What is Hiding under your Fan Shroud?

[Jeff Higgins]

I'm two days into the teardown of my 3.0 MFI motor. I started a thread on that, but didn't want to distract from it with this.

I've spent two days tearing off the ancillaries - intake, exhaust, tin, fan, shroud. And cleaning. Mostly cleaning. On the surface, from the outside, my motor has always looked pretty clean, top and bottom. Any leaks are addressed pretty quickly, and I regularly use engine cleaning products on it. I hate a dirty, leaky motor.

In light of that, I was ill-prepared for what awaited me under that fan shroud. Just an unholy, grimy mess. Then it struck me - just how does all of this built-up spooge affect cooling? It was on top of and between cylinder and cylinder head cooling fins, it was starting to plug up the top of the engine oil cooler. Shirley, this cannot help.

My motor is 18 years old with about 125,000 miles on it, plus at least 80 track days. Not really "old", or "high mileage", by 3.0 liter motor standards. It was assembled with all of the latest and greatest sealants, assembled with a good deal of care, and kept, at least externally, "clean". I cannot imagine what an untouched, original, high mileage motor must look like under that shroud. I think the "air" part of "air cooled" must be a misnomer on many of them.

I don't see any way to improve this situation. This is going to happen to all of these things, assuming they are driven. I'm starting to think that maybe, going forward, this might have to be a "winter project" every year - drop the motor, disassemble the induction and remove the shroud, and de-grease.

Thoughts?

[fanaudical]

I'm well aware of the mess you speak of. I found a ridiculous mess of oily grime under my fan shroud when I rebuilt my engine. I pull the fan about once a year and use of those USB borescope gadgets to peer under the shroud and make sure nothing is leaking and that the oil cooler isn't clogged with something. So far I see nothing other than some dust accumulation after several years. Maybe I'm not driving it enough...

[GH85Carrera]

It does obviously affect cooling. My car had 150,000 miles before it was time for a rebuild. It runs a LOT cooler now.

[pampadori]

My experience (your's may vary) The crankcase breather hose and the breather cover itself cause a lot of this mess. The cover where the hose barb is doesn't have a good bead for the hose and clamp to truly seal so oil will slowly but constantly drip down under the shroud and the fan will blow it all around.

The four studs for the cover also don't seem to keep things evenly tightened so the gasket on mine is usually a source of leak. I think that spot would be a good candidate for a silicone/rubber gasket. And of course the studs could probably be a path for oil to leak at as well since I think they go all the way through and aren't enclosed. A nylock nut with a crush washer could do the trick there. I think I used standard steel washers without considering this when i had mine apart last.

[TeeJayHoward]

Yup.

[kltarga72]

My 1980 SC had a mouse nest over the oil cooler and cylinder #6. It sat for 8 years before I purchased it.

[Jeff Higgins]

Originally Posted by pampadori

My experience (your's may vary) The crankcase breather hose and the breather cover itself cause a lot of this mess. The cover where the hose barb is doesn't have a good bead for the hose and clamp to truly seal so oil will slowly but constantly drip down under the shroud and the fan will blow it all around.

The four studs for the cover also don't seem to keep things evenly tightened so the gasket on mine is usually a source of leak. I think that spot would be a good candidate for a silicone/rubber gasket. And of course the studs could probably be a path for oil to leak at as well since I think they go all the way through and aren't enclosed. A nylock nut with a crush washer could do the trick there. I think I used standard steel washers without considering this when i had mine apart last.

Yup, pretty common area of concern on these motors. Fortunately, that area is very easy to access on my motor, being MFI. Maybe even easier than carbs. Certainly not like the CIS on an SC. So, I have always been able to stay on top of the leaks in that area. Doing so may be part of what lulled me into complacent.

Originally Posted by TeeJayHoward

Yup.

Yup. Now add a fair amount of dirt road driving to that unholy gooey mix (I love bombing our local fire/logging roads in my 911). The end result is what we in the airplane biz coined the highly technical term of "spooge" to describe. The only place I have ever seen a worse accumulation is in the main landing gear wells of a 50 year old 747.

So, yeah, this just has to have an affect on cooling, as Glen notes. The question is, what do we do about it? Some cars (SC's, Carreras, 964's, 993's) are such a monumental PIA to get the shroud off of (even mine would be an engine drop), that this is a very daunting proposition.

Wouldn't it be cool if there were some magic spooge eating foam or something we could shoot in past a spinning fan, which would distribute it across the top of the motor? Wait an hour while it dissolves the spooge, stick a hose in there and let 'er rip, and viola - spooge abatement.

Why hasn't someone thought of this?

[SpyderMike]

I recently ended up wearing a lot of that on my 255,000 mile original drivetrain 1985. The f-er just keeps running and making me happy though...grime and all.

[Jonny042]

Maybe just schedule an engine drop every 3 or 4 years? Or 10 track days, whichever comes first?

(EDIT) - just re-read the first post more carefully. Besides LOL'ing at "Shirley" I noticed you suggested dropping the motor each winter. Yes. This. You might even be able to narrow down the source of the "spooge" and be able to push it out to every few years.

[al lkosmal]

The "Triangle of death" (breather, sensor and T'stat)....easily seen on a carbed, MFI or EFI/ITB motor . even when appearing ok from the top of the shroud, leading you into a false sense of well being....tends to weep/leak/seep under the shroud and onto the top of the motor and run between the cylinders etc.....I've seen the spoogiest

al