Can I run with no thermostat?
 

The car never runs in winter, why would I want a thermostat? What are the consequences?

It helps the car reach operating temp faster and it also slows down the flow of coolant through the engine(which is a good thing, gives it more time absorb heat)

I would had thought the opposite.

Since the coolant goes faster it absords more heat because it cools faster.

If you are insistent on running with no thermostat, you need to at least plug the bypass hole in the water pump housing. Without the thermostat there to close it, a lot of coolant actually bypasses the radiator.

Really though, a thermostat is about $20 at the dealer. :) Just replace it. The thermostat is there to regulate the engine into operating at a specific temperature, and maintaining that temperature. If you don't run the thermostat you will find that your engine temp will fluctuate wildly leading to poor mileage and performance.

Not to mention that on a 7 overheating is often lethal to the motor. Don't take that risk. ESPECIALLY since it's a summer car. Having free flowing coolant will make the motor stay very cool, and fuel apparently atomizes better when you have a warm block (but cool air is good so it compresses well), not a cold one. You would most likely get terrible mileage and it might not even run well. These cars do better when they get a little time to warm up compared to piston engines, right? If anything EVER happens to your coolant (well, you may have the coolant level buzzer still) like if it gets contaminated or really dirty it could make things bad by raising the temperature dangerously and you would never know it while driving because you'd have nothing to drive your temp gauge.

you are an idiot :pat:

I had this question too....does the thermostat attach to the bottom of the radiator? I'm thinking that it does, due to the fact down there is a little thing dangling...looks like it snapped off the radiator....if that IS the thermostat, how would I go about reconnecting that? IT's not like it can snap on..looks like it needs welded?

tHE THERMOSTAT IS JUST ABOVE THE WATER PUMP.

sry for caps..

The thermostat is inside the water pump neck. FSM.

Actually, in a way what he said is true. A more accurate way of saying it is that the thermostat regulates the flow of coolant through the radiator so the coolant flow is proportional to engine temperature.

And next time, don't reply with an insult.

he is true to an extent

but what he is forgetting is that, even if each oz of water isnt doing as much cooling, there are many oz of water that flows through it that will....
not sure if that make sense...

think of it like a fan on a heatsink for your CPU. a higher cfm will always yield a closer temperature with ambient - even though each air molecule doesnt stay on the heatsink 'long enough to pick up the heat'

He's right in the fact that it helps the car reach operating temp faster, but he is completely wrong in the part that slpin quoted.

A given volume of water that hasn't absorbed heat (energy) will absorb more heat than the same volume of water that has already absorbed heat. You will get greater cooling by movign the water through there quickly than you will by slowing it down.

That doesnt mean you WANT that though. In the case of the engine operating temp is better than a cooler engine.

BC

if madza didnt want to use a thermistat in the rx-7, they wouldnt have put it there.

my $0.02

Its OK, I've been called worse by better.

I came to this thinking after a race car was doing strange things in the cooling area. I thought about how you can run your finger through a flame quickly and it doesn't burn you but if you do it slowly it will hurt. It may be a function of our body and feeling pain but it made sense after staring at the car holding a beer( OK maybe a few beers) and we made the hole in our blanking plate smaller and the car quit overheating.

Let me try to clear this up for everybody.

When the coolant is at its lowest temperature it will absorb heat at a higher rate, however, as soon as it starts absorbing heat that rate at which it absorbs heat decreases. Now, if you didn't cycle coolant at all, the coolant in the motor would absorb about all the heat it could manage, BUT since that maximum absorbed heat is less than the motor puts out, the whole motor will overheat. So that's a rough case for when there's no pump or the thermostat is stuck completely shut.

The other case is where there's no thermostat or it's stuck all the way open. Coolant rushes through the veins, absorbing heat at a very fast rate and dissipates it through the radiator as it flows quite easily. It certainly won't cool the engine to anywhere near the outside temperature, but it will be much lower than desired. Don't think of it as a finger over a flame, I'll give you a better example. Gases are fluids, too, so fluid thermodynamics apply to both liquids and gases. So, you're outside on a warm day wearing shorts and a t-shirt. Forget what temperature exactly, just think of it as your ideal temperature plus 5 degrees Fahrenheit. A cool breeze would be really nice, because it's 5 over your comfort zone. A strong wind could make it cold because even though that air isn't resting around you as long as with no breeze or a slight breeze, it's robbing you of your heat very quickly. Each particle you would come in contact with MIGHT not take quite as much heat than if it was traveling slower, but you're coming in contact with many more particles, and the harder molecules collide the more thermal energy they can transfer.

Any questions?

Thanks for the eloquent explanation. Are you sure you don't want to throw an insult around to fit in? :rlaugh:

I've long forgotten which car this was an issue on but thinking more about it it was probably a water pump cavitation problem. I've always run a blanking plate since then and have never had the same problem show up on any other car.

I looked this up because firefox was telling me I was wrong, but it turns out I was right. Yet another word to add to its dictionary. So when I looked it up I discovered it can also mean pitting of a solid surface, but I assume you meant the first definition.

cavitate:
1. The sudden formation and collapse of low-pressure bubbles in liquids by means of mechanical forces, such as those resulting from rotation of a marine propeller.
2. The pitting of a solid surface.
3. Medicine The formation of cavities in a body tissue or an organ, especially those formed in the lung as a result of tuberculosis.


Anyway, if the pump is cavitating in the first sense I would think something's very wrong with the pump (like it might be the wrong pump altogether).

Number 1, water pumps on RX-7's with the stock pulley set-up cavitate at around 6500rpm. It can actually show up on dyno runs as a loss in HP from the drag. It also will stop the flow of coolant.

Well that sucks, I can't believe they didn't engineer a fix for that before selling the car. So what are some fixes for that? I'd hate for engine temps to spike if I was running at 6500-7000 RPM for 30 or so.

Actually most engines will have this problem at some high RPM. Its all on how much the water pump is over driven from the crank/eshaft speed.
A smaller eshaft pulley is the first thing then with the extra room you get from that you go with a bigger waterpump pulley. Mazdaspeed sells both, Mazdatrix will sell them to you if you aren't a racer.

If you aren't a racer? What do you mean?

I dont know if anyone said it yet or not but the thermostat will actually cool your engine more evenly by slowing down the water and allowing it to absorb the heat from the engine.

Mazdaspeed is the factory parts support connection. If you race your car in just about any organized group like SCCA, NASA, NHRA etc. they will sell you parts directly at dealer cost.

Careful xfeastonarex, slpin will call you an idiot...

What do you mean 'evenly'? By having the thermostat work right the whole block might have a lower standard deviation of temperature (temp points taken from all points within the block) than if it ran colder or warmer than it's supposed to, but I can't think of any other way to make sense of what you said.

So, is dealer cost higher or lower than 'Joe Schmoe' cost?
Dealer cost from a normal parts store is cheaper than that same part from a mechanic's shop, because the mechanic buys the part from the store (at what I understand as dealer cost) then charges you up the butt for it.

Since he's actually right, and running without a thermostat or restrictor plate is known to cause cooling problems, which of you is the greater idiot? :)

Not necessarily. For a given situation there is an ideal flow rate that will remove heat at the greatest rate. Reducing flow will not remove heat fast enough and greater flow will not transfer as much heat to the coolant. Heat transfer is not an instantaneous process, so the coolant needs to be in the engine for the right amount of time, not the shortest amount. The system is designed to keep the coolant flow rate close to ideal as often as possible. Anything that reduces or increases coolant flow (including removing flow restrictions) will change that.

Cavitation reduces flow, it doesn't stop it.

It doesn't need a "fix" because it's not broken. The cooling system has been engineered to work across a wide range of driving conditions, and is obviously optimised for what it does most of the time. Running at a constant high engine speed is not exactly normal usage for a street car, but constant low-medium engine speed is. As is extended idle and low-speed time. It's far more important for a street car cooling system to work properly in these conditions.

Underdrive the water pump, as is done on race-prepped engines. Then you risk cooling problems at low rpm.

when you increase the amount of water flowing to it, each water has to pick up less heat for the same effect.

Can you rephrase that so it makes sense? :confused:

I hadn't considered that just about any car could face wp cavitation at high RPM's, I was guessing that this was more an issue for rotaries.

cavitation can also be very destructive to any pump. It can severely pit and in some instances crack and break the blades of the pump. Effectively, as the pump blade hits a bit of low pressure vapor, it speeds up (cause theres less drag/pressure holding it back). Then it hits the far side of this bubble and rapidly slows down. This pump now not only requires a lot more power to drive, but the wear rate on all the components is increased, proportionally to the severity of cavitation.

Disclaimer: This is all for centrifugal pumps in general, not specifically our water pump

Most of the stuff bolted to our engines is no different to that on a piston engine, and works just the same. People make a big deal about rotaries being so different, but until you actually need to pull the engine apart, they're not really. :)

I realize that, but like I said before I thought since rotaries can sustain higher RPM's that the problem might be isolated to rotaries.

Most motorcycle engines run much higher RPMs than a rotary.
As NZC pointed out, once you get past the shortblock there is little difference between our engines and a piston unit.

I know that, too, man. But aren't motorcycle motors usually air cooled? Thus, not even having a water pump? :rolleyes:

NzConvert, I agree with what you are saying about the coolant flow, now my other question is, will the slower or more controlled flow of coolant disipate more heat at the radiator since its regulated instead of flowing quickly and not being allowed to disipate all its heat?

I just want to make sure im on the right track.

And I forget who was compairing a CPU heat sink and fan to our cooling system, but I would not use that as an example for coolant absorbing the heat, instead use that for the fan that is drawing air through the radiator or use it for air cooled engines.

Yes, but you will still run the coldest possible with no thermostat at all.

Plenty of bike motors are water cooled. It's a bit hard to air-cool a motor when the bike's covered in fairings, i.e. most modern sports bikes. :)

Yep, it's basically the same process. Heat is conducted from the metal engine parts to the coolant, the coolant travels to the radiator, the heat is conducted from the coolant to the radiator then from the radiator to the air passing through it.

Only at low engine load, because the engine is being dramatically over-cooled. At high load the lack of flow restriction hampers the cooling system's efficiency and overheating can result. This is a long-know phenomenon.

That and you can get hot spots in your housings and such running without a thermo..but yep i agree totally ..

By slowing the water down, thermostat installed, it will be allowed to absorb heat from high temp areas (hotspots) on the block more effeciently than allowing the water to flow past unregulated. This would result in a more even temperature across the block as a whole by keeping the hotspots cooler and the cooler areas warmer.

Yeah, that was the only way I could make sense of you saying 'evenly'. I just wanted to be sure because it seems there are a lot of people around here that spout off retarded crap without thinking about it. I've been mistaken before, too, but I can be reasoned with...

I thought about what I wrote before I wrote it, I just tried to make it sound simple for the people who spout off retarded crap ;)
Its all about inspiring thought... :)