Highway and running hot

[Cruiserhead05]

Ok i've been batteling a heat issue for awhile now. i took it in and had it looked at. they said it needed a new fan clutch, did that and well it help the 40 stay cool while sitting but on the highway it stills run rediculously hot. what could i do. i have to take it on a 6 hr trip here in a few days. could it be bad water/anitfreeze mix, a faulty radiator cap, thermostat, water pump. the guy at the shop said that something might be blocking the radiator. first thing that comes to mind is a huge winch and fog lights.? any thoughts

 

[IDave]

Well, if your water jacket has as much crud in it as mine did, that would be a possibility.

Yes, it could also be the thermostat, and an easy way to check that would be to pull it out and the problem should go away immediately.

I suppose it could be the water pump, but you ought to be able to hear or see something going on pretty easily with that.

 

[Cruiserhead05]

how do you clean and get to the water jacket. where is it located
Also, is it bad to run it with a thermostat at all

 

[Mike S]

Do you have an overflow bottle? If not, install one. New rad cap? If not, get one. Still hot? Easy enough to pull the radiator, take it to a shop and have it rodded out and pressure tested. When re-installing, add new upper and lower hoses. Refill with OEM collant. If this does not fix it, you can rule out the radiator and hoses and focus on water pump and in-engine coolant circulation.

I suspect that the treatment above will fix the problem, tho'.

 

[IDave]

Check out my waterjacket thread that's a couple down right now on the list. You pull that plug, and then you flush, unless it's crudded up, in which case you gotta dig.

Running without a thermostat just means it will take a bit longer for the engine to warm up, which won't be a problem really this time of year, unless you're on the wrong side of the planet. Far better than running it too hot, because the thermostat won't open. Then the coolant just stays in the engine and doesn't circulate through the radiator.

I suppose your radiator could be filled with crud, too, in which case you need to try flushing it out.

 

[Cruiserhead05]

ok. i will start on all those. the radiator is only two years old though. i would imagine it is stilll good. i do recall someome telling me a it had a 90/10 anitfreeze/water mix. i think i may start be doing this over, then a rad cap, then take the winch off, if known of those then i will check the thermostat.

 

[CruisinGA]

If I had to get it goin for a highway trip immediatly, I would get a bottle or two of coolant flush (acidic stuff that eats crud,) and run that through, then refill with proper 50-50 mixture, personally I wouldn't pay for Toyota coolant in a 40. See where you are then, and if there are still issues, pull the thermostat. If it fixes the problem, you know what to replace. Just run down to Napa and get a new one.
You can also feel your radiator for cool spots, if you have a fancy infrared thermo this is easy, or be old school and use your hand, it should be about the same temp over the entire surface area, if not there is a blockage.

 

[mancinator]

pure water is supposed to be the best disipator of heat in the coolign system, however coolant/antifreeze is necassary to help prevent corrossion and of course antifreesing....seen as that isnt a worry this time of year you may want to try a differnet mixture. i think i read 25%coolant 75 water will give you the best coolign along with the necassary protection from corrosion and cold weather. that is for my big block thouhg.....so take it for what its worth.
there are also products out there that are suppsedly miraculous in their function...water wetter comes to mind but i dont have any experiance with it (yet) as i am still trying to track down a local store that sells it.

 

[Landpimp]

from what I have gathered over the years, talking the t-stat out of a F/2f/3fe will not make it run cooler it will make it run hoter on some of the cylinders as it will not get enough water(or it goes thru too fast) to cool it properly.

IMOP , new t-stat(both gaskets), new cap, flush rad. if thats not it pull rad and get roded out or get a new one.

water cools better than anti freeze, so unless you added more than 1/2 anti freeze thats not your problem.

winch and lights are not the problem.

oh and untill you get it figured out, don't bother adding anti freeze, as you might have to dump it again. water alone is fine.

its not the water pump, they give some warning, like leaking or making noise or wobbleing.

John H

Check out my waterjacket thread that's a couple down right now on the list. You pull that plug, and then you flush, unless it's crudded up, in which case you gotta dig.

Running without a thermostat just means it will take a bit longer for the engine to warm up, which won't be a problem really this time of year, unless you're on the wrong side of the planet. Far better than running it too hot, because the thermostat won't open. Then the coolant just stays in the engine and doesn't circulate through the radiator.

I suppose your radiator could be filled with crud, too, in which case you need to try flushing it out.

 

[IDave]

That's an interesting observation, John. Something in my (somewhat limited) physics background tells me that the rate of coolant flow through the radiator would not affect the cooling capacity: same number of calories removed from a fixed total volume of fluid over the same period of time. But I can imagine that totally removing the thermostat would possibly alter the current vectors in the thermostat housing causing coolant to bypass the radiator. And that might then reduce the cooling capacity.

It makes me wonder if the reason that someone put this threaded cap in my original thermostat housing and drilled a hole in it had something to do with directing flow. Any ideas? (I'm going to post this question again in the forum, so as not to hijack).

 

[Landpimp]

I think the coolent just moves thru too fast and can not pick up the heat of the motor....so it doesn't cool correctly, and can run hot.

 

[Jman]

I think fluid moving more quickly will pick up heat more quickly in the engine--the heat transfer is greatest when there is the greatest difference in temperature, so as water/coolant warms up, it receives heat more slowly.

In other words, you want to keep your coolant at the lowest possibe temperature and moving through the engine as quickly as possible.

Think of it this way--when exercising on a hot day, would you be cooler if someone restricted your blood flow?

 

[Landpimp]

Not that this is gospil but its close

from the LCML and Mark Whatley

Clipped from previous post....

"What will happen if i remove the thermo of the ridtator, so I can let the
water circle all the time, and to cool the engine becuase I live in a hot
place.

Karim "


Your rig will take longer to warm up to operating temperature (which
will increase wear a little, and decrease performance until it is warm). It
may overheat, or at least warm hotter without the thermostat installed. This
is because the coolant will pass throught the engine and radiator at a faster
rate. It may not absorb as much heat from the engine, and it may not exchange
as much through the radiator. The system is designed with the restriction of
the thermostat taken into account. It varies from one engine design to
another, but often removing the radiator will decrease cooling system
effeciency, rather than increaseing it as one might expect.
If you have a bad thermostat, and you have to remove it to get home,
go right ahead. But if you are thinking of removing a good one to improve
your cooling, it will probably be counterproductive...


Mark....

 

[Jman]

Okay, after reading that, I realize where my misunderstanding is.

If you had a garden hose hooked up to your engine and were pumping 54 degree water in there, it would cool more quickly the faster the you pumped it through.

But the cooling system is a closed system, and where it fails if it's flowing too swiftly is in the radiator. Given an "perfect, infinite" radiator that cools the fluid down to ambient temperture before it returns to the engine, faster flow would be fine. But since this is a finite radiator, coolant running quickly through the radiator cannot dump enough heat and therefore is too hot when it runs back into the engine.

 

[theo]

Good topic!

I'm leaning toward longer residence time being more efficient than high flow. Water has a much higher heat capacity than most fluids; it gains and loses heat "reluctantly". So at high flow there is less "opportunity" for removing engine heat and "giving it up" at the radiator.

 

[pbgbottle]

thats right you need the thermostast in there to close and restrict the flow so the water in the rad can stay in there longer to cool off . once the engine gets hot enough the t-stat opens allowing the cool water from the rad to rush in cooling the engine ,in turn cooling the t-stat .t-stat closes .water slows ,stops circulating so the hot water in the rad can cool again . in a normal operating cooling system the t-stat is continuosly opening and closing .

jake

 

[theo]

Good topic!

I'm leaning toward longer residence time being more efficient than high flow. Water has a much higher heat capacity than most fluids; it gains and loses heat "reluctantly". So at high flow there is less "opportunity" for removing engine heat and "giving it up" at the radiator.

"reluctantly" is not the right word here. I should have said that there is a lot of heat that needs to be moved. Water has the capacity to do it but it takes time to transfer it.

 

[theo]

. . . the rate of coolant flow through the radiator would not affect the cooling capacity: same number of calories removed from a fixed total volume of fluid over the same period of time.

Maybe. I do know that heat transfer rate is dependent on the temperature difference between the two fluids (air and water in our case). If the coolant was not allowed time to accept heat from the block, delta T would be smaller and heat loss rate at the radiator would decrease??

Ok, shutting up now.

 

[Jman]

Maybe. I do know that heat transfer rate is dependent on the temperature difference between the two fluids (air and water in our case). If the coolant was not allowed time to accept heat from the block, delta T would be smaller and heat loss rate at the radiator would decrease??

Ok, shutting up now.

Yes, heat loss rate at the radiator would decrease because temperature difference would be less, BUT, the idea that the water can't "accept the heat" because it's not there long enough doesn't make sense. The heat doesn't care how long the water has been there: with a given surface area and a given medium and a given temperature of that medium, heat transfer would be the same no matter how fast that medium was moving. And in the case of the engine block, since water that stuck around a bit would actually warm up, the heat transfer would slow down as the water warmed up, so slower flow would take out less heat, not faster flow. It's on the radiator end that it makes the difference, because the heat transfer from the radiator to the air would be sub-optimal.

Does that make sense?

 

[theo]

the idea that the water can't "accept the heat" because it's not there long enough doesn't make sense. The heat doesn't care how long the water has been there: with a given surface area and a given medium and a given temperature of that medium, heat transfer would be the same no matter how fast that medium was moving.

The heat transfer rate would be the same, but the total heat transfered might not be. What I'm trying to say is that since water has an unusually high heat capacity, it can take a lot of heat without a large temperature increase. So you can slow the flow down long enough to maximize heat transfer from the block to the coolant without the coolant getting too hot. If the flow is too fast you aren't taking full advantage of water's superior ability to accept heat.

And in the case of the engine block, since water that stuck around a bit would actually warm up, the heat transfer would slow down as the water warmed up, so slower flow would take out less heat, not faster flow.

Agreed, but again, only if the flow is so slow that the coolant temperature goes too high.

Does that make sense?

I think we're standing around barking at the same coon in the same tree. Maybe someone will come along and chase the coon down so we can get a better look at it!