Coolant temp while towing.

[JoshuaHufford]

07 V8, towing a camper that weights about 3500lbs. I always use the Torque app while towing to keep an eye on the trans and coolant temps.

While going up a decent grade about a half mile long, trans had to downshift to 3rd to maintain 60mph. By the time I got to the top the coolant temp had hit 220F. Is this normal or anything to be worried about?

The ambient temp was about 85F, I had the AC on. Up to this point I had been driving for about 90 minutes averaging between 50-60mph, on a windy, hilly road, but most of the hills are small until this one. The temps had been between 190-200F for most of the drive.

I live in Missouri so this is about the as tough as towing gets around here, but at some point we would like to take a trip out west with the camper, obviously the air will be thinner and the mountains will be a lot steeper and longer, don't want to run into trouble!

 

[MT Runner]

Your engine coolant hit 220? Or your trans temp hit 220?

I tow a similar weight with my V6 here in Montana, so I see a lot of pretty good size hills. Elevation is between 3,400 and 6,000ft pretty much anywhere I go.

My engine coolant is between 198-204 no matter what I’m doing. Driving around town without a trailer or towing my camper up a hill in the summer at 60mph.

Trans temp can vary greatly. When I’m towing the camper on flat ground on the interstate and cruising in 4th gear, trans temp is usually around 160-170.
Its pretty common for me to get around 200 on a hill if it’s decent size, but it drops right back down as soon as I’m over the hill.

The highest temp I’ve ever seen on my scangauge for the trans was 232, it was a long, gradual hill, with a headwind and I had been towing for over 3 hours at that point. It cooled back down once I finally hit level ground again.

I think if you hit that 220-230 range going up a hill but then it drops back down to well under 200 under your normal driving conditions, you should be fine.
220 isn’t an extreme temp necessarily, but you definitely wouldn’t want to tow a long distance at that temp. It’s getting on the warm side for sure, but nothing I would stress too much about if it’s not at that temp for the majority of your trip.

I’m not positive on this but I believe I’ve read that the “dummy” light for the trans will kick on at 265 degrees, but by the time that does kick on, that’s way too hot.

 

[MT Runner]

One other question, are you towing in 4th or 5th gear?

190-200 seems a bit high for towing on flat ground. If you tow in 5th the trans is going to be constantly searching for the right gear even on the most minor of hills. Try towing in 4th for a little while next time and see where your trans temp is.

 

[nevada]

07 V8, towing a camper that weights about 3500lbs. I always use the Torque app while towing to keep an eye on the trans and coolant temps.

While going up a decent grade about a half mile long, trans had to downshift to 3rd to maintain 60mph. By the time I got to the top the coolant temp had hit 220F. Is this normal or anything to be worried about?

The ambient temp was about 85F, I had the AC on. Up to this point I had been driving for about 90 minutes averaging between 50-60mph, on a windy, hilly road, but most of the hills are small until this one. The temps had been between 190-200F for most of the drive.

I live in Missouri so this is about the as tough as towing gets around here, but at some point we would like to take a trip out west with the camper, obviously the air will be thinner and the mountains will be a lot steeper and longer, don't want to run into trouble!

220 is still considered safe. but, I think its higher than it should be in that scenario.


how is the condenser? full of bugs and dirt? same with the radiator. I have seen them get very dirty directly behind the condenser, where its difficult clean.


also, how is the fan clutch. at that temp, it should have been engage, and likely you could have heard the roar. especially in 3rd at 60mph. if the clutch is getting weak, and not flowing quite enough air at heave loads, you could build some excess heat.

 

[RonJR]

A few miles at 220 or even 240 degrees isn't going to hurt a thing. The rate of breakdown of transmission fluid doubles roughly every 20 degrees F above 180 degrees. So, if transmission fluid lasts 100,000 miles at 180 degrees, it will last 50,000 miles at 200 degrees, 25,000 at 220, etc. If you extrapolate this out to 300 degrees, you will find the lifetime is about 1000 miles. Do an internet search on transmission fluid lifetime vs. temperature and you will see multiple web pages showing this relationship.

Now, you don't run at 220-240 degrees constantly when towing, just for short periods. So, a more useful way of looking at this is, every mile at 200 degrees is the same as 2 miles at 180. Every mile at 220 degrees is the same as 4 miles at 180. Every mile at 240 degrees is the same as 8 miles at 180.

So, if you pull a long, 7 mile grade in the Rockies with your transmission at a constant 240 degrees, you've just subtracted 56 (7x8) miles from your transmission fluid life. If you did that only once it would mean that, instead of changing fluid at 100K miles, you need to change it at 99,944 miles instead. Not a big change.

However, you'll generally run above 180 degrees fairly often when towing, which is why Toyota recommends a 50,000 mile fluid change interval for vehicles that regularly tow. It's kind of a simple rule of thumb that takes most of the above into account for the "average" person who uses their 4runner for towing.

I pulled our 3500lb Rpod up into the Snowy Range west of Laramie, Wyoming, last week. That's a 7 mile 8% grade. Outside air temperature was around 70 deg. I was running about 40 mph in 3rd and 2nd. Torque converter temps hit 240, and pan temps ran around 228. Pan temp is probably most important, because that's where the fluid spends most of it's time.

 

[MT Runner]

A few miles at 220 or even 240 degrees isn't going to hurt a thing. The rate of breakdown of transmission fluid doubles roughly every 20 degrees F above 180 degrees. So, if transmission fluid lasts 100,000 miles at 180 degrees, it will last 50,000 miles at 200 degrees, 25,000 at 220, etc. If you extrapolate this out to 300 degrees, you will find the lifetime is about 1000 miles. Do an internet search on transmission fluid lifetime vs. temperature and you will see multiple web pages showing this relationship.

Now, you don't run at 220-240 degrees constantly when towing, just for short periods. So, a more useful way of looking at this is, every mile at 200 degrees is the same as 2 miles at 180. Every mile at 220 degrees is the same as 4 miles at 180. Every mile at 240 degrees is the same as 8 miles at 180.

So, if you pull a long, 7 mile grade in the Rockies with your transmission at a constant 240 degrees, you've just subtracted 56 (7x8) miles from your transmission fluid life. If you did that only once it would mean that, instead of changing fluid at 100K miles, you need to change it at 99,944 miles instead. Not a big change.

However, you'll generally run above 180 degrees fairly often when towing, which is why Toyota recommends a 50,000 mile fluid change interval for vehicles that regularly tow. It's kind of a simple rule of thumb that takes most of the above into account for the "average" person who uses their 4runner for towing.

I pulled our 3500lb Rpod up into the Snowy Range west of Laramie, Wyoming, last week. That's a 7 mile 8% grade. Outside air temperature was around 70 deg. I was running about 40 mph in 3rd and 2nd. Torque converter temps hit 240, and pan temps ran around 228. Pan temp is probably most important, because that's where the fluid spends most of it's time.

A little off subject, but what RPod do you have? We just sold our old camper this spring and got a 176T this summer. Only got to use it a few times, but really like it so far.

 

[RonJR]

A little off subject, but what RPod do you have? We just sold our old camper this spring and got a 176T this summer. Only got to use it a few times, but really like it so far.

We have a 179. Just got it last spring, and we like it a lot. We call it our "Happy houR Pod".

 

[rdruss]

I would guess your coolant temp went up because trans temp went up when downshifted to 3rd and operated there for awhile. If trans is cooled by engine coolant, then for sure, if not and air-to-oil cooler, then is cooler in radiator air stream? If so, then the extra heat rejected from it into the rad airstream could be the cause.

 

[JoshuaHufford]

I'm talking about engine coolant here, not transmission fluid temp.

The trans temp went up as well but nothing that I thought was dangerous.

I had been running in 4th gear the whole trip, if I'm on level ground with the camper I can run in 5th gear, but any kind of hills I loose too much speed so I usually always put it in 4th when towing the camper.

I'll check for bugs, other obstructions etc. I've heard the fan clutch engage when stopped for a while in hot weather, but I didn't hear it engage this time, but I would think it would be hard to hear at 60mph, but maybe not? Maybe replacing the fan clutch as a precaution would be a good idea.

 

[nevada]

I'm talking about engine coolant here, not transmission fluid temp.

The trans temp went up as well but nothing that I thought was dangerous.

I had been running in 4th gear the whole trip, if I'm on level ground with the camper I can run in 5th gear, but any kind of hills I loose too much speed so I usually always put it in 4th when towing the camper.

I'll check for bugs, other obstructions etc. I've heard the fan clutch engage when stopped for a while in hot weather, but I didn't hear it engage this time, but I would think it would be hard to hear at 60mph, but maybe not? Maybe replacing the fan clutch as a precaution would be a good idea.

the fan in my 06 isn't nearly as easy to hear as in my 85.


however... that might be because it has never came on lol. I can for sure hear it even at 60. and with a worn engine pushing 37's, its working HARD. lol

 

[UrbanRunner651]

You should be fine. Most coolants don't start to boil until around +250.