'84 GSL SE, 124k, no efan
I've owned the car since October and have put less than 2k on it. It's never heated up past about 1/3 up the temp gauge, and has always stayed there. I've been driving it more since the weather has been warmer and have not seen it rise at all - until Saturday. It warmed up to 1/2 way up the gauge and stayed there. It would dip slightly when I would idle but would jump back up when driving. I only put about 10 miles on it while at this temp, with a turn off/cool down/drive cycle in the middle. I know where to look to solve a problem like this (thermo, water pump, rad, fluid, belt tension, fan clutch) but would like to know the likelihood of each. Thermo is first. Rad flush or core-out and fluid is second. But where to from there. I think the fan clutch is operating correctly, but how do you check? (I forgot.) How likely is it that I blew a coolant seal? No white smoke so no exhaust seal leak, right? What about the intake coolant seal? (Am I right, is there such a thing? I only know to ask after reading other threads about this problem.) Haynes manual not much help. I've yet to download a FSM. (No printer right now.) Any help appreciated.

 

Make sure your radiator is completely full. If its not, check for visible leaks (hoses and fittings). Check or buy a new radiator cap. Check that the overflow bottle cap is snapped on properly and the tube connected to it has not fallen off into the bottle. When the coolant heats up it expands past the 11 psi seal on the radiator cap. Some runs into the overflow bottle. When the coolant cools down it contracts. The coolant that expanded into the bottle is now sucked back into the radiator. Anything that breaks the seal in the overflow system will not allow the coolant to get back to the radiator. Soon your coolant level gets low and the car starts running warmer.

 

make sure your clutch fan is working properly, then install a new "mazda factory" thermostat.

 

Coolant level is normal and has not lost any prior to this heating up or after. Thermostat is on its way and fan clutch operation will be verified. What is the likelihood of this problem being a coolant seal? I'm deathly afraid of a costly repair or rebuild right now.

 

Coolant seal would be low on the list of probable causes. Especially if your coolant level is good. Plus you'd see lots of smoke.

 

Also, what temp. thermo is best for dd car? Mazdatrix sells a 180 degree. I know I've seen recommendations for other temps here but can't find them right now.

 

stick with oem t-stat. how old is the radiator? check and make sure its clean and that the airflow to the core is not obstructed with leaves. if you have a/c and still have a condensor, make sure it is also clear and clean, as air has to flow through it before it flows to the radiator.

 

It won't be your fan clutch, but if you want to check it start the car, get it up to operating temp, turn it off, and try and spin your fan. if it spins freely its bad. if it spins about 1 turn and stops your all good. but a bad fan would result in overheating while idling. your thermostat could be stuck in the middle. I'd do a good coolant flush new tstat.

Also to check if your radiator is clogged take your fan and shroud off. warm up the car. feel the radiator for cold spots. It should be uniformly warm/hot. be careful not to burn yourself. You should be fine. My cars gone to the half way mark a few times. I still have good compression, and no issues. I really need to get a fan.

If its none of these. I'd look into your water pump. could of just rusted away. http://www.rockauto.com has them pretty cheap. aswell as radiators. Just don't buy a cap for it from them. It won't fit.

 

Could just be that your local temperature is now a good bit warmer than it was in October...

My -7 traditionally runs cold (less than 1/5th up the water temp guage, oil temp around 160) but I was driving it home in stop-and-go on Monday. It was 100 degrees outside, traffic was moving around 20, 25 mph. Water temp guage rose about to the 1/3 mark, & oil temp made it to about 175.

I'm pretty sure I used a 160 thermostat on the engine last rebuild, because of overheat probs in bad traffic with my previous build. Probably was unnecessary, as the car has run colder than optimum since then.

 

In cali it got to 100 degrees over the weekend. Driving on the freeway at 70 I noticed my temp gauge got up to half way. It normally stays just above the second mark on the left side. I kinda figured it was just the warm weather. Its hanging around where it normally does now, and the weather is a lot cooler this week.