i have a 1987 mazda rx7 turbo...I have the following enigne mods..
Street ported 13B
TO4E turbo with S5 exhaust side
corksport 3" wide front mount
mazdatrix intercooler piping
hks bov
Rtek 2.1 standalone system
Full turboback apexi exhaust
550cc primary injectors and 1600cc secondary
etc....

now this is my issue...about 2 weeks after i purchased the car it started overheating...the guy who had it before me told me the radiator was bad and it didnt have a shroud fan or belt driven fan but instead was powered by an electrical fan...i hardly ever drive the car and i have never pushed it past 3/4 temp...The following stats are 50psi of oil pressure at idle and around 75psi at full boost, 12.1 across the wideband at full boost and no misfire condition that could make be believe its heating up from leaning out...the overflow tank does boil over and results in an aftermarket overflow tank cap to blow off...the car doesn't overheat at idle and i have even left it running for almost 20mins and still no overheating...its only when i put the car is first gear and drive the car for over 10mins and even if i do a hard pull you can see the temp actually go down until i come to a complete stop and the cars temp gradually starts to clime..i replaced the following parts
installed new OEM radiator
new thermostat
installed fan clutch and fan shroud
brand new electric universal fan 16inches
also p/s and a/c have been eliminated
also turbo exhaust side has been wrapped for heat reduction and charge pipes are about 2 1/2 inches wide
car is running a universal coolant temp sensor which controls the electric fan only and works very effectively

The car won't overheat at idle but starts overheating when i start driving it...The car dynoed 386rwhp and 311 torque which i no is much more than stock oem...I have noticed the follow symtoms which make be have about 4 theories...

1. water pump can be turned by hand even with the belt...now when i pinched the belt and take out some of the slack the water pump cant be turned by hand, so maybe the belt is slipping at high rpms which isn't rotating the water pump fast enough...But i dont hear a belt squeal...theres is now only one belt on the car and it runs the water pump, altenator, and rotor shaft pully..

2. Water pump could be bad but i see no leaks of any sort...which could maybe go back to my original theory...

3. Radiator cant support the amount of power that im putting down and the heat cant disperse fast enough...i currently am running the belt driven clutch fan, fan shroud, and an electric fan at the same time...the radiator that i installed in the rx7 came with another cap which was rated at .9psi which turns the stock one cap housing system into a 2 cap same bar system...i eliminated the radiator cap by installing a sealed cap and ever since i did that the aftermarket overflow tank cap keeps blowing off...the aftermarket overflow tank cap isnt a screw on type....
4. and the worst of them all...Blown coolant seal...There is absolutely no water in the oil and the car does not smoke unless for sitting for a long period of time...and when it smokes it only smokes for about 45 seconds and its not even alot then clears up...

Please im am looking for an educated response and not some Headgasket theory which rx7's have no head nor a headgasket...please Mazda certified ONLY!!! or if u have had the same issue or no a thing or 2 about rotaries..

thanks,
aaron

 

What about the Oil cooler?

The OEM is good for mildly higher hp, but i cant say for 300+, most people go with a KOYO.

Do you have a Aftermarket temp gauge, it would be nice to have temp numbers.

You will not get water in the oil from the normal water seal failure, on RARE accusations the outer water seal lets go and then water will get in the oil.

Remember that the oil cooler takes about 40% of the heat out of the motor, Also do you have the stock under tray, that is very important to direct the air thru the rad instead of below it.

The easiest way to check for a blown coolant seal is, from a cold start, open the upper rad cap and make sure it is full, start car, check level agian fill as needed, then look for micro bubbles. If there are bubbles then it is a good possibility that it is a coolant seal problem.

 

I is much more than stock, a T2 with all bolts on will be at the 225-250 RWHP (more or less)

You should be able to turn the water pump by hand, which in turn will turn the main pulley and alternator; with that said, you will have to force in order to turn it.

1st of all - Use Mazda OEM radiator caps (on both sides)

Is the e-fan pulling or pushing?

I was told by a Mazda mechanic, that if you remove the radiator cap and bring the engine to normal temp; you should NOT see any type of bubbles coming out. If you have a constant stream of tiny bubbles, the water seals "should" be bad (or so I was told)...

Do a pressure test on the cooling system...

 

I havent even considered the oil cooler...is there any way to check if the oil cooler is bad?
i am using the factory temp gauge and the stock under tray is gone...i dont no why the previous owner did that but its not there...i did wat u said about starting the motor up and taking off the upper cap...within a minute after starting the car the coolant rose and started overflowing from the upper cap....

 

the electric fan is pulling...does it matter which side the fan is on as long as its pulling right? i have it on the opposite side of the fan shroud...
(is it would go in order from closest to the front of the car....electric fan...radiator...fan shroud, then clutch fan...) also when the electric fan is on and the engine is off you can see the fan clutch rotating from the amount of air coming from the electric fan...does this mean the fan clutch could be bad?

 

That's not a good sign...

If the efan is on teh other side of the mechanica fan, then it should be set to "PUSH".

 

my two cents are. you need to get a bigger or an aluminum radiator (I went with a Koyo on mine) and find an undertray so you can route the air thru the radiator and not under the car. the radiator the car has from factory is not designed to suport that kind of heat.

about the coolant overflowing. At what RPM's does your car idle? remember the thermostat will be closed when the car is operating cold and it will start building pressure. if the system is open that pressure is going to find its way out. If it starts overflowing and you increase the idle speed the water should continue its flow in the engine and stop overflowing. if the car starts spitting water when the lid is off then yes I would be worried. but if it is just overflowing i wouldnt even pay attention to it just watch for the bubbles. Something else you want to look at is that your cooling system operates at 13psi you mentioned that you have a 9psi cap that is the reason your overflow keeps on filling up, boiling and blows the cap off. I dont think the belt is your problem because you said your car is overflowing so the belt and pump are doing their job however you are not supposed to be able to spin the waterpump by itself when you turn it by hand you need to tighten it a little. good luck and I hope this info is helpful to you.

 

sorry for the confusion but im actually running a 0.9 bar cap which is the 13psi...ill try taking off the cap tomorrow and revving the motor and see if the coolant stops overflowing...but yeah friday im installing a new water pump and the belt...ill let u guys no the status by sat....thanks for all the help and hopefully this will fix the issue...please if any other comment or recommendations just post on here because i check this forum daily...thanks again

aaron

 

i doubt you have a blown coolant seal, most likely you would see air bubbles in the radiator and/or white stinky smoke/steam coming out the tailpipe

there are a lot of reasons your car may run hot... usually has to do with a weak fan or no ducting... make sure the fan moves enough air and that it is properly shrouded... also make sure the plastic under pan is installed

other items would be a bad or loose belt... most loose belts are actually bad belts

you may have an air bubble trapped in the system... remove the cap from the cold engine, run engine until hot... when the thermostat opens the coolant will start to flow (some may flow over ) at the same time any air should bubble out... hold the RPM at about 1200 - 1500 RPM to help the coolant along... once your satisfied the air is out, replace the cap and let cool

here is a cool filling tool
http://www.lislecorp.com/tool_detail.cfm?detail=244




make sure you have the appropriate amount of coolant in the catch bottle, so that it doesn't suck air back in as it cools

your thermostat may not be working... buy a OE Mazda one to replace it

your radiator may be full of crap... best to buy a new one

take a few pictures of your setup... the radiator and the duct work

FMIC can really do a number on water temps

your oil cooler also cools the engine... make sure it is clean of debris

 

BS somke does not always come out the exhaust when you have blown coolant seals and thats 90% of the time fools!It will not while running because the cimbustion will bleed into your cooling system.
When off it can bleed coolant into your combustion chambers then steam it's way out the exhaust but the smoke/steam will not be thick.

All the clients who brought their rx7's to me with blown coolant seals did not smoke one bit!

 

+1 for the nut