Running temperature questions...

My car runs @ 210* normally. But I am pretty sure my radiator is done.

I'd agree:

If it was running at that temp while on the highway and you have a 195* t-stat, that's about right. If you have a 180* stat and the air dam under the car, that's an indication that you are not rejecting heat as efficiently as you could be.

FWIW, low speed comes on at ~208*F and high at ~228*F.

Good luck.

my car doesnt get over 178*. i am running a 160 thermostat though.

stprorolla49 said:

alright, i guess i was a bit off then...that makes a lot more sense because it woul get up to almost 230, then it would cool down...i guess the high speed fans were coming on?

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Remember, the fan should kick off once you reach about 45 mph. So if you were on the highway, something else is going on (and it hanging at 230 was coincidence).
If this was happening at lower speeds, you should see if low speed is coming on naturally, and ensure that HS comes on with the AC on.

Just in case anything is of interest or helps you, here's a draft of a tech note I'm writing for Wes's webpage:

General Cooling system diagnostics.
For any questions, corrections or concerns, please contact HISSIN50.

If the car is running what is deemed to be too hot, the temperature must be checked with a real gauge. As an alternative (better yet, as a back-up), the ECT reading can be interpolated.

Generalities:
If you have recently had the cooling system open, ensure air is bled out of it. Erratic gauge readings which sway much faster than one would think possible is a sign of air in the system.

If a car runs hot at speed:
Ensure the coil is not clogged with debris.
Ensure the air dam is present under the car.
If the above is true and the car becomes even hotter and struggles to cool down with the A/C being on, that can suggest the coil is simply unable to reject enough heat. A new radiator is often the best move from a monetary standpoint (as this allows an upgrade at the same time. Nice for hotter climates or modified engines).

If a car runs hot at slow speeds or while stationary but cools well at speed (40 mph +):
Ensure the cooling fan is up to par.
The stock 94-95 GT fan is a two speed unit.
Low speed comes on at ~208*F.
High speed comes on at ~226-228*F.
To check if the appropriate fan is being triggered by the computer:
To check low speed fan operation, look for 12 volts at CCRM pin 14 with ECT temps greater than ~208*F
To check high speed fan triggering, look for continuity to ground at CCRM Pin 17.

There is a fuse for the fan in the underhood fuse box so don’t forget to check it. There is also an EDF fuse. Don’t forget about it either.

If the car cools decently while going slow for a bit but then heats up until shut off and restarted later (where this cycle repeats), check to see if a circuit breaker was installed on the fan harness. When thermal thresholds are reached, the breaker opens, turning the fan off.

The fan connector/interface itself was known for heating excessively. Unclip the fan connector from the fan motor and ensure that the connector itself and wires and terminals don’t show signs of overheating. Often times, this is overtly evident. Some cars have a circuit breaker retrofitted to the fan connector. If it seems like the fan stops working after a bit of operation, see if this breaker has opened the circuit. This has been known to occur (the breaker was an attempt to keep fan motors/wiring from overloading and catching on fire).

Many desire to install switches to control the fan speeds manually. One would connect CCRM Pin 14 to twelve volts via a switch for low speed switching. One would connect CCRM Pin 17 to ground via a switch for high speed fan operation. Do not run both speeds at once (either via the switches or accidental clashing of one fan switch and the OEM control). A write-up for this modification exists elsewhere already and provides more specific details.

If you should decide to do away with the OEM fan control, which many do as it leaves quite a bit to be desired, a soft start or variable fan controller is a popular and wise option. Flexalite, SPAL and Dc Control all offer such controllers. This user chooses to use a Dc Controller (www.DcControl.com). It uses pulsewidth modulation to provide infinitely variable fan control. I have used the controller in 115*F ambient temps while stuck in traffic and the unit excels.

Don’t overlook your thermostat. A performance thermostat is well worth the few extra dollars one costs. I’m familiar with the Mr Gasket line, which is a quality piece. It is fully balanced, which means it doesn’t suffer from hysteresis as inferior thermostats can. It opens fully sooner and includes a jiggle valve to help the system self-bleed.

Ensure the system is holding adequate pressure. Each PSI in the system raises the effective boiling point almost 3*F. A 16 PSI cap raises the effective boiling point almost 50*F.

A common misconception is that more coolant will allow greater cooling. Water rejects heat ~2.6 times more effectively than ethyl glycol coolant. Coolant itself is useful for freeze protection, raising the boiling point (which is partially offset because the coolant itself is displacing water which could be in the system, so coolant temps might not have gotten as high in the first place), rust inhibition and lubrication. While some folks like to run straight water with a cooling system additive (for rust protection and lubrication), on a daily driver in all but the hottest climate, I don’t like to run less than 30% coolant. If a cooling system needs to run less coolant to function, there are likely other issues at hand which should be addressed.

And always use water deprived of minerals. Distilled water purchased from the store or premixed coolant and water solutions are common ways to achieve this. Some people like to use products which reduce surface tension (Redline and Royal Purple, for two, offer such products).

Here's some low and high speed fan diagnostic pathways:

If low speed isn’t coming on, but you are getting 12 volts to CCRM Pin 14 at or greater than 208*F and the fuses are intact,
Check CCRM Pins 1 and 2 for 12 volts when the fan should be on. If there’s not 12 volts:
Check Pin 15 for ground.
Check pins 3 and 4 for constant 12 volts.

If high speed doesn’t come on at ~228F or with the A/C turned on, but CCRM Pin 17 shows continuity to ground:
Check CCRM pins 6 and 7 for 12 volts when the high speed fan should be on.
Check Pins 3 and 4 for constant 12 volts.
Check Pin 13 for key-on 12 volts.

Thats a great write-up, JT
Question: What does "EDF" stand for? Seems to me its the low-speed fan fuse, but 10A seems kind of low for that.

Stephane, EDF is Electro-Driven Fan (and HEDF is High-EDF) as I recall. You're right-on - it's the fan. There is an EDF solid state module and I believe that is what the fuse is for.
As I recall from the wiring pathways, the low speed fan actually comes on naturally with the key - it's the PCM that shuts it off until car reaches 208*F. This is part of the system safeguard (if things take a dump, the fan comes on. It's not just an open ECT circuit which causes that to happen). It's a cool way to wire things if it works.

Michael, if you have the air dam present, that sounds good. One thing I didnt get into with that little tech note thing is that a bad t-stat can actually at up at sustained higher RPM. It didnt sound like this was an issue for you but was worth mentioning.

This is indeed the time of year when radiators show that they've gone south.

Good luck.

having the same issues, Michael.

currently, i have a stock replacement radiator and a Mr. Gasket high performance 180* tstat.

going to upgrade to the Mishimoto aluminum 2-row radiator andhope that fixes the prob.

watching the temp guauge constantly flicker up and down is nerve-wrecking.


btw: hell of a write-up, JT!!!

stprorolla49 said:

JT- I do not have the air damn on the car right now, in fact i dont even own it anymore, idk what happened to it, but i lost it sometime during the painting process. I just got a cobra bumper to replace my wrecked GT bumper...the cobra bumper has the air dam molded in, correct?

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I'm not real familiar with the cobra specifics, but I would think the air dam would/should be there no matter which bumper you have. One of the Cobra guys can say for sure. WHen I got the 94, it was also missing. 12 bucks at the dealership for a new one (LRS had them for about the same price as well).

I really would run one if you're supposed to. It not only directs air upwards towards the radiator but also creates a low pressure area behind the coil (helping to pull air through the radiator).
Good luck.

I *think* the cobra bumper has it molded into it...maybe someone else with one can let us know

HISSIN50 said:

I'm not real familiar with the cobra specifics, but I would think the air dam would/should be there no matter which bumper you have. One of the Cobra guys can say for sure. WHen I got the 94, it was also missing. 12 bucks at the dealership for a new one (LRS had them for about the same price as well).

I really would run one if you're supposed to. It not only directs air upwards towards the radiator but also creates a low pressure area behind the coil (helping to pull air through the radiator).
Good luck.

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If I get hot when going 70 and when driving in the city, that should be NOT caused by the lack of an air dam right?

Therian said:

I *think* the cobra bumper has it molded into it...maybe someone else with one can let us know

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I have a Cobra bumper and still put the air dam on the bottom of the radiator support

The Green GT said:

If I get hot when going 70 and when driving in the city, that should be NOT caused by the lack of an air dam right?

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You got it Eric. When crawling in traffic, it doesnt matter if you have the air dam or not.