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bnmotorsgt
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Jan 9, 2010, 6:15 PM
Post #1 of 22
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Overheating Issues
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1994 Mazda Protege 1.8L SOHC 81K Miles. I had luke warm air in the vehicle. Flushed the radiator and heater core (it was stopped up). Changed the thermostat with OEM 192*. As per the gauge, the temp now is 3/4 to full hot. Front fan on radiator doesn't come on. Is that my problem? Any suggestions will be appreciated.
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steve01832
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Jan 10, 2010, 6:23 AM
Post #2 of 22
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Re: Overheating Issues
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When the guage is getting up there, grab the upper and lower hoses (Carefully). If one is hot and the other is cold, you don't have circulation thru the radiator. This could be a faulty thermostat or air trapped in the system. If both hoses are hot and you have good circulation thru the radiator, post back so we can go further.
Steve
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bnmotorsgt
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Jan 10, 2010, 9:31 AM
Post #3 of 22
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Re: Overheating Issues
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After driving the vehicle to normal operating temp., the upper hose is much warmer than the lower. Is this not normal since the water is cooled as it passes through the radiator?
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steve01832
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Jan 10, 2010, 9:39 AM
Post #4 of 22
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Re: Overheating Issues
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What you can try is feeling all of the radiator coils. If one section is cooler than the other, chances are the radiator core is restricted. Do this only after you have confirmed the water pump and thermostat are working properly.
Steve
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bnmotorsgt
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Jan 10, 2010, 4:24 PM
Post #5 of 22
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Re: Overheating Issues
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I believe the radiator is fine. I ran the water hose from the top and it came out the bottom just fine. I put a 180* t-stat in it and the temp came down. The gauge still cycles up and down.
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Tom Greenleaf
Ultimate Carjunky
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Jan 11, 2010, 12:42 AM
Post #6 of 22
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Re: Overheating Issues
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Wrong t-stat - get that one out!
T
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bnmotorsgt
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Jan 11, 2010, 7:51 AM
Post #7 of 22
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Re: Overheating Issues
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Can you tell me why you think it's the wrong one? According to the Mazda dealer, it's an acceptable alternate.
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Tom Greenleaf
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Jan 11, 2010, 12:05 PM
Post #8 of 22
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Re: Overheating Issues
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Too cold! Car may think it's not warmed up screwing up engine controls,
T
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bnmotorsgt
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Jan 13, 2010, 4:35 PM
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Re: Overheating Issues
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OK... I have changed the T-stat to 195* per dealer and replaced the radiator. The temperature difference between top and bottom was around 70*. Was told the radiator was partially plugged. STILL have the same problem (fluctuating temp gauge from about 1/2 to hot). Will go all the way to Hot before coming back down. Checked timing, spark plugs, fan and protection level of coolant (around -30*). All in proper settings. Any OTHER suggestions????? Mazda Service dept. wasn't even sure what is going on. (talked with them on the phone). Trying NOTto have to take it in. 
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Tom Greenleaf
Ultimate Carjunky
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Jan 13, 2010, 5:34 PM
Post #10 of 22
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Re: Overheating Issues
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Factory recommended T-stat is 192F (195F is close enough)
Reason: As said, engine controls expect the higher temp or it could think it's not warmed up yet and make wrong adjustments for timing and fuel mixture.
  Price: $12.99
Application:
OE recommended temperature
Notes: 192 degrees
**************** Both a 180 or 195F are both wide open at 200F or so. Temp fluctuations are as already said - air in system, fan(s) are not coming on at proper times, and other things. Lower hoses can collapse was a tricky problem to find getting sucked shut by water pump and cars subject to that would put a spring inside hose. Also - a bypass system must be clear and working to tell thermostat the engine's temp. Some use a separate hose and some even use the heater core for bypass system allowing all coolant in engine to be uniform, T
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bnmotorsgt
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Jan 14, 2010, 6:04 PM
Post #11 of 22
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Re: Overheating Issues
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Is there a difference between a "regular" t-stat vs one like you pictured? Difference I mean is the way it operates? Would the type you mentioned help with the fluctuation? What's the best way to bleed the system?
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Tom Greenleaf
Ultimate Carjunky
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Jan 14, 2010, 7:52 PM
Post #12 of 22
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Re: Overheating Issues
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It needs to be the correct thermostat as there are different ways they detect temps to open. When all things are equal I like what I call the "Robertshaw" style used commonly in marine use as they are faster to react and can tolerate debris better for raw water automotive style marine engines. Not sure - get one from a dealer.
This is my fav when fit and temp is right........
The one shown a few posts back is slower and less tolerant of debris - the reaction of debris is it would run too cold and doesn't self center as well/dependably when closed.
The whole idea is to keep the temp uniform as water pump is still circulating coolant throughout engine as wild differences side to side/or front to rear isn't good for gaskets and harder for dissimilar metals now common. When everything was cast iron there was less trouble.
You mentioned in first post that the fan didn't come on! That alone is a problem if not solved yet. Transverse engines and some regular ones require powered electric air flow for low speeds. Many will just stay on with defrost or A/C request.
You can mist the radiator if water available and temp should stay stable when warmed up. If it can't do that there's still more to find and fix.
One more for this post - if there's sealer in the system it needs to be flushed out and leak fixed,
T
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Sidom
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Jan 14, 2010, 10:44 PM
Post #13 of 22
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Re: Overheating Issues
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I have just a couple of questions and a few observations.
Did the flush solve the heat problem? Is the car actually overheating or just reading hot? Is the cooling fan coming on?
A lot of cars have front mounted pusher fans that are designed to come on with the a/c system, I would have to check but that could be the case here.
Steve had a few good points I didn't see any clear answers to. One being a restricted radiator, which he gave some good pointers on checking out. Also, I'm not sure how you flushed the system but if chemicals were used then if the impellers on the water pump were maginal, the flush could of made it worse............
1st step would be verify the engine is in fact running hot & the gauge reading is accurate. Then verify the few tests Steve made and depending on those results....go from there.........
If I'm reading this correctly you've already followed Tom's advise on the T stat?
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bnmotorsgt
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Jan 15, 2010, 6:25 AM
Post #14 of 22
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Re: Overheating Issues
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It's at the dealer now and they're going to put a t-stat in. None of the parts stores had the t-stat that is pictured several posts back. Maybe the second coil in that one helps control a steady temp. The cooling fan comes on even when the engine is cold. Not sure that's supposed to happen. The front mounted fan comes on when the A/C is activated. No chemicals used when flushing. Radiator has been changed and temp is nearly uniform over the entire radiator now.
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brager
User
Jan 15, 2010, 6:41 AM
Post #15 of 22
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Re: Overheating Issues
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a few basic things as sugested from us
can you tell us if your cooling fan comes on ?
and do you have the right thermostat in it ?
you could have a air lock wich means a big air bubble in the cooling
system look for the coolant bleeder screw and open it while its running
then rev your engine to about 12-1,500 rpm no more for a minute
after close it.... up if that still dont do it
let it cool down for 15 minutes then i whant you to unscrew the rad cap off
start the engine then reach down to your "lower rad hose and squeeze it hard 8-10 or more"
this should help... keep us posted
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bnmotorsgt
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Jan 15, 2010, 9:15 AM
Post #16 of 22
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Re: Overheating Issues
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Brager,
Apparently you haven't read all the posts. But to answer the questions (again) the cooling fan is coming on, in fact, it comes on as soon as the key is turned on. It's at the Dealer getting "their" t-stat. There is no bleeder valve in this system. I've already done the hose squeeze thing. They're also checking the second speed of the fan to make sure it's working.
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Tom Greenleaf
Ultimate Carjunky
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Jan 15, 2010, 11:13 AM
Post #17 of 22
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Re: Overheating Issues
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Quote>>Front fan on radiator doesn't come on. << From first post.
bnmotorsgt: There's a lot to take in with this thread alone never mind the thousands some of us read and can easily misread something.
Everything I've seen is techs offering their best ideas and suggestions on what this might be. Much harder than having a vehicle right in front of you but the site has a pretty good record of finding answers. Really hope you get the right tech from the dealer which can still be a maybe
T
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bnmotorsgt
User
Jan 15, 2010, 3:38 PM
Post #18 of 22
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Re: Overheating Issues
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I'll let you guys know the outcome from the dealer (if they can figure it out). A lot of great suggestions have come from this thread and I appreciate them all.
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bnmotorsgt
User
Jan 15, 2010, 8:10 PM
Post #19 of 22
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Re: Overheating Issues
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dealer installed a Mazda t-stat. Same symptom except at a lower temp. Only thing left, I think, is the water pump. The only other thing would be the gauge sending unit putting out some wierd signals. Usually they work or they don't. Thinking of bypassing heater core just to eliminate it from the equation. Wouldn't think it would cause this.
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nickwarner
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Jan 25, 2010, 1:13 AM
Post #20 of 22
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Re: Overheating Issues
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No reason to bypass your heater core. It cannot cause your problem. When you turn your heat control knob to the blue, it shuts a valve that allows coolant into the core. So obviously it has a way to bypass when this happens. Because of this, you would be wasting your time and taking working heat away from your car without any benefit.
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bnmotorsgt
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Jan 25, 2010, 5:04 AM
Post #21 of 22
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Re: Overheating Issues
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I think you're mistaken about what you said. Coolant is actually travelling through the heater core at all times. The only thing the lever inside the car does is direct where the air comes from. At any rate, I think I've already ruled it out.
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Tom Greenleaf
Ultimate Carjunky
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Jan 25, 2010, 7:08 AM
Post #22 of 22
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Re: Overheating Issues
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Long thread already - Many vehicles use the heater core as part of the by-pass system and it's in use all the time - just air % thru it is controlled. Reason was when it's shut down completely from any flow sediment is more likely to settle there. It's still done both ways even so, so you have to know each engine.
The return side I've never seen a flow control valve on so if a core leaked it would just get pressure backwards even on those that truly do shut down the flow completely via inlet hose. Making a loop (like faking a heater core) is the best way to go as uneven internal engine temps due to lack of by-pass if involving the heater is risking warpage!
This is another reason why you should NEVER take a thermostat out as even wide open the water pump should still have enough extra to circulate coolant within the engine keeping it uniform. Without one you may only be cooling part and the far end overheating unknown by gauge!
T
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