Overheating

H

hpmaxim

Member
:
2003 Mazda Protege5
To make matters worse between my fuel and vacuum issue, my car overheated on the way to work.

I was in stop and go traffic and noticed an odd smell. About a minute later I saw steam coming from under the hood and then noticed the coolant temp gauge was on H.

About a half mile later I managed to pull over. The coolant in the reservoir appeared full but was boiling. I let it sit for an hour. The coolant level dropped to near the bottom. Serpentine belt seemed fine. I had heard no odd noises. There was only a very small amount of coolant on the ground and no obvious dripping.

I decided to head back out since traffic had subsided and the car cooled. I figured as long as I kept it at highway speed I was probably safe. I turned the heat on full blast. At first there was a squeaking sound that I don't remember but it went away after several hundred feet.

The car seemed fine but coolant temp started rising, slowly at first then quickly. I turned the car off and kept going. I continued this cycle of accelerate and shut the car off and made it to work without further incident although the temp gauge while never reaching H did climb above midway multiple times. The air out of the vents was hot.

So... what is it? I assume the coolant pump is okay because vents were hot. I assume radiator fan is irrelevant cause I was going 60 mph. I assume thermostats normally fail open. My only theories at this point are: rad fan failed, car overheated in traffic and I lost so much coolant it can't keep cool any more, or a blockage in the radiator or lines to the radiator which likely means catastrophic engine damage, although engine seemed fine. HELP!
 
I had something similar happen a few years ago. Turned out it was a bad t-stat. I replaced it along with the gasket and hoses, then filled the system and have had no reoccurring issues. A few years later I changed the t-stat and hoses again but only because my rad had a leak and I was replacing it, so I figured I might as well while everything was torn apart. I'd do it sooner than later though to risk any possible/further damage. I got lucky and had no head gasket issues.

But first things first, check the fans to make sure they are running properly. Might be something as simple as a new sensor.

Good luck!
 
CT3, googling P5 overheat it seems everyone who is having a problem is having a problem with the T-stat. Thing is driving at 60 mph should keep the radiator cool without the fan. If there's 1 sq ft of frontal area, 60 mph = 5280 cfm, a REALLY powerful 12V fan is about half that. So unless losing coolant caused the continued overheating, its NOT the fan or something controlling the fan.

The thing that surprises me is that I thought thermostats were designed with safeties so they failed open. So if they failed, you'd never get the car to temperature but it wouldn't overheat. But, I guess not. I'm wondering if this is something that I could try in the parking lot at work. What I worry about is refilling and bleeding the coolant....
 
I am dealing with this now...

Coolant tank boiling and overflows, then when car is cool, the bottle is near empty.

Finally got around to pulling the spark plugs and looking into the cylinder that had the white deposits on the spark plug, and there is indeed wet coolant on top of the cold piston.

Motor pushes the 180psi air from the cylinder with the gasket fault into the 16psi cooling system. This new air pocket in the cooling system allows the coolant to boil and the pressure pushes out the coolant into the overflow bottle. As the car cools, the coolant is suctioned back from the reservoir, and the 16psi cooling system pushes the coolant into the faulty cylinder upon shutdown because it is now 0psi in the cylinder.

In my case it is a: Blown head gasket... caused by an overheat, caused by worn out brushes on the Primary Electric Cooling Fan.
 
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Actually if that much coolant got sucked back into the cylinder shouldn't it hydrolock the engine. The friend I called thought it was just water contacting from boiling to normal. Coolant level is only slightly lower than it was before. It could have just cooled off more. It's an hour later. Radiator was cold to the touch. Engine and thermostat housing was still hot.
 
If the gauge is showing hot, and the upper/lower hose and radiator are cold, the thermostat is usually to blame.

Some thermostats have fail-safes built in, some stick open, and some will stick closed. It's all dependent on the design.

Normally a fail-safe thermostat will have a heat-sensitive clip that locks the thermostat in the open position if the engine ever overheats. A quality factory replacement thermostat is a better option, IMO.
 
Its been too long to know if they just cooled off at this point or if they weren't getting hot. But about an hour after it overheated, radiator was cold engine block was still quite hot. Of course, the radiator is designed to shed heat and the engine isn't. Local Mazda dealer wants 24 bucks for thermostat and seals, so I'll just do that. Is there a particular type of coolant I should use? The stuff in there is bluish, and I assume is factory fill.
 
hpmaxim said:
Actually if that much coolant got sucked back into the cylinder shouldn't it hydrolock the engine. The friend I called thought it was just water contacting from boiling to normal. Coolant level is only slightly lower than it was before. It could have just cooled off more. It's an hour later. Radiator was cold to the touch. Engine and thermostat housing was still hot.
Click to expand...

Well I guess it would depend on the pistons stopping location in the 4cycle, and the size of the leak with regards to the possibility of a hydrolock.

In my case, I am going to have to get a combustion gas leak detector for the cooling system to finalize my analysis.


Now back to yours... The cooling fan should come on at 205F. Tap on the relay in the fuse box, and tap on the back of the drivers side cooling fan to see if it starts moving...

In my case the brushes in the fan motor were worn out to the point where they could not touch the armature and spin the motor anymore.

Try out the A/C fan on the passenger side by turning on your A/C... does that fan work either?
 
I just had a similar issue with mine. turns out the rad cap went bad and car would seep coolant from the top. I replaced the rad cap and not 10 miles later i blew the fitting on the bottom of the rad for the auto tranny lines. That dumped all my coolant and it got hot quick. after a new rad and another new cap its running great. just be sure to bleed the air from the cooling system before you travel on down the road.
 
What does the A/C fan have to do with this? If the fan failed and it was overheating while driving at speed on the highway it's almost certain the headgasket is blown or there is some other really serious damage.

I wasn't clear from what you wrote how to test the fan, but even if the fan came on that doesn't prove the system is working because it could still be the switch that controls the fan.

I think my next step is replace thermostat, fill with water and hope problem is resolved. Then drive home and flush water till its clear and refill with coolant mix. I wish I had been able to get the car back home.
 
Sleepr, not sure I followed the only trace of lost coolant I could see was near the hose from the reservoir cap. So I don't think that's the problem, radiator was bone dry and i didn't lose that much coolant.

What's the bleed procedure? Is it just lift front of the car, heat on full and idle with occasional revving to 3k? Is there a bleed screw?
 
i wasnt leaking onto the ground at first. i noticed my temp guage running higher than usual. opened the hood to see a few drips around rad filler neck. tested the cap and it failed. replaced that and i assume the pressure blew out a corroded fitting and then all hell broke loose. im sorry i thought your system was full but you ran hot. a rad cap is cheap place to start but sounds like the tstat might be the culprit.
yes lift the front fill slow and then run with heat on. idle for a few min til up to temp then 2k for a few min. install the cap and fill overflow to between fill and max. drive around let it cool and top off if necessary. no bleeder screw i am aware of
 
hpmaxim said:
What's the bleed procedure? Is it just lift front of the car, heat on full and idle with occasional revving to 3k? Is there a bleed screw?
Click to expand...

There is no bleeder scew.

When I did mine I didn't lift the car and I left the cap off and waited for the t-stat to open.... You can see it start to flow. Then just kept adding fluid as the level dropped.

I also pumped the upper rad hose to force out some bubbles.

If there is any small bubbles left they will work themselves out in the heating cooling cycle.

Keep an eye on the overflow tank level.


Here's what the FSM says...








 
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hpmaxim said:
What does the A/C fan have to do with this? If the fan failed and it was overheating while driving at speed on the highway it's almost certain the headgasket is blown or there is some other really serious damage.

I wasn't clear from what you wrote how to test the fan, but even if the fan came on that doesn't prove the system is working because it could still be the switch that controls the fan.

I think my next step is replace thermostat, fill with water and hope problem is resolved. Then drive home and flush water till its clear and refill with coolant mix. I wish I had been able to get the car back home.
Click to expand...

OK, there are 2 fans on the front radiator of the car. One comes on at 205 degrees, the other fan, the AC fan comes on at 235 degrees. Are your fans turning on?? If you unplug the coolant sensor connector, your fan should turn on.

To test the fan, either check for continuity across the fan motor terminals, or apply 12volts battery power to the connector and see if it works.
 
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I just went out and started my car ( cold)...

No fans were running.

Turned on my AC... Both fans came on.

Turned off AC... Both fans shut off.

Easy way to test the fans (but maybe not the temp sensor...)
 
I left the car at work and got a ride home, so I can't answer that, I'll give it a shot though.
 
I remember reading that if you overheat turn on the AC....

I thought that no sense because that would just add more heat to the rads and engine bay ???

I guess if the ECU is not instructing the fans properly, this overrides our dimly ECU ??
 
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