Radiator Fan Trigger Temp

All, I am wrestling with what temperature of the coolant in intake manifold I need to be turning on the radiator fans. For those who have run a GT40, what has been your experience with this??

I found a 195° temperature switch from a late model mustang to put in the intake, but have been unable to find a lower one. My temperature gauge sender is bad (ordered a new one this morning) and I have wimped out before letting the engine get hot enough to trigger the fans since I don't know the temp for sure . I tested the switch in a pan of water, which is how I figured out the gauge sender was bad, and it did turn on. I understand that SPA makes and adjustable temp switch, but I want to make sure that I am not being paranoid before buying it.

At 180 if you're in traffic you want your fans on. A small oil rad fan helps very much.

Lynn,

My fan is set up with a small capillary tube
below the radiator tube. It leads to an adjustable thermostat, that allows you to dial in the temperature at which the fan kicks on.
It is a nice feature, as it allows you to adjust for summer/winter or city/open road
driving. I also have a fan over ride switch.

Bill

[ April 01, 2002: Message edited by: Bill Bayard ]

Perhaps the system on my car may be of interest...

I have two fans, each controlled by it's own adjustable Kenlow temp switches, set to come on at different temperatures (can't remebember what!). This way, the second fan only cuts in when needed & helps maintain a more constant running temperature.

Right now my system is setup to kick on both fans together when: temp in block reaches 195, the A/C pressure reaches a certain pessure (this works as I topped off the 134A last night) or I flip a toggle just below the H20 temp gauge which has an amber indicator to tell me when the fans are on.

There was a unit on the market a few years back that had a couple of different ways to sense temp (including a sensor that clipped in the fins of the radiator.)The marketing info sounded much like your system Julian, but it was pulled off the market- no idea why. CSI makes a temp gauge with the smarts in the gauge to control whatever at an adjustable temp- even comes with a relay. I also discovered a company with a local rep called Thermodisc that makes all kinds of temp sensors/controllers. The rep, who goes to the same church as I do, is looking into it for me. I'll post what I find.

Thanks MK-IV J6 for your post, but would really like to hear some more temp settings. Bill your set up sounds ideal. What temps do you use (summer/winter)?? As you can see, I've been on the CSI web site.

Summit has a Painless temp contoller with thermo switches that can be purchased seperately for $32. One is 185/160 and the other is like 200/180.

Never drive without at least half an eye on your temp gagues. Hard wired manual overide switches are a good idea. Also make sure you use relays for fans. Fan on lights are also usefull.

Lynn,

My fan thermostat is set at 180*F, but that

will change with the weather and driving

conditions. I have no thermostat installed

yet, but will be putting in a 180* stat

after a few miles. I want to be certain that

any air pockets have been purged first.

I will be adding an idiot light to the fan

circuit, as a safeguard. MK IV, thanks for

that great idea! I'm not a great fan of

idiot lights, but in this instance, as a

backup to the gauge, I'll definitely make an

exception.

I have run my engine at various RPMs, no

load, but have not driven the car yet, so I

don't know where the thermo will end up.

I had to pull my gearbox, due to a starter/

ring gear problem. I should have it back

together by tonight. Then I will have a

better idea of engine temp under load!


Bill

Speaking of purging the system, I have seen several photos in books of GT40s with the rear ends jacked several feet up in order to burp the cooling system of air pockets. Is this necessary on all the newer cars? I recall someone mentioning something about a swirl pot; does this purge the system automatically? I have been through the cooling system purging/air pocket dilemma on marine engines, what a pain, and would not like to go through it again. What's recommended?

I presently have two bleed lines coming from the two high points in the system. One comes from the top of the radiator and the other as mentioned from the top of the inverted U from the thermostat housing. this one is about an inch higher than the top of the expansion tank where both of these bleeder lines go. The thought is that any gases will bleed into the expansion tank and be trapped there and purged out to an overflow tank where they are released. As the system cools and contracts, only liquid is pulled back into the system. Thus all gases should be eliminated from the system; or so it says here in fine print ;-)

I found the temp controller, or a similar one, in J.C. Whitney. They have a mechanical unit that is around $20 and a solid state, with a little more range, for $45. Both have temp sensors that attach to fins of the radiator. I may go with this and keep the block switch as a backup. Thanks - Lynn