I've recently installed a NA engine in my rx7 and i am losing coolant. every 50 miles or so im losin the whole overflow bucket of water. I am not runnin coolant, but that should make a difference. Well, my temps are runnin about 1/2 so.... i think somethin is whack. There is rust in the coolant. hmm, nothin else really. Temp doesnt stay right at half, kinda wavers around, but never lower than 1/3 and sometimes a tad above 1/2. What could be wrong? there is a lower sensor on the radiator im thinkin might be the culprit, its the one with two snap on round plugs on the lower driver side part of the radiator, can that leak? the previous guy had teflon tape in the threads so i think it might be leakin out of that, but other than that what could it be? there isnt anythin comin out the exhaust or nothin(no coolant comin out there) no bubbles in the coolant either. Can my engine be toast? dont be afraid to give me worst case senario's, i like the truth,
thanks guys,
Luke, in WA

 

try a coolant flush and use the powder stuff you mix up. I saw a dramatic improvement in temps & all the crap that gets in there was cleaned out nicely.

Just be sure to thoroughly flush the coolant system with distilled water after you use the powder premix.

 

the mazda water temp gauges are crappy but in the 2 7s ive owned. a na and t2 ive never seen the needle go up to or past half. same with all the others ive test driven. so thats wierd.
you cant see where it is leaking? if there are no signs of external leaks my guess would be and internal coolant seal leak.

 

you might be losing some through the weep hole on the water pump. how many miles are on it?

 

well, the engine's got 99k on it, i guess i'll do a coolant flush, but thats not gonna help the missing coolant i wouldnt think. I'll do some leak testing tommorow

 

Besides a yet undiscovered leak, here are some long shot possibilities:
1) The fan clutch will slowly start slipping as it ages. The fan should pull really hard up to about 4k when the motor is hot. It should maintain about 4k as the motor revs higher. Sometimes you can get more life from it by bending outward the bi-metal strip on the front of the fan clutch. The cut-in for the series 4 fan clutch is gradual – it pulls some even when cold. The series 5 fan clutch is more on/off.
2) Replace the thermostat. Make sure it fits. The spring loaded disc under the stat valve must close the bypass port, or guess what?

 

My standard reply when coolant is "disappearing" is to do a simple pressure test when the engine is cold, that is if you have a tester available. Simply pump up to 16/17 lbs and wait for the obvious. It may take some time if leak is small, but you'll find it. Don't know if parts store rent them.

 

Im not worried about my temp. that was just another symptom i thought might be related to the coolant disappearing. I'll do that pressure test i guess, i'll try renting it at Pep Boys.
thanks guys,
any chance its a bad seal inside the engine? wouldnt i see coolant in the exhaust or bubbles in the coolant though?
BTW, in my sig, you can see i have an e-fan off a fiero installed so its not a bad clutch or nothin.
thanks,
Luke