TheSamba.com :: View topic - Fanshroud & Oil Cooler Sealing Frame (Hoover Bit) Combos

Wed Jun 03, 2009 6:29 pm

Not all fanshrouds are created equal. By now, most people on the forums here have heard of the doghouse sealing tin (or more commonly referred to as the "Hoover Bit"). They may not know that not all fanshrouds will work with this piece, and in one case the seal isn't needed at all.

So, let's give a visual explanation as to the different setups to find out what fits what:

Original German Fanshroud - sealing frame fits, no surprise

PUMA low-profile Fanshroud - sealing frame also fits

New VW Mexico Fanshroud - no frame required, no room for one (despite the lower screw fastener cutout)

Scat Fanshroud - frame required, but needs to be modified to work
(Other 36 hp aftermarket fanshrouds compare similar)

Scat Fanshroud (again) - modified frame

This subject was touched upon in the Split Window Bus forum recently, but I wanted to post this here for a broader audience that this subject relates to.

Wed Jun 03, 2009 6:32 pm

Mark... many thanks for the pics.

Wed Jun 03, 2009 8:15 pm

Good stuff!

- Scott

Sat Jun 06, 2009 3:47 am

Required reading for everyone. Now I have a link to point folks to. The Scat photo is especially good since you left it in the CAD color you can really see the big gap.
They should really fix that!

Mon Jun 08, 2009 8:42 pm

From my bus blog
don.ville wrote: Based on forum feedback, I added a rivet to the foam hoover bit seal to prevent it from getting sucked away by the fan.

I had to angle the new piece downwards too since

the SCAT shroud was made that way...

Thu Jun 25, 2009 10:10 am

this is one very informative post to other forum regarding Scat shrouds

Wed Aug 05, 2009 12:51 am

As I've just taken a Scat 36 HP shroud with air outlets off my motor, I thought I'd post a comparison photo or two with the stock shroud I'm about to put on :)

Scat 36 HP next to Stock

The biggest differences I found are coming up, but some of the smaller differences are harder to spot.

The sealing part to the hoover bit has been included on this scat shroud, but it stands a bit further back off the cooler and at the wrong angle

The curved aerofoil adjacent to the cooler, the one visible in the pics, is a different shape to the stock aerofoil. It extends further to the right and is not as curved... the only effect I can see from this is that it's directing air into the wrong place, but thats just a supposition, not tested.

The other thing I noticed was that the rear of the shroud (the bit against the firewall) was not parallel to the front and the fan was not as close fitting as it is in the stock shroud

Also, the opening to the cylinder tin on the left (over #1 and #2) is not as big as the stock shroud

The following two photos show the vent openings supplying air to numbers 3 and 4 cylinders. With the air outlet on the 36HP shroud as it is, and the wrong shaped aerofoil, the amount af cross sectional area is drastically reduced. The stock shrouds airway is very clear and directed.

This is likely the reason why I've been having heat issues at higher speeds.

Fri Aug 07, 2009 10:03 am

Since discovering this issue, I have started modifying all the SCAT fan shrouds I deal with to eliminate this problem. I use the Zerks hoover bit & remove the little piece of tin in the SCAT shroud and weld on a new piece that properly fills the gap, eliminating the problem. Now that I know about the problem, no fan shroud leave the shop without this modification.

PS - the EMPI brand shroud has the same issues.

Mon Aug 31, 2009 10:25 am

another possible approach:

Fri Sep 04, 2009 9:24 am

thats pretty nice,has it been tested to see the defrance? also the bubble top cases are defrent. is any one making the shroud for them?I modifyed my old one but it is now probly useless for my spair moter ,witch is fixen to go in pretty soon. a nice set of stamped properly profiled pieces to weld/rivet with epoxie would be nice,just trim old shroud to a template then add the new peaces!!!

Thu Sep 24, 2009 1:12 am

Mark I believe it doesn´t need to be tested. With this mod we are only returning the condition of engine tins to the state factory produced them. You definitely want all the cooling air to be spend on the oil cooler and cylinders and heads and not going through large gaps to your engine bay.

Fri Oct 02, 2009 9:31 pm

I discovered something very interesting recently regarding fan shrouds.
Here is a shroud from a fuel injected beetle.

basically the same except for the added venturi ring, also there is no scoop surrounding the opening to the oil cooler. as like the earlier shroud pictured below

I have used both shrouds on my 1955cc, with the FI shroud the head temp stays around 300 most of the time, if i'm stopping and going its like 250-275, pulling hills on the freeway 350 is the hottest its gotten. (this is measured with a VDO guage and sender at spark plug 3)

with the standard doghouse my head temp was 325ish most of the time.
but i had a problem with my oil pressure!! somehow my oil was not getting cooled properly with the standard shroud. after cruising for a while, when i came to a stop my oil light would come on and my psi would be at like 5 and my cruising psi would gradually get lower too. my oil was breaking down and thinning out.

the only thing i changed was the shroud, I went back to the FI shroud and after driving all day my psi at idle never got below 12ish (idle is about 900 rpm) I did not change oil either, its rotella 15-40.

I just thought this experiment was interesting.

Wed Oct 14, 2009 1:04 am

vugbug68 wrote: I discovered something very interesting recently regarding fan shrouds.
Here is a shroud from a fuel injected beetle.

does your FI shroud have the long oil slot with no scoop or the small "peanut" slot?

Wed Oct 14, 2009 7:47 am

derluftwagen wrote: vugbug68 wrote: I discovered something very interesting recently regarding fan shrouds.
Here is a shroud from a fuel injected beetle.

does your FI shroud have the long oil slot with no scoop or the small "peanut" slot?

it looks just like the one in the picture except without that scoop around the opening. the opening is the same length, i dont think i've seen one with the "peanut slot"

Wed Oct 14, 2009 12:15 pm

Here is a pic of an industrial shroud from the gallery. My FI shroud has the fresh air ducts and the small slot.

Wed Oct 14, 2009 2:41 pm

interesting, no mine is how i mentioned earlier with the large slot. I wonder if anyone has done any tests with FI shrouds?

Tue Nov 24, 2009 6:35 pm

I put together this little video on how to install the hoover bit. I know it seems obvious to most of us, but some folks need to see it done to absorb it.

Thu Nov 26, 2009 8:40 pm

If you are thinking of buying a SCAT doghouse fan housing kit..BEWARE...some seem to be worse then others....mine is of VERY poor quality.
Here is the link to the photos:

http://www.facebook.com/album.php?aid=168339&id=649920489&l=e1661e1929

Thu Nov 26, 2009 8:43 pm

vintagevinni wrote: If you are thinking of buying a SCAT doghouse fan housing kit..BEWARE...some seem to be worse then others....mine is of VERY poor quality.
Here is the link to the photos:

http://www.facebook.com/album.php?aid=168339&id=649920489&l=e1661e1929
OEM

Fri Nov 27, 2009 8:23 am

yes, the aftermarket stuff needs work. That is why I modify all of the doghouse oil cooler exhausts to line up properly, modifiy the hoover bit area to flow proper, etc.