Wondering about my cooling system
 

Yesterday I dove my car around noon and was getting a little nervous about my coolant temps. Just typical highway driving, little to no boost, avg 70 mph. Before I shut down when I got to my destination I took some notes just so I can start a manual coolant temp vs. outside temp log to trend if needed. I noted that the ambient temp was 83 deg F, with 58% humidity. There was light breeze and no clouds. When I parked my car my coolant temps were right at 95 deg C (powerFC).

My coolant setup:
Koyo radiator
FC Thermoswitch
PowerFC set to run both fans at 85 deg
mishimoto hoses
no ast
TB bypassed
50/50 mix w/ water wetter
stock thermostat
stock fans
I am not running a FMIC.

Yes I know 95 is nothing to worry about at this moment. I'm just wondering if 95 is what my temps should be given my mods and the weather yesterday. My concern is that in KC in the dead summer we can see 100 deg days with 100% humidity and wondering if there's anything I can do to lower or prevent my car from overheating on those days. If not I just won't drive it. If I can take my car to the track eventually like I'm hoping, I want to make sure I have the proper cooling so I don't overheat.

No expert here, but would just like to note that on a stock FD with A/C off, the first (lowest) fan speed is triggered by the PCME at 100 - 104°C. So cannot see why anything below that would ever be a problem, and even in the 100 - 104°C range the engine should still be fine, assuming a good pressure cap.

Is this 50% coolant with 50% water

or

50% water with 50% water wetter?


If: 50% coolant with 50% water
This is a good mixture. . .for winter. . .do you drive your car in the winter?

If: 50% water with 50% water wetter
Way too much water wetter. . .

All I use is water with 1 bottle of WW. . .I've had no heating issues, even gridlocked for an hour and a half at 32 centigrade. . .

50/50 water/coolant with 1 bottle of water wetter added. I don't drive in the winter but don't feel the need to change the coolant twice a year. KC has hot summers and cold winters.

Driving home today, 86* ambient, 53% humidity, slight breeze, partly cloudy. Coolant temp highest point was 103*. Got nervous, turned off the A/C and it went down to 98* about 5 minutes later.

seems high. One the dragon the two FD's I rode in didn't get that hot when they were being pushed (no A/C running)

Got ducting? How's the oil side temps? changing out the T-stat is cheap enough.

In stock form, the fans don't kick on until 105 C. You are fine. Be worried if you see 115 C.

The radiator is ducted pretty well to make sure air's not going out the sides. I'm not sure on my oil temps yet, I can't seem to get the gauge working yet. I need to find my multimeter so I can test the wires an double check to make sure it's no the wiring. The T-stat is about a month old so it's good. OEM from Ray @ Malloy.

Here's the fan settings on my powerFC:
https://lh5.googleusercontent.com/_G...0/fantemps.jpg

I don't disagree that 95 (or 103) is nothing to really worry about.

But when I had my Ron Davis radiator (smaller than the big-ass Koyo N-flow I have now), I was seeing temperatures no greater than 87C in traffic, with the fans set to come on at 86C. When I had that radiator, it was in a stock mount configuration, unducted, with stock fans. I did not have the FC thermoswitch, and still do not. I was also running 50/50, without water wetter. So I think you are having some kind of issue here.

I live in Houston, btw. I'm no stranger to 100*F days with 100% humidity. You definitely have some kind of issue.

Which Koyo is it?

You should try to figure out why the temperature decreases when the AC is off. That turns the fans on their highest speed. Doing so has only ever cooled my car down, never caused temperatures to rise.

its because the a/c condenser was working - thus flowing heated air on to the radiator. Turning off the A/C stopped putting a load on the system.

Replaced both caps with the T-Stat?

When I bough the car last year it had a .9 cap installed. I bought a stant .9 2 weeks ago to test with, and they're both providing the same result. I only have 1 cap, unless there's one hiding I don't know about. :scratch:

Let me chime in,
When i first bought the car, I would see temps like yours on hot days with the PFC and fans set to STOCK settings. after I set the fans to 84c I noticed a difference but still would heat up on hot days especially in traffic or uphill.


Now: I have a V-mount, ducted, 75%water/25%coolant, r1 stock dual oil coolers, the cheapest koyo radiator modified for the v-mount and will see 84-87c city/hwy driving in ANY weather. Even 105degree days.

Let me say that initiall with my vmount I used to always see 89c intown and even hit 105c at the track on hot days and be forced to cool down; Till I changed my thermostat and then it always stayed at 84c daily or 100c at the track. One thing I could recommend you do is to drill a few holes in your t-stat. OEM t-stats are known to be bad quality sometimes. FD racers swear that drilling the t-stat is the secret to keeping their cooling in-check when racing. The only side-affect may be delayed warm-ups on cold days.

While we are on this topic, what could cause the stock temp gauge rise above normal before the fans kick in if it is set to turn on at 105C? Mine seems to do that, but only when I'm at a stop of park the car before I shut it off. Temperature is always a little bit below normal when the car is moving, but will rise if I sit at a stop light long enough, or let the car cool down before I shut it off. The temp gauge will get up to maybe 1/8 above normal then the fans will kick in to cool it back down, it really bothers me.

Agreed doofy. IMHO, you could go with a little more water, maybe get some upholstery foam to plug gaps around the radiator but probably fine for driving the streets. Before you track the car, I would add a second oil cooler.
You need an aftermarket temperature gauge. The stock gauge isn't linear and is worthless. No conclusions can be reached on whether or not your really running hot based on the stock gauge.

I think you have a problem. With the fans set to 85, you should not be exceeding 85 given freeway driving, and not much boost. Maybe you should get a different t-stat.

So true. . .after comparing the oem gauge to the power fc and an aftermarket gauge, you'll never trust oem again. . .(unless you get it calibrated)

not 100% sure which koyo it is. It was purchased/installed by previous owner. I have the documentation in my cabinet at home but got focused on my tests tonight/tomorrow last night.

I guess I could drain a little bit of coolant and replace with water. I'm pretty sure my ratio is at 50/50 with all of the refilling I've had to do lately. Drain out about a gallon work of coolant and add a gallon of water (yes I know to use distilled water, not tap)? It does have foam on the sides (that's what I mean by ducting earlier). I have plans to do a second oil cooler or a big single, I just haven't gotten to that point yet.

Even though the t-stat is about a month old and has at most 100 miles on it?

I do know certain parts of the cooling system work. I did a coolant pressure test this past weekend because there were a few small leaks. After the pressure remained constant for 14 hours, burped my coolant system with the lisle funnel. I heard the fan come on right at 84* and both fans at 85*. I could also see the coolant rising into the lisle funnel as the car continued to get warmer so I know the t-stat was opening, although I didn't take note of temps. Something I was thinking about this morning driving to work is that when I took ownership of the car I drained the old coolant and replaced it. I did cycle plain distilled water through the system before filling with coolant, but I didn't use any sort of cleaning agents like zerex (http://www.valvoline.com/products/br...-treatments/44). I'm wondering if I should give that a shot? I've heard of people also using CLR, but I would think that would be hard on our coolant gaskets.

doofy are you running Dual Oil Coolers?
2 years ago I saw similar cooling issues with the stock rad. With AC on a VERY hot day , I would hit 103/104. I swapped out my Stock Rad for the Nflow, and I put in Dual R1 Oil Coolers.

In traffic, 87-89 is about all i see now. The second oil cooler does a great job of lowering overall engine temps... I think this is one of the most underrated mods to the FD, if you don't have it already.

I'm just running the single touring at the moment. Are your lower temps because of the nflow or the dual oil coolers? Since you did them both at the same time (unless I read your post wrong), it would be difficult to say which is the bigger reason why your temps are lower.

I am probably going to do something to improve the oil cooling next month. I have not fixed my oil temp gauge yet so I have no idea what my oil temps are like when my coolant is at 103*. I looked for my multimeter last night and couldn't find it, I think my buddy borrowed it and forgot to bring it back. I'm going to a tuning event in a couple weeks and don't know how much toy money I'll have left afterwards. I don't want to spend my rebuild money yet just in case the tuning goes bad. :(

Mixture has a lot to do with temps. Last summer I was running peak 50/50 coolant and my temps were awesome. 180f cruising on the highway and a solid 190f at a stop with the fans on. Sometimes even 185f. Add 5-8 degrees to both numbers with sprinted driving.

This year I had a coolant hose burst and filled the system with an unknown ratio. I used prestone straight coolant, the orange one and poland spring water lol.

I don't know the mixture I just added a lil of both cause I didn't want to run straight of either.

Anyway hottest day so far this year was 75f and I was out driving, not even boosted yet and temps went as high as 190 on the highway. With almost 200f at a stop with the fans on. I wonder what it will be when its 90 degrees out.

I will see you there at the tuning event! Look for the black '94 with IL plates, should be there just after you.

Back on topic, I did them both at the same time. I run 70/30 Water/coolant and change it every year. No wetter. I have also ducted my car fairly well. In my opinion the Nflow made a big difference, but I think the second oil cooler is what really helps me keep temps constant.

Verify that your fans are coming on a the temperature you have them set. If that's not happening, then you need to make sure they are working. Other than that, you don't have a problem as your current temperatures are well within normal operating range. There is no need to set the fans to come on than 95 C as all you are doing is adding more wear to them.

I think I'll add some water just for arguments sake, it's cheap/easy. I have a siphon at home so I can measure/replace exactly and not spill.

wow, I didn't even notice the s/n. I'll be in the '93 with custom red paint.

They are coming on at 84*/85* like I set them in the datalogit software. I know that it is still operating normally, but you know I'm paranoid after reading all the stories. :nod: Why does it not help to turn on the fans sooner than 95?

This is why I started the thread. My FD is my summer car, so If I can't drive it in the summer because of overheating I'm going to be not happy.

Although your temps aren't alarming, I agree that something is off, especially if you're not running a FMIC. As far as replacing the t-stat goes, if you're overheating (or temps are creeping up), replacing the t-stat isn't going to help if it's fully open. FWIW, I'm running a 160 deg t-stat (down from the 180), and it doesn't run it much colder than the 180 once the car is warmed up. This is because the t-stat is completely open, and coolant is dumping through the rad as quickly as possible.

If I were you I'd dump the coolant and go with a 70/30 mix (water/coolant). :icon_tup: Right now I'm at a 50/50 with Fluidyne radiator, 160 deg t-stat, dual oil coolers, Greddy FMIC, and fans kicking on @ 180. Typically in traffic I see 87-89, and on hot days while running the A/C it will continue to rise until I kick the A/C off. :( My guess is because the condenser is right in front of the rad, so any air that flows through the rad is hotter than ambient air since the A/C is running.