Possible Cause of Cooling issues

[SUMOTOY]

Guys:
I've been reviewing a lot of threads regarding 80 cooling issues over the last couple years. The reason being, I'm convinced we may need another data point. While trying to get TRU on board regarding VC operation, humping and failure mode, another thought came to mind on overheat. What if the trans fluid is getting really hot, possibly from a sticking VC in our HF2AV trucks?

What surprises me is an aboslute lack of any problems with VC operation or replacement. It's pretty well documented, that when they fail, they generate a massive amount of heat, quite possibly causing an undue stress on the radiator and condenser (pre heat soak). It would also explain how 300f could be seen at the fan VC.

Right now just some food for thought. I do remember engaging in a thread several months ago regarding trans oil warning light after a guy did a prorally run in the woods. Could it be that we are addressing the result and not the problem? Could it be RT story about when he rolled his truck down a hill with the front Driveshaft removed and got lockup, he had a locked up VC already?

VC failure is quite common in the Jeeps. When it fails, it usually fails locked up (or prematurely locks up with overheated/bad fluid) It's also well documented that some VC warrantees are void if tire circumference measures are not identical. Even tire wear differences can cause some preloading of VC's. Not trying to create panic, I've just seen zero mention of VC failures here. Knowing how diffs work in extreme environments, I just don't believe that.

I also believe they could have failed, and our cooling systems just suck up the heat, or not. I'll work on a drive test for this, but in the meantime, make sure your tires are inflated to the same psi, are of the same size and brand, and think about your spare tire. If running a mismatched spare, I'd be real tempted to run the center diff locked.

Scott Justusson
QSHIPQ Performance Tuning
Chicago

 

[cruiserdan]

The VC in the 80 is not in the "transmission loop" and would not directly heat the transmission, only the transfer case.

 

[sleeoffroad]

VC failures are pretty uncommon. I think in 5 years we have seen two at the shop. Both cases it failed locked and the truck was just about undrivable due to drivetrain bind-up.

 

[cruiserdan]

Landtoy (Kurt) also, thats about it. So, 3 out of?

 

[SUMOTOY]

My first question would be, "define failure". I believe that doesn't necessarily mean fully locked up, only dragging. I might define 'a trans issue' if trans temps get high, or a VC failure if it causes the trans temps to get high. A good concurrent measure with cooling systems might be a trans cooler temp measure for those with the means.

I had 200-210 at the cooler inlet with 190+ at the outlet of the aux trans cooler at idle in my condenser temp testing yesterday.

That's a big heat sink in front of the condenser boys. Add the standard radiator cooler in the tank, (which by my measure has an outlet temp of 210F) sounds like a lot of heat. Run in a hot environment or high load situation, many have 'new' cooling systems, but heat problems under those conditions. That trans cooler could very well be sucking up a lot of engine cooling capacity.

My focus may not be so much on the VC if they prove bulletproof, but more directly targetted at the transmission temps as a possible way to maximize radiator and condenser efficiency.

I'm not even to Part II of my fan mod posts, and I'm already seeing more work...

SJ

 

[SUMOTOY]

The VC in the 80 is not in the "transmission loop" and would not directly heat the transmission, only the transfer case.

Agree it's not in the direct *fluid* loop, but it certainly would heat the transmission, since it's directly attached. FSM shows 302-on 248-off for 'transmission' temp overheat light. It also states
"The A/T fluid may become extremely (hot) when the temp is under an extreme load as when driving on sand or climbing uphill"

The driving on sand part sounds like extended wheel slip overheat to me. Transfer case a heat sink.

Go back to the radiator, a 248-300F A/T fluid temp going into the radiator is considered normal. so we could have a 300F trans cooler heating up th rad, say 290 now at the trans cooler in front of the condenser and rad, a 186F condenser, and a radiator in overheat mode. All this with technically 'proper' operation of all components - no lights.

I could see a 100 degree day causing some undue stress on the best of fans.

Scott Justusson

 

[cruiserdan]

I would like to figure out a suitable way to take the transmission cooler in the radiator completely out of the loop so that the radiator is only dealing with engine coolant.

I guess it's time to convert to a manual transmission......

 

[SUMOTOY]

I would like to figure out a suitable way to take the transmission cooler in the radiator completely out of the loop so that the radiator is only dealing with engine coolant.

I guess it's time to convert to a manual transmission......

Might be the easiest thing in the long run, if we can't get some of these temps in line. The accepted practice of trans cooling is to keep the trans fluid circulating thru the radiator, so that the trans fluid gets up to operating temp quicker. More important in cold climes (but high torque on cold fluid would include a supercharger in warmer climes), but *getting to* temp is part of the in radiator tank function. A more viable solution might be to move the aux cooler to another location, like under the truck somewhere with a scoop or fan. This would free up the condensor, and give another location for a additonal aux fan if one so desires.

SJ

 

[Peyoteboy]

Interesting conversation that may just apply to my current problem. I have 223k miles on my truck and dont recall it ever being replaced.

When you mention the "aux cooler" is this the tran cooler in front of the condenser? At work now so cant look at the service manual, and this is an area i have never worked on myself.

I am thinking about the truck and cant really think of a place to put it though. Anyone have any idea where a legitimate place to put it would be?

 

[SUMOTOY]

Interesting conversation that may just apply to my current problem. I have 223k miles on my truck and dont recall it ever being replaced.

When you mention the "aux cooler" is this the tran cooler in front of the condenser? At work now so cant look at the service manual, and this is an area i have never worked on myself.

I am thinking about the truck and cant really think of a place to put it though. Anyone have any idea where a legitimate place to put it would be?

One of the first tools I'd recommend to *anyone* with an 80, is one of the Raytek (or equivelent) IR temp guns. Point and shoot laser, mail order around 100bucks. Even the snap-on truck one was 130. Very high usefulness factor for low bannana mechanics. And you can check temps of things you never thought of before, in the house, office or truck.

Especially for your heating problems, quantifying/isolating that would be key to getting help. Sounds like plenty of high bannana guys didn't do very well so far.

HTH

Scott Justusson

 

[Darwood]

The driving on sand part sounds like extended wheel slip overheat to me. Transfer case a heat sink.

I'm pretty sure the driving on sand overheating is referring to the torque converter heating up. 80's don't generally spin their tires in the sand but they do use the torque converter. Same with up hill; both tend to be unlocked torque converter moments.

 

[SUMOTOY]

I'm pretty sure the driving on sand overheating is referring to the torque converter heating up. 80's don't generally spin their tires in the sand but they do use the torque converter. Same with up hill; both tend to be unlocked torque converter moments.

Could be, I could see that in uphill situations, but not so convinced in sand situations. I would think with hi>low cf conditions (or specifically varying hi>low cf conditions) you have a LOT of VC activation, causing a lot of heat. Sand is varying cf with massive torque loadings of axles at tractive moments. And massive heat generation right at the very back of the transmission where fluid circulation is minimal at best. Certainly the reference to sand makes me think of VC more than torque converter lockup. Rock crawling, offroading, a lot of other unlocked torque converter moments seem to be lacking from the same specific address.

Might be interesting to see if that's common to the non VC HF2A Transfer.

Scott Justusson

 

[Darwood]

Once you drive an 80 in sand you will be convinced. The tires don't spin on these fat pigs in the sand, just the torque converter. (forced induction guys need not respond )

 

[clownmidget]

(forced induction guys need not respond )

oh I was so READY to jump into this... I've seen 37's spin


I'm still not sure what gets the AT temps to climb so dramatically under the conditions id'd above. Incidentally, I think Scott is referring to my experiences - eg, climbing South Park Canyon in snow - and both times I've gotten my AT temp light to come on I was not CDL locked, just open and in high. I also have what I imagine must be a little better AT cooler (Mazda RX7 turbo oil cooler) mounted below the intercooler and was still able to get the AT temp light to come on. Both times were in DV so I generally just stay away and nothing bad happens.

 

[cruiserdan]

I think maybe a big fat cooler under the body in the open area below the driver's seat. Plumb it in in place of the one in front of the radiator and put an electric fan on it.

 

[Grench]

That or a big fat cooler behind the pasenger's seat.

Both feet on brake.
Shift to Neutral.
Grab beverage.
Drink beverage.
Finish beverage.
Shift to L1.
Move right foot to gas.
Go.

Trying to be funny, isn't probably working. Just let the trany cool down if possible or convenient before moving on. Don't put it in park on a hill though or you'll be sorry...

Which begs a question about opperating limits. What are the maximum angles that the engine in an FZJ80 can run in continuously before being starved for oil?

 

[landtank]

the tranny temp sensor, from what I can remember, is on the return side of the cooling lines and the fluid passes through the rad and then onto the aux cooler and then back to the tranny. I'm not sure how you were able to get the ATF temp light on without seeing the same in your engine temp gauge.

As for the VC in the t-case, I can't beleive it adds any amount of heat to the engine temps. Landtoy actually diagnosed his VC problem to the thing locking up when it got hot. Once that thing locks up no more heat is made, right.

 

[Darwood]

oh I was so READY to jump into this... I've seen 37's spin

I had to cut you guys off at the pass ;p

 

[SUMOTOY]

the tranny temp sensor, from what I can remember, is on the return side of the cooling lines and the fluid passes through the rad and then onto the aux cooler and then back to the tranny. I'm not sure how you were able to get the ATF temp light on without seeing the same in your engine temp gauge.

Bad exchange efficiency in cold weather? I personally don't think that trans cooler is very efficient. I could certainly see overheating the trans without overheating the radiator in snow. BTDT. Add in Clownmidgets VC working overtime, a lot of heat in that trans.

As for the VC in the t-case, I can't beleive it adds any amount of heat to the engine temps. Landtoy actually diagnosed his VC problem to the thing locking up when it got hot. Once that thing locks up no more heat is made, right.

I think it adds a bunch of heat to the back of the trans, as it's attached to it. It runs gear oil, so it will run hotter without 'overheat' of the transfer, but it certainly is a fine heat soaker for the back of the trans.

Remember too, VC's can totally lock up, or they can preload sooner than designed, or stick a bit, in which case, you'd have a lot of heat, without necessarily locking up - er, permanent humping (insert joke). Even fully locked up VC, you have those plates moving or attempting to move causing heat.

This toyota transmission runs hot, and can be too hot many times. If we move that thinking over to the radiator and condenser, neither trans cooler is doing good things for engine heat.

Moving the aux cooler to under the truck seems to be a good solution to relieve our condenser, radiator and underhood temps a bit. Serious offroad guys can cool it with a fan, those less inclined to bend scoops might do both. I don't see this replacement of the aux cooler happening without a fan.

I would also think putting a scoop right near the front axle pivot arms, might add a level of protection to it.

Hood vents first, for me, then I'll go after the trans cooler.

Scott Justusson
94 Supercharged

 

[SUMOTOY]

I had to cut you guys off at the pass ;p

Me too I guess. I'm still not convinced that sand is a torque converter thing, what's the difference between high drag sand, and me and CDan dragging at a stoplight?

Torque converter lockup in 3 or 4 is activated by the switch, I can't see any shifting causing torque converter overheat exclusive to sand, and the overdrive brake is only active in 4th

I'm sure I'm missing something obvious.

Scott Justusson
94 FZJ80 Supercharged, spins tires often...