Fanshroud Flaps / Thermostat

[Shorty]

I may be about to get shot down in a ball of flames, but, I'm in the process of building my engine up and a fellow VW enthusiast has told me to take extra care when fitting these as they can be easy to get wrong..

now, I'm not looking to take any short cuts, definitely not, but until tonight, I'd never seen or heard of them..

Does everyone else have these? or are they generally omitted to stop them rusting in the shut position potentially causing an engine overheat....?

Experience, pointers and opinions appreciated..

 

[RICH-I-AM]

I left mine out when i built my engine as i wasnt sure either.
But it would cause the engine to warm up slower due to overcooling.
I leave mine to idle for a minute or two and never thrash my van.
Havnt had any problems yet .
Apparently if the stat siezes it does it in the open position so not to leave the flaps shut and not cook your engine.

Rich

 

[Shorty]

Hmmnnn... having never seen one before (and I've spent a lot of time in a workshop in the last 12 months full of engines), I'm beginning to wonder if most people leave them out.......

Keep your comments coming guys n gals please..

 

[Geeze]

They fail open unless you have one of the shonky modern wax stats which do just the opposite.
Have known them 'fail' shut or fail to open fully but that was mostly back in the days of junkyard engines stored in less than ideal circumstances and they would seize up.

It's easy to tell if your engine has them, if you feel around the back at the bottom of the fanhousing, there should be a bar across (operates the flaps). Ideal world, fit a thermostat - better warm up times and longer lasting motors. But the problem these days is finding the thermostats themselves in good working condition.

I've run for years (including dailies through winter) on engines with no thermostat and they didn't cause massive problems, same with most people I know who ran them through the 90s. One thing I do recommend though is fitting the flaps even if you haven't got a thermostat. Fully open, they're part of the ducting design for distributing the air evenly as it exits the fanshroud. 8)

 

[Oh.go.on.then]

My engine builder recommended fitting the flaps welded open as they direct air but don't necessarily worry about a thermostat. He told me a thermostat is partly to direct more air through heat exchangers in cold weather and therefore not imperative to have it. I'm sure it must be to warm the engine up faster too.

I think if you have a thermostat and the flaps corroded, they would corrode closed as the thermostat would be contracted when cold.

I've refitted all of the thermostat flaps and thermostat and it appears to work. Have I noticed any difference? - no - apart from a lighter wallet. I kind of feel better that its there though.

 

[Shorty]

My engine builder recommended fitting the flaps welded open as they direct air but don't necessarily worry about a thermostat. He told me a thermostat is partly to direct more air through heat exchangers in cold weather and therefore not imperative to have it. I'm sure it must be to warm the engine up faster too.

I think if you have a thermostat and the flaps corroded, they would corrode closed as the thermostat would be contracted when cold.

I've refitted all of the thermostat flaps and thermostat and it appears to work. Have I noticed any difference? - no - apart from a lighter wallet. I kind of feel better that its there though.

And here is the problem, the first you'll ever know about it is when you're engine overheats :shock:

I'm not planning on fitting heat exchangers at the moment as I'm going down the propex route... so I'm steadily being convinced not to bother with this...

 

[mattd1984]

As said above if the thermostat fails the flaps will fail open.

Funny enough I fitted flaps myself last week on my 1776 that the engine builder said don't worry about flaps you don't need them. Well I always thought my engine ran a bit hot. Fitted this flaps this weekend and went for a long fairly hard drive. Result cooler running temps.

Also as a note I fitted the deflector plates that were also never installed. So this will probably be adding to the engine temps.

 

[Tofufi]

I always fit them, and advise other people to fit them.

Not only does it improve the flow of de-misting air at start up (which won't matter to you if you don't have heat exchangers) it also improves the engine warm up, and as a result your engine will run more nicely.

In winter, your engine will never get up to temperature without the 'stat fitted - in winter, mine never opens fully.
Running your engine over-cool will increase engine wear, and lead to higher fuel consumption.

VW didn't fit it for no reason.

 

[Shorty]

drive in winter????? :lol:

Joking aside, you have made some good points, so thank you for that..

What I am failing to understand at the moment is how they can fail in the open state..

In my mind, when the bus is tucked up in bed, the flaps are closed and will remain such until a time when the heat acting upon the thermostat is sufficient for it to expand and activate the mechanism that opens the flaps...

So, with that logic, if there was any corrosion or A.N.Other failure, the flaps would actually be in the closed state and potentially cause an engine over heat situation?

Have I missed something from my logic?

 

[dubdubz]

He told me a thermostat is partly to direct more air through heat exchangers in cold weather and therefore not imperative to have it.

This is incorrect - the flaps being closed does force the air out of the heater outets on the fan housing - it's part of the design function.
Also the flaps never fully close, even when the stat is set properly - well not in my case.

I don't think there has been any publically available information on a controlled test - 2 identical cars doing identical mileage with identical fuel for several 100o's of miles and then strip the engines down to diagnose any increased wear on the one without flaps and stat, compared to the other.

My engine warms up quicker which is good for demisting and my sanity, than without. a combination of flaps/stat/deflector plates and tinware all correct must help protect my investment. The other thing is other things must be in place too help. So an incorrect CR or mixture which results in high temps - won't be fixed by a stat. I suspect if you had an in spec CR, all tinware complete, and didn't thrash it - then possibly you wouldn't notice.

 

[dubdubz]

have a look at this too...

http://www.vw-resource.com/vanes_thermostat.html" onclick="window.open(this.href);return false;

 

[Shorty]

have a look at this too...

http://www.vw-resource.com/vanes_thermostat.html" onclick="window.open(this.href);return false;

Probably some of the most convincing arguments yet!

 

[Tofufi]

drive in winter????? :lol:

Mine gets used all year round, in all weathers

If your flaps might seize shut due to corrosion, you're not driving it enough

 

[Shorty]

Touché

 

[Tofufi]

Touché

On a slightly more serious note, the thermostat will always fail open because...

It is a sealed unit, filled with a liquid which boils (and therefore expands significantly) at a set temperature.

The most common failure is of the thermostat (where it fatigues or punctures, causing it to become not sealed) rather than a failure of the flaps. When it does this, it will expand of its own accord. In addition, the spring on the flap arrangement can easily pull it open if help is required.

It isn't common, but if you are that worried about the flap mechanism failing, it'd be very easy to grease it when fitting, and then lubricate the flaps with every service.

You can read more on it thermostat construction:

http://www.ratwell.com/technical/Thermostats.html" onclick="window.open(this.href);return false;

 

[Shorty]

I'd just like to thank you all for your contributions and help.. This forum never let's me down.. You're a great and knowledgable bunch!

 

[chippy]

Taken out years ago. I was going to put them back when the engine came out last but didnt find any so left out again.I agree about the air flow and warm up so refitted with quality parts would not be a bad idea. Ive had no problems without 25+mpg.

 

[Shorty]

Thanks for your help guys.. I'm gonna search around and find a kit to fit to my engine... As some have said, VW fitted them for a reason at the end of the day..

 

[vertecal]

Have a look here... http://www.awesomepowdercoat.com" onclick="window.open(this.href);return false;
They sell thermo assemblies already powdercoated.

Sent from my Nexus 4 using Tapatalk 2

 

[six]

Touché

On a slightly more serious note, the thermostat will always fail open because...

l

thought that the brazillian ones though fail closed?! the german ones fail open?

I think its worth noting thought that often cited with these debates is people say the reasoning that vw designed them for a purpose. This is correct no question there. However I so often then see them run on engines without heat exchangers. Again vw designed the engine to run the way it was designed. that means with heat exchangers too. When you remove heat exchangers and run jtubes, the heat from the exhaust causes the thermostat to prematurely open. reducing the benefit of these.

Thankfully again, Vw sorted this issue out with their industrial application engines with the shields, also on the trekkers.

therefore, if you are going to run a thermostat with jtubes then is it also wise to run the shields too to get the real benefit. the stock thermostat opens at 55-65 deg c ambient temp under the heads. i know from measuring the temp there without the shields, stainless jtubes just with flaps installed, that 60 degree air temp arrives alot sooner than it would be possible to heat that amount of metal, if stat, HE's etc were in place. and I did wonder how much benifit that just a stat and no shields would bring.

cheers