2nd Generation Specific 1986-1992 Discussion

Overpressurizing Of Coolant System?

Old 12-18-2003, 09:43 PM
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Driving home the other day, my upper radiator hose busted. Split from one end to the other. I immediately shut the car off and pulled over. I replaced the hose, drove home, and didnt worry about it. Today, I drove my car, and opened my hood after a 5 min drive to the store to adjust my timing, and noticed my upper radiator hose was almost double its original size. But the car never got hot. The water temp was just above 180 degrees when running, and after about 30 seconds of having the engine off, it went below 180 degrees, and my e-fan shut off. I let the car sit and cool down. Engine completely cold, hose was still swollen. I open the radiator cap, and it releases all the pressure. Some coolant came out, but there was air present.



What could cause so much pressure in my cooling system, without the engine ever overheating, or even getting past the cool part of the normal range? There was pressure in both the upper and lower radiator lines, so I dont believe its a clogged radiator or stuck thermostat. Also, the temperatures stayed well within normal. I bought a new radiator cap, but have yet to try it out.



Anyone have ideas on what else could cause this?
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Old 12-18-2003, 11:44 PM
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Im not sure bout the pressure being so insane, but something i didnt know that could be useful, is that little tab on the lid on your overflow. I didnt think it actually mattered which direction that faced....and my car kept puking coolant and sucking in air into the system........now i know, the tab faces towards the motor.



Just a random coolant thought...



Id try bleeding the cooling system see if you get any air....turn on your heat, start the car, pop the cap off let it move around, maybe you'll pass some large air bubbles out the system...??
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Old 12-19-2003, 12:31 AM
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The stock pressure cap bleeds off the air and draws in water from the overflow tank when working properly. Ive never seen overpressurization from air bubbles. I got a new radiator cap, and Im hoping its somethign so simple, but the old cap didnt seemt o be stuck or anything. I could move it with my hands. Also, air bubbles cause hot spots, and if theres air in the system, it wont pressurize properly, as the air will simply compress as the pressure increases.
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Old 12-19-2003, 12:31 AM
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change your radiator cap w/ a mazda oem one, and if it pops the top off of the overflow tank you might have a bad coolant seal
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Old 12-19-2003, 12:32 AM
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The motor has 4K miles. Its not a coolant seal. Its nothing side the motor.
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Old 12-19-2003, 01:28 AM
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don't completely ruled out your coolant seals, i mean i know you have built many a engine but everybody CAN **** up once in a while, i thought i heard one time that the rad caps are supposed to bleed off extra pressure if they have to,,, maybe this was also the case?
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Old 12-19-2003, 12:27 PM
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Originally Posted by BigTurbo74' date='Dec 19 2003, 03:28 AM
don't completely ruled out your coolant seals, i mean i know you have built many a engine but everybody CAN **** up once in a while, i thought i heard one time that the rad caps are supposed to bleed off extra pressure if they have to,,, maybe this was also the case?
With bad coolant seals, the motor will heat up faster than normal, and will run hotter than normal. My car does neither. The thermostat is functioning properly. I checked it today, as well as flush my cooling system and replace the radiator cap.



And yes, radiator caps are supposed to bleed off any pressure beyond what theyre rated for. Stock is 13 psi, and there had to be more than 13 psi to make my radiator hose double in size...
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Old 12-19-2003, 02:13 PM
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Fixed. The cap for the coolant overflow bottle was clogged.
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Old 12-19-2003, 02:51 PM
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sweet
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Old 12-20-2003, 11:16 AM
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LOL. Glad it was something simple. I was stumped..
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