removing the thermostat

"Do not remove the thermostat in the engine cooling system as this may cause the engine to overheat. The thermostat is designed to con-
trol the flow of coolant to keep the temperature of the engine within the specified operating range"
From a Toyota manual. I thought removing the thermostat could cause the engine to underheat, never reach proper operating temperature.
Do I know more about this than Toyota?
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On 20/09/2017 9:25 PM, micky wrote:

That depends entirely on the function(s) of the thermostat.
In general, you are correct. In more specific terms, it depends.
The thermostat's most basic function is to bring the car up to temperature from cold quickly. It does that by blocking off coolant flow to the radiator. Note that the coolant will still need to continue to circulate around the cylinder block and head. It does that through the use of a bypass mechanism. The other function of a thermostat is to maintain the temperature above a set minimum temperature. For example, when you are going downhill, the throttle will be closed and minimal, if any, fuel will enter the cylinders to be combusted. In that situation, the cooling in the radiator will drop the temperature below the specified setting. The thermostat will close, isolating the radiator, thereby preventing any further temperature drop. The same thing will occur if the radiator is oversized. If the cooling system is too efficient, the radiator may overcool even during light throttle cruising.
The issue of overheating can be caused by a *secondary function of some thermostats, This will explain it in detail;
http://www.are.com.au/feat/techt/thermostat.htm
It's not a new idea by any means. I had this *feature* in cars of the 60s and 70s.
The problem of overheating will occur without a thermostat or with an incorrect thermostat fitted.
HTH
--

Xeno

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On 9/20/2017 10:26 AM, Xeno wrote:

It is a misconception that a the absence of a thermostat will result in overheating; it WILL NOT. The resulting high flow rate may however collapse a hose and restrict flow if the hose is either weak walled or missing an "inflating" spring.
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On 21/09/2017 1:48 AM, . wrote:

Nothing to do with a high flow rate collapsing a hose. That sort of event requires a *restriction to flow*, usually upstream of the water pump, that creates a low pressure area. That means it's usually the bottom radiator hose collapsing due to a restricted flow radiator. The thermostat is on the outflow side of the pump.
The scenario to which I am referring is where the coolant takes the path of least resistance, hence the need for a bypass valve. The diagrams in the link I provided should have made that clear.
What actually happens is that the water flow will take the path of least resistance which, in the case of the cooling system, will be the shorter bypass circuit back through the block.
You will still be getting flow through the radiator but the percentage lost back through the bypass means that the effect may only be felt under load or during times of extreme ambient temperature. That certainly has been my experience. One such car I had required a thermostat with two valves. Since I bought the car used, I didn't know that it had the incorrect one fitted, the one sans the bypass valve. That meant the bypass circuit wasn't restricted in any way. This car performed perfectly, never overheated, during normal operation. I only discovered the incorrect thermostat had been fitted when traveling on summer holidays with a fully loaded car on 40C+ days on the highways with lots of long hills. That small amount of lost cooling effect was just enough to tip the balance. On other makes and models, they could boil even under mild conditions and removing the thermostat entirely is no guarantee. It certainly wasn't in my case even though the flow area in the region of the thermostat effectively doubled. A new correct thermostat solved the issue.
--

Xeno

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On 9/21/2017 1:26 AM, Xeno wrote:

And the sky is blue and water is wet.

Bypass circuits are more restricted than the normal flow AND you obviously don't understand parallel flow.

Just a lot of nonsense: if you're claiming that an engine will run hotter without a thermostat, then you are simply wrong.
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On 21/09/2017 10:36 PM, . wrote:

It is not me claiming it. It is the auto manufacturers making that claim. I have *experienced it first hand*. I can vouch for the possibility of overheating due to the complete absence of a thermostat or the fitment of the incorrect type of thermostat. It's all due to cooling system design.
I have no problem understanding parallel flows. What occurs in the case of cars with a bypass shutoff thermostat is that the bypass flow is removed from the circuit. All coolant is forced to run through the radiator. If the wrong thermostat is fitted, one that cannot shut off the bypass circuit, then a percentage of the coolant flow will flow through the bypass circuit and *not be cooled*. The risk of overheating will be determined by two factors, the percentage of the flow bypassing the radiator, and the load factor on the engine. A third factor which can come into play here is the age of the radiator and the percentage of blockage it is experiencing. It may be the case where it would take extreme conditions to create the overheating situation, as was the case with my vehicle, or it could be occurring under normal conditions. That is all dependent on the design of the cooling system and the reserve capacity built into the radiator.
Regardless - overheating has occurred in the field else the manufacturers would not be issuing the warning.
--

Xeno

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On 9/21/2017 9:42 AM, Xeno wrote:

Cite so much as a SINGLE example of any engine or vehicle manufacturer supporting a claim of overheating due to the absence of a thermostat. What they DON'T like is the increased wear and open loop operation that can result from its absence.
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On Wednesday, September 20, 2017 at 1:25:51 AM UTC-10, micky wrote:

My guess is that you don't know more about this than Toyota. If you use a r egular type thermostat on a system that requires a bypass type thermostat, part of the coolant is going to bypass the radiator. How much coolant is go ing to bypass the radiator? I don't know but my guess is that the coolant i s going to flow in the path of least resistance and that path is probably n ot through the radiator.
If your engine overheats and the cooling system appears to be working prope rly, it would be a good idea to check if you're using the correct thermosta t.
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On 9/21/2017 12:00 PM, dsi1 wrote:

No, the bypass system is of smaller cross sectional area and more restrictive than that of the normal path to and through the radiator.

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On Thursday, September 21, 2017 at 7:14:51 AM UTC-10, . wrote:

a regular type thermostat on a system that requires a bypass type thermost at, part of the coolant is going to bypass the radiator. How much coolant i s going to bypass the radiator? I don't know but my guess is that the coola nt is going to flow in the path of least resistance and that path is probab ly not through the radiator.

roperly, it would be a good idea to check if you're using the correct therm ostat.
It sounds like you're saying that the path through the engine block is more restrictive than the path through the radiator and the engine block. How d oes that work?
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On 9/21/2017 2:10 PM, dsi1 wrote:

Are you vision impaired. Ever seen a bypass hose?
http://www.hotrodders.com/gallery/data/3537/IMG_7051.JPG
The heat exchanger in a vehicle (w/o shutoff) generally provides the same function as the classic bypass system.
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On Thursday, September 21, 2017 at 10:04:12 AM UTC-10, . wrote:

I don't believe that's what we're talking about. My guess is that engines that use a bypass thermostat won't have an additional bypass hose.
My eyes are just fine. How's your eyes? It appears that you weren't able to read or comprehend my post. If you can find anything in it that is untrue please let me know. You won't because I have a crack legal team reading everything I post.
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On 9/21/2017 3:21 PM, dsi1 wrote:

Then you don't understand the function of a bypass system or even heater core flow.

Provide SOMETHING to support your "guess".

How unfortunate that none are engineers, know anything regarding applied mechanics and certainly don't have the first clue about fluid mechanics.
You truly sound beyond hope.
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On 22/09/2017 6:52 AM, . wrote:

You may have some understanding of fluid mechanics but what we're dealing with here is a specific application of those principles you don't seem to be able to comprehend. I know from my 50 years of experience in the automotive industry exactly what can happen if the issue of the bypass port is ignored when replacing thermostats. I have made significant sums of money from those people who don't understand the significance of that little port and overheat their engines as a direct consequence. You just go on, in your ignorance, proving the old adage that *a little knowledge is a dangerous thing*.
--

Xeno

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On 9/21/2017 4:51 PM, Xeno wrote:

You couldn't begin to get my briefcase off of the ground with a gantry crane, junior.
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On Thursday, September 21, 2017 at 10:52:18 AM UTC-10, . wrote:

Are you saying that automobile engines have two radiator bypass route? One external and one internal? Are you sure of this?
OTOH, don't bother with responding. My crack team of legal professionals ha ve advised me that, if you cannot produce any evidence that I have misrepre sented, misspoke, or lied, about anything in my post, I should not respond to your ranting. Sorry but I have to listen to their expert opinion and any way, I don't want to be led through your fantasy wonderland on your leash.
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On 9/21/2017 5:22 PM, dsi1 wrote:

You require legal representation or at least assistance for reading and writing usenet posts?
Despite what I suppose were your hopes and dreams, none of it comes off as remotely clever.
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On 22/09/2017 8:22 AM, dsi1 wrote:

His *theoretical* fantasy wonderland.
He really needs to get down to the shop floor to see what is really happening in the wide world outside
--

Xeno

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On 9/21/2017 5:29 PM, Xeno wrote:

All any competent professional need do is read through this entire thread; 'nuff said.
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On 22/09/2017 8:40 AM, . wrote:

And we're still waiting for one of those. Your first post in this thread removed any doubt that you were one.
As I said, the door ------->
Watch that ego as you make your way to the exit.
--

Xeno

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