Weird Overheating Issue with my 93

Sun, 08/16/2009 - 7:55am — Tripseleven

Hope someone can help me out! I have a bone stock 93 miata with a strange overheating problem. When I run the car for more than 20 minutes, usually on the highway, and then come to a stop, my temp gauge instantly spikes towards overheating. I know (or atleast think I know) that this car has linear gauges and would correctly show that the temp is a bit higher when air is not being forced into it. However, my temp gauge goes right to the the line next to the H, but has never actually overheated. I have replaced the thermostat, and my fans are working, but the problem still exists. I have been told that it might be due to a bad radiator (not losing antifreeze), a bad water pump, bad antifreeze or a head gasket. Is this a normal range for this car or should I be worried and if so what should I do? I do have an aftermarket bra on the car, bit the grill openning is large and the front plate is installed dead center. Thanks in advance for your help, any time is greatly appreciated! Brian and Deborah

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Fri, 10/09/2009 - 9:06pm — jrbpse

Poor cooling system design

Your 1993 may have the same issue as my 1990. On mine all the coolant has to flow through the heater core before it gets back to the radiator/engine. It's a poor design as I expected the normal bypass valve that allowed coolant to bypass heater core when the temperature slider was put to cool. In effect, there would be a parallel path that bypassed the header core.

Replacing the heater core is very expensive as the entire dash has to come out to do it. So I elected to makey my own bypass mechanism using 1/2 inch copper fittings.

Don't know if this is your problem, but the symptoms are exactly like mine.

John