Hi all, I have an rx-8 and my friend has an

FD 93 rx-7 with approx 70k miles, new engine about 5 years ago.
we just installed some nice PLX gauges on his FD.

One thing that we have noticed is that he seems to be running at 234 degrees nearly all the time and about 220 while driving highway. also after a drive it seems like his radiator fans are on for a good 15min after he shuts it down

I have read that 210 is normal but far beyond and its an issue. I have been searching on here, google, and here through google and can't find what i am looking for

there is plenty of coolant, nothing in front of the radiator, which is more likely to be our issue here?
thermostat issue?
waterpump?
dirty radiator

any input would be appriciated

thanks
Branden

 

here's a thread on some problems i had with overheating on my stock rx7, but there's a link in the thread that's really helpful on understanding the coolant system.

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/running-hot-higher-rpms-861702/

 

You shouldn't see 210 unless you are on a track on a supper hot day and even then that's high. Is the car buffing white smoke at idle?

 

My advice is to first replace the thermostat with an OEM unit. You should not see 220 degrees in normal highway driving. That's about 30-35 degrees more than I would expect to see. If the thermostat replacement doesn't do the trick, move on to a good flush of the radiator.

 

no smoke at idle, car seems to run fine other then starting to get a little hot, thanks for the thread links
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/big-fat-fd3s-cooling-thread-571088/
that thread is very useful, thanks everyone, I will update

plan is to flush coolent and change thermostate

thanks again

 

Good luck. I'd also change to a 2nd gen thermoswitch that should kick the fans on at 207F or something like that. That keeps the overall coolant temps down.

Also, do his radiator fans operate in all speeds? There are 4 speeds for the fans, and if one of the relays or wiring is not correct, may prevent the fans from running at the speed required for the cooling load.

 

Stock FD fans come on at 221, so over 210 is ok but still getting hot. Generally you won't see 221 unless its over 90 degrees out side or sitting in traffic. Especially not on the freeway, although I've seen 220 going over the grape vine when it was 90 degrees outside. With a Koyo radiator.

FC thermoswitch is a good idea. Also flushing your cooling system, making sure it's not dirty is a good idea. Make sure he has the under tray on as this helps direct air flow to the radiator.

 

Yes, yes the undertray is vitally important. In fact make sure it snugly fits around the front of the radiator and bumper, or else airflow will bypass the radiator and do little good.

David

 

well we did the thermostat, coolant was very clean added some water weter. got the air bubbles out. cleaned the intercooler and air filter while we where at it, then took it for a drive..... there might be a few more bubbles.

car warmed up to 230 and stayed steady there cruising....
airflow seems to be good to radiator. sadly it was about 60ish degrees outside.....
and under tray was firm

and to boot boost goes to 11psi then as the RPMS climb boost goes to ZERO and stayed. I think the secondary turbo is not engaging....

could the ecu be detecting the 230 and killing boost?
not sure what to do next, short of a new radiator...

 

What kind of intercooler are you running?

How are you measuring temps? What kind of gauge and where is the sensor located?

Post some pics of the radiator setup and undertray.

 

Stock Intercooler
PLX lcd gauge face with moduals, used included sensor, sensor is right from the top of the throttle body T in with copper fittings

hold on for pictures....

 

pictures




Did a trip to tricities in the evening and stayed around 209 for coolant temp, but once the in town driving began it went to the 230

 

What are your oil temps like? Do you have a dual oil cooler setup or only single?

I had a problem with a bent dual oil cooler hardline (result from a bent stock sway bar mount) which restricted oil flow and caused my water temps to hover around the same temps you're seeing.

 

oil temp I believe is the same as water temp but I could be wrong am alwasy staring at water temp, I have this same problem with the bent stock sway bar mounts, thank you I will get to looking at that tonight

there is only one oil cooler!

 

Oil accounts for nearly 30% of cooling in rotaries, so there's a good suggestion. Make sure you have enough oil, and no kinks. And good air flow to your oil cooler as well.

 

checked oil lines, they where good, the strut support is close but not kinking anything, Direct airflow. maybe a second oil cooler is in order?

after replacing several hoses, and a silinoid, still have no boost after operating temp 230 past 4krpms,

 

Quite odd. Where is the stock coolant gauge when this one is saying 230*? It could be that this aftermarket gauge is calibrated differently.
Check this thread for the best coolant system thread for 3rd gens:
https://www.rx7club.com/showthread.php?t=571088

The boost issue is probably unrelated. If you get no boost after 4k RPMs, then you should start going through the boost troubleshooting procedures. There are links in the 3rd gen FAQ:
https://www.rx7club.com/3rd-generation-specific-1993-2002-16/faq-3rd-gen-other-useful-links-68640/
like this one:
http://www.autosportracetech.com/RX-...erOverview.htm

 

these are great threads, the stock gauges reads normal, I too wonder if plx gauge needs calibration. we have done the FC thermostat, engine fan sensor mod, after-market down pipe, new coolant.

I am thinking about taking out the AC condenser, I believe I have a free-on leak in the cabin anyways.

as for the boost issue, I replaced the charge relief valve and tested the waste-gate and turbo pre-control solenoids and they work, I am thinking its the charge control or turbo control, there are alot of solid vacuum lines too, I should redo them but when I started I broke the nipple off the charge relief valve, hence the new one, and haven't got'n the nerve to continue.

I am betting its a stupid vacuum line though, the car heats up and no boost, when warm like 190 there was a good 12, 8, 5psi, but after the 235 its like 8psi to zero!!!

do the 99spec turbos have a different vacuum line setup?

 

lil things effect it too. make sure the coolant is bled right and dont restrict airflow to the radiator. are the fans on all the time or only when its getting really hot. i have switch wired into mine and i turn it on when i start to go over normal.

 

the new sensor does this for me, I beleive the fan will turn on around 180 to 200 can't remember

 

good deal man. im new to this forum so im putting my knowledge out there to help

 

as you can see with my whole 18 posts I am too

 

I'd pull the sensor and check it against a thermometer in a pot of water.

The 99 twins use the same vac routing as USDM twins. Check the FAQ thread for vac diagrams and turbo troubleshooting links.