View Full Version : Electric Fan " Pull or Push"

Russ Austin
04-06-2002, 11:16 PM
I recently installed an electric fan for cooling in my TR3A. I have it set up to pull air thru the radiator, any ideas on whats best for cooling push or pull. graemlins/jester.gif

04-09-2002, 05:15 PM
definately pull cold air in from outside rather than push engine heated air out

04-09-2002, 07:54 PM
Really, either way is probably OK....but here's the typical considerations:

If the fan is in front of the radiator (pushing air thru), the electric motor is away from the car engine, allowing it to run cooler and with longer life. Also, "packaging" the unit may be easier, since the fan has to be pretty slim to squeeze between the rad and water pump. The downside of locating it in front of the rad involves the fact that it actually blocks some of the cooling fin area.

Alternatively, if the fan is "behind", (pulling air), the front of the rad is 100% exposed to airflow.

In applications where an electric fan is standard, you tend to see it both ways.

04-10-2002, 09:41 AM
I remember reading an article in a magazine describing a problem that an owner in the UK had, after he had inadvertently reversed the fan in his car. In traffic the car was fine, but on the open road, it would overheat. The "push" setup worked in traffic, but once on the move, the incoming air counteracted the effect of the fan, hence overheating. Pull, definitely!

Russ Austin
04-11-2002, 10:25 PM
In the last week or so I have driven the car every chance I get. I have noticed that sitting in traffic the temp go's up more than it should 190 - 215. On the road it stays quite cool 185 - 190. The fan is pulling air through the radiator. It looks like I'm going to move it in front, so it can push. See how that works. Before elec fan no overheating problems at all. images/icons/shocked.gif

05-02-2002, 09:23 PM
I have installed a pusher fan (mounted in front of the radiator) on the two TR3A's. I used a 10" fan with a thermostatic probe that is inserted between the fins off the radiator to control it. I wired it so that it will only run when the ignition is on. This has worked well in keeping water temperature around 180 deg F when driving in stop and go traffic. My experience is that the TR3 will run all day at highway speeds and water temperature will stay about 180, but slow down below 25 and temperature will sky rocket until you can move again. The original fan is not very efficient, but I left it installed, another reason for the pusher fan. The fan is not symmetrical, so I was concerned that removing it might affect engine balance.

08-10-2002, 06:32 AM
When I worked at the Desert Proving Grounds for GM I had the chance to talk to some of the best cooling people in the biz.
I will try to remember some of the basics of what they told me and hope they are of helpfull to you.
This info is from GM guys about GM vehicals, but I am shur that a heat exchanger is a heat exchanger or the laws of thermodynamics will come unraveled.
1 Close finned rads will cool well at stoplights.
2 Large spaced finn rads will cool at speed.
3 180 f air behind the rad is optimal
4 Electric fans free up HP
5 A larger radiator is not nessasarily beter.
6 pusher fans tend to block air flow at speed
7 Pusher fans if used with a puller fan will block air flow if the are not of simmilar blabe type, RPM, and cfm.( they pack up the air because they are out of sync.)i.e. idle
8 Shrouds are critical!
9 If one uses an electric fan use one of the 400 what type.

Their are other reasons for your car to run hot!

1 Too much advance on your timming will run hot and ruin your engine.
2 A flash rust on your thermostat can make even a new t-stat only open to 90% which in the southwest in the summer will cause a car to overheat.
3 Blown headgaskett
4 weak waterpump
5 low coolent
6 High Head pressure in the AC
8 Road debris in the rad, or between the rad and the condencer
9 lose belt
Their are a few others I am sure I forgot to mention.

If pushers worked why does 99% of oem use pullers.
Be carfull where one measures temp. if the port is close to the cylinder it will read high every time one steps on the pedel

Wild Guess
You are too advanced
your rads clogged with goo
your shroud is missing
your high speed fan setting( if equipped is inop)
your T-stat is marginal.

What would I do?

Make sure belt does not slip

Run the car at idle untill hot while pressing my hand on the rad surface to see if it is flowing evenly. If not have rad repaired,

Start car when cold and see ig the rad hose gets rock hard imeadiatly. (blown head)

Check fan op

inspect rad for debris

Check timming with a quality light

If none of the above work install 160* t-stat

If that does not work replace water pump.

If all else fails put in a 400W fan (puller)
Put in the biggest one that can be shrouded, and run that with a thermister in the rad.
Termister switches are availible from performance rags everywhere.


Sounds like an airflow problem; but dont discount the t-stat


08-13-2002, 09:29 PM
Re the great cooling debate. You need as much space between the fan and the rad you can obtain.The fan must be shrouded as that no hot air from the compartment will recirculate through the rad. As to fans a balanced fan with an eccentric blade pattern is desired. The reasoning is that it simply moves more air.Also the only air entering the compartment must go through the rad.In my tiger with the 351 one of the best move was a single core aluminum rad.
Hope this helps.

08-16-2002, 05:48 AM
We run alot of big block cars at the track and have found that one of the best rads is from the newer chevy F cars. Biger is not always beter.
I agree that moving the fan as far away from the rad as it can go is a great Idea as long as it is properly shrouded.
If you are using a fan that is mechanical, leave room for engine movement clearence, about 2 to 2.5 inches around the edge of the blade. The closer the beter, but depending on HP and mounts too far is beter than contact.
Here is a good tip.
On fans that one has to build ones own shroud place the edge of the fan blade 1/2 of the way outside the edge of the end of the shroud and one half of the way in as viewed from the top.

11-12-2002, 01:46 AM
The best cure in my experience is also the cheapest. Take the stock fan and saw its arms off. Take this hub to the import salvage yard and buy a plastic fan that is a good fit(watch the diameter of the blades)Center this on the hub and drill mounting holes. If the blades are too long they are easily trimmed without upsetting balance since they weigh next to nothing.Bolt it on, and be amazed at the volumn of air these little monsters pull. On the tr3/4 the radiator is really too deep for the pityfull 4 paddle fan to draw through. Pushers are good but have the drawbacks that have been discussed in the other postings.Only a sick old tr runs hot after this conversion.

Gary Pope
11-14-2002, 11:27 AM
One thing to remember if you put an electric fan in front of the rad: You lose the ability to have an oil cooler mounted in the correct location. The fan will fill the place where an oil cooler goes. I use a 10" fan in front of the rad, however, it is inadequate in 90+ temperatures in slow traffic etc.

11-14-2002, 02:48 PM
Hello Russ,

an interesting debate you have started.
I have a pusher fan (made by Kenlowe, a UK company) fitted to my Triumph 2,500 saloon purely because of space limitation. (I still have room for the oil cooler radiator) This is installed, as the manufacturer insist, as close to the core as possible. It is thermostatically controlled and it rarely ever comes on when cruising, even motorways in high summer. (I do not have a mechanical fan any longer)
The airflow through the radiator when moving is much higher than any car fan, which is why pushing air from inside the engine bay will not work, except when stopped.
I don't believe, that all things being equal, it matters whether you pull or push as long as air flows front to rear.

graemlins/thirsty.gif graemlins/thirsty.gif

spit6 guy
11-14-2002, 02:53 PM
I just thought I would put in my 2 cents,over this past year I have gone through every plan I could find on the internet and in books to keep my spit 6 cool on days that are over 90 and none seem to work the most costly being the pri air dam
and valance wicth is no longer on the car also the cheapest and the one that kept the engnie the coolest is header wrap , but even this is not going to keep the car cool on those hot summer days the problem is the inadequate cooling ability
of the down flow raditor so I an going to change this to a cross flow double pass raditor this winter so I will keep you posted on my progress

spit6 guy graemlins/cheers.gif