A/C and Overheating Question

[sammm]

I'll have to see about replacing the t-stat. Not sure how to do that. Not sure where it is.

Thermostats are easy if you want to tackle it yourself! Here's a write-up from Miata.net. It shows a 1.6 engine, but the 1.8 is very similiar. The only thing I wouldn't do is use the RTV sealant shown. A gasket alone is fine as long as you clean the mounting surfaces.

http://www.miata.net/garage/tstat/index.html

[Sharpie]

Pre-mix 50/50 is too much for the miata. The like about 70% water to 30% antifreeze. I've fixed at least 3 overheating miatas just by flushing the system and decreasing the ratio.

[Billy Blaze]

Sammm makes a very good point, make sure you clean every bit of the old gasket off and try not to gouge the aluminum housing if your knife is too sharp...just make sure the blade is flat against the surface you are scraping and it should work fine with no cuts in the housing.
It is a real easy job, and you will feel better about working on these cars yourself rather than getting someone else to do it at a shop at $65.00 an hour.
I have only owned mine since January and have done the T-stat, flush and fill on the radiator, installed the header, muffler, springs, shocks, and radiator myself...you will understand your cars functions better and have a sense of bonding with your car and pride in doing it yourself and of coarse save a Butt load of money.
I should also mention that I have done all this work without knowing anything about these cars, but all the people here have been kind enough to offer up info on how to tackle every job.
This place is a wealth of knowledge.
I and many others here would be more than happy to help you out, just let us know.

That's good info Sharpie, I have never tried that...I may try that out next time.

[altiain]

Pre-mix 50/50 is too much for the miata. The like about 70% water to 30% antifreeze. I've fixed at least 3 overheating miatas just by flushing the system and decreasing the ratio.

Yeah, if but the t-stat is stuck closed and the radiator cap won't hold any pressure, then the mixture isn't going to matter.

I agree the mixture is important. But I'd check the cap and the t-stat first, as I've found these two items to typically be the source of the cooling issues with my own car, instead of the coolant mixture.

[Sharpie]

Yeah, if but the t-stat is stuck closed and the radiator cap won't hold any pressure, then the mixture isn't going to matter.

I agree the mixture is important. But I'd check the cap and the t-stat first, as I've found these two items to typically be the source of the cooling issues with my own car, instead of the coolant mixture.

I never disputed that. I trying to keep him from filling up with the 50:50 and still having a problem.

[POS Racing]

I never disputed that. I trying to keep him from filling up with the 50:50 and still having a problem.

Wouldn't a lower ratio actually decrease the boilover temperature?

[altiain]

It has less to do with boiling point, and more to do with heat conduction and capacity. Pure water is one of the more efficient mediums for heat conduction. For example, water conducts thermal energy at approximately twenty-five times the rate that air does, which is why being immersed in 65-degree water feels very cold, while 65-degree air temps are merely pleasant. The 65-degree water is leaching heat out of the surface of your body at twenty-five times the rate that the air is.

Antifreeze lowers the thermal conductivity of the coolant mixture, therefore making the cooling system less effective at getting the heat out of the engine. Here's a chart, measuring the thermal condictivity of some selected substances that are liquid at room temp:

Mercury 	            8.3
Water 	                    0.67
3M Flourinert FC-43 	    0.66
Methanol 	            0.25
Glycol, Antifreeze 	    0.25
Ethanol 	            0.14
Liquid Nitrogen 	    0.14

In addition, antifreeze has a lower specific heat than water (about half as much), which means that it takes twice as much heat energy to raise the temperature of water than it does to cause a similar temperature increase in an equivalent amount of antifreeze.

In other words, if it takes me "X" amount of heat to raise the temperature of a gallon of water by 100 degrees, the same amount of heat will raise the temperature of a gallon of antifreeze by two hundred degrees! This also means that 100% water can actually absorb about twice as much heat from the engine as 100% antifreeze before it reaches the boiling point.

Combine these two effects, and you can see that while the actual physical boiling point might increase, the reduction in thermal conductivity and capacity more than offset the increase in boiling point, and as a result a coolant mixture with more antifreeze is less effective than one with very little antifreeze.

[POS Racing]

Blah, Blah, Blah, Blah, Blah.......

Gee thanks Mr. Wizzard!

Actually I really do appreciate the information!

[Sharpie]

Thanks Iain. I couldn't explain it, but knew I was correct about the ratios. :hockey:
Great info. learning is what this board is for.

[Treibenschnell]

... learning is what this board is for.

No. Making fun of others is what this board is for.

[TurboDuane]

Thanks Iain, I've always wondered why water felt colder than air at the same temp.

[EVOrange]

I'm beginning to think that there may be another problem. This is only a guess, but would the water pump make a squeal when the car is first started and moved in any gear? I start the car and everything is fine. Then when I shift into reverse or first and let the clutch up, a squeal is heard. It's not like a belt sound, but what I can only assume is a water pump sound. I guess what I asking is what does a failing water pump sound like?

Also, thanks for the offer to help. I may take you up on your offer channelmaniac.

Grant

[channelmaniac]

I'm beginning to think that there may be another problem. This is only a guess, but would the water pump make a squeal when the car is first started and moved in any gear? I start the car and everything is fine. Then when I shift into reverse or first and let the clutch up, a squeal is heard. It's not like a belt sound, but what I can only assume is a water pump sound. I guess what I asking is what does a failing water pump sound like?

Also, thanks for the offer to help. I may take you up on your offer channelmaniac.

Grant

I'd say that's probably a clutch problem... I had a throwout bearing that would do that on my B&T before one day it finally gave up the ghost.

Saturday is First Saturday, and family will be over in the afternoon... so if you want to do it on Sunday mid-afternoon (Zoom-Zoom live is in the morning!) I'm available.

RJ

[onething]

No. Making fun of others is what this board is for.

He'll be here all week folks . . .

I actually worked for an engineer once who had a new engine put in his Chevy, drained the radiator and filled it with pure antifreeze before heading to El Paso to visit his Mom. Engine seized before he made it home.

I may not have the technical expertise of Mr. Wizard, but after this many years, I've got war stories and personal experience.

[Sharpie]

EVO, you have a PM (private message)

[POS Racing]

If the water pump was going bad wouldn't you feel play in the pulley, plus you’d hear a constant RPM dependent grumble from the water pump? Either that or having it leak is the two signs of a failing water pump.

Does the car overheat if you are not on the highway with the A/C running?

[TurboDuane]

Another source for the squeel you're hearing could be at the clutch where the slave cylinder and the clutch throw out arm come into contact. It's easily remedied by putting a little grease between them by loosening the slave cylinder and greasing this contact and reinstalling the slave cylinder. I have to grease mine about once a year, then all is quiet for a while.