Thermastat

[Lost_Supra]

I have an 87 turbo and as far as I know the thermostat has never been replaced. Because here in Florida the temperature is never that cold I was thinking of taking the thermostat out completely. I would think it would affect startup temps (taking a little longer to get to operating temps) but other than what is the negative effect? :dunno:

A little more wear on the radiator is all I can see.

I'm doing this because I have a slight over heating problem every once in a while.. not constantly. not worried about BHG.

Thanks for any responses..

Lost

 

[CPT Furious]

I personally would not run without a thermostat. Some people here do and I'm sure they will chime in, but the thermostat helps control the temp. It is a really easy item to replace and if you are still having an overheating problem, I would try to track down what the REAL problem is instead of trying to get rid of the symptoms. Air in the system? Bad fan clutch? Clogged radiator? Failing water pump? Just a place to start...not trying to be rude. When I try running with no T-stat (and I was in FL at the time), my car wouldn't run right. HTH...

 

[Lost_Supra]

What is the stock thermostat? 180 or 190. What about running a 160?

I have stuff I need to look into for the cooling but thought I would remove/replace the thermostat while I'm messing with it just to be sure.

I need an AC condensor fan and for some reason my intercooler fan will not come on. I hooked a 12V to it and it turned on so I know the motor works. There's no air in the radiator and the main fan seems to work fine, I've never seen it off anyway. I'll be flushing the coolant system and check for clogs then too.

Thanks for the response.

 

[CPT Furious]

I think stock was 195, but I use a 160 now. Works great! My car didn't have a third fan, so I'm not sure what to tell you there, but it might be thermostatically controlled. In the TSRM I think there is a test for the switch for fan #3, but I'll have to go look for it. Is the fan for the intercooler or the AC condensor? For the fan clutch, make sure that it doesn't just spin TOO freely when cold. There should be some resistance there.

 

[mrnickleye]

NEVER run on the street without a thermostat !! Period !!! WHY ??? YOU ASK???
Fact:
#1...The thermo slows the flow of water down enough to allow it to cool in the radiator. It won't cool down sufficiently if it 'zips' thru the radiator.

#2...You need at least 160* coolant temp for the computer to go into 'closed loop' operation. WHAT IS THAT ??? YOU ASK ???
The ECU will operate in a pre-programmed (open-loop) mode until 160*. Then it starts using all the data from the many sensors (knock, TPS, O2, AFM, coolant, etc) in the system to adjust fuel mixture & timing.

One thing to remember, everyone, is that a car manufacturer is NOT going to spend $ on building that car with parts it doesn't need. Every dollar saved on leaving a part off the car is profit in their pocket. (That extra screw they should have put in on some door panel, or speaker mount, or spare tire air stem cap, is $$ in their pocket. It ads up to millions $$$.

If you want, I'll fill you in on what I did (less than $100) to keep cool here in the Mojave Desert.

 

[Shawndude]

#1...The thermo slows the flow of water down enough to allow it to cool in the radiator. It won't cool down sufficiently if it 'zips' thru the radiator.

Please stop spreading urban legends around. That is totally wrong.

 

[MKIII87Turbo]

Having a thermostat in does slow the water down so it will cool. It is not an urban legend.

 

[Shawndude]

Having a thermostat in does slow the water down so it will cool. It is not an urban legend.

If you slow down the coolant going through the radiator, what happens to the coolant in the engine?

Think about it. And yes it is an urban legend, and totally incorrect.

 

[PynkEye]

lol theres no such thing, when a thermostat opens, it opens..dosnt open half way or 3/4 whatever. Of course it might not flow as fast as if you would have no thermostat..tehre is a little restriciton by the mecaniqual part of the thermostat (size).

 

[IJ.]

Don't know about it being an Urban legend or if it's applicable to a 7M due to the flow of the design but in the old days with a SBChev I never ran a T Stat but I used a set of Moroso restrictor plates to "tune my running temp" as without a T Stat it would cook it's brains out!

I've read a few posts on people NOT using a T Stat in a 7M with no such issues and from what I've observed the coolant flow/speed does seem to be quite slow when free revved so maybe Toyota took that into account when they designed the system.(by comparison coolant flow through a Chev with no restriction is VERY fast)

<edit> Pynk: they do open gradualy according to temp but are full open at their rated temp (drop one in a pot of water and bring to the boil with a thermometer and watch it open)

 

[MKIII87Turbo]

If you slow down the coolant going through the radiator, what happens to the coolant in the engine?

Think about it. And yes it is an urban legend, and totally incorrect.

I'm an ASE certified mechanic, course that dosen't prove anything and I have been working on vehicles for the last 25 years. In one of my automotive books it states, "Today's theromostats are also designed to slow down coolant flow when they are open. This helps to prevent overheating, which can result from the coolant moving too quickly, through the engine, to absorb enough heat".

 

[Shawndude]

In a closed system, you really cannot move the coolant "too fast". In one way system like an intercooler, sure, you need time for the heat transfer, but this totally doesn't apply to a cooling system. The higher the temperature differential between the two mediums (water/air) the faster the heat transfer. There really is no dwell time required for the two mediums to stay in contact, since the coolant is just going around and around. The hotter you can get the radiator, the better it will cool off (higher temperature differential). Only way to do that, is to speed up the coolant flow. And that's exactly how thermostats regulate the amount of cooling in the first place. Need more cooling? Open more and let the coolant circulate faster. Need less? Slow it down. Any thermodynamics textbook will make this blatantly obvious.

Anyway, the following sounds like a plausible explanation of where this "urban legend" started.

http://www.stewartcomponents.com/tech_tips/Tech_Tips_3.htm

A common misconception is that if coolant flows too quickly through the system, that it will not have time to cool properly. However the cooling system is a closed loop, so if you are keeping the coolant in the radiator longer to allow it to cool, you are also allowing it to stay in the engine longer, which increases coolant temperatures. Coolant in the engine will actually boil away from critical heat areas within the cooling system if not forced through the cooling system at a sufficiently high velocity. This situation is a common cause of so-called "hot spots", which can lead to failures.

Years ago, cars used low pressure radiator caps with upright-style radiators. At high RPM, the water pump pressure would overcome the radiator cap's rating and force coolant out, resulting in an overheated engine. Many enthusiasts mistakenly believed that these situations were caused because the coolant was flowing through the radiator so quickly, that it did not have time to cool. Using restrictors or slowing water pump speed prevented the coolant from being forced out, and allowed the engine to run cooler. However, cars built in the past thirty years have used cross flow radiators that position the radiator cap on the low pressure (suction) side of the system. This type of system does not subject the radiator cap to pressure from the water pump, so it benefits from maximizing coolant flow, not restricting it.

Lucky us, we have the "old style" type radiators, but we also have wimpy pumps, so it works ok without the restrictors (or higher rated radiator caps).

Best Regards.

 

[shaeff]

if you run without a thermostat, your car will run cooler. period. ask me how i know

and if you run with no T-stat in the winter in new york... you have no heat... aske me how i know.

if you put the t-stat back in, in the winter in new york, you get heat. ask me how i know

put it this way, if you have a 10'x10' piece of black steel laying in the yard baking in the sun, and you drop it in a 11'x11' kiddie pool filled with 2" of water, the cooling effects will NOT be as great as if you keep spraying it with a garden hose.

-shaeff

 

[TONY!]

…In one of my automotive books it states, "Today's theromostats are also designed to slow down coolant flow when they are open. This helps to prevent overheating, which can result from the coolant moving too quickly, through the engine, to absorb enough heat".

It may have very well said that but keep in mind that no one or source is omnipotent (knowing absolutely everything). Any outside source, just as members, can make mistakes too.

I would definitely agree that the coolant within the radiator would have a cooler temperature if flow is reduced, but where the coolant is needed, in the engine, the coolant would be hotter. You can’t deny that at an extreme (very low to no circulation) the coolant within the radiator would be cool, but the coolant within the engine would be hot, and the heat exchange between the radiator and the ambient air would be minimal.

The more you increase flow, the hotter the radiator will be because it will have more coolant rushing in from the engine within a given time interval. The same effect will also occur to the engine: as you increase flow to the engine, it will run cooler because it will have more coolant rushing through it from the radiator at a given time interval. A higher flowing system would also have more consistent temperatures at various points within the system.

As stated, more flow will increase the temperature of the radiator, and with a hotter radiator, there will be more of a heat exchange between it and the ambient air. Increased temperature variations between the radiator and the ambient air means more heat exchange during a given time interval and more heat loss overall.

In a closed system, you really cannot move the coolant "too fast"…

Yes, but downfalls and reasons why manufacturers don’t make even higher flowing systems is because it would be overkill (not necessary), it would also rob some HP (very little), and increase wear on the water pump -- if the same basic pump was used but made to spin much faster.


About running a car without a thermostat:
Long ago my neighbor convinced me to try it -- I did. With our cars being as sophisticated as they are, the computers won’t like or know how to deal with a much cooler running temperature. When the car is cold, more gas is injected in the cylinders and you will have a higher fuel to air ratio. In my experience at 30F, I could easily see smoke (that is how rich it was) coming from the exhaust while I did a highway run for a couple of miles. Needless to say, I don’t want my cat’s blocked with carbon, or more carbon on my pistons which increase the chance for detonation, or want lower fuel efficiency, so I put a thermostat back on within hours of that experiment.

EDIT:

From now on I won't bother posting after Shawndude because he made some of the same points I did. In my defense I'd say that I was distracted while making this post and he beat me to it.