I'm doing a custom installation of a 13B RE Cosmo engine. The water pump housing for the Cosmo has a 90 degree bend of the radiator inlet tube, and h as no provision for a heater hose connection . On the recommendation of Chris Sanders at Banzai Racing, I obtained a new FD water pump housing. It has a myriad of nipples and ports for water hoses and sensors, and I'm trying to figure out what they are all for, and whether I need them on my project. I did consult the coolant flow diagram I found elsewhere on this site. I have attached 4 photos of the water pump housing, and identified those features I want to know about. The features are numbered as below, and the same feature is identified in each of the view in which it appears. See below for questions about each one.
1. This appears to be a coolant level sensor that was included with the housing. It appears to be a simple switch, grounded through the engine. Is this an SPSAD switch? Open or closed when the coolant level is low?
2. I was not able to figure out what this nipple is for. Help!
3. This large nipple appears to be a heater hose connection at the water pump. Correct?
4. This appears to be a connection to the air separation tank on the RX7 FD. In my installation, the radiator may be the highest point in the cooling system, so I may not need a separate air separation tank. If I don't, I may cap this off or run it directly to an overflow cannister. Any thoughts or ideas?
5. This appears to be a hot water return from the throttle body. As I understand the coolant flow diagram, water that flows through the engine is routed from the rear of the engine to the throttle body, and the outlet from the throttle body is returned to the water pump at this nipple. (What is the purpose of providing hot water to the throttle body?)
6 This nipple appears to supply cool water to the turbos. I will be running an HKS GTIII-4R turbo so will need to create cooling lines to the turbo. It was not apparent to me from the cooling flow diagram how the hot water from the turbos is returned to the water pump. Can anyone tell me?
7. From posts on this site, this appears to be a port for a coolant temp sensor which is used by the ECU. I may have this sensor on the Cosmo water pump housing and if I don't this sensor seems to be readily available from RX7 suppliers. I will probably need a mating connector and pigtail for my custom wiring harness. Any ideas on where to get one?
8. Fan switch. This appears to be an SPST switch that turns the fan on when the temperature reaches a specified value. There appear to be a variety of these available for different years and configurations. I will be running a turbo setup with a manual transmission. Which switch should I use? There may be one on the Cosmo housing. Or, if I run a separate control on the electric fan, I may not need at all. Thoughts?

Thanks in advance for any info, thoughts, or recommendations you offer!

FD water pump housing radiator side

FD water pump housing left side

FD water pump housing engine side

FD water pump housing right side

 

Look for "the big fat cooling thread" and it will answer all of your questions with a color coded diagram

 

That's where I got most of the info I gave in the post. But there was some that was not clear in the diagram, and some questions that were not addressed in the thread. Lookinbg for confirmation that I interpreted the ionfo correctly. Thanks!

 

all of your questions have been covered in great detail throughout many threads. i get wanting to verify but you are looking at ducks and asking if they're ducks. the diagram does show all of the ports you have circled and if unsure, looking at a picture of an REW or an FD engine bay will give you the clarification you are looking for. the fan switch is not required when using an aftermarket ecu to include the power fc. do some reading on an AST delete and HOW to do it to answer your question about that and why your assumption is incorrect.

you are attempting to do something that requires a level of "do for self" that should very easily take you through this step. going single has a lot of options and paths that can be taken and if you are requiring this level of assistance in simply identifying coolant ports, you may be in too deep with this project. you have a tremendous amount of supporting mods, ecu set up, routing and nut and bolt configuration ahead of you. i can not stress enough that if you are having difficulty at this stage, it would be best to stop and reevaluate. there's nothing wrong with asking questions but there are certain types of questions that are indicators of a persons capabilities when taking on a project or any type.

 

That is a lot of questions all in one post, but I appreciate that they are numbered.

1. Yes, the coolant level sensor. It will be closed (connect to ground) when fluid is present, and open (not connect to ground) when fluid is not present. On the FD, this activates a buzzer and red light when the switch is open (not connect to ground, no fluid present).
2. This is the coolant return, the water pump pulls water from the turbochargers.
3. Yes, that is the return from the heater, the water pump pulls water in from that pipe. The heater feed (pressure) pipe is on the rear iron, near the oil pressure sensor.
4. Correct, that goes out to the AST on a stock setup. Plenty of FD owners have capped that port, but that was usually with the older 2-piece thermostat housing which allows them to replace the filler neck with a different part that includes a pressure relief nipple/port for when the radiator cap needs to vend pressure. If you want to cap this, you'll need to modify the filler neck so it has a pressure relief port/nipple. I've seen someone drill and tap a hole in the one-piece thermostat housing like you have, but I'm having trouble finding that thread.
5. Correct. I think hot coolant to the throttle body is partly for the factory thermowax valve, it moves the throttle stop by about 5% when the engine is cold. I've heard some people claim it can prevent the throttle blade from freezing, and I've seen similar coolant hoses on other cars that use drive-by-wire throttle and don't need a thermowax valve for idle. Personally I removed that system on my car, with a standalone ECU the idle valve can add enough air to idle without stalling even at near-freezing temperatures.
6. Correct, that sends coolant to the turbos. The water going into the turbochargers isn't necessarily cold, it has been through the engine but has not been through the radiator.
7. Corsa-Technic.com is a great resource to buy connectors. There is also a great website with pictures and part numbers for most of the RX7 harness connectors: https://stocksray.com/emharness.html
8. If keeping the factory FD cooling fan control, I would find the lower temperature Mazda switch so the fans trigger at a reasonable temperature. I think this was called the FC Fan Switch mod decades ago, search and you might find part numbers. If you're not using the factory FD radiator fan relays, it might be better to just have your aftermarket ECU trigger a single cooling fan relay using the coolant temp sensor. If the ECU knows the cooling fan is getting triggered, it can adjust the idle by a little bit to avoid stalling.

 

Thanks for taking the time to reply in detail. Your reply was extremely helpful to my understanding of how the cooling system works. I appreciate your willingness to put up with my "stupid" questions to assure my understanding. Thanks again.