Hope someone can assist. I'm new to the rotary world. Just bought an 86 non-turbo. Car runs great but I have aquestion. How can I tell if my water pump has failed? Heres my problem.... Engine is not overheating but coolant seems to be bypassing the radiator and flowing to the overflow tank. I've already read many of the threads containing similar problem which points to coolant seal problem however I suspect something else. I'm still awaiting an FSM to delve further int testing so could someone help with this. I run engine aprox 10-15 mins @ idle with tstat removed before coolant begins to fill overflow. Thanx

 

First install a Mazda Thermo stat, second make sure your raditor cap is good. If problem presist and there is white smoke coming from exhuast, chances are you blew a coolent seal.

 

Had the same problem replaced the thermo and rad capand it still overflowed. white smoke kept coming out of exhuast for a few minutes. It sounds like your coolant seals. As we speak I am having a mild streetport rebuild. if car has high milage it pays to rebuild.
bigzman

 

When a water pump fails you will get coolant leaking through the shaft seal & out the weep hole under the shaft bearing and/or the bearings will get loose & noisy.

I suspect you have a bad stat or a leak you havn't spotted yet.

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

 

Sureshot, I think you just helped me out. Thanks...