hello, I just got a used '93 rx-7. The car seemed to have been well maintained, however, I have ran into a problem I have never encountered with any of my previous rx-7's. when I turn the car off I can hear the coolant boiling.. I dont know if this could be due to a rich coolant to water ratio or what, any ideas on what I could do about this would be greatly appreciated.
thanks

 

That's actually not uncommon. FD's are heat monsters.

Do you have 2 oil coolers? The additional oil cooler helps A LOT to keep temps down. You could run a lower ratio of antifreeze (but you need some to lube the pump and keep corrosion down). Also do a search on FC thermoswitch, it brings the fans on at a lower temp to help cool things down.

Also just do some low speed easy driving after spirited runs to cool down.

Vented hoods help, it lowered my temps a lot. Or you could just leave the hood open a while to help cool it down when you park it.

 

50/50 of antifreeze to water is ideal. the antifreeze increases the boiling point of water. is this boiling sound ur only proof it's running hot or does the temp gauge also indicate this? check to make sure the fan is working properly. could also be the t-stat may be not opening fully or poor flow in the radiator. maybe this boiling water sound isn't the coolant boiling at all but something else that just sounds like it.

 

The coolant will expand and contract as it heats up and cools. You may hear noises as coolant is sucked and/or returned from the overflow tank. Also, once the car is off, the coolant is no longer moving so they can be some localized boiling. However, since you just got the car, do a complete coolant flush with a proper water/coolant mixture. Burp the system and see if the noise still persist.

 

exactly! to explain, when you turn the engine off, coolant stops circulating to the radiator, where airflow normally takes the heat away from the coolant, and then gets circulated back to the engine. since this is no longer happening, the coolant's temp will rise for a while until it eventually cools off. unless the temp guage is higher than normal while you drive, it shouldn't get to the point of damaging your engine. a coolant flush on a car you just bought used sure can't hurt though. likely hasn't been done in some time.

 

thanks guys, I did test the coolant mixture and it is pretty rich (-60), The car still has a stock temp. gauge which i hear is not very reliable, however, that gauge does not show the car getting to hot. I have also spoken to the original owner of the car and he informed me that it never had that problem before, so perhaps moving the car from phoenix (1000ft) to the mountains (7500ft) may have a part to play. Would changing out the radiator cap help at all? or is it possible that the thermostat is sticking?

 

As I said, start with a full coolant flush with proper burping.

The stock temp gauge is not linear. Basically, the middle of the gauge is a range from around 170F - 240F.