914 2.0 cooling question, Any potential downside to this proposed modification? Options

[parrish911]

I have a '73 2.0 that is primarily used for auto-x with occasional weekend drives. I live in Tampa, FL. There is a copper bellows type thermostat that is used to control a flapper valve that routes cooling air. The bellows expands with heat and gradually opens the flapper valve, directing more air to the cylinders.

My question, is there any downside to bypassing the bellows and leaving the flapper valve in the always open position? I don't really deal with 'cold' weather and I am not convinced there is any benefit to having this on the engine, given how I am using the car.

I would welcome your thoughts on this.

Thanks,

Steve

[bandjoey]

I don't think it matters in hot weather. I keep mine open in Texas from March to October. Open in cold weather it just slows down the warmup.

[parrish911]

Thanks Bill. I was thinking the same thing. Plus, I am a big believer in the simpler I make the car, the less things there are to malfunction.

Steve

[nathansnathan]

Without the thermostat, the engine will take a long time to warm up. My work is 12 miles away freeway driving. With the flaps open, water in the oil will not burn off. You will see a frothy sludge in your filler cap.

[Bleyseng]

Leave it in as it speeds warmup as VW/Porsche had a real reason to do this.

[Drums66]

.....Modus Operandi! (IMG:style_emoticons/default/idea.gif)
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[Rand]

Yes, as said, it means slower warmup. Would you remove the thermostat from every other daily driver that shipped with it from the factory? Is there a reason it's a good idea that every car comes with a thermostat?

I guess I should fix mine some day. (IMG:style_emoticons/default/biggrin.gif)

[SirAndy]

Without the thermostat, the engine will take a long time to warm up. My work is 12 miles away freeway driving. With the flaps open, water in the oil will not burn off. You will see a frothy sludge in your filler cap.

(IMG:style_emoticons/default/agree.gif)

I ran my 2056 without the thermostat here in MidCal and i had the same problem since most of my driving are rather short trips (less than 20 miles).

Not enough heat in the engine to boil off the water in the oil and massive sludge buildup on the filler cap and neck.

If you stay on top of this and clean off the sludge often (really messy affair) you might be OK.

But what do you think is the downside of running the thermostat? (IMG:style_emoticons/default/confused24.gif)
It only helps warming up the engine to normal operating temp, after that, the flaps are fully opened anyways.
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[Rand]

But what do you think is the downside of running the thermostat? (IMG:style_emoticons/default/confused24.gif)
It only helps warming up the engine to normal operating temp, after that, the flaps are fully opened anyways.
(IMG:style_emoticons/default/popcorn[1].gif)

I'm curious about a response to this too. Is your thermostat functioning? If so, why would you want to remove it? It's not complicated or heavy.

And to answer your specific question, there is absolutely a downside to removing it and I hope you will be convinced there is a benefit to keeping it.

[parrish911]

Wow, thanks for all the responses. I will try to answer the questions posed. My concern with the thermostat was @ 40 yrs old it may not be fully functional and is really not needed here in Florida. I did not think about cooking off the water in the oil. I did test the thermostat in water and it does appear to function. I measured a heated length of 46mm @ 155 F (I found this test in the Porsche shop manual).

Dumb question: is this thermostat present in all 914/4 engines?

Bill Andrews, have you seen the oil/water sludge with your 914 during Texas summers?

Again, I really appreciate all the responses. As everything appears to be functional, I think I will lube everything up (flap hinges & cable pulley) and reattach it.

Steve

[Dave_Darling]

The thermostat is present in all 914-4 engines as they were delivered from the factory. A number of people decided that the cooling flaps were not needed, nor was the thermostat.

Removing the cooling flaps, interestingly, tends to lead to hot running.

--DD

[Cap'n Krusty]

The failure mode of the thermostat would be in the fully open (running) mode. The coil spring on the flap rod holds the flaps where you want them to be, in the default position.

The Cap'n

[Elliot Cannon]

My thermostat/bellows have been removed since the engine was built by FAT Performance about 25,000 miles ago. It's not a daily driver, takes awhile to warm up but that has never been a concern for me. Having said that, your engine undergoes much more wear prior to operating temperature when cold, than it does when finally at operating temp. The sooner you can get the engine to operating temperature the better.

[mrholland2]

My engine installing mechanic installed the flaps in the always open mode. I drive 5.63 miles a day each way to work, which takes me about 20 or more minutes. It is nearly time for an oil change and no sludge . . frothy or otherwise.

The concern wasn't the thermostat as much as it was the mechanics of the flapper device/rods/springs going kerflooey and sticking shut.

Sean

[bandjoey]

My daily drive is 30 miles each way. I don't have sludge but probably due to distance driven every time I start the motor

[SirAndy]

The concern wasn't the thermostat as much as it was the mechanics of the flapper device/rods/springs going kerflooey and sticking shut.

They can't get stuck closed. Their failure mode is wide open for max. cooling.
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[Dave_Darling]

Oh yes, they can get stuck closed! Trust me on this. If the linkage binds up, they can stick in any position, including closed.

--DD

[SirAndy]

Oh yes, they can get stuck closed! Trust me on this. If the linkage binds up, they can stick in any position, including closed.

Have you seen the spring on that thing?

One would have to seriously go at the linkage with a BFH (IMG:style_emoticons/default/smash.gif) to get it to bind.
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[ww914]

The failure mode of the thermostat would be in the fully open (running) mode. The coil spring on the flap rod holds the flaps where you want them to be, in the default position.

The Cap'n

Cap'n

Are you saying that the default position is holding the flaps wide open? I could be wrong but it seems that the spring holds the flaps closed and the thermostat, when working, opens them up. I have CHT gauges on all 4 cylinders, and with full tension on the wire, the cylinders show much lower temperatures. I wished I would have taken a closer look at it when I had it apart.

[Dave_Darling]

Have you seen the spring on that thing?

One would have to seriously go at the linkage with a BFH (IMG:style_emoticons/default/smash.gif) to get it to bind.
(IMG:style_emoticons/default/shades.gif)

Yes, I have seen it. And no, it doesn't require a BFH to get it to bind.



The spring moves the flaps to the "maximum cooling" position, the thermostat pulls them into the "warm the engine up" position. The failure mode is almost always to go to max cooling.

--DD