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Overheat on Idle?

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Old 09-02-06, 08:30 AM
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Overheat on Idle?

Any one had this problem, I've searched but couldn't find an answer. I always let my car idle for a little while before I drive to warm it up. Well the other day I heard the rpms go up a bit like the ac had come on or something. I went over and noticed the temp guage was rising a bit over half. (my 89 vert typically stays at half). I immediately turned it off and opened the hood. Water was going into the resevoir. I let it cool completely and then cranked it up and went for a drive (close to home) It came to normal temp and never got hot. Opened hood / no water in reservoir. What the hell. Can it be that the summer air is so hot here that it will heat up with no wind from driving. I've been driving this car for 12 years without this problem. I did switch to royal purple 20/50 last week which really seems to smooth out the engine. But I thought that stuff was supposed to be "Cooler". Obviously could be a thermostat , but why just at Idle?
Any help
thanks
Old 09-02-06, 09:32 AM
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Start here for cooling system troubleshooting:

http://www.aaroncake.net/rx-7/cooling.htm

It sounds like you may have a sticking thermostat.

Keep in mind that there is no need to "warm up" the car before you drive it. Doing so just wastes gas and time.
Old 09-02-06, 09:40 AM
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Thanks Aaron very informative.!
Old 09-02-06, 01:02 PM
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If you have a stock fan, don't these cars have fan clutches? Could it be that?

Sorry for the noob reply.
Old 09-02-06, 01:11 PM
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yes, they do have fan clutches. And yes that could very well be the problem.
Old 09-02-06, 03:49 PM
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Marclong- any cooling system that is as old as ours... where you have a radiator that is prob 5-10% clogged... you are going to have a problem with "getting warm" especially with the weather we have been having here in Atlanta.... I would suggest pulling your radiator out and flushing it well... There is a company here in Marietta that does it CHEAP... Actually... I would be willing to help you... I would imagine your radiator is does not have good flow.... I mean hell... look into a new radiator...

Also- make sure your coolant/water mix is correct... this will not prevent it from getting hot...however in the event that you overheat it...it will ensure that you have the highest boiling point possible...

Where in Atlanta are you?
Old 09-02-06, 04:56 PM
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I am not sure about the warning up part Aaron........at least let it get to operating temperature.......and if you drive right away SHIFT at 3K RPMs until you've reached operating temps.

Could clogged cats cause overheating?
Old 09-02-06, 06:21 PM
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There is no need to wait until the engine is fully warmed up to drive it. You just take is easy and keep the revs down until then, just like every other car.
Old 09-02-06, 11:03 PM
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I'm betting on the thermostat

I would replace the thermostat first, unless you have a Mazda stat in that you replaced recently.

I just replaced my thermostat neck (brittle plastic broke) and while I was at it I purchased a Mazda stat and rubber seal. The old stat was oem, but the rubber gasket was falling apart. I have had the car for nearly two years and I am sure the previous owner had not replaced it. I test heated it in a pan of water and some of the wax came out in the water. The stat did not open up nearly all the way. It was failing.

After replacing the thermostat and warming up the car for the first time, I have never before seen the coolant flowing so fast through the top tank. Adddionally, I am sure that the gasket seal failing would have caused my slight system leak under vacuum during cool off.

BTW, I got the part at Rotary Performance in Dallas, TX. They only use and sell OEM.
Old 09-03-06, 09:10 AM
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Thanks for the replys. I put in a brand new radiator when I installed a mazda engine about 40,000 miles ago, also thermostat. I'm leaning towards the fan clutch as it is original and has 221000 miles. While driving everything is perfect. Even tends to stay slightly under half, I think its a little cooler with the royal purple oil I put in last week. I wonder how much Mazda is ripping people off for a new fan and or fan clutch.
Old 09-03-06, 09:48 AM
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Originally Posted by Madrx7racer
I am not sure about the warning up part Aaron........at least let it get to operating temperature.......and if you drive right away SHIFT at 3K RPMs until you've reached operating temps.
I think there have been threads in the past discussing this. There is no need to "warm up" any modern car. The EFI system compensates for engne temp differences and the engine tolerances have been designed to keep the engine happy from dead cold to fully warm. Also the fluid grades are chosen by Mazda to assure proper flow at all temperatures.

Just don't beat on the car until it has reached operating temperature. This is true of any vehicle.
Old 09-03-06, 12:49 PM
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Hey great I think since I started this thread my situation got a lot worse. Blew a coolant seal. Noticed some white smoke and shitty Idle at startup. Drove around to the parts store fine. Got back in white smoke and shitty Idle for about ten seconds. Thought I had used to much premix in the gas( Replaced OMP last week and premixed gas just to be safe.) Filled up the gas and same thing. But was driving fine, and no over heat. Then after like an hour later then temp gauge skyrocketed. I was like Fu**Ck. Well it dropped back really quick so I just kept cruising. Got home and the reservoir is full. Think when it over heated the other day I fried a seal.

****
Old 09-03-06, 04:03 PM
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Here is the final deal. The resevoir was full like I said in the last post. After an hour or so I went back out to start it , all the coolant had gone back into the radiator. No smoke, and goof Idle on start. All I can figure is that since most of the coolant had gone to the reservoir maybe not much stayed in the engine. Curiously I did the radiator cap bubble check, lots of big bubbles, no gushing. I let it get to normal temp then shut her down. Gave it a few minutes and started it up. White smok , and bad idle. Hardly revs for about 25 seconds. than fine. Another note-- Coolant steadily coming into the reservoir. Felt upper radiator hose it is got a LOT of pressure on it but is cold? Radiator cold? I would think bad thermostat. But that wouldn't explain the white smoke and bad starts.

Anyone know who can replace these water seals here in N. Georgia. I do not have the patience to pull this engine again nor the proper tools.
Also if anyone has any alternate ideas please let me know. Otherwise I figure I'm taking over to Mazcare in Marrietta, They are suppossed to be some of the best around.
Old 09-03-06, 04:37 PM
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Kevin at www.rotaryresurrection.com is in Tennesee near Knoxville. Hes probably your best bet.

Last edited by Sideways7; 09-03-06 at 04:40 PM.
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