hi. i just purchased my 86 rx7 and am experiencing very weird overheating problems. before you get on me for not searching, i have but im still puzzled about why my car is running so hot. i test drove the car and the car runs fun for short periods of time with no problems. the temperature reads steady at the center of the meter and the car runs beautifully. however, after a 30 minute drive home i arrived at my house with the temperature gauge all the way up and the warning light lit. the buzzer was sounding as smoke came from under the hood. i could see the coolant bubbling and coming out the blow out tube on the coolant reservoir.

Here's what puzzles me. the previous owner has recently changed the radiator and the water pump. he also had the thermostat removed.

what else could be causing the car to overheat? the car does not leak any coolant nor does it burn coolant. it recently passed smog and does not smoke heavily.

im lost. if anyone can help or provide any advice i would greatly appreciate it. thanks.

 

Might want to put a thermostat in there and hope you didn't warp your engine block.

Also it should 1/4 of the way for a S4 FC.

 

i was reading a post earlier that said that coolant could be leaking into the cumbustion chamber, and just burning off. which would require a rebuld.. This kidna scares me, because i just bought an 86 gxl with overheating problems. I have the haynes manual, and it says to check to make sure the water pump belt

 

If you think coolent seal is gone, you can do the "bubble test" and there will white smoke coming from exhuast if it is indeed a coolent seal. But it could be a simple problem like a stuck thermostat. So check the basics before you go and rebuild your engine.

search around there are many threads on this topic.

 

Make sure it's a Mazda T-Stat.

 

i thought it was odd that the owner had removed the thermostat entirely, however i was told by a friend that this is a common thing to do to relieve some of the overheating problems. the only downside as i was told was that the car might run rough while cold or in cold weather. it sort of makes sense to keep the coolant flowing constantly without a thermostat regulating it, but i dont see how installing a thermostat would relieve overheating problems if not having one at all didn't.

i have since installed a thermostat, but have not had a chance to run the car hard to find out if it was the cause of overheating. are there any other possibilities? what else makes up the cooling system on the car besides the radiator, thermostat, hoses, engine seals, and water pump? i have pretty much eliminated all of these possibilities.

 

yeah you have chunked a coolant seal no doubt. But I agree that in the summer i will not run a thermostat. Their is no need really.

 

I really don't think its a coolant seal. I've had two cars so far with blown seals and I am familiar with the symptoms. My car does not smoke heavily, the idle is steady, and there is no smell of burning coolant. Are there any other possibilities? thanks for all the help thus far.

 

Sureshot’s Overheating – check list
1) Replace the thermostat. Make sure it fits. The spring loaded disc under the stat valve must close the bypass port, or guess what?
2) Replace the radiator cap. Low pressure = steam bubbles = spit out coolant.
3) Look for leaks. (same symptoms as #2) Some can be very hard to find. You may have to pressure test it. A common failure spot is the 3/8” coolant line that runs from the top of the rear housing (under the intake runners) to the throttle body, to the BAC, to the water pump. Another one is the heater hose under the oil filter.
4) 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.
Banzaitoyota’s checklist
1.Are the Oil Cooler fins clear of debris and clean?
2.Does the Oil Cooler thermostat function properly?
3.Are the Radiator Fins clean of debris?
4.Is the Stock Bottom shroud still in place?
5.If the air pump is removed, are you running a Dual Belt Pulley on the Alt?
6.Did you install a NEW Water Pump when you installed the engine?
7.Is the bottom hose collapsing under load?
8.Did you have the Radiator and Oil Cooler cleaned and Flushed when installing the rebuild ( AS required by MOST REPUTABLE REBUILDERS)?
9. Have you verified water temps with a real gauge instead of the sock POS?
10. What ratio Coolant to Water are you running?
11. Are you running a new STOCK MAZDA OEM thermostat?
12. Mazda Rad Caps?
13. Stock Fan Shroud installed ( For those of you running stock Mechanical Fan)
14. Electric Fan users: Do you have a Shroud installed at all. Most installations only draw air directly across ~60% of the available core surface area.
15. are the stock deflectors installed around the relays forward of the Radiator Core Support?
16. If 15 is a no: Do you have an plate mounted across the support to direct air-flow?
17. Install a spring in the lower rad hose to keep it from collapsing at high RPM

 

Actually not running a thermostat will make it more likely to have overheating issues after driving, and lead to illregular cooling during driving.

The coolant is flowing so fast, that the coolant temp gauge does not accuratly report the engine temp.

 

Whitout a stat, the pump will suck hot outlet coolant right back into the engine without going through the radiator at all

 

As mentioned, the thermostat in the RX-7 is a bypass thermostat. Removing it will simply cause hot coolant to circulate around the block, very little of it reaching the rad...

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

 

wow. thanks a lot. some very good info. i'll definitely check all of the common culprits.

last question, how much more significant will an OEM thermostat perform versus an aftermarket replacement brand? why?

thanks again.

 

my car has almost overheated today and it was fine yesterday. will flushing the system help? i've also changed the radiator caps,

the water pump was changed and the thermostat is working, i don't know if the thermostat is OEM but i know it was working. if anyone knows where i can get one msg me! i also found some rubber piece floating at the top of my radiator i don't think it's a seal because my car isn't smoking and it still has alot of power =( i've searched alot and can't find anything solid

 

o yeah and it didn't reach the H or the line above i was also driving normally when it began to raise i pulled over to let it cool down and heard bubbling from the inside of the engine or some lines the coolant was being drained from the coolant bottle fast

 

the oem thermostat can be found at a local mazda dealer. your symptoms sound similar to mine. my coolant was bubbling out of the overflow reservoir.

 

im thinking the rubber is a piece of the thermostat hmmmm im gonna change it and write back with results

 

allllright im back with results i found out my car didn't even have a thermostat!!!!!!! thats no good man but i put an OEM thermostat in and it runs great now thanks alot guys! o yeah i flushed out my radiator too.

 

Yea only use Mazda OEM T-stats they are proven to work good, last long, and they aren't expensive come on guys...!

 

Mazda used to have great thermostats. They looked high quality but more importantly they had a larger port to let more water flow when they open.

Unfortunately now they are just common generic thermostats. I called Mazdamotorsports last year to get the good ones and they said that all Mazdas use the same thermostat now.

oh well...
ed

 

Humm, doubt I'd settle for their response. Most of my OEM parts come from Mazdaformance and their T-stats look and work the same as original

 

I'm sure there are plenty of dealers that still have a few of the older thermostats but the thermostat that I got from Mazda was identicle to the generic I wanted to remove from my car. At the same time I had an older failed thermostat from Mazda that was clearly superior.

I don't see where I could have got better information than Mazdamotorsports (now Mazdaspeed).

ed