Car Overheating. New Thermostat. New Coolant. New Water Pump.

Posted in Internal Engine Parts

A few months ago I replaced the water pump because it started leaking. It continue to heat up 3/4 of the way at random times then went back down. I replaced the thermostat recently with an OEM one. I had replaced it before with an aftermarket. No white smoke when start in morning or when driven. I also replaced the air filter. Checked all sensors and relays. Fan’s come on. AC works. Heater works. What could it be? No signs of oil in coolant or coolant in oil. It happens randomly but a lot more lately. Sometimes higher RPM’s will cool it down sometimes it doesn’t. What can it be? Mazda v6 is the car.
No coolant leaks. Checked the coolant before and it would still be full for over a month. I recently replaced the coolant so it’s top off. I checked it. I will try bleeding the system. I did tried to bleed the system following instructions the manual before with the other thermostat and it still overheat 3/4 of the way then I would cool it down by carefully spraying some water over the radiator.
I checked the temperature gauge and I do believe it’s working. The car does get very hot. The fan(s) do come on at certain temperature.

There are 7 Answers for "Car Overheating. New Thermostat. New Coolant. New Water Pump."

    1. Brian D says:

      Did you properly bleed the cooling system?

    2. Chevyriddinhigh says:

      My truck’s doing the same thing….it has a slight leak in the coolant system so every time i fill it up it drains slowly…when it gets down past a certin level it will only properly cool part of the time meaning: it will cruise and 1/2 to 3/4 heat and then spike to full danger for a couple seconds before cooling back…..longer i go without topping off my coolent with more water, the worse the spikes get.

      hope this helps

    3. Mikrp says:

      Possible blocked radiator, i would suggest buying some cooling system flush at the local auto parts store and follow the directions, or most “quick lube” places will do a coolant flush. Also are you sure the temp gauge is accurate? you didn’t say how old this car was but temp sensors are know to go out of calibration. i would test water temp with a thermometer first to see if you actually have a problem with temp or temp gauge

    4. Moe Fugger says:

      It could be many things. I’d get it to a reputable shop and have the cooling system pressure tested, should cost you a whole 20 dollars, and also have it block tested, then you will have your answer.

    5. Ttompetty says:

      Change thermostat for a 160 degrees thermostat,, also make sure coolant is proper amount, water will not cool and engine,,, if all that doesnt do it then your radiatir has to be blocked,,

    6. Glenn Z says:

      I am going to assume with my answer that the car overheated because of the low coolant level due to the water pump leak and low coolant level.
      A sealed cooling system will hold coolant indefinitely and not need topping off too often.

      I have the same problem. I blew a hose at highway speeds during rush hour. I had the car running no more than 20 seconds to get to the shoulder but the damage was done. The temp shot all the way to the redline on the temp gauge before I shut he car down. I noticed a coolant leak around the intake within a week or two.
      Now after replacing the intake manifold gasket, thermostat hoses and flushing the system, I exhibit the same symptoms you have but I also blow coolant out of the coolant bottle after 1/2 hour of highway driving due to exhaust gases entering the cooling sysytem. This is a classic symptom of a blown head gasket and/or warped head(s).
      These are the only symptoms but they are it is persistent and wont go away and will require the top end be torn down and rebuilt.
      I have 100,000 miles on my engine and have owned since new. I’ll spend the 150.00 in parts and redo the work I’ve already done and now do the head gasket. I plan on keeping my ride for another 10 years barring my tranny going out.

    7. Michael says:

      If the cooling system has had tap water added to it, including to dilute the antifreeze 50%, I suspect the radiator is plugged. No flush will deal with hard water deposits that severe so replacement is the way to go if that is the problem.

      Diagnosis is simple enough – drain the system, disconnect the hoses from the radiator and try to run water from a garden hose through it. A good radiator will pass all the water you can put in, a plugged one will not.