Paulc19

Summer just Hit down in Florida and I've been driving my rx7 Turbo recently. My temp gauge has not been reading correctly (I think) ever since I did the turbo II swap (Using the stock gauge on the N/A cluster with a T2 sender). On idle the temp reads about 1/4 of the way up, that's before I had this heating issue. i was doing a freeway drive and I wasn't having much problem until I hit traffic, the gauge then spiked to around half way and stopped, but when I got moving again the gauge went back down the 1/4.
Based on what I know, my clutch fan is bad, the issue is, this is the 2nd clutch fan I've been through. My question regarding this is do the stock clutch fans break this easily or is it just my luck? Im going to pick up a new one, however I want to make sure I don't accidentally buy and 3rd one and have I go bad on me. I hear you can get a good one off of a salvage yard and I have one close to my house.

regarding my temps, I don't have my under tray, and was wondering if it really makes that much of a difference temp wise. I am also wondering why my gauge is reading so low, or is 1/4 considered normal temps since the H side of the gauge is considered the "boned zone" (as in its too late and your way overheated already)? Just a little info, im currently running a koyorad all aluminum racing radiator and am running a stock setup.

I made a post about this a while back but no one commented on it so I thought I'd try again with a little more detail this time, Ive been looking for weeks to find a proper answer and could REALLY use the help.

DC5Daniel

iTrader: (10)

Well do you keep buying used clutches? You have to remember they're 30+ years old, and rely on heat to engage. I don't think that's out of the realm of reasonability to experience some failures.

If this is an S4, yes 1/3-1/4ish is considered "normal" for the temp gauge. If you think it's not reading correctly you can test per the FSM values with a variable resistor/decade box. I have characterized several clusters and can tell you because of the way they operate, it's not exactly a precision instrument. That's why the stock gauge should be treated as a sanity check; either the temp is normal, or the car is overheating.

Yes, the undertray makes a significant different. Since you're already familiar with thIs advice I'm sure you've read the dozens of threads detailing this...not sure why you doubt it, as it's a very intuitive example of fluid dynamics at work.

Paulc19

the car is an s4 but the engine itself is a bit of a mystery. It has the s5 housings but s4 intake, not sure about the turbo or the irons either (if there is a difference between the s4 and s5 turbo/irons).
I had 2 clutches. One was from the N/A motor I swapped out, the other was in with the lot I bought that included my turbo II motor. Is it possible to even get a new or refurbished clutch? Not sure this is something you can answer, but has anyone ever tried to crack one open and rebuild it or is it even worth the time?

The temp sender is brand new from Mazda so I have not doubt its reading correctly if that is the case, but was wondering if the resistances between the N/A and turbo senders were any different.

I was wondering if anyone had any numbers they could throw out regarding the under tray, but I guess that may be asking for a bit much. Thanks for the reply though

DC5Daniel

iTrader: (10)

Never seen any numbers that I recall. Overheating without the tray, and normal temp with the tray is good enough

Paulc19

On a completely different note, I've noticed people talking about electric fans and the thermoswitch at the bottom of the radiator. the FSM talks about electric fans on the FC, but My N/A never had any electric fans. Is the turbo supposed to have them?

DC5Daniel

iTrader: (10)

Certain models had a "helper" fan on the AC condenser; it was not an electric fan for the radiator. There are serval thermo switches/sensors, the one in the bottom of the radiator was just a switch used for ECU enrichment. The thermo switch for the electric fan was on the top of thermostat housing. The sensor that reports to the ECU is on the back of the thermostat housing. The sensor that reports to the cluster is on the drivers side of the motor by the oil filter.

Hot_Dog

In my experience, the Mazda fan clutches usually have a long lifespan. On my '90 GXL, I first replaced my fan clutch in June 2001. Bought a new Mazda replacement from Ray Crowe at Malloy. The fan clutch was always free wheeling. Problem was similar to yours. In traffic, the temp gauge would creep up a little above its normal position which is normally mid-scale.

In March 2020, my fan clutch went bad again. Problem was just the opposite this time. The fan clutch was never free wheeling. I'd get a loud screeching noise that sounded like a loose belt every time the tach hit exactly 3000 rpm or higher. I didn't want to spend the ~$250 for a new Mazda fan clutch so I bought a used one off Ebay. I was hesitant on buying a used clutch because with used parts you never know what your getting. I paid $20 not including shipping for the used fan clutch and fan blades. Turned out that it was in very good condition with no corrosion and so far is working very good.

So, yes these fan clutches do fail but they have a long lifespan and they can apparently fail by either not free wheeling or always free wheeling.

DR_Knight

iTrader: (23)

Use the under tray. Been there, had the same problems. Undergrad is there for a reason. And think of upgrading to a Fd alternator and an Efan.