Hi my name is Ian,
I recently bought an rx7 tII s4 1987. It has a j-spec motor in it if that makes a difference. I know that it is very bad for the rx7 to be overheated. I was driving mine today and stock temp gauge went slightly (maybe up to 3 or 4mm) above were it normally sits, around 1/4 to 1/3 of the way up. I pulled over and turned the car off and ran the heat. When it cooled down I drove it the rest of the way home, parked turned it off and ran the heat. After the engine cooled down I did the check to see if there were bubbles in the coolant, there were none. I went to autozone and bought an aftermarket temperature gauge, but i haven't hooked it up yet. Upon doing some further research I found out the the s4 gauge is linear, and read this "1/4 of the way up on the S4 gauge is about 180F. 1/2 way is about 200F and 3/4 is about 220F." I was first wondering to what extent is this statement correct. How accurate is the stock gauge. And could someone with an s4 post a picture of their gauge when the car is warmed up. I'd like to see where other peoples sit. I'm probably being overly cautious but I want to be very responsible with this car.

P.S- I checked the coolant level, it is over the full line in the overflow bottle when the car is hot or cold. I say one very small drop of coolant on a hose below the radiator cap but I cannot find any leaks or any more fluid.

 

so it went up that little bit one time? did you boost right before it?

200 really is not all that bad

 

I turned the car on again and let it warm up later because I thought I was just being paroniod. The temp again seem to go a little higher than normal, and no I haven't been boosting at all because I have a new clutch.

 

did you recently get the car?
A good thing to do might be to put a new thermostat in and flush the coolant, start off fresh.
See how the car runs.

 

Ya i got the car a 3 weeks ago but the clutch gave out, so it's been running for 3 days after the clutch got fixed. Ya i'll get new fluids in there and change the thermostat. I was wondering at what point should I start getting worried on the stock s4 coolant gauge, I know the after market one I bought would be best but I'm scared to tap into the water pump. Is there anyway I can mount the gauge in the upper radiator hose with an adapter or something?

http://www.fc3s.co.uk/How%20To/Top%2...top%20hose.php

I have the mechanical gauge you get from autozone

 

Yes, you can use an adapter. Ideally though you want to tap into the water pump housing, or find some spot that you can use BEFORE the thermostat. That way, if the thermostat were to fail and stick you would see be able to see the rise in water temp sooner, before the motor blows.

 

O, O.K. that makes sense. I though the coolant flowed the opposite way. Is drilling and tapping into the water pump hard. The gauge I bought came with bungs, would it be better just to drill hole and weld that on. My senor is 2" long if that makes a difference

Edit: I am a novice at working on car, I have tools available, but I'm scared to mess my water pump up. If I take my time and read up should I be able to do it without a problem

 

Absolutely. Removing and replacing the water pump was the very first major thing I did on a car ever, and it was on my first RX-7. Took me the better part of four hours. There is an excellent write up in the archives on how to do it.

https://www.rx7club.com/2nd-gen-archive-72/tips-water-pump-replacement-documentation-writeup-485755/

There ya go! Just be careful drilling and tapping. TAKE YOUR TIME!!!! Just do like an eighth or quarter turn at a time then back out and repeat when tapping.

 

bro i think we have two of the same car. My car needs a new clutch, pressure plate, throwout bearing, master and slave cylinder, gaskets, and now today i found that i have a water pump failure causing the car to spew out coolant every time i drive it.

Hopefully you can get yours to work

 

Ya man, I hope you get as lucky with me for the clutch, the person who sold me the car helped me install it. The seller velocity tech on ebay has oem exeedy kits for 140$ with a pressure plate, throw out bearing, and clutch.

Edit: but the shipping can be pretty slow, 2 weeks for me

 

Thank you so much for the help guys, Ill drain the coolant, and replace the thermostat, and install the water temperature gauge. I was just wondering for peace of mind. Since I shut off the car and at the max, the needle was less than 1/2 the way up the stock s4 water temp gauge, That shouldn't have done any damage to the engine, right?

 

Yeah go ahead and redo the coolant, check all hoses replace the thermostat with an OEM. and make sure to tap and squeeze the hoses slowly to get rid of air pockets.

 

You're fine, halfway is like 205-210. It takes more than that to cook a motor. Wouldn't cruise around for extended periods if they get any higher though, just to be safe.

 

Ya, I stopped driving it. I called atkins rotary, they told me I should take the radiator and get the flow checked. I took out the whole radiator today. I'm debating just buying a Koyo radaitor from the rx7 store .
http://www.rx7store.net/product_p/koyofc86.htm .

Have any of you guys had experience with this radiator.

Since I took the radiator off, I had to drain all the coolant, I'm going to flush the system when I get the radiator back in. Change the thermostat, and tap the water pump so I can put an aftermarket mechanical gauge in there. Is there anything I'm missing. I noticed I had only one belt going to the water pump, isn't it usually 2. Also where would I get my radiator flow tested

 

there should be 2, if someone removed the PS, AC, and air pump there might only be one.
There is a dual belt alternator pulley you can buy so that you can run 2 belts

 

A koyo is a great bet. If you've got the dough, pick it up and your car will love you for it.

 

Ok, I'm going to get the koyo. I also think I'm going to replace all my coolant lines, radiator cap, thermometer, and then completely flush the cooling system with pure water. Thanks to everyone in this thread for helping me out.

 

Distilled water! Always use only distilled water.

 

ya thanks thats what i meant by pure water

 

O also i was just wondering if the koyo radiator had a spot for the low coolant sensor?

 

yes