clutch.
Had mine fail and since covered by 7/100,000 Toyota replaced the whole tranny with new TC.
 
How big is the cooler?
Which cooler (OEM or aftermarket) is second in the chain?
How are your engine temperatures?
Click to expand...
It's ~ 8"x9" and is second in the chain, after oem one. Coolant temps are 187-190 at calm driving and 195-200 at city traffic. Only once seen 210-213 when A/T oil overheated at 265

Can you verify the torque converter lock up actually works? Or are you always partially unlocked, sometimes more unlocked - sometimes almost locked?
Click to expand...
It does lock the trans in 3rd gear when I push O/D button. Don't know about your second question though. How to check that ?

Are you sure your rad fan is working properly?
Is the fan shroud on?
What are you driving?
Click to expand...
The fan clutch seems to me a bit on loose side when hot, but coolant temps stay within acceptable range. And yes, the shroud is on and no sticky brakes. It's 2000 4WD
 
Test fan clutch - though at highway speeds it should not matter as much but if its heating up when slowing down and waiting at lights with stop/go maybe it will climb fast.

Thought of adding a Fan - I have one yet only need it when towing thru stop/go (highest was 217 with no fan and 175 with it on so if makes a big diff).

So are you using both the OEM cooling/preheating thru the radiator And an aux cooler?

Is it clean (grass easily gets in there) between the AC condensor and radiator (especially at bottom where trans cooler is on OEM radiator)?

Guessing you have swapped the tired old fluid - best of luck.
 
Like jgue467 says, check the fan.

The engine has a thermostat and a large rad to help cooling so a poor fan might impact the trans more than the engine.

Is the trans cooler as close to the rad as possible?

I've attached a drawing showing how my lines are routed.
Mine cools well.

It looks like it was drawn by a 3 year old but no, it was done by me.
 

Attachments

  • my trans cooler lines.jpg
    my trans cooler lines.jpg
    40.6 KB · Views: 137
You should start your own thread.
It doesn't help the OP when you mega hijack.

Endlessblockades said:
What's a good way to test the rear brakes for sticking? Pull the wheels, jack it up and spin/listen? I have had the parking brake warning light come on intermittently for a year or so but it seemed mostly to occur when wet from crossings or during rain, so I thought is was just a switch/connection issue. Not to hijack this thread, but I have had heat issues with both the engine coolant and ATF on and off and for no obvious reason. They both run hot when airflow is low and especially when creeping off road. I do a lot of driving with the heater on and OD off to compensate. I have replaced the TStat twice (OEM both temp ranges), new fan shroud, Clutch & fan (Aisin), Radiator (Koyorad - no change), a new, bigger dedicated transmission cooler (replaced Tru-Cool in series), hoses + lines (OEM), internal transmission filter and burped the heck out of the system with each drain/fill. Been using an Ultragauge II programmed for ATF temps for about 4 years. My engine and AT temps are right in the perfect range over 60mph, even climbing mountains but can soar in sand or rocks. As a last resort, I am throwing a metal-blade flex fan at it shortly. Anyway, my front brakes are good - I do them myself, but I have no idea about the rear drums or parking brake. I'll start a new thread when the flex fan doesn't help, but will be following this one. Hopefully the OP gets this sorted. Good luck and thanks for the piggyback ride.....


Edit - I hadn't seen the posts after the brake question. RE: The drawing....I like it. Do you not have an AC condenser between the AT cooler and the radiator, tho?
Click to expand...
 
stunt2 said:
It's ~ 8"x9" and is second in the chain, after oem one. Coolant temps are 187-190 at calm driving and 195-200 at city traffic. Only once seen 210-213 when A/T oil overheated at 265
Click to expand...
Sounds like a bad fan clutch is hurting the issue, though you could also have an upside down thermostat. (5vz is mounted upside down from nearly every other engine, with the jiggle valve DOWN, not up)

When the cooling system is working 100%, you should never see above 200* on the engine temp, and rarely above 193*F or so. (those temps aren't damaging the engine, it just indicates something is wrong)

So, suspect fan clutch first (use an Aisin replacement), then thermostat, then we will go down the rabbit hole further.

Trans temp, as read by the ECU (reported via OBD-II for '99-'02) often can go above 200*, even with correct cooling with the right (errr... wrong?) conditions. It should stay below maybe 220*F with an cooler like you have though and well under 200* whenever the torque converter is locked (highway speeds).

-Charlie
 
Maybe this is not the correct way to check the fan clutch... So correct if needed..:) How I check mine is on startup.. When engine cold starting like sitting all night I start the engine... If the clutch is good it will roar with the engine for a 30 seconds to a min then disengage. You can tell by the engine sound when the fan clutch is on or not.. Well I can by the sounds most Toyota engines.

If it starts up engages good then disengages.. I say its good. Granted, I live in PA and We mostly never go much above 90s here in the Summer.

If it never engages on cold start its junk. I have not seen a lot of these go bad over the years. Unless they start leaking or something in my environment.

I would also make sure your radiator is clean of dirt and debris plus how old is your Radiator? Aluminum when it starts to oxidize will majorly loose its heat transfer abilities..Thus can't cool as well..





Another thought not mentioned is how clean is this fluid? Has the internal screen filter ever been changed and replaced with a new one. I seen transmission fluid start to get a lot warmer then those internal filters start to clog with debris. As the flow of fluid and pressure will start to drop, your internal fluid temperature will start climbing.

If I use a rig to tow or haul its complete exchange of filter and all fluid every 50K miles or less.

If not hauling I mostly change the filter and Fluid every 100K miles.

Some prefer the spill and fills which is also good. Some prefer to silicone the pans back on. Which was how the factory did them. However, in the later models of Toyota's they went back to using Gaskets on the transmission pans.
So I use an aftermarket feel pro gaskets on my 3rd gens. IF you use a gasket. You only have to hand tighten the pan bolts to snug. As you cant use the torque spec if you put a gasket in.. If it seeps you just go over the pan bolts again slightly tighter it will stop.

Hope this information helps. :-)
 
phattyduck said:
Sounds like a bad fan clutch is hurting the issue, though you could also have an upside down thermostat. (5vz is mounted upside down from nearly every other engine, with the jiggle valve DOWN, not up)

When the cooling system is working 100%, you should never see above 200* on the engine temp, and rarely above 193*F or so. (those temps aren't damaging the engine, it just indicates something is wrong)

So, suspect fan clutch first (use an Aisin replacement), then thermostat, then we will go down the rabbit hole further.

Trans temp, as read by the ECU (reported via OBD-II for '99-'02) often can go above 200*, even with correct cooling with the right (errr... wrong?) conditions. It should stay below maybe 220*F with an cooler like you have though and well under 200* whenever the torque converter is locked (highway speeds).

-Charlie
Click to expand...

I'm thinking about going that way too. Will change the fan clutch and rule it out.
As for thermostat, I've already swapped it myself for the new one and jiggle valve is at 6 o'clock :thumb3:
 
So, here are new reults : changed fan clutch with brand new original Aisin unit. Engine temps stays at 186-188 at heavy city traffic with a/c on. Trans temp howers around 175-180.
Gave it a pretty hard hit at 12-15 mile mountain road with steep windy roads. No load, but OD on and A/C on. Air temp was 86-96 outside (obd registered 120 degrees intake air temp though). So, the highest water temp seen was 194 and highest trans temp was 234.

Any thoughts ?
 
stunt2 said:
So, here are new reults : changed fan clutch with brand new original Aisin unit. Engine temps stays at 186-188 at heavy city traffic with a/c on. Trans temp howers around 175-180.
Gave it a pretty hard hit at 12-15 mile mountain road with steep windy roads. No load, but OD on and A/C on. Air temp was 86-96 outside (obd registered 120 degrees intake air temp though). So, the highest water temp seen was 194 and highest trans temp was 234.

Any thoughts ?
Click to expand...
How long was it at 234?
What was the average?
 
You must log in or register to reply here.

Members online

Total: 881 (members: 1, guests: 880)

Forum statistics

Threads
278,312
Messages
3,554,085
Members
248,016
Latest member
Advally Service

Share this page

Trending content

Back
Top