Help: Overheating WITHOUT a thermostat
 

As the weather generally gets warmer, so does my temp. I "cored" a thermostat I picked up at Autozone yesterday as a temporary fix until I got the time to get a Mazda one. But, the car still runs too warm. I did the coolant seal test a few mins ago, (take EGI fuse out, take filler cap off, crank) but no coolant came out. I'm thinking maybe a clogged radiator or heater core. Any help or past experiences with this problem would be great.

Edit: I bought all belts, changing them tomorrow

When the engine is very warm.. Check for cold spots on the radiator, signifying a clog.

Or you could drop all the coolant... And do a full flush, see what happens

Read up on this ....
http://www.mazdamotorsports.com/weba...ubject=cooling

Also, do you have your underpan still installed?

BEfore you freak out on temps...you really need to get an aftermarket water temp gauge to see what is REALLY going on.

James

Yes, I've still got the underpan, and I'll pick up a temp gauge tomorrow

I have different issues with overheating\loosing coolant!

1 - My first experience, the car would loose coolant while the engine was running, it never really overheated. Turns out the housings were corroded!

2 - The second expierience, the car was loosing coolan, turns out it was the radiator cap.

3 - The third one, overheating while crusing, turns out it was cloged radiator; i also replaced teh water pump because it had a small leak.

4 - The fourth one, jut like yours, turns out that the efan was connected as a pusher instead of puller.

Not surprising. The Mazda thermostat is a bypass type. If you run without one, or a cored thermostat, the bypass hole in the bottom of the thermostat neck will not be closed. This will cause the majority of coolant to totally bypass the rad.

Start by installing a proper Mazda thermostat. Then, check out http://www.aaroncake.net/rx-7/cooling.htm for cooling system troubleshooting.

That is hardly the issue, I ran my FC in PR without a TS for yeasr, not a problem what so ever.

Aaron is right. If you don't have one the water will just flow back into the engine without going through the rad. Get a Genuine MAZDA thermostat. If your still having heat issues it's a dirty rad or your fan is not working like it should. Electric fan or clutch type? And yeah you wanna keep the underpan on to keep air flowing through and not around the radiator.

Take 'em to church Aaron.

OK, thanks for the input. I've replaced the rad. cap. I've still got the stock clutch fan that is still good(doesnt spin freely when you spin it). And the cored t-stat, as I said, is a temporary fix until the mechanics at the dealership get back to work on Monday so I can order one.

Woah, dude! please elaborate on #1 for me. My car has been losing coolant like a mofo recently, it has to be while driving because there is not as much as a spot under the car no matter how long it sits. It doesnt overheat either. I dont know where it is going!

i cant believe that. i was running much too hot at one point so i pulled the tstat. the car never got above 1/8 on the temp guage.. ran much cooler than before i yanked it. this is on an s4 se.. maybe the tstats are different for years and models?

http://fc3spro.com/TECH/PROBLEMS/P1/...OT/coolant.htm


-Ted

Have you run a FC without thermostat?

Your Tstat was probably to old, however I am not surpirsed that after the removal, it NEVER overheated ;)

Did you replaced the radiator cap?

On my first issue, I could literally see water coming out of the overflow tank :eek:

Have you gone through any of the troubleshooting I posted? Even an afermarket thermostat will be better then the cored unit.

How is that?

Again, have you run a FC without Tstat during the summer?

I understand were you are coming from, and it is true for road racing applications. At the end, yes I would run a OEM Tstat, but just saying that not running one will cause the car to overheat, is just not true.

You nailed it, ordering a new radiator later tonite.

Not me, since I understand how the cooling system works and don't hack it. But I have dealt with two seperate cars that were overheating constantly, traced to the removal of the thermostat without blocking off the bypass port.

Really, there is NO REASON to remove the thermostat unless it's a track car.

That's funny, I ran my car for years without one, on a constant 90 degrees weather, without a single overheating issue. Not to mention, that this has been said before on this board.

I am not arguing the fact that it is better to use a tstat for the street, but don't agree with the overheating issue due to no tstat; and I have experience on that one.

For some people, it seems to work. Probably has a lot to do with the weather, their coolant/water mix, the state of the rest of the system, e-fan or clutch fan, etc.

But I still don't know why people would remove the thermostat. It doesn't improve cooling, and has only negative effects.

If you have a track car and actually have a reason to remove the thermostat, then go ahead. Just remember to block that bypass hole in the water pump housing.

You have to be careful when you say 'the car never ran hot without the thermostat'. What you are saying is that the coolant temperature never read more than a certain temperature. Other than bypassing the radiator, the thermostat is there to slow the flow of coolant throughout the engine. If the coolant is travelling too quickly throughout the motor, it cannot properly and efficiently absorb heat. In essence, the transfer of heat from the engine to the coolant cannot happen well enough.

So, while the coolant temperature (and that on the guage) may seem ok, the engine is cooking. What may read 1/4 on the guage may actually be 3/4. You need the thermostat in there to regulate the flow rate (and therefor heat transfer rate) of the coolant as well as the flow path.

Agree 100%

The first tiem I ran the car without a tsta, was because it stopped working, so I did as a temporary fix. Turns out that the temporary part wasn't so temporary...

So, you are saying that the temp gauges will read right when there is a tstat, but their readings will be way off if there is no tstat?

Actually the second time I ran the car without a Tstat was when I was having some overheating issues on my newly na to T2 conversion. The stock sensor was on the stock location, and the aftermarket sensor was next to the tstat location. After fixing the overheating issue, both gauges, plus the E6K sensor showed the same readings (at least the aftermarket temp sensor and E6k, can't really tell the exact temp on the stock gauge), and there was no sign of overheating at all. This time, I ended up putting the tstat back when winter arrived.

All of the sensors will read the same, as they are reading the temperature of the coolant. The problem is that the coolant temperature is cooler than it should be. The coolant is flowing too fast to absorb a lot of the heat from the metal. So every guage in the world will be reading the same nice low temps - as they are measuring the coolant temp. But the metal is hotter than it should be. In essence, the coolant isn't cooling the metal like it should. You need the t-stat in there to ensure that the coolant will flow at a rate that will allow a proper heat-transfer.

side note, if you remove the thermostat place an 18mm plug in the water pump housing to keep it from recirculating, if it hasn't been posted already.... :)

Sounds good in theory, however how much hotter are we talking about?

This is BS.

Running without a restrictor is not a problem because the coolant will flow too fast, you want fast flow! That crap about it moving too fast to pickup heat is not true, it's a myth.

The problem with running restrictor-less is the water pressure inside the engine will drop. If the water pressure drops too low you will get hot spots, the water will boil around the exhaust ports and if you start getting localized areas with boiling those areas are not going to be cooled effectively anymore. You need pressure.

What you want is to balance flow and pressure, the higher the flow, the better, as long as you do not compromise pressure too much in the process.

Now I know this is going to get flamed, but here I will quote a pretty reliable source of information on the subject, I've quoted from this book on the forum before:

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4 stroke performance tuning - A. Graham Bell, lubrication and cooling section page 300.

However, what if the engine was too hot on the first test with the 16mm restrictor If going t oa 19mm hole did not bring the temperature down and we were losing block pressure, we would have three options: a larger radiator, more pump speed, or a combination of both. Assuming that it was a hot day test I would go for more pump speed with a limit of around 6200 rpm. However, if the temperature was way up on a cold day, more pump speed might not get you out of trouble when the weather warmed up. Therefore a larger radiator might be the way to go.

Some of course would just go for bigger and bigger restrictors, or discard the restrictor altogether. This is not a good move; certainly the temperature gauge may come down to where you want it, but consider what is happening inside the engine. With no outlet restriction, water pressure in the block and head will be right down. With lowered water pressure steam pockets will form in the hottest areas of the engine. The combustion chamber, exhaust valve, and piston crown will then overheat, driving the engine into detonation. At this point hp will fall, and if the situation continues the engine will be destroyed.

An old wives' tale states that if you discard the thermostat or the restrictor the engine is damaged because the water is flowing through it too quickly to draw off excess heat, or it is flowing through the radiator too fast to give up its heat. This is not so; what causes the engine damage is insufficient water pressure to pack the coolant in tight around hot spots in the engine. Then any water that hits these hot spots dances about like water droplets on a sizzling barbecue plate without drawing off any heat. As the water boils off, the size of hte hot spot grows as a bigger and bigger steam pocket forms.

In reality we want reasonably rapid flow through an engine, as this tends to reduce the incidence of stagnant high-temperature pools. Additionally the rapid flow will scrub off gas bubbles as they appear in the hottest parts of the engine before they have a chance to congregate into an impenetrable steam pocket. In fact, the solution to cooling problems is not so much a matter of moving more water through an engine, as moving less more rapidly. This will pay large dividends in more hp and better engine reliability.


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Smokey Yunick goes into this a bit also, but I don't feel like typing it out.

Thanks for the tech info, now my question still remains, if there were hot spots, will it show on a gauge?

You're welcome.

And no, localized hot spots that are not right at the gauge sender will not show on the gauge. I imagine they will eventually though, after the hot spot has spread, if it gets bad enough to do that. There would be some damage by then though and I imagine pretty obvious overheating signs, boiling out of the overflow etc.

That creates a problem then...

A motor could be toasted because of hot spots, but they are hard (or almost impossible) to find :eek: