Temp now creeps up at highway speed with new fan?

[LowBuckX]

I installed a Taurus 2 speed fan of the 2 speed variety that works great in normal driving conditions but not at sustained speeds of 40 mph+ for exstended periods of time. .
standing still at idle for over 20 minutes it never got over 175 but on the freeway at 65MPH and 3500 RPM it started to creep to 200 but did not go over that.

Keep in mind outside temps are 40 degs. so at 90 in the summer Im sure it will creep higher.
The shroud covers 100% of the core. Im thinking somehow the fan needs to be shut off at 40 mph.. But how besides a toggle that could be forgotten about.
Or some sort of "BLOW OFF" doors that are spring loaded to pop open if pressure builds in the shroud...

give me some ideas

[derekf]

Or some sort of "BLOW OFF" doors that are spring loaded to pop open if pressure builds in the shroud...

That'd be my thought. I've seen them where they're just a hole in the shroud with a rubber flap over it, where the flap is mounted from the back so airflow can push it open but if the fan is actively drawing air they'll seal themselves.

[sinned]

You need to turn the fan off at speeds, running it stalls the air. The is a point where the natural push of the air from road speed overcomes the fans pull and it creates a low pressure area directly in front of the air, you need to turn the fan off so the air force through naturally.

[CAMAROBOY69]

Simple answer. The radiator is not big enough or not working properly. If you are driving down the road and your car is getting hot you simply dont have a big enough radiator. Especially on the older cars that get constant air flow forced thru the front of the car. Even without a shroud a car should stay cool enough if your driving down the road. In 40 degree temps there is no reason the fan would need to be on at all unless you sat for a while.
What are the specs on the radiator?

[Steve1968LS2]

You need to turn the fan off at speeds, running it stalls the air. The is a point where the natural push of the air from road speed overcomes the fans pull and it creates a low pressure area directly in front of the air, you need to turn the fan off so the air force through naturally.

Very true.. my '68 did the same thing on the highway when the gear vendors wouldn't come one.

At high RPM you engine makes a lot more heat so you either need to drop the RPM's (an overdrive trans) or increase your ability to cool the water and thus your engine.

Put your fan on a relay so it only comes on at a certain temp. Having the fans on a switch is not as effective. Getting an OD trans would help also. I had a big BeCool radiator and my car did exactly what yours does so a bigger radiator is not always the answer.

Are you running an elec water pump or regular one?

My SPAL fans had rubber "flaps" that would allow air through at speed but would seal at low speed.

[Steven]

I had the same problem when I changed to electric fans and used the stock radiator. At idle it was fine, going down the road it got real hot. I changed to a BeCool radiator and the problem went away. I started out using BeCool's dual electric fans and their hook up relays. ( I know about all the write up on Mark IV fans, I'm not that good on manfacturing mounting brackets) I like drop in, plug and play, but it's always my luck, something has to be modified to get it to work.

[LowBuckX]

Relays I have 3 of them... 1 for low speed one for high speed one to shut low off when high kicks in. Temp switches Ive got 2 one comes on at 180 and the other comes on at 205 for the high speed.

The radiator is not the problem This only started after the electric fan was intalled.
I know it is the air stalling at speed. with the fan acting as a blocker. The radiator this fan came off of was only 90% covered by the shroud giving a 10% free space. I will add a blow of door this winter or get a radiator with more core area.

[gmachinz]

You really need to get a DC Controller. It reads the coolant temp. at the radiator outlet and that determines fan speed. If the air rushing through your radiator is under whatever setpoint you have the controller at, the fan will not come on, which is what you want to have happen. Dennis is absolutely correct on the airflow overcoming the pull of the fan-you have two forces fighting against each other and it's creating turbulent airflow.

[Alumitech Reproductions]

What
others have stated is true ,with the back presure created by blockage of the fan shroud ...as the owner stated there was not a problem before the shroud and fans were installed .. and the taurus unit may not be a hight cfm rating ... in witch case the fans may be also creating a back presure at speed as they can not keep up with air flow ... I.E more back presure .

indeed also a good aluminum radiator with a proper fan set up I.E Spal
twin 11 inch 2800 cfm with 6 rubber flaps to releave back presure is the whip set up .

here to help with cooling problems
Don