How does the thermostat work?

[froggy]

Was cleaning stuff up today ready for the engine rebuild and was hoping some one could shed some light on the thermostat. How does it work? It just looks like a metal coil with a long rod that goes between the barrels and fits onto the rear of the fan housing and connects to some flaps. But how does it actually work? Cant see how the rod is pulled to open the flaps allowing full cooling onto the engine. Is it worth re-fitting the thermostat, is there a way of propping open the flaps to allow full cooling all the time?

 

[Clarkson46]

It doesn't pull, it pushes. When it heats up the bellows expand and the rod is pushed upwards opening the flaps in the fan housing. Test it by dipping it in hot water and see if it expands.

 

[noddy]

Don't drop it in boiling water its designed to be fully open at 70C.

IMO it is worth having. I just refitted the full system to my engine which was missing when I bought the van. Now it seem to run much better more pull up hill etc.

Make sure the flaps are free (move without any resistance), also make sure the fail safe spring is fitted (item 22) to the connecting bar at the back (front of vehicle) fan housing, its a coil spring which connects the flat strap to the fan housing. If the thermostat fails this spring pulls the flaps open.

The classic hot rodding books I have recommend, even if you don,t use the thermostat leave the flaps in the fan house as the direct the air to the correct parts of the heads and barrels. In my professional opinion (Bentley engineer) VW engineers would not have fitted a system that cost the company money unless there was a good reason.

 

[ronmidg]

there is a topic somewhere (here or the ssvc) with an explanation, the bellows are made containing a drop of alcohol and then sealed, when this boils the bellows expand

 

[67 BAY]

Rather than the hot water method,you could use a hot air gun from about 12-18 inches.

 

[cyberdyne systems]

I tested a used one (the fact that the bellows are closed tells you its good anyhow) with a hair dryer, it was amazing to see it expand, and to see VW's simple yet effect method of speeding up engine warm up and heat regulation.

I'd deffinately install the thermostat, if it ever failed it would expand and open the flaps. But the main point is quicker warm up which equals less wear and better running.

Gareth

 

[matt-me]

Help needed on this front. Am getting to know my first bus and discovered yesterday that i do not have a thermostat, rod etc. Found a stud on the bottom of the casing but nothing attached. From noddy's helpful extract i would say i haven't got any of the lower right hand group of bits and maybe more.

On the fan tinware, i have a black vertical arm about two and a half inches long, which looks like it is the link to the flaps (but i can't pick it out on the extract) it is i think in the two o'clock position. Two questions, a) are the rest of the bits in this extract within the fan housing? b) if it is two o'clock position are the flaps open or closed?

When i move the arm to the left (approx two inches of travel) i can hear something moving on the left hand side within the tinware, so i am hoping it is all connected and working internally, just don't have the outer parts.

Once i know what i need i will try and locate parts needed

Also. if you're seeing this noddy i can't get all the number references on your extract, can you expand?
ta

 

[noddy]

Hi Matt

Th info you need can be obtained from this web site http://www.vagcat.com" onclick="window.open(this.href);return false;.

You need to register and then go to model type, and year. The data is broken down by area the cooling system is under the engine area. Any problems drop me a personal message.

If your at the back of your van looking to front the link bar on the fan intake side of the fan housings should be to the left to open the flaps, you should have item 22 in place this forces the flap link bar to open if th thermostat fails. If your flaps were closed you would get overheating very quickly i.e. 10 miles driving, quick test is, when you've been driving for a while (long enough to get engine hot) pull the dip stick out if you can hold the end without getting burnt your engine is running at about the correct temperature (will feal too hot after you have held it for about 8 seconds).

 

[mattp]

Hope this picture helps, this is a set up from a twin part engine. The single port engine have a longer connecting bar at the rear of the fanhousing and no links at either end [the links are the two pieces to the left of the thermostat. (this is for sale if you are interested)

 

[matt-me]

MattP, thanks, i am interested, these defo look to me to be the bits i need, how much are you after? i am only in Carshalton so easy to get to you to pick up. I await your reply. pm me if you prefer.

Noddy thanks also, will keep hold of this site details. All a great help a a prompt response. The other day i had thought things seemed v hot.

Al (sorry not matt, long story)

 

[noddy]

No problem Al.

What engine you got? are you still on the original oil bath air filter if so is it the type with two flaps on the intake one with a weight on and another in front that switches between warm air and cold air intake, see this link http://www.thesamba.com/vw/archives/manuals/stoermer/70ownmanpage52.jpg" onclick="window.open(this.href);return false;

If you have this warm air intake flap it defaults to warm air intake if not help open, late 1970 onwards the cable operated flap was replaced with an Independence thermostat see http://www.thesamba.com/vw/classifieds/detail.php?id=662665" onclick="window.open(this.href);return false;

This does contribute to engine getting overly hot as I found out on a motorway when bus started slowing down for no apparent reason. Also what distributor are you running and where is it timed 7.5 before tcd etc?

 

[matt-me]

Thanks noddy. The original air filter has just been removed as have gone down the twin carb route. Now running a SVDA dissy (had a 009 before), the best timing set up i have found is about 8.5 degrees btdc. I still have all the parts so will check what i may have had set up but i know the thermostat had long gone before i changed carbs. I am going to buy that set up from mattp and he has an engine set up so i can see how all the bits go together as still not sure how the bits in your extract/mattp's photo fit together. Hopfully all will become clear when i get the bits

 

[noddy]

Best way to set timing is at full advance which I think should be all in at 3200RPM absolute max advance should be 32 deg BTCD.

As for the cooling flaps, they are prity strait foward, bar that connects to the flaps needs to be fitted at the same time as the flaps so becomes part of you fan house assembly, joggel in bar at flap end is to back of van, use 4mm washer one side and push nut/star washer other side. Push rod goes down between cylinders hot down hole in the head (found this out when fitting mine) it needs a bit of a shove to get it through.

The arm that links the flaps is help on using eith some special clips or small spring which are the same as the ones which hold the heater and cooling system togeter under the dash, put a washer at the back of the link bar to stop it jamming the flaps, and then fit fail safe spring and you should be good to go.

Set thermostat cold, losen thermostat bracket from engine case, disconect thermostat from bracket, push themostat and bracket up till the flaps are fully open. Clap bracket to engine case, the bolt thermostat to bracket. You should end up with space between the top of the bracket and the thermostat.

Refitting the system to my stock 1600 SP made more difference than I expected to how the van performs. I suspect that with out any flap in the fan housing the cylinders and heads run with hot and cold spots. As before I refitted I was getting signs of valve guide wear on No 3 cylinder exhaust valve and the enging had only done 3K, also valves adjustment on not 3 and 4 kept being a problem, since I fitted the cooling and thermostatic system No3 and 4 have stayed in adjustment for the last 2K and no more problem with guide wear.

 

[matt-me]

Thanks for the help Noddy. Can you let me know how many of the componets (if any) should be within the fan housing itself? I am sort of hoping most of the items detailed are within my fan housing and i am missing the thermostat, bracket, rod and some other bits (ie bits external to the housing) only are missing and the rest are already withing my fan housing. As i said before i can see a lever which comes out of the fan housing which looks like it might be half of one of the levers shown in mattp's photo of bits, to the left hand side if the bellows unit. I can move this to the left and it seems to connect to other bits in the fan housing (when moving it to the left i can hear a noise on the left hand side within the casing). I suppose i am hoping someone has just not re-installed the bits external to the housing, including the above parts. Hope that makes sense and all will become clear when i see matt's bits and his engine. In the absence of getting all of this up and running if i temporarily hold this lever 'open' (ie to the left?) will this be better than leaving it closed? Am trying to get the last usage of the bus before i store it, and work on it, over the winter.

If the componenets are within the fan housing can i work on these with the engine in-site?

I should have said also that i believe the engine is a re-con engine but most other componets seem to be there. It was an oil filled air filter and will have a look at this tonight to see if it shows up any other clues.

Thanks again, much appreciated. Al

 

[noddy]

Al

The only thing which end up inside the fan housing are the flap assemblies and the thermostat connecting rob.

The link bar is on the front (blind side) of the fan housing also the spring clips and fail safe spring.

The rest is connected to the engine case i.e. thermostat bracket and thermostat.

You wont have a problem the engineering is about as simple as it gets.

 

[matt-me]

Noddy thanks for this. It took ages for it to dawn on me that everything i have been looking for was on the other (front) side of the engine. Still need the thermostat, rod and bracket, as far as i know. I can feel the other bits when i scrape my hand round to the front. When i pushed the straight metal bit, this lever i have been talking about at the back moves so it is connected in some way.

Am getting the bits from mattp, but then will have to decide when i go for the engine removal to hook everything up properly; as needed it would appear.

ta Al