Im been having some heating issues latelly with my s4 turbo 2 rx7, i know is because i need a better radiator. Im planning to overhaul my hole entire cooling system but im just wondering if the series 5 turbo 2 (89-91) water pump and housing is better than the s4 (87-88) pump setup? Thanks

Eddie

 

They are not interchangeable unless you take the whole water pump housing and use it too.
You can't just change the pump as the bolt pattern is different.It will leak.
Besides the S5 uses a plastic Thermostat neck.You can however fix that and get an aluminum after market neck but they are about 80 bucks...roughly.

 

You're in the right neighborhood, but barking up the wrong tree. The S5 pump is not notably any better, if at all.

What you do want to transplant is a Koyo N-Flow radiator, which was only offered for the S5. It's an easy fit, all you need are S5 radiator brackets or slightly modify your existing brackets with a Dremel.

 

Thanks for the opinion. I have a hole entire s5 turbo 2 water pump and housing with a aluminum neck already here from a previous rx7 i had. I didnt know wich one was better because i never experimented in the past wich one was better. Anyways i do plan to get a koyo n flow one or a ron davis radiator. Im going to throw back the AC in the car and i dont want any issue with cooling problem.

 

Well one of the things about S5 is that the neck is just a Neck..no Cap on the top.
That is about the only thing I like about the neck.

Then again the cap on the S4 makes it a bit easier to burp the system..

So,6 of one..half a dozen of the other..
I ran an S5 KOYO N Flow on my car..great rad..used a Villager fan.

 

the actual impellers are basically the same between S4 and S5, so per shaft Rpm they should move about the same amount of water.

the S5 has a slightly different ratio, and you should be able to rev it a little higher before it cavitates, but its probably only like 100rpm

the thermostats are the same temp (82c), but the S5 one has a rubber seal, so it should warm up more quickly than the S4.

the biggest difference is that the lower hose comes out at a different angle, because the S5 needs to clear the metering pump.

 

I have a$20 dollar junkyard ford escort fan on mine wich is been fine so far. Theres probably a better junkyard choice out there i dont know about. Right now i just think i need a radiator because it doesnt get hot right away. It does it on a long drive above 80 degree outside and when im boosting it hard. i cant complain still the original 28 year old rad.