JeffRX7

A couple weeks ago my 87 N/A started overheating real bad on my drive home from work. I found a small crack in one of the vanes of my fluidyne radiator which appeared to be where the coolant was coming from. I nursed the car home, pulled the radiator, and sent it back to be warrantied since it was just under a year old... while i was waiting for it back, i took the stock radiator out of my TII(in need of j-spec) and put it in the N/A. It seemed to work fine at first, but after 20mins of driving, the heat was ice cold and the temp ga was rising. i pulled over and checked under the car, no leaks, under the hood all i could here was massive bubbling(and yes i bled the cooling system) coming from the whole engine it seemed. i opened the relief valve and it blew out a ton of steam so i figured i just had some air still in there somehow. Drove it home, let it finish bubbling then topped off the coolant. the next morning it stayed perfectly cool on the 30min drive to work, but when i left work, it started heating up real bad again, still, no loss of coolant. i bled the steam again and it stayed cool most the way home then got real hot again. my fluidyne came back , so i put it in, hoping it was a clogged radiator or somethin, but fired it up and it did somethin kinda weird... it overheated very quickly again, but the radiator was still COLD as well as the intake and heater return line(and no heat was coming from the heater). the upper radiator hose was pumped up rock hard and the bottom hose seemed relatively soft... i figured my block must be clogged or somethin, so i first tried taking out the thermostat incase it was sticking, with it completely out, it stayed nice and cool, heater blew heat, and i drove it here to work today like that. its mostly highway so it worked great with no stat, barely even got warm. im gonna try a different stat tonight, hopefully the otherone is jsut junk, but it is only a couple months old! 2mths ago i replaced the waterpump, stat, all gaskets and pullys. What scares me is everytime i start it up now, i get a puff of smoke from the pipes and it takes a sec to idle smooth. it doesnt smoke after its started, and it still has great power... sorry this post is so long, just trying to be detailed. If anyone has any advice or solutions for me, PLEASE let me know, I'm baffled. one other thing, its seems to be flooding pretty regularly now, and it never did once before the initial overheat that started all this...

Thanks again!
Jeff

J-Rat

iTrader: (2)

Well here is my opinion:

You may have very well blown a coolant seal. There is a test that you can do to check this. You fill the system cold, then you leave the cap off (the water has to be COMPLETELY fillied). Then you pull your deflooding fuses (EGI INJ and EGI COMP), and you crank the motor. If the coolant comes gushing out of the filler neck during cranking, your water seal is shot, and you need a rebuild.

Second possible problem is that you are not using Mazda OEM thermostats. Is this the case?

Jarrett

http://www.aaroncake.net/rx-7/cooling.htm

JeffRX7

The thermostat I used when I did the waterpump and everything was a OEM mazda one from mazdatrix. I made sure to go OEM because everyone seems to say they are a ton better. I was just gonna put my old thermostat back in because i know that one worked fine, just replaced it cuz it was all apart. I will try that test for a bad coolant seal, one question though, should i do that with the thermostat in or removed? if i leave it in i wouldn't assume any fluid would be able to come up to gush over since it would be closed. I'm not sure exactially how this test works, but would fluid be forced up through the radiator and then overflow if a seal is bad? Thanks for your help!

Aaron Cake

iTrader: (1)

Leave the thermostat in.

If the "bubble test" does not provide reliable results, have the system pressure tested. Keep it pressurized for 12 or more hours, then starte the car. You will know immediately if you have a blown coolant seal becasue the car will produce large clouds of sweet-smelling smoke as it burns off the coolant...