Will_s

iTrader: (7)

First off let me start off by saying that I know second gen rx7's pretty well but can't seem to figure out why my rebuild is overheating. The car is a series 4 with a rebuilt series 5 engine. I made new wiring harnesses to run the series 5 ecu and everything functions like a s5. Engine was rebuilt by me with a large street port and is a non-turbo.
-racing beat headers to racing beat revII exaust
-all emissions removed except vdi and 5th 6th ports
-K&n drop in filter
-electric fan with fd alternator
-rtek 2.1 chip

Now for the serious overheating issue. If I just sit in my drive way and hold the rpm's at around 3500+ the temperature will steadily climb to dangerous levels. Same thing with short 10 min drives the temp will be over 220 by the time I get back. I have removed thermostat, changed radiators and installed a bigger e-fan to no avail. System was bled properly, filled with the correct fluid, the coolant seals are fine and no leaks anywere.

I have a couple of theories but need your help.
-Will running a s4 thermosensor connected to an s5 ecu show the wrong temperature on my rtek. Same with the dash gauge with a s5 sending unit.
What I am proposing is that the real temp is in check however it is being conveyed wrong.
-I can't remember what series pulley hub and pulley I used. They may be mix matched. Heard something about timing marks being different. When I rebuilt my old cj2a jeep the timing was way off causing a promt overheat condition, could a rotary have the same symptom Overheat from the timing being way off.

I really need your thoughts guys I almost didn't make it to my parents house in the mountains today. Lets just say I hit somewhere around 135 degrees using the palm to view temperature.

AGreen

iTrader: (11)

Well, is it actually overheating? You say you don't know, but is it boiling over in the reservoir?

You have an electric fan, but is it wired up correctly and coming on at temperature? On that note, did you just slap a little e-fan on the radiator, or did you put a proper-sized fan with a shroud on it? Are you using a MAZDA thermostat, or an aftermarket one? Is your water pump actually pumping water?

You said that you know the coolant seals are good because there aren't any leaks, but how do you know the INNER seals are good?

Will_s

iTrader: (7)

^ Electric fan was from my 5.0 and is turning on at 180 degrees, I know inner coolant seals are good, fresh from rebuild, no bubbles, over overpressurizing or white smoke. Thermostat was a brand new oem, that I even removed to narrow my search. Fluid was not boiling into overflow, should it at 135 degrees with a stock rad cap. After seven stock I am going to install a gauge to know for sure.

AGreen

iTrader: (11)

If you have some sort of thermometer, you can read the engine's actual temperature at the thermostat housing. And I'm pretty sure that the thermosensor for the engine is different from the one for the dash gage... not 100% on that one though.

jackhild59

iTrader: (7)

You need to work on basic trouble shooting before you assume the sender is incompatible.

Do you see coolant 'rushing' past the radiator opening? Check this out. When the thermostat reaches opening temps you should be able to see coolant rushing by the opening of the rad. Maybe you are getting no circulation from the water pump? Is it possible that you left something blocking the opening of the waterpump housing to the block, like too much silicone, a badly cut or slipped gasket?

Did you possibly wire the efan backwards? If so, the fan actually hurts cooling while you are driving!

How are you controlling the fan? What temp does it switch on and of? Does the fan come on at a temp that *looks* normal on the gauge or on your Rtek readout?

Have you done *anything* to measure the actual temperature of the coolant in the engine? The radiator? Until you do, you are working with little actual information.

http://www.summitracing.com/search/B.../?autoview=sku

Good luck, let us know how it goes.

gkarmadi

iTrader: (20)

^^^ will efan turns on if u wire ur efan backward?? (I always tought polarity matter).


To OP: are you running an s5 cluster?? Do u have aftermarket water temp gauge?
I "think", normal temp on s4 is 1/4 of the gauge (stock) and s5 normal temp is 1/2 of the stock gauge.

HAILERS

Series four and series five water thermo sesnors are the same from 1984-1982, so the RTEK should be displaying the correct water temperature. RTEK beat aftermarket water temp gauges all to heck and back. 100* reliable.

jackhild59

iTrader: (7)

Yes, an efan will run backwards if you hook it up with reverse polarity. In fact, many aftermarket fans are designed to be either a pusher or a puller, depending on the polarity chosen. On some of those fans the blade must be flipped over so the fan blades are correctly oriented for the direction of the spin. If the blade is not flipped, the fan does not move nearly as much air as it is rated to move.

I have seen more than one thread in the past where polarity or the fan blade flip was an issue.

Will_s

iTrader: (7)

The fan is turning the right direction, I think maybe part of my problem is that I don't have a shroud. I am using the same fan that cooled my v8 swap and it worked just fine. I am also under the assumption that v8's make more heat maybe I am wrong and need to upsize the CFM. Thanks for the answers guys but I was really hoping for some radical suggestions as I have checked everything else. A little more info that points to the fan, car ran great to seven-stock and back never climbing above 212 as long as I kept it above 70mph.

clokker

iTrader: (2)

The fan may well be part of the problem but not all of it, I fear.
At a steady state 70mph (@ 2500 RPM or so) your temp should be closer to 180F and the fan should be off.

I'd investigate your theory regarding the timing being off and failing that, look at the waterpump itself.

jackhild59

iTrader: (7)

No shroud? You may have trouble cooling the car if you have an efan with no shroud. Most RX7's will not cool with a efan and no shroud. Many of us are using OEm type fans that come with nice shrouds. Pontiac Fiero, Ford Taurus are two of the most commonly used. I am using Taurus as is clokker.

What size, brand of fan do you have? Do you know the published amperage? How is it attached to the radiator?

Also, be aware that if you have the A/C condenser in the car, those numbers Clokker sez might not apply; the airflow through the radiator is greatly increased by having the condenser removed.

Do you have the plastic undertray on the car? This undertray is considered essential for making sure that the ram airflow goes through both the radiator and the oil cooler. Rotaries rely on the oil cooler for a large amount of the engine cooling.

clokker

iTrader: (2)

Ah, right...forgot about the AC thing.
Been a long time since I've had that.

Even so, approaching 212F on the highway seems excessive.

And Jack...
I would posit that this would be better on the highway as the airflow would improve through the matrix.
In a perfect (read: magical) world, when the fan wasn't on the shroud and the fan would disappear completely leaving the radiator totally unobstructed.
Obviously, not possible but I'm jus sayin...the fan and it's shrouding- or lack thereof- shouldn't be a factor when talking about high highway temps.

hella24

iTrader: (8)

You cannot run without a thermostat without first blocking the bypass hole in the water pump. The bypass is the hole under the thermostat. The coolant will not get pumped through the system. Race cars run a gutted thermostat or a restriction disc to slow the coolant through the system along with a plug in the bypass.

How clean (internally and externally) is your radiator?

Will_s

iTrader: (7)

As far as highway driving goes it was over 100 degrees outside with the usual stop and go in some areas. I reinstalled my thermostat since I know it is working fine and I have a new 3.8 liter taurus fan being shipped. I also completely drained my coolant and refilled with water and Water Wetter with about 10% anti-freeze. When my fan gets here I will let you know how the test drive goes.

Scrims

iTrader: (2)

+1 for the plastic belly pan. I forgot to install mine after I did my rebuild and was freaking out about overheating for several days. Installed it and all problems went away.

jackhild59

iTrader: (7)

The airflow may well be better, but I simply have no experience with cooling sans A/C condenser. I can say that my car will not stay cool on the highway with no fan. It wouldn't with my Aftermarket all metal replacement radiator and it still won't with my 'new' Griffin radiator. The fan must cycle on or the temp climbs to 200+. It will ram cool in cool weather, but not in hot or even warm weather.

Your experience illustrates much the condenser affects ram-airflow to the rad. Add to that the number of threads concerning fmic cooling problems, I am pretty certain that I will never go FMIC either.

clokker

iTrader: (2)

Having just the oil cooler and rad obviously makes a huge difference.
During my last biannual blast from Denver to Chicago this July (90 F +) the only time the fan came on was after heatsoaking at a gas pump. Back on the road, temp drops and fan is inactive for another 250 miles.

The past week or so we've had a taste of fall with temps in the 60's and for three days the fan never came on at all, even in stop-n-go traffic.
My low speed trigger activates at 195F and I never even hit that.

Unobstructed airflow...you can't beat it.

jackhild59

iTrader: (7)