Need help diagnosing coolant leak/overheating problem on P5.

Dumbledore

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2002 Mazda Protege5
So while I was on the highway my car overheated and shut itself off. I was able to get it to a mechanic about a mile from that spot and they checked it out and said it was a faulty radiator cap causing it to leak fluid. They charged me 80 bucks for the diagnostic and part and sent me on my way (they also said they kept it under pressure for an hour and couldn't find any other leaks) . I drove back to town and by the time I was there I could see it was overheating again. I opened the hood and was looking for leaks since I could smell antifreeze and saw it was dripping down off the frame in the front right section of the car. There appears to be no leaks near the head gaskets, the upper or lower radiator hose or the water pump as far as I can tell. The water reservoir tank is pretty brittle and has a few cracks that could definitely cause fluid to come out. My question is would that alone be cause enough for the car to overheat? Is there other places to look for leaks? Other possible causes that could cause overheating problems. The check engine light is on and the car is idling very strangely and not very strong. Sort of sputtery compared to its usual idle. Any help greatly appreciated.
 
From what I see on here, thermostats are the usual culprit for overheating.

I'd be a little upset with the shop, since they must not have not even test drove it after throwing on a cap.

A cracked reservoir would not cause overheating.

I prefer to do a real quick block test to rule out a head gasket, especially on a car that has been overheated a few times. Parts stores will loan the tester for free.
 
Would a faulty thermostat cause leaking or just bad readings on my gauge? Thanks for the reply I actually have a new thermostat right now I just bought since I thought it might be part of the issue.
 
Have you changed your timing belt ? I solved the crap idle sputtering after a similar over heating event with a timing belt and water pump ( figured it might have over heated if the pump wasn't moving the coolant well enough ). Also just to be safe I grabbed an engine coolant sensor from a scrap yard.

Found a few threads in this forum that might help.

https://www.google.ca/search?q=mazda+p5+engine+coolant+sensor+site:www.mazdas247.com

Good luck !
 
actually the tank would cause the engine to over heat. mine was brittle and was overheating, once I change the tank no more overheating.
 
Have you changed your timing belt ? I solved the crap idle sputtering after a similar over heating event with a timing belt and water pump ( figured it might have over heated if the pump wasn't moving the coolant well enough ). Also just to be safe I grabbed an engine coolant sensor from a scrap yard.

Found a few threads in this forum that might help.

https://www.google.ca/search?q=mazda+p5+engine+coolant+sensor+site:www.mazdas247.com

Good luck !

The timing belt was changed before I bought the car in February so it should be good. I don't have receipts from the guy though so I'll check that out for myself just to be sure. When you say engine coolant sensor is that a thermostat or a different part altogether?
 
Just overheating.

It can cause a leak indirectly by overheating, then boiling the coolant out of the overflow.

Good to know. That makes sense I can't find a spot that it's leaking from but it does look more like it's coming out of the overflow considering it has coolant puddles right below it.
 
The coolant sensor is on your water pipe from the top hose from your rad, It is the brass unit with 2 leads attached to your harness. Mine had brittle wires from a severe overheating event and required a bit of a re-worked wiring to clear a engine coolant circuit open error on a OBDII reader. ( worth the $100 imho ).

Any luck ?

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The coolant sensor is on your water pipe from the top hose from your rad, It is the brass unit with 2 leads attached to your harness. Mine had brittle wires from a severe overheating event and required a bit of a re-worked wiring to clear a engine coolant circuit open error on a OBDII reader. ( worth the $100 imho ).

Any luck ?

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Not just yet, need to gather up a few more parts. Gonna redo the radiator as well since I'm replacing most of the other stuff like the overflow bottle. I'll look into the coolant sensor for sure though, thanks.
 
Mine overheated several years ago due to the thermostat failing. Changed the thermostat, rad cap and hoses but the car was still running hot. Someone here suggested replacing the coolant sensor. Upon doing this, I never had an issue again.
 
Yikes! If motor is not running right, I would find out what the check engine light code is.

If the coolant has been kept clean, and it is not leaking, I would leave the radiator alone.

Start by fixing your KNOWN FAILED items like your Coolant overflow bottle first... anyone can DIY this...

A cracked coolant reservoir will allow the hot coolant to leak out upon expansion... then when the system cools and the coolant is normally drawn back into the radiator from the tank, there is now less coolant due to the leak...this continues each time, until the coolant becomes low, causing the motor to run hotter, causing it to eject even more coolant into the expansion tank as the temp increases.

Verify that both of the electric cooling fans are operating as they should....Then bleed the cooling system properly, and see if you have any more overheating problems...

If YES, then I would look at testing the thermostat and the temp sensor, and inspecting your sparkplugs to see if there is coolant being burned in one of the cylinders from a head gasket failure.
 
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I am losing coolant. My overflow reservoir is good. I put the tester on the radiator and pumped it up to 17.8 psi and ti wont hold pressure, but cannot see any coolant leaking anywhere while pressurized.
You indicated that i should check my spark plugs. What would I be looking for on the spark plugs?
 
I am losing coolant. My overflow reservoir is good. I put the tester on the radiator and pumped it up to 17.8 psi and ti wont hold pressure, but cannot see any coolant leaking anywhere while pressurized.
You indicated that i should check my spark plugs. What would I be looking for on the spark plugs?

Signs of coolant on the spark plugs, usually ash deposits, and one or sometimes 2 plugs will look completely different then the others. because they have been burning coolant.
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I put the tester on the radiator and pumped it up to 17.8 psi and ti wont hold pressure, but cannot see any coolant leaking..

Make sure your filler neck on your rad isn't worn or damaged.
The rad cap and tester may not be sealing properly.
 
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