i just started my 13b 4port, it has two 10" fans a three row radiator "that looks like its flowing good" and no thermostat. the car was running for like 15mins at night and the autometer temp gauge got to 220...... now i know i am running a little rich on my mikuni, but would that have anything to do with it??? or could it be a bad radiator?

 

just cause it looks like it's flowing good doesn't mean it is. repair shops have equipment that can test the flow rate.

 

Yeah, with that setup i would expect you wouldnt have a problem keeping your engine cool. Stock 2nd gen's run 2 fans and a 2 row radiator and my car never has probs keeping cool. I'd say you had a flow problem.

 

Remove the radiator cap, then start the car. If there is a flow issue, water will come pouring out of the radiator. Since you're not running a thermostat, keep it running until it is hot (but don't actually overheat it!). Still flowing good but wants to overheat? If that is the case, then how good is the flow (is your water pump working correctly)? Fans coming on when they should?

 

Another quick check you could make, would be to make sure that your timing is correct. If you don't have a timing light, at least verify that you still have good spark on the leading ignition. If all of that checks out, then you might want to think about your exhaust system (is it clogged?), but that would be my last guess. Good luck!

 

Thanks, for the advise, i know it cant be the exhaust, cause its new and free flowing, someone told me that if i dont have a thermostat, that i should plug the 3/4 hole where the thermostat sits in..... has anyone ever heard of this????

the radiator was used when i installed it, but it looked pretty clean. the timing is correct. the only thing i know is that the carb is running real rich. the intake gets ice cold when i start the car for the first 5mins.

 

running it rich wont cause it to overheat. i have heard that not running a thermostat will make it run hot because the water flows through the radiator too quickly. the thermostat slows the flow so the fins on the rad. have time too cool it.
i run my dellorto real, real rich and my **** runs super cool.

 

actually ive heard of people using a plate with a 5/8" hole.
what this does is slow down the water flow. with no thermostat the water rushes thru the engine too quickly to pick up any heat from the motor.

 

Please explain this phenomena. It runs counter to my understanding of the laws of physics.

 

the longer water stays in the same place the more heat it can absorb, same applies to it being in the radiator longer to release the heat.

either get a thermostat or gut one properly.

 

Well, then I guess we should stop flow so it can stay in place longer, then ?

It's a conductance thing... thermal transfer of heat energy from engine to water and from water to radiator fins and released into atmosphere.

Water won't go so fast that it can't pick up any heat. Now cavitation might be a mechanical interference that interrupts flow and/or thermal tranfer, but I doubt the 15 minutes of running wasn't at WOT high RPMs.

 

what do u mean by "GUT ONE PROPERLY"??

 

run your hand over your radiator and see if you have any "cool" spots when your engine is warm and running. that would indicate if you have any plugged spots.

 

why dont you just put a $2 thermostat in and see if that solves your problem???

 

if you remove the thermostat you must plug the bypass hole in the waterpump housing. i tapped that housing and threaded in a 1/2" bolt with jbweld to be sure it don't back out.

if you dont plug the bypass hole then your coolant will overheat. first things first.

you want a little restriction in the coolant system. gut the thermostat. take your dremel tool and cut innards out of thermostat, leaving just the brass ring. gasket / silicone that ring in per norm.

 

if i gut the thermostat, do i still have to plug the hole in the housing?? should i try putting back the stock fan, instead of the two 10" fans i have on there now? or should i buy a new radiator to start?.

 

Is there any particular reason that you don't want to use a thermostat?

 

Put a mazda tstat in and start over. It will be harder to diagnose problems when the system is corrupt to begin with. Kinda like the bush whitehouse. Thats just my idea.

 

YES, if thermostat is gutted or removed u must plug the bypass hole. FYI no thermostat is overkill for street use and only reccomended for track only.

If it were me, I'd put a stock MAZDA replacement thermostat in there and start over. If the radiator has not been flushed and cleaned in the last year now is the time. Prestone super flush is great and i have had excellent success pulling the radiator and filling it with a bunch of .99cent store lime away. removes corrosion well. CLR great too. flush it with water real good before reinstalling.

THEN we can start blaming the dual fans if it is not cool.

 

ok im going to install the thermostat today, lets se if thats the problem. i'll keep u guys posted. thanks for all the advise.

 

Carb = ok to run without it. F/I is a must.
I have been using gutted t-stat for and never plug the by-pass hole for many years No problem of what so ever except for the usual "take longer to warm up." I think TimS posted from his experience that a plugged by-pass is a MUST when racing.

My expereince:
Gutted t-stat is better than "no t-stat." On a stop & go traffic, a gutted t-stat will allow the coolant to absorb more heat instead of flowing freely.

At freway speed, free air cools the entire block.

 

At idle, fan or clogged radiator.
How is it at freeway speed?

 

Slowing down the coolant flow will not increase the cooling effect of the entire cooling system.

What you are saying is contrary to many laws of physics like the other bloke posted.

I'm a second year engineer and I can tell you with a definite response that what they taught me in my last year of highschool physics is right, and any further physics I have done have further re-inforced your wrongness.

You might think that the coolant can take away more heat if the flow is lower, but there is always coolant in the system touching that particular place of passage inside the rotor housing, as is there inside the radiator.

The unit surface area of radiator/engine is still being exposed to the same "time" of coolant, and if anything the cooling effect is increased with greater coolant flow.

The reason this guy is experiencing overheating is because his lack of thermostat is not blocking the coolant bypass inside the engine.

When this is open, the water is not forced to travel through the engine, this means overheating....

Increasing coolant flow past a certain point will do **** for the efficiency of the cooling system tho, this is because the radiator will not become more efficient past a certain amount of Gallons/hour, or Litres/hour (in the more developed nations :P).

Care to argue more and I will bust out the textbooks

 

Your "gutted" thermostat is infact blowing the bypass hole, and that is why you've never experiences any problems.

And the reason why you really don't want to run a fuel injected car without a thermostat is because the fuel mix will stay rich for the now extended warmup cycle.

Which as I stated above, there really is no reason to remove/gut your thermostat when the additional coolant flow will really do jack **** once the car is warm anyway.

All you are doing is causing more engine wear by not letting your car warm in 3mins instead of 15.

And if you are overheating with a thermostat, and taking it out solves them, all you are really doing is prolonging the symptoms of the overheat condition to come out...

 

Now that's hitting below the belt. Almost all engineers in the US use metrics anyway lol

It is correct though, that slowing down the flow will not keep things any cooler. If it is flowing more quickly, the average temperature of the coolant will be lower and more thermal units will be able to transfer in the same period of time. The more thermal energy that the coolant absorbs, the less effective it becomes until it passes through the radiator again.