hey guy/girls great forum you have up. tons of info.i had an 87 2+2 a few years back and just love rotarys. ok so here is my ?, my lil bro just picked up an 86 i believe and is having overheating probs. i just heard about this yesterday so bear with me on the details. he can add water to it and about 10 mins later be over half way to hot. the PO supposedly took out the thermostat. lame ass i know. but it steams up and releases pressure through the cap on the neck and rad. plus it boils over and steams out of the overflow tank. ok now i've read on here, you know trying to do homework first. and i cal tell him to check the 2 caps, therostat(which might not be there), or the cooling jacket seal(internally, big problem). am i missing anything? thanks for all the help, sorry it's long. great site again

can someone move my topic to the 2nd gen. thread and not the for sale thread? thanks

Does it smoke out the exhaust on start up? Overheating is very BAD on the rotary. If he's got white, sweet-smelling exhaust, then he most likely popped a coolant seal and will need a rebuild.

You need the thermostat to prevent hot spots on the engine. You cant run without a t-stat in a rotary.

The 13B thermostat has two valves.

When the motor warms up the main valve moves down to open, and a spring loaded disc in the bottom closes of the BYPASS PORT.



With no stat, the bypass is always open giving symtoms like a blocked radiator.



The rest of the cooling system troubleshooting is just like any other car.



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.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

Sure they can. The bypass port just needs to be plugged. Everyone from Mazdaspeed to Racing Beat recommends removing the thermostat and plugging the bypass for competition purposes. That's not what we have here. But there are rotarys that run without t-stats.

Right, but this guy isnt doing that. Maybe i should have included "stock" in there somewhere to keep the uptight at bay.

thanks for all the help guys. yeh it seems like it's time for a rebuild. thanks again.

the fan clutch is thermostatic, i dunno about the fc but the gsl-se turns on @91c and turned off at about 89-90c and cooler than that and it should freewheel