Mods:
New Koyo Radiator
New Factory Radiator Caps (13 psi)
New Factory Thermostat (Full open at 95C)
New Factory Radiator Hoses
New Factory Ducting in place (lower foam installed)
Single 34 row earls oil cooler with -10AN lines (my drivers side one is damaged & bypassed until I change it this weekend)
Autometer oil temp gauge (sensor at oil filter)
Autometer water temp gauge (sensor at T-Stat outlet)
Freshly evaculated and serviced AC system (R-12 fill)
Newly Installed Power FC

Coolant Combo:
84.4% Distilled water
12.5% Prestone Green Antifreeze
3.1% Redline Water Wetter (that's spec)

It's been 104-105F here the last couple days. I was seeing 225-230F coolant temps on my Autometer gauge...freightening. I installed my PowerFC today to turn the fans on earlier. I tested the fans by setting them to come on at 80C and they were blasting away. Cruising with the A/C off in 101F-95F ambient temps I recorded 93-95C (199-203F) coolant temps on the PowerFC (and the Autometer agreed). Well...that's OK I guess for the ambient temp. Turn on the A/C and coolant temps started creeping up to 100C (212F) then went up pretty quickly to 104C (219F) when I got into traffic. After I got out of traffic and was cruising at 49-54 mph it just stayed at 104C (219F) and refused to move. Both fans were still on max. Oil temps were constantly 15-19F under coolant temps.

A few things
- It uses no coolant
- No bubbling in the AST or filler
- Theres a hair bit of brown particular matter under the fill cap. I don't think that's a problem though.

For more background I just completed a 1600 mile round trip up to Salt Lake City and back with the car. Water temps were 179F-207F the whole time depending on load (lotsa hill climbs), ambient temps, and A/C usage. On the way home going thru Phoenix it was 95F and I saw a peak of 210F (99C) while cruisng at 64 mph with the AC on. When it was cool out (<80F) the thing just stuck at 181-185F the whole time with the A/C on (or off) at any speed up to 84 MPH.

I can see how you guys that live in average climates could be running 85C or less. I'd like to see you try 100-105F on for size...I don't think you'd be so quick to yell "victory!" like the norm around here.

So anyway...I've got some things on my mind. Installing some aluminum sheets to the radiator endtanks to seal off the sides of the radiator. I don't think that's going to do much for my problem though....maybe 1-2F. A vented hood. Something like the knight sports model. I'm not sure how much that will do for me. Problem is I'm strapped for cash now so that will have to wait. The other thing on the plate is 4 gallons of Evans NPG-R coolant that are sitting downstairs waiting to be installed. I've run NPG+ before in my Stealth. It brought coolant temps up (some) but there was absolutely no chance of boiling over. With better ducting and good oil cooling I was able to dump the Evans and the car is fine now on conventional coolant. Too bad the seven won't cooperate like that.

Is there anything else you guys see that I can do better? I'm avoiding the NPG-R but it's looking like that's my last option. The peak summer temps are still about a week or two away so I need to get this resolved....or at least minimalized.

 

It sounds like you have done everything right. 225 degree coolant temps, although high, are not in the danger zone. Just be sure you take it easy when the temps are hot, and you will be fine. Setting your fans to come on at a lower temp is a good idea.

Radiator ducting isn't going to help when you are drivng slow, which is your main problem area.

 

not trying to hijack the tread, but i'm having a similar issue right now (i don't have all the mods and its not "quite" as hot here as that, it was about 98F ambient here for the last two or three days. my problem turned out to be that one of my cooling fans (the passanger side one which is MUCH more difficult to see with the battery in stock location and an SMIC with a duct blocking most of the viewable area of the fan) stopped working... the electric motor had done this to me before. It needed to be taken apart, cleaned, and repacked with grease. Eventually (Fall) i'm going to just buy a new one when i have a little upkeep done on my car but for now, its going back to the shop to get repacked.

long story short, be absolutely positive that both of your fans are working not just "think" that they are working. if it is 100F here and i have my A/C on and everything is running as it should, i see 95C all day, but that's as high as it gets.

 

many people have said that the coolant temps parallel what the oil temps are doing. Can you explain what happened or how you have the drivers side oil cooler bypassed?

 

sealing the sides of the radiator is a big improvement, it's next on my list of mods. search for damian's posts about it

 

If you didn't seal the sides of the rad with foam (like oem) or aluminum, you just reduced your cooling capacity. On hiway, this provides a bypass for air vs going through the thick koyo and ac core. In traffic, hot air exiting the fans will loop back by the sides of the rad, and recirc through the cores, with less new "cool" going into the bumper opening.

Fix this 1st. Pressure test system (tee at ast). You should have better performance than you did before.

Whatever was done to make the system run hotter must be fixed, before considering NPG+.

 

Correct - NPG has less heat capacity, so it will make the coolant run even hotter!

 

Roger...Wilco. Good ideas guys.

I'm not sbsolutely certain that both fans are operating but I can hear the difference between the fans when the A/C is on and they're barely on and when the power FC kicks everything up to high. It's quite loud...I can't see that being just one fan. Regardless though I will pull the intake box and ops check both fans visually to ensure they're on.

My oil temps are under coolant temps because I have upgraded oil coolers. Two 34 row Earls coolers. One of them is damaged (an R1 lip nutplate chaffed a hole in it) so its bypassed with a -10AN union until I replace it this weekend. Even on one cooler though I still run sub 185-200F oil temps when the coolant is pushing upwards of 220F.

I didn't make the connection that sealing the sides of the radiator would make such a big difference. So now that you mention that when feeling in the front bumper for airflow with the fans on max I feel air moving/swirling (its not linear towards the radiator) and its much warmer than ambient. I think you guys may be correct about the fans recirculating already heated air.

I know all about the NPG's specific heat. That's why I'm avoiding it until I've exhausted all other options.

One more thing to throw out there...the new revision ?96 or 99? fans. Are they direct bolt ons? Do they move more air?

 

I changed over to the 99 fans. They are not bolt ons. The inner diameter is larger that the stock one. You need to make a little shim for it to fit.

https://www.rx7club.com/forum/showth...highlight=shim

Honestly, it "feels" like they move more air but I could easily be mistaken. I recently switched over to Evans as my car actually runs too cold. With the PFC set to have the fans come on at 91 degrees C, the temp will hold there for me even in stop and go traffic (limited) in texas heat.

 

Althought you know what you are doing,i have to ask:do you have the underbelly pan installed?

 

Yep...the underbody is on there. It wasn't when I picked the car up from Chicago though. I had to buy a new one from Malloy.

 

I'm having similar problems as you.

Do you have a FMIC or SMIC?

I have a blitz FMIC and my radiator sits quite far back in my engine bay. I don't think enough fresh air is getting back to it. I used to have it ducted so that the center section of the radiator was sealed against the IC and the condensor. I have since removed some of the ducting to promote more fresh air to the radiator with some sucess.

I have a mazdaspeed replica hood and honestly, I'm kinda dissapointed on how hot my engine bay gets. I may need to make some ducting to pull air out.


I have a fairly new radiator, both fans work and a vented hood and I still have creeping temps. Once I get on the highway, things stay fairly cool though. (200F w A/C on, <190F w/o A/C)

Has anyone had good luck with Royal Purple Purple Ice?

 

Run a higher pressure cap 19 psi as the car was originally designed to run with 19-21 psi. This will give you some headroom till boilover. Shut the car off after a hot run; wait 15 minutes and watch your gauge go up to 280F, hence the gurgling noise.

The brown crud, I would watch that carefully.

 

Meh, this topic's depressing, do other turbo'd vehicles ever have this problem (Spare me the LS1 posts...)? Never had to worry with My Mr2-Turbo....Supras?

I hope its something simple, that 13psi vs. 19psi Cap someone just brought up changes a great deal on how the coolant works if I am not mistaken, it's all about pressure....

 

I'm on the stock SMIC until my backordered ASP Medium gets here.

I'm all for the 19 psi cap. Matter of fact I run a 21.3 psi cap on my Stealth for the same reason. The thing that kept me from getting even a 16 psi cap is that Mazda actually changed from a 16 psi down to a 13 psi right? Whats the reasoning? I seem to remember rumblings that it was the coolant seals...is that correct? I mean the service manual has you pressure check the system up to 20.6 psi so its not that crazy. I'm still leary of anything over 13 psi though.

3000GTs & Stealths don't normally have cooling problems unless something actually fails or you install a FMIC without any ducting. Things get ugly without ducting.

 

whats the lbs on the ast cap? I upgraded mine to a 22-25lbs cap and the temps went down a bit

 

Wow...now that's a testimonial if I ever heard one. 22psi? Geeze! 19 should be no problem then...hmmm.

 

yeah, mine is really loud too but if you've only listened to it with one fan running, you'd never know the difference... hell, i've heard both and still couldn't figure it out without looking at the fans themselves when they were supposed to be on.

i highly recommend sealing the sides of your radiator and checking those fans out, be careful when examining the driver's side fan (which i just realized is the one i have issues with, not the passanger) it can look like its moving if the fan blade stops in the right place and actually not be moving at all (this is only an issue if you look at it without removing the IC duct).

good luck

p.s. if you DO end up needing a new fan motor, i just priced them out from Malloy Mazda and its $203ea.

 

Oh...forgot to post. I watched both fans operating yesterday while working the idle with the Power FC. They're fine.

I'm going to tear into the car tomorrow morn to seal off the sides of the rad and replace my holy driver's side oil cooler.

 

Yup! That and blowing hoses (turbo-coolant, for example).

 

A worn water pump will also make it run hotter.

 

I did some mods today.

- Sealed off the forward most open areas on the sides of the stock underbody tray
- Sealed off the drivers side of the radiator
- Installed an SR Motorsports air box (which semi-seals off the passenger side of the radiator and draws air from there)
- Installed the upper Bomex intake pipe (the lower is impossible to install with this airbox)

The new airbox leaves a little bit of open area next to the SMIC. Defintely helps the passenger side fan move some air out of the radiator.

Coolant temps droped down to 88C (190F) but my autometer temp gauge showed 194F. Once I turned on the A/C it went up to 100C (212F) and once I started beating on the car hard it hit 101C (214F) and wouldn't go up any more from there. The Autometer pretty much agreed with the PowerFC. Ambient temp was 101F, I was cruising at 55mph or less with occasional stoplights, I'm still on one 34 row oil cooler, and fans come on max at 95C.

That's better...still not great though.

I'm thinking about a 16 psi AST cap. I'd like to install a vented hood too but I don't have the mooola.

I don't know...I think its getting to be NPG-R time. There not much left to do besides those two things and replacing that drivers side oil cooler. The thing is low oil temps don't seem to drag down coolant temps near as much as they do in a piston motor.

 

flush your system and use evans ngp+ waterless coolant

 

Says the guy from Canada.




I thought my cooling system was great until I moved to where it gets really hot...

 

That sounds pretty good to me, especially with the Arizona heat. I wouldn't worry about it if you aren't seeing temps above 220F... heck, the stock ECU doesn't even turn the fans on until 226F!

BTW, how much was the undertray from Malloy?