I have been attempting to troubleshoot an overheating problem for several weeks now on my '84 GS 12A. My pride & joy is testing my patience. It has been running VERY hot for weeks, now (it has not been a daily driver for almost 10 years). In the past few weeks, I have replaced leaking intake water jacket seals, the fan clutch (tested marginally bad), thermostat and water pump. I have also thoroughly flushed out the cooling system. The thermostat appears to be opening at the proper temperature (about 180 degrees) when tested. In fact, the one I replaced checks out OK, too. I have pretty much narrowed it down to either the radiator or the internal water seal (ouch!). The temperature of the surface of the radiator feels pretty even to me after turning the motor off. There is no tell-tale sign of white smoke at the tail pipe nor a steady steam of bubbles under the radiator cap, which would indicate a bad water seal o-ring. I am seeing a bit of unexpected debris and a few bubbles in the overflow tank, however. I also found some pieces of rubber floating in the radiator (but that may have been from the bad intake o-rings). Does anybody have any sure-fire ideas to determine what the problem might be? I'd hate to rod out the radiator (or replace it) and then find out I need to tear down the engine to replace the o-ring seal (or visa versa). I AM GRATEFUL FOR ANY SUGGESTIONS!

 

Check for a clogged cat yet? Is the car still running ok?

 

Radiator, probably. Have it flow tested. The only places water could leak due to a bad coolant seal would either be into the combustion chamber, or into the oil pan. Since I doubt either are happining to your engine, I'd say it's the radiator.

Does the top of the core look nasty when you take the cap off? Did you look while the level was low during your intake manifold O ring swap?

Could it be a faulty temp gauge?

 

The car is running great. I replaced the cats last year and have hardly driven it since. The top of the core doesn't look too bad. The ends of the slotted openings have some build up, though and there definitely is some scale in there. Hmmm. Maybe I better check the oil for coolant? I just changed it a couple of weeks ago and didn't really notice any, though. I don't think the gauge is faulty, because the engine feels hotter than usual and the radiator seems to be on the verge of boiling after running for a while. Yeah, maybe a flow test is the next step! THANKS.

 

Have you checked the radiator cap? A bad cap will do the same thing as a stuck thermostat.

 

usually when a radiator is clogged or in need of replacing, it will get hot on the highway or at constant or high rpm use. an easy way to test this is while driving, switch the heat on and see if the temp drops a little. if it does, it means you are having radiator issues. all of my most recent cooling problems have been culpret to a faulty radiator. remember, these parts are nearly 20 years old and they calcify easily. i would have it professionally cleaned or replaced. www.radiators.com has a radiator that works awesome and is better priced than anyone i have bought locally.

 

I forgot to mention. I have a new radiator cap, too (13 lb). Yes, I have noticed the temps rise considerably on the highway...or after idling a long time. I'll give the radiator the heater test next. I REALLY HOPE it is the radiator. Does anyone know if you can have a leaking internal o-ring water seal WITHOUT seeing white smoke at the tailpipe? Thanks for the link!

 

yes you can. if the water seal has deteriorated but not fallen apart, the exhaust will only heat up the coolant to unsafe temps, not burn it.

 

Eureka! As it turned out, the problem WAS the radiator. I got a great price on a new one here: http://www.arrowheadradiator.com/. $118 with free shipping! Also, NAPA carries a "block tester" ($50), which I used to check for combustion gas leaks in the cooling system (negative!). The price for the test kit was a bit steep, but I figure I can recover most of my investment by reselling it on eBay - since I may never need it again. BTW, when I removed the old radiator; it was so corroded, it literally fell apart. A word to the wise - if you are having cooling problems and the radiator in your 20+ year old RX7 is original - it is likely the culprit. I learned the hard way.