A/C and Overheating Question

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09-25-2005, 05:47 PM
EVOrange

A/C and Overheating Question

I've been in the Miata.net forum and someone said I should check to see if anyone was having a tech day around DFW. I would just like someone to look at my cooling system to see if my water pump or thermostat could be the problem. The car gets extremely hot on the highway with the a/c on, but I had the radiator replaced about a year ago with a metal one at the dealer. It doesn't overheat, but comes very close. A lot of simple fixes have been recommended, but I don't know where to look for them or how to try them. I hate going to the shop with no knowledge of the problem because it always seems to result in a huge bill. If no one is doing a tech day, or doesn't want to mess with someone else's car, could you recommend an honest mechanic or shop. I live in Denton, but would take the car to Dallas if the work is honest.

Thanks for your time

Grant
09-25-2005, 06:00 PM
altiain

Welcome to the board, Grant. :chug:

Chances are it's a simple and inexpensive fix. The t-stats and radiator caps on these cars really ought to be replaced every spring, imho. It's not hard to do yourself, and the parts should cost you less than $20 total at your local Autozone or the like.

Keep your eyes and ears posted, as we have a tech day coming up in the next couple of weeks. Either that, or one of us might be able to help you fix the problem one afternoon or evening - it doesn't take long to do.
09-25-2005, 06:04 PM
EVOrange

Thanks for the reply.

I live in Denton. Is there an email list I can join for the tech day or should I just check back on here?
09-25-2005, 06:19 PM
POS Racing

Quote:

Originally Posted by EVOrange

Is there an email list I can join for the tech day or should I just check back on here?

Just check back here! :cool:

What have you replaced so far in your efforts to get it to cool down, I know you said you got a new radiator, but what else have you done??
09-25-2005, 06:24 PM
sammm

Quote:

Originally Posted by EVOrange

Is there an email list I can join for the tech day or should I just check back on here?

No email list to join. You'll soon find a lot of the members on our forum like to AutoCross! The season is winding down and Tech Days are bound to pop-up once the season is over. Welcome aboard!

Like altiain stated, replace your t-stat and radiator cap for starters...that may be all you need. Keep us posted.
09-25-2005, 06:33 PM
EVOrange

The car has 63,000 miles. Things replaced so far:

Brakes
Radiator
Belts
Plugs and Coil Pack

Everything on the car is stock. All work thus far has been done by the dealer. I bought the car used in 2000 with 8,000 miles on it. I'd like to keep the car stock, I'm not really into aftermarket modifications. Before this Miata, I had a 1990 Miata that I bought in 1997 when I was 17. I traded it with 142,000 miles for the 2000. Except for my first year driving, I've only driven Miatas. My step-dad did all the work, or at least the pre-shop consultation, but he passed on in 2003. Since then, I've been trying to figure out the problems on my own. I'd like to come to the tech day, so I'll keep an eye on the site.

Thanks
09-25-2005, 06:51 PM
Majik

The tech day is something that is really helpful here. Especially for someone like you who seems to have little knowledge of working on cars. (Not a bad thing, no one knows before they start) The reason, is that it gives you an opertunity to get your hands dirty and learn what you are doing, while experienced people help. Like Altiain said, the thermostat and radiator cap are easiest and cheapest. They are also very likely to solve the problem. Why was the radiator replaced? To solve this problem? I would recommend the radiator cap first, since that might take 30 seconds if you count raising the hood. You need no tools, and it is about like opening a coke bottle.
09-25-2005, 06:54 PM
POS Racing

Quote:

Originally Posted by Majik

I would recommend the radiator cap first, since that might take 30 seconds if you count raising the hood. You need no tools, and it is about like opening a coke bottle.

Yep that would be a good starting point!

Another question has the car been loosing any antifreeze out of the overflow bottle?
http://www.harrisonindustrial.com/im...Overflow02.JPG
09-25-2005, 06:58 PM
EVOrange

When I took the car in for the brake job, I was told that the radiator had a crack in it. My first Miata left me stranded from a cracked radiator, so I felt that this was a legitimate problem. I asked for a metal one instead of the plastic, because they seem to have cracking problems. I'll replace the cap, but I think I'll wait for the tech day to look at the thermostat. The car does fine around town, it's just highway drives longer than 30 mins that seem to raise the temp. Thanks for all the advice.
09-25-2005, 07:00 PM
EVOrange

Also, fluid levels have remained the same.
09-25-2005, 07:07 PM
POS Racing

Quote:

Originally Posted by EVOrange

Also, fluid levels have remained the same.

I noticed today on our '02 the level had dropped down a touch, upon further review it looks like the Radiator Cap may have a slight leak! But it's past time since for it since it is the original cap! :oops:

Hey does anyone happen to know the Mazda P/N for the NB's radiator cap? I notice it has a 1.1 rating where the one on my '92 has a 0.9 rating!
09-25-2005, 08:16 PM
Majik

Quick question, where is your liscense plate? Billy Blaze had a problem like yours a few months ago. I think his front plate was actually in the grill and not on a bracket on the nose.

Edit: Here is the thread about that. I think we gave some good clues as to what you can change.
09-25-2005, 08:19 PM
blackzx3_13

Does he need a "stiffy"? :geek:
09-25-2005, 08:20 PM
Majik

Quote:

Originally Posted by POS Racing

I noticed today on our '02 the level had dropped down a touch, upon further review it looks like the Radiator Cap may have a slight leak! But it's past time since for it since it is the original cap! :oops:

Hey does anyone happen to know the Mazda P/N for the NB's radiator cap? I notice it has a 1.1 rating where the one on my '92 has a 0.9 rating!

KL01-15-205

Mazdastuff.com has it for 10.04
Mazdamotorsports for 7.60
09-25-2005, 08:20 PM
Majik

Quote:

Originally Posted by blackzx3_13

Does he need a "stiffy"? :geek:

I would have to say that isnt my business! :shock:
09-26-2005, 08:16 AM
Sharpie

Grant, you and I met awhile back where you worked. I'm still in Denton. I have some suggestions too. The first one is what is the ratio of water to antifreeze. I'll help you if I can. Shoot me a PM with your phone #.
09-26-2005, 09:19 AM
Billy Blaze

Hi EV!, I was having the same problem earlier this Summer.
Everyone was real helpful in getting mine back to good.
Here's what I did....
1.) Bought a New Radiator Cap
2.) Bought a New Thermostat
3.) Bought some 50/50 (distilled water/coolant).
4.) you will more than likely need a new thermostat housing gasket, I had to scrape mine off with a pocket knife.

I replaced all this and ran a couple of gallons of Distilled water through the radiator to flush it out.

After I put the new T-Stat in and new gasket on, flushed and filled the radiator with new coolant the problem stopped.
Many people have commented at how well the Miata's cooling system is Stock, after I did the above procedure mine was working well with or without the A/C running.
tip: Whatever you do, don't lose or over tighten the plastic Radiator bolt.
also make sure your license plate isn't obstructing your radiator, that was a problem with mine as well.

Later this Summer and just recently I replaced the Radiator with a PWR double core Radiator, it is for HOT Climates, and running forced induction...if you want added insurance that may be an option for you.
However I beleve that doing the above will cure your problem as it did mine.

Hope this helps, feel free to IM me if I can help with any further questions.
09-26-2005, 07:08 PM
EVOrange

I'm going to buy a new radiator cap tomorrow. I'll have to see about replacing the t-stat. Not sure how to do that. Not sure where it is. :)

I'll keep you posted.

Grant
09-26-2005, 07:11 PM
POS Racing

Let us know we are here to help! :cool:
09-26-2005, 07:22 PM
channelmaniac

Grant,

If you want to drive down to Lewisville, I'll be happy to help ya with it... I've done several thermostats...

You'll need a new thermostat & a gasket... and while you're at it, get a gallon of pre-mix antifreeze.

If you want to do a flush/fill on the antifreeze, you'll want to get two... probably only need one, but it's best to be prepared...
RJ
09-26-2005, 07:46 PM
sammm

Quote:

Originally Posted by EVOrange

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
09-27-2005, 10:29 AM
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.
09-27-2005, 10:53 AM
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.
09-27-2005, 01:03 PM
altiain

Quote:

Originally Posted by 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.

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. :wink:

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.
09-27-2005, 01:08 PM
Sharpie

Quote:

Originally Posted by altiain

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. :wink:

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. :bash:
09-27-2005, 01:19 PM
POS Racing

Quote:

Originally Posted by Sharpie

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

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

http://www.peakantifreeze.com/images...tion_chart.jpg
09-27-2005, 06:23 PM
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:

Quote:

Code:

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.
09-27-2005, 07:13 PM
POS Racing

Quote:

Originally Posted by altiain

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

Gee thanks Mr. Wizzard! :mrgreen:
http://www.museum.tv/archives/etv/W/...watchmrwiz.jpg
Actually I really do appreciate the information! :cheers:
09-27-2005, 07:21 PM
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.
09-27-2005, 07:25 PM
Treibenschnell

Quote:

Originally Posted by Sharpie

... learning is what this board is for.

No. Making fun of others is what this board is for. ;) :D
09-27-2005, 08:31 PM
TurboDuane

Thanks Iain, I've always wondered why water felt colder than air at the same temp.
09-27-2005, 08:32 PM
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
09-27-2005, 09:47 PM
channelmaniac

Quote:

Originally Posted by 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

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
09-28-2005, 07:05 AM
onething

Quote:

Originally Posted by Treibenschnell

No. Making fun of others is what this board is for. ;) :D

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. :dwarf:
09-28-2005, 09:26 AM
Sharpie

EVO, you have a PM (private message)
09-28-2005, 10:23 AM
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?
10-01-2005, 11:29 PM
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.