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  #21  
Old 10-15-2008, 10:47 PM
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yeah, no sweat man..

you know you can throw the thermosat in boiling water and it should open... easy way to check it.

I wonder if it is your guage not reading right. throw in a cheap mechanical gauge just to see.
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  #22  
Old 10-16-2008, 08:02 AM
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So I don't want to keep beating this dead horse, but...

The radiator flow is from bottom to top right? So if I take temperatures across the radiator they should be more or less the same?

With the laser thermometer about 2/3 of the width of the radiator is at about 50 degrees when the truck is heated up. On the driver's side it's at about 140 degrees, with a steep gradient. So my guess is that I have some blocked passages, but it's not overheating so I don't know?

Man this is like having mood swings, back and forth and it doesn't make sense...
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  #23  
Old 10-16-2008, 08:27 AM
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Quote:
Originally Posted by subzali View Post
The radiator flow is from bottom to top right? So if I take temperatures across the radiator they should be more or less the same?
Radiators flow in at the top and out at the bottom. IOW, hot coolant in at the top and cooled coolant out at the bottom. Heat rises and having the flow in at the bottom would be working against the efficiency of the radiator. There should be a temp gradient across the radiator, otherwise it's not working. But if it's cool coming in and you're overheating, then the problem is something like the t-stat, heater core, coolant passages, etc. It's got to come into the radiator hot.

This is a cross flow radiator and a gradient like this would indicate a bad cross flow, but using your imagination the temp gradient on a traditional radiator should look like this.

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  #24  
Old 10-16-2008, 12:16 PM
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Righto about working against the efficiency of the radiator, so it has to be from top to bottom flow. Imagine though that the gradient is right-to-left, that's what's happening. And it's a very steep one, one that's mostly cool all the way across the width of the radiator, but then sharply increases on the inlet (driver's) side.

Dave - where why and how do you always have these fancy graphics to perfectly illustrate what you're talking about?
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  #25  
Old 10-16-2008, 12:41 PM
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That's what I measured last time I check a couple nights ago. And that's what's confusing me now, because if some passages are blocked then I should be having overheating issues.

Your PE must be showing through because I cannot get anything like that to show up on Google
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  #26  
Old 10-16-2008, 12:53 PM
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That's what I measured last time I check a couple nights ago. And that's what's confusing me now, because if some passages are blocked then I should be having overheating issues.
Not necessarily, if the radiator is big enough you might not overheat. Also if the heat load is small enough or vertical flow is particularly good, the gradient could certainly not be so ideal. Also, since the inlet and outlet are offset, there will be a rotation of the gradient, too. The top inlet side will be a bit warmer than the other side of the tank, for example. Conceptually, the key is that the top should be hot, the bottom should be cooler and the temperature horizontally should be fairly consistent. Naturally in the real world the actual measured temps won't look like a textbook. If the temp entering the radiator is somewhere above the opening temp of the t-stat, that is right. If the exiting temp of the coolant from the radiator is significantly colder, that is also good. If you didn't overheat in the summer, then your radiator could be fine.
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  #27  
Old 10-16-2008, 04:46 PM
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Thermodynamics/hydraulics of Land Cruiser Radiators: The cores (passages) are vertical. The hot coolant from the t-stat from the head comes in at the top driver's side corner. Exits the bottom (opposite) passenger side corner. It would be totally expected that the driver's side would be hotter than the passenger side. I haven't done an IR scan, but that's what I would expect. Liquid will follow the laws of hydraulics, and it's temperature will follow the laws of thermodynamics. The highest pressure of the liquid (coolant) will be where it comes in, and that is where flow will be greatest as a result. Thus, more (and hotter coolant) will flow downward through the cores at the inlet side, resulting in greater delta T's, and a higher T reading on an IR scan. Also something to take into consideration is that because the (passenger) side will have a lower flow rate through the cores, that is where sediment and deposits may build up, further exacerbating the difference in T's from left to right by decreasing the thermal conductivity in those passages.

In any case, the real question is, what's the actual coolant temperature at the t-stat??? That's really all that matters. Once that question is answered, then the troubleshooting goes down the list.
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  #28  
Old 10-16-2008, 06:38 PM
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Matt- I replaced my radiator with a 4 core from radiator barn. My gauge shows really low too, but I always have good heat.

Trusting 32 year old factory gauges for anything other than general read-outs is kinda foolish in my opinion. Are you connected at the temp sensor, maybe it could use a replacing?

I don't worry about it, my truck runs fine, and heats fine too.

Sorry didn't catch this till now.

Drew
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  #29  
Old 10-16-2008, 06:47 PM
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Quote:
Originally Posted by Rzeppa View Post
...In any case, the real question is, what's the actual coolant temperature at the t-stat??? That's really all that matters. Once that question is answered, then the troubleshooting goes down the list.
I would guess 140.
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  #30  
Old 10-16-2008, 09:32 PM
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The t-stat is an 82 degree C, which is about 180 F.
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