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Engine Specific Info and Questions => IDI Engine => Topic started by: ORCoaster on July 24, 2011, 09:36:53 pm

Title: Them thar rubber flappers
Post by: ORCoaster on July 24, 2011, 09:36:53 pm: I was pulling the grill off the car today in prep for a paint job later in the summer. as I had my head down next to the radiator I got to thinking if I should be tucking those rubber flaps up into the keepers for the summer. Anyone do that or do we just run them as is and let the fan cycle more in the stop and go traffic? I was wondering if it makes any difference at all if you are doing mostly highway miles.

Let me know. Thanks.
Title: Re: Them thar rubber flappers
Post by: R.O.R-2.0 on July 24, 2011, 11:54:45 pm: those rubber flaps are open when there is pressure going thru the radiator.. then when you are stopped, and the fan is running, it sucks them closed and seals everything up..

leave them be..
Title: Re: Them thar rubber flappers
Post by: guy plain on July 24, 2011, 11:56:40 pm: mine seemed to take awhile to cool down...i was missing one of those flaps...went to the parts car and grabed one from there ...now it seems to cool alot quicker.....i think they help the fan pull air over the whole rad...with out it the fans just pulling what ever the diamiter of your fan blade is...
Title: Re: Them thar rubber flappers
Post by: Wayland on July 25, 2011, 08:13:05 am: The rubber flaps stop the fan from recycling hot air from the engine compartment when the car is stopped, fan running. The flaps suck shut and make sure all the air the fan is drawing comes through the rad. They open up at road speed, fan off, to allow maximum "wind" through the rad.
Title: Re: Them thar rubber flappers
Post by: ORCoaster on July 25, 2011, 12:22:49 pm: Thanks guys, didn't think about the whole radiator cooling process at a stop. Nice they did and put in a mechanism to deal with it. So no playing with the flappers, got it. And they don't even have to be spring loaded the fan just sucks em up. I love it.
Title: Re: Them thar rubber flappers
Post by: R.O.R-2.0 on July 25, 2011, 01:21:51 pm: Quote from: ORCoaster on July 25, 2011, 12:22:49 pm
Thanks guys, didn't think about the whole radiator cooling process at a stop. Nice they did and put in a mechanism to deal with it. So no playing with the flappers, got it. And they don't even have to be spring loaded the fan just sucks em up. I love it.

yea, they just kinda lay there.. when the radiator shroud is pressurized (driving down the road) they let air thru the radiator..

when the radiator shroud has a vacuum (stopped with the cooling fan on) then they suck closed so the fan only pulls air thru the radiator, not hot air from the engine room.
Title: Re: Them thar rubber flappers
Post by: rabbitman on August 01, 2011, 01:58:06 pm: Quote from: ORCoaster on July 25, 2011, 12:22:49 pm
And they don't even have to be spring loaded the fan just sucks em up. I love it.

Yup pretty clever, mine used to have a plastic "stiffener" so it couldn't swing too far towards the engine but over the years I've broke 'em off accidentally.
Title: Re: Them thar rubber flappers
Post by: ORCoaster on August 01, 2011, 07:54:17 pm: My plastic limiters are still in good shape. That is what got me to thinking that maybe you used them to flip and tuck the flaps up there for the summer. But the advice seems to be "Back away from the radiator and keep the flaps where we can see them".
Title: Re: Them thar rubber flappers
Post by: nathan_b on August 01, 2011, 11:29:17 pm: mk5 and 6 vw shrouds have the same flappers, but they are like 6in wide and 2.5in tall. same-ish material.