Thermostat removed...overheating more.

[roger longman]

That's it Glenn. In a nutshell....kinda.....Roger.

 

[birdman11]

chip

Have an 84, 75K miles.

Had water pump and radiator replaced a couple weeks ago. My mechanic removed the thermostat for the summer. Engine got up 245 going up my driveway with a/c on yesterday. Fan goes on around 230.

Runs about 10-15 degrees hotter with a/c on. Was removing the thermostat a good idea?

Thanks!

Yeah, don't ever do that. You need the thermostat. If you want to lower the operating temperatures you need a lower temp thermostat and the fan temps lowered inside of the programming (the chip). I know where you can get a chip customized for $50.

 

[roger longman]

The pros and cons of using a thermostat that opens at a lower temperature, has been covered extensively, on this forum. The overwhelming concensus is logically, that it isn't a good idea......Roger.

 

[Hot Rod Roy]

The coolant moving too quickly through the engine and radiator IS NOT ONE. To suggest that it is, shows a lack of understanding of both mathematics and physics.

If the water moved through at 1 gallon per minute, or 100, it would make no difference in its ability to absorb heat in the engine or dissipate it in the radiator. I will explain with math, as it's the easiest. for the sake of simplicity, let's assume that, as it moves all the way through the cooling system, a single water molecule would spend half it's time in the engine and half it's time in the radiator. In an hour of driving, that molecule will spend a half hour in the radiator and a half hour in the engine, NO MATTER HOW FAST IT IS MOVING.
If this doesn't make sense to you, try this simple test of physics. Heat a pot of water, stick in a thermostat, or your finger, with it sitting still. Record the temperature and how quickly the thermostat achieved it, or how badly you burned your finger. Then quickly take the same pot and swirl the water so it is moving quickly in one direction in the pot and stick the thermometer or finger in again, and it will heat the thermometer, or burn your finger, exactly the same. This means that the heat transferred was the same whether the water was moving or not.

DDC5, you're not making any friends with this post. Your water molecule will ALWAYS spend half its time in the engine and half its time in the radiator, regardless of the engine temperature. The only thing that controls the temperature of the engine is the amount that the thermostat is open. Cool engine . . . low (slow) flow. Hot engine . . . high (fast) flow. What's your point? Your "hot pot" test does not contain any verifiable scientific information.

I think SHOWMAN"s problem is that his driveway is too long!

 

[navy2kcoupe]

I think that one of the problems is that the engine is a "variable" source of heat
in that it is able to generate "low all the way to high" levels of heat, but the radiator
is only capable of dissipating that heat under the designed specs. If you pull out
the thermostat, you're changing the design parameters of the system and it doesn't
work like it should. You could tinker around with that scenario until you got a successful
system that worked without a thermostat, and if you then put a thermostat into the
system, you would have problems with it. That's why it's referred to as a
"cooling SYSTEM". When you change the "system" around, you become the design
engineer and it's up to you to make your design work. It would be like removing
2 spark plugs, plugging the holes and wondering why your engine doesn't run right!
You've changed the system design, and YOUR design doesn't work like you want it to.
Andy

 

[85RedSled]

You can talk physics and math all you want but I dont believe it is cut and dried as all that. I have also experienced a near overheat condition without a thermostat in a 4 cylinder. At a steady pace of 60 mph, after about 20-30 miles I noticed temps slowly rising to near red line and never dropped until I turned the vehicle off. This is with a brand new radiator, fresh flush and new coolant/water mix. When filling the cooling system I noticed the coolant was moving extremely fast out of the radiator tubes but thought nothing of it at the time. I have left out thermostats in the past in other vehicles but never experienced the build up of engine heat as I did without the thermostat in that vehicle. Installing a correct temp thermostat solved the issue and I never experienced the high temps again.

I think it has to do with the radiator being able to do what it is supposed to with a certain flow rate. Coolant spending half its time in the engine and half in the radiator doesnt sound like apples to apples to me. This may be true but I think you would have to factor in the amount of surface area of both the engine and the radiator. Factor in how well iron transfers heat and then how well an aluminum radiator dissipates heat If the engine creates more heat than the radiator is capable of dissipating and overheat situation will occur. I would think radiators are most efficient at a certain flow rate. Coolant moving faster or slower than this rate surely would affect its efficiency.

This is my $0.02 and unless someone can come up with another real world, not on a calculator reason I will always believe that the coolant was just not staying in the radiator long enough to dissipate heat faster than heat was applied by the engine.

I might not be the sharpest tack in the box but have been hobby (necessity really) wrenching since I bought my first POS 4X4 back in 1977. I have owned my '85 for 7 years and the only time it has been to a mechanic was when I bought it for a professional assessment. I spend most weekends struggling to keep ahead of what breaks on my DD Vette and so far, fingers crossed, I make it to work everyday.

Ahhh the joy of owning a high mileage, 28 year old sports car!

First post here might as well start with a bang! I look forward to sharing my experiences with all of you fine folks and learning more about my C4.

 

[Loubiere]

Cooling

First, I believe you should run a thermostat. The concept of the water running too fast thru the radiator to cool is a myth. But-Too high a flow can cause other REAL problems. If the flow rate is too high, the suction of the pump will drop in pressure. This can cause cavitation (gassing of the coolant). This will cause too low of a flow and higher temperature.

In fluid mechanics, higher flow = better heat transfer.

 

[WhalePirot]

DDC5, you're not making any friends with this post. Your "hot pot" test does not contain any verifiable scientific information!

How many times have we seen 'physics' or some other 'science' applied here? More correctly: misapplied. The theory may be sound and even proven but it turns out to, 1) either not solely apply or 2) be overridden by other factors. At times, it seems some seem driven to bless the rest of us with their knowledge, however misapplied it may be.

I'll go with BeCool's info, because it worked, thanks.

 

[Loubiere]

Finger Test

Maybe I can explain it in a different way not involving thermodynamics. Using your finger test see what period of time goes by before you feel the heat. Next repeat the same experiment except swish you finger in the hot water and measure the time. I recommend that you do not use water temperature that will burn you.