Neutral cruising at fast speeds = high heat

[Gurr]

I have tried searching for several phrases to find something related to this, yet I'm not finding much on this problem. I'm not sure if it's too big of a problem either, I would just like some reassurance.

Going on the freeway there are ups and downs, and of course with the downhills come the neutral cruising. However, I find that if I am going down a hill for about 30 seconds in neutral the temperature gauge has climbed about halfway in the white zone, which is the highest I've seen this truck go as it normally runs barely in the white at all. I just want to know if this is something to worry about.

Does this have to do with the fan being mechanical? Or maybe there is more air being sucked in at those high RPMs therefor cooling the truck more? I just wouldn't think it would affect the temperature as much as it does.

 

[2mbb]

When you shut your engine off the temperature should climb, because there is residual heat in the engine, and water is not flowing through the radiator to dissipate the heat. So you could be experiencing something like this when coasting in neutral. The engine speed drops to idle, the water pump slows and your radiator becomes less efficient at removing heat because there is less water running through it. Therefore the engine temperature increases. This would be exacerbated because going downhill implies you've just been going uphill, generating more heat in the engine.

Still, I would check to make sure the v-belt that drives the water pump is tight.

Also, if your normal temperature is "barely in the white", then your thermostat may not be working properly.

 

[RockDoc]

x2, sounds like "heat soak" working out of the metal bits when the coolant flow is low. Casting temp dropping, but coolant temp climbing.

 

[Elbert]

don't know why you shift to neutral on down-hill slope, but have you thought about the engine speed in neutral vs. when the transmission is engaged going down hill. The radiator fan speed is dependent on the engine rpm. In neutral (all things equal) you are essentially idling at whatever speed you are coasting downhill. I realze at speed that you have air flow across the radiator.

Why not drive the truck normally and do not shift into neutral on down-hill slope and see what it does? I assume all you are doing is shifting to neutral on down hill slope.

 

[slcfj62]

Coasting downhill in neutral probably won't increase your fuel economy any. And I'm with 2mbb, it sounds like your engine is not routinely coming up to temp. Your engine not coming up to temp will probably impact your fuel economy more in a negative way than coasting downhill in neutral will impact it in a positive way.

 

[mountainibis]

I've always heard that riding in neutral for a long time is bad for the throw-out bearing. Not sure if it's true or not, but I thought I'd put it out there.

 

[Gurr]

When you shut your engine off the temperature should climb, because there is residual heat in the engine, and water is not flowing through the radiator to dissipate the heat. So you could be experiencing something like this when coasting in neutral. The engine speed drops to idle, the water pump slows and your radiator becomes less efficient at removing heat because there is less water running through it. Therefore the engine temperature increases. This would be exacerbated because going downhill implies you've just been going uphill, generating more heat in the engine.

Still, I would check to make sure the v-belt that drives the water pump is tight.

Also, if your normal temperature is "barely in the white", then your thermostat may not be working properly.

Coasting downhill in neutral probably won't increase your fuel economy any. And I'm with 2mbb, it sounds like your engine is not routinely coming up to temp. Your engine not coming up to temp will probably impact your fuel economy more in a negative way than coasting downhill in neutral will impact it in a positive way.

don't know why you shift to neutral on down-hill slope, but have you thought about the engine speed in neutral vs. when the transmission is engaged going down hill. The radiator fan speed is dependent on the engine rpm. In neutral (all things equal) you are essentially idling at whatever speed you are coasting downhill. I realze at speed that you have air flow across the radiator.

Why not drive the truck normally and do not shift into neutral on down-hill slope and see what it does? I assume all you are doing is shifting to neutral on down hill slope.

It's a rebuilt motor with 3,000 miles, in that the belts were tightened more recently than that and the thermostat was replaced in the rebuild.

Also, I just figured that coasting downhill was the best option because of less RPMs and less wear and tear on the t-case just made more sense until I noticed this temperature fluctuation. Also the less resistance with the truck not in gear let me speed up without the gas pedal, so I got more speed with no gas. Although the clutch is also used more to put it in and out of gear on the freeway, and I knew that was a negative impact.

x2, sounds like "heat soak" working out of the metal bits when the coolant flow is low. Casting temp dropping, but coolant temp climbing.

That makes sense, equalizing the temperature between both while it's not flowing through the motor as fast as it was before. However, when I get off the freeway on an exit ramp, I don't think the temperature doesn't get as hot. I'll have to try it.

 

[slcfj62]

I've always heard that riding in neutral for a long time is bad for the throw-out bearing. Not sure if it's true or not, but I thought I'd put it out there.

The throw-out bearing only comes in to play when you push in the clutch. So if you were coasting with the clutch pushed in, that would have an impact on the throw-out bearing. But with the transmission in neutral and the clutch out, it shouldn't hurt anything.

 

[2mbb]

It's a rebuilt motor with 3,000 miles, in that the belts were tightened more recently than that and the thermostat was replaced in the rebuild.

Under stand that the engine is new. However, when operating properly the thermostat should control the temperature to one that does show within the white band on the temperature guage. Mine usually runs about 1/3 the way up the white band. While the thermostat might be new, if the o-ring gasket was not installed on top of the thermostat, it won't control flow properly. Most thermostats only have one gasket, this one has two and mechanics not intimate with Land Cruisers may not know to install it.

 

[Gurr]

I do remember there being 2 gaskets, the rubber o ring with the thermostat and the one that came in the rebuild kit for the housing. I do want to double check and open the housing, I don't think I have to replace the gasket because I opened it right?

and mechanics not intimate with Land Cruisers may not know to install it.

...I did not know you had THAT kind of relationship with your cruiser 2mbb.

 

[Elbert]

Nothing gained by letting truck run down-hill in neutral, in fact most "driving manuals" will advise not to do this for safety reasons.

My advice...drive truck nomrally... problem will go away.

 

[TheJackRabbit]

I coast on a few grades regularly traveled. One is a mile long and steep. My 60 gets up to 85 MPH which would be kind of challenging if I were in gear. The temp guage cools down. Then I coast the next uphill slowing to about 40 and then down the next and up the next and down the last one. It is about four miles all together. Cannot say how it impacts mileage. Normal cruising on level ground at 65 MPH means about 2800-2900 on the tach with 4:56 gearing, H55 tranny and 33 inch wheels.

At least it is a little quieter.

 

[Gurr]

Well, I learned something new today.

Thanks for the help guys!

 

[jb welda]

i cant believe people are standing around acting like coasting, regularly especially, down hills in neutral is even some kind of acceptable driving technique. it is not. it is out of control and in fact is probably illegal in most states (it is for sure in california). and it doesnt do anything good for the vehicle and in fact causes it to be much more likely you are exceeding the capacity of your brakes not to mention compromising your ability to swerve the vehicle to avoid a sudden obstacle. ranks right up there with talking on the phone, no, make that texting like a teenager, while at the wheel.

and now i notice you live in santa cruz and are probably talking about that hwy over the hill into silicone valley...or along skyline drive. thats suicide, which probably wouldnt be so bad, but youre liable to take out innocent people with you. so please stop.

by the way, presumably that will cure your overheating problem so its a win-win.

one love
jah bill

 

[Gurr]

i cant believe people are standing around acting like coasting, regularly especially, down hills in neutral is even some kind of acceptable driving technique. it is not. it is out of control and in fact is probably illegal in most states (it is for sure in california). and it doesnt do anything good for the vehicle and in fact causes it to be much more likely you are exceeding the capacity of your brakes not to mention compromising your ability to swerve the vehicle to avoid a sudden obstacle. ranks right up there with talking on the phone, no, make that texting like a teenager, while at the wheel.

and now i notice you live in santa cruz and are probably talking about that hwy over the hill into silicone valley...or along skyline drive. thats suicide, which probably wouldnt be so bad, but youre liable to take out innocent people with you. so please stop.

by the way, presumably that will cure your overheating problem so its a win-win.

one love
jah bill

wtf? What's wrong with you? I am at a loss of words for how idiotic you sound right now. Also, If you're going to be so disrespectful, don't tag on some Rastafarian s*** thinking it's all alright...

I already figured the heating up was caused by the neutral cruising if you couldn't tell from the title of the thread.

 

[Matt60]

yo' bumbaclot- what kind of gauge do you use? i prefer the mechanical one. but thats me iandi as my temps always run around 180.. that little gasket if not properly installed ontop of the thermostat could get pushed into the radiator and cause some slowing of circulation... salaam alaikum

 

[phishincruisin]

i cant believe people are standing around acting like coasting, regularly especially, down hills in neutral is even some kind of acceptable driving technique. it is not. it is out of control and in fact is probably illegal in most states (it is for sure in california). and it doesnt do anything good for the vehicle and in fact causes it to be much more likely you are exceeding the capacity of your brakes not to mention compromising your ability to swerve the vehicle to avoid a sudden obstacle. ranks right up there with talking on the phone, no, make that texting like a teenager, while at the wheel.

and now i notice you live in santa cruz and are probably talking about that hwy over the hill into silicone valley...or along skyline drive. thats suicide, which probably wouldnt be so bad, but youre liable to take out innocent people with you. so please stop.

by the way, presumably that will cure your overheating problem so its a win-win.

one love
jah bill

wtf? What's wrong with you? I am at a loss of words for how idiotic you sound right now. Also, If you're going to be so disrespectful, don't tag on some Rastafarian s*** thinking it's all alright...

I already figured the heating up was caused by the neutral cruising if you couldn't tell from the title of the thread.

Sorry, but I'm going to have to agree with those saying that coasting downhill is dangerous. It doesn't net any better fuel economy. It is exactly why I don't enjoy driving automatics. You just don't have the speed control that you do using the engine with a manual transmission, so if a deer, child, or another vehicle happen to run out in front of you all of a sudden, your stopping abilities are much less since you don't have the braking power from the engine.
Also, JB welda always signs, or almost always, signs his posts one love, jah bill. I don't see how the hostility towards jb welda is necessary here. This is mud, not pirate. He wasn't being disrespectful at all, but rather informing you about the hazards of neutral cruising. He's just trying to protect you, those in your vehicle, and those on the road with you
Your transfer case and transmission are still spinning while you neutral coast, so it isn't really saving those at all. And, if you're really good you can shift in and out of gear without your clutch!

 

[2mbb]

coasting downhill in neutral is not legal in California: V.C. Section 21710 - Coasting Prohibited

 

[Gurr]

Well, don't I have my foot in my mouth.:whoops: Sorry to all, especially JB Welda. Thanks for calling me out on that one. I'll be more careful with my words next time. I have never heard of that law before and the first time I read that post, it came off as offensive to me. Now that I've read it again on a different day, I don't really see what I saw a few days ago.

Once again I am sorry about my interpretation of that post.

 

[Butt Ugly Chuck]

I don't put it in neutral but I regularly push the clutch in and coast long grades around here, letting the clutch out now and then to keep speed in check. I'm always 'in gear' and the way I do it anyhow, is no more dangerous than driving up the hill under power at the speed limit. I'm selective where and under what conditions I'll coast and I suppose that's part of the difference. The rest of the equation probably comes from years of surviving thousands of miles of mountainous twisty road every year and taking "hurry" out of my driving style long ago.

Now with that long-winded qualification out of the way so I hopefully don't get scolded for being a reckless menace to society .....
I don't experience any heating while coasting and in fact the temps will come down if I've raised them cresting the hill.

2mbb is probably already on to your issue suspecting the thermostat, and that the spike in temp you see is maybe the rare occasion your rig reaches normal operating range. Do your temps come up at idle while NOT coasting down a hill? If you're genuinely observing HIGH temps, maybe your water pump deserves some investigation too.

Butt