Neutral cruising at fast speeds = high heat

[60wag]

Since the engine was rebuilt recently, there is the possibility that some bit of crud (gasket scraping) is floating around in the cooling system and getting stuck in the tstat. I would expect it to run cold but it might be worth opening the tstat housing to have a look.

I too am wondering why you would put it in neutral. I see no gains mechanical or economic.

 

[Gurr]

It just made sense to me. As I said earlier, less resistance, less gas, less time that the motor and the t-case were in gear seemed to give longevity to the whole setup. However, now I see that is DEFINITELY not the case. If it saves gas than it is a very small amount, revving the motor up to the right RPMs to put it in gear is more likely to be negative as well. Plus the clutch is being used much more, unless I do what was mentioned by Phishincruisin and just do non-clutch shifting perfectly all the time, which I can't.

I am also just using the stock gauges. Plus in the rebuild I replaced the insulator between the manifolds with a solid one, and that keeps the motor running cooler, but I guess it wouldn't be running as cold as my cruiser seems to be running?

 

[Elbert]

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

holding the clutch in or shifting to neutral is basically the same thing.... "coasting".

You guys can do what you want, but I don't understand why anyone wants to coast down the hills (either in neutral or with the clutch pedal depressed).

Its not a safe practice...no matter what method you choose.

IF you get to "coasting" too fast one day and either release the clutch pedal at the high rate of speed or you can't get the truck back in gear....its not going to be a good thing.

What is the purpose of "Coasting"? Do you do this towing too?

 

[Butt Ugly Chuck]

I knew I should have laid low instead of opening this can of worms!

holding the clutch in or shifting to neutral is basically the same thing.... "coasting".

Yup

You guys can do what you want, but I don't understand why anyone wants to coast down the hills (either in neutral or with the clutch pedal depressed).

They're long freekin hills. A 60 is MUCH quieter coasting. Gravity is cheaper than gas

Its not a safe practice...no matter what method you choose.

I think you'd come around if you rode with me and realize there are places and conditions under which this can be done without being an idiot. There is absolutely nothing 'white knuckle' about the way I drive on the road, including going downhill. In fact most folks with auto trans these days don't know enough to realize if they don't shift out of OD during long down grades they're essentially coasting and depending entirely on their brakes. I can smell their brakes way too often. THAT is far more dangerous than what I do. Unlike vast majority of drivers on the same roads, I hardly use my brakes because I'm scrubbing speed as needed with engine compression well before things get 'hairy'.

IF you get to "coasting" too fast one day and either release the clutch pedal at the high rate of speed or you can't get the truck back in gear....its not going to be a good thing.

Agreed. But the maneuver required to avoid coasting too fast is neither precise or high risk, especially if you're careful under which conditions you choose to coast.[/QUOTE]

What is the purpose of "Coasting"?

Covered^

Do you do this towing too?

Yes but less often, with a light trailer, and under FAR choosier circumstances.

 

[Elbert]

Ok... enough about the fine art of coasting...

I promise to enforce the "don't ask ...don't tell" policy.

 

[Butt Ugly Chuck]

Ok... enough about the fine art of coasting...

I promise to enforce the "don't ask ...don't tell" policy.

Butt

 

[Josie'sLandCruiser]

Hi All:

Any thoughts about the clutch fan going out on the rig in question?

Regards,

Alan

 

[Gurr]

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

I'm glad I'm not all alone in this technique.

Hi All:

Any thoughts about the clutch fan going out on the rig in question?

Regards,

Alan

I've just looked up a few threads on the fan clutch, I'll check it tomorrow morning to see if it needs a refurbishing.

 

[Spike Strip]

My thoughts are possibly the fan clutch, too... But if you're coasting, that should move enough air to cool the rad, but who knows...

Easy to test the fan clutch though -- Warm up the rig to temp i.e. "hot", and using a rolled up newspaper, try and stop the fan when it's spinning... If you can slow the fan down or stop it significantly, it's probably bad. If it's locked up and can't be slowed, it's good.

Do I need to mention, don't use your hand for this ?!?

 

[Gurr]

Sounds good. I spun it before I started my truck this morning and I could spin it with force, but it wouldn't spin freely. However, I forgot to try at running temperature because of distractions involving a gas shortage...

 

[Gurr]

I guess the fan clutch needs some attention as the newspaper only took a few good whacks before it stopped the fan. I'm still going to open up that thermostat housing and check it out over the weekend.

 

[Spike Strip]

Yup - fix or replace fan clutch.

 

[satchel]

You didn't mention whether you tested the fan clutch at operating temps or not. I'm assuming it was at op temp, but just wanted to double check. It must be for this to work.

 

[Gurr]

Oh, yea it was at operating temp. It was warmed up and driven for about 20 minutes.

 

[fliphkd778]

I have some new data on the highway heat soak from my recent trip. Here is a graph illustrating the speed and temp relationship relative to time. Truck specs are: rebuilt 2f, new water pump, tested thermostat, pressure tested system, new 7000cst fan clutch fluid, older cst radiator of unknown age, and no a/c. Terrain was very flat at sea level. Speeds are via gps, and temperature through a new Equus electrical temp gauge probed in the original sender's location.
-Truck runs fine at 185 in 110* heat index and heavy traffic.
-I stopped for gas twice, being where the temps spike and speed dips.
-Notice how the truck runs at the thermostat's 185 temperature initially, then seems to get overrun as time goes by.

Any insight or interpretation is appreciated.