'74 2.0 D-jet engine thermostat

[George Simmons]

Will damage be done if I continue to run with a broken one? How much trouble are they to replace? Any tips?

[3D914]

George,

I wouldn't suggest it. The thermostat controls the important cooling flaps. Without it your engine will run hotter, and will be prone to overheating - no water in this case, just plenty of melted metal.

When I rebuilt my 2.0 liter, I tested the existing thermo in boiling water - it failed. A replacement is pretty cheap insurance for longer engine life.

Forgot instructions:
First disconnect the thermostat wire from the linkage that spans the two flaps. It runs in front of the oil filler.
Then you'll have to remove the air guide plate that screws into the thermo's bracket.
Then disconnect the back of the thermo from its bracket. It should then slide out sideways. Remove the cable from the front of the thermo, and attach it to the new one.
Install in reverse. Make sure that the cable is tight when connecting the cable to the flap linkage.

My $.02

Regards,


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Gerard
74-914 2.0L
3D914
rodrigos6@juno.com

[This message has been edited by 3D914 (edited 10-22-2001).]

[JP Noonan]

The way I understood it the flaps fail in the OPEN position. So the motor takes longer to get to opperating temp (which does lower life span, especially in cold weather) but once there it opperates the same as if the thermostat was there.

If you live in Panama then don't worry, anywhere else you should fix it. The further north (or south after the equator) you live the sooner I would fix it.

[retro74]

Just fixed my wire and cleaned mine up too.

Is your wire broken?

I have a header and no warm air guides, but if you have the stock exhaust, remove the warm air guide on the driver's side. The thermostat is on the outer edge near the rear pushrod tubes. There are two 10mm nuts and washers to remove. I used my favorite tool, a micro rachet 1/4" drive for the task.

The wire is on a brass nut and the thermostat bellows is held in with a short bolt (probably 13mm). Mine was 100% cooked in oil and grease. I started with WD-40 and some rags. I noted which side the bolt was on and the orientation of the thermostat and then took out the 13mm bolt. More WD-40 and a small brass brush. Looks almost new now.

Y9ou can test it in the oven or with super hot water.

The wire to the flaps is twisted stainless steel cable. I used a bicycle deraleur cable (@ $1.50) with the small barrel end, but PP sells the real thing. Remove the brass cable retainer (10mm open ended) and replace the cable.

Cable goes through the opening of the thermostat mounting bracket around a pulley and up in to the engine compartment. I was able to use a coat hanger from the top and pull the cable up. Some people told me it is too thick, so a piece of wire or string might do the trick to fish it up (tape the wire to the fishing line...)

The flaps use a 7mm bolt. The flaps are spring loaded to the open (cooling) position by default. So... With the engine cold and the thermostat cold, the wire pulls the flap spring closed. Therefore, you should take a medium screwdriver against the hinge and gently hold the flaps closed while you pull hard and tighten the cable. You won't get it 100% tight, but you will get it tight. You can also leave the brass cable nut loose at the thermostat and then tighten it after you pull the cable tight from the top. I left 1.5" of cable hanging out. Some shrink wrap will keep it from cutting you when your done.

As the car heats up, the thermostat bellows will expand, while being pulled by the spring pressure and weight of the flaps. This will allow more air to cool the now warmed motor.

Good Luck

Joe

[pbanders]

Like others said, they generally fail open with a broken wire. If it is left inoperative, the engine heats up slower, which increases emissions and fuel usage. Oil pressure is also higher, leaving the bypass circuit on longer. I'd recommend fixing it

Brad Anders

[T4 Motornut]

George & respondees:
Best of luck locating genuine replacements - the word is that the supplier of such things has bellied up and the T4 thermostats are NLA. Buy 'em up if you can find 'em - my favorite VW/Porsche FLAPS guy had one last one on his shelf, and HIS supplier wanted around $50 for the last one in the warehouse...
Just on GP, I had stockpiled a quite a few (over the years) in my travelling parts box, which due to an unfortunate turn of events, was stolen out of my Westy down in Mexico - moment of silence, please.
On the bright side, I hear told that Type 1 FI-motor thermostats can be used if you twist/unthread the extension rod (?) piece and thread your cable into it. I haven't had the nerve to try it out yet, but may have to when the last of my T4 stock runs out...

[3D914]

Guys,

I hate to be contrary, but if he has the thermo installed, the cold position is with flaps CLOSED. When the thermo expands at 160? degrees (I forget the exact number), the flaps are opened to increase air flow over cylinders.

When you refer to the failed position, you mean without the thermo connected and the wire is loose - in which case you are correct (since the spring on the linkage forces them open).

Please correct me if I'm wrong.

Regards,



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Gerard
74-914 2.0L
3D914
rodrigos6@juno.com

[SteveStromberg]

I can Supply New Thermostats and related parts. Steve

[norustscott]

True. T-stat failure, It fails to open when heated, the flaps will remain closed. You would have to disconnect the cable to release the flaps to the open position.

Should the cable break or come loose, the flaps would spring to the open position.

[914GOD]

I disagree....that is a fail-safe item. It fails by allowing the flaps to open! Also, if the cable breaks that is also fail-safe.

By the way, Steve, how much do you want for a good stat?

Sean

[JP Noonan]

All the broken ones I've seen (not a lot mind you, maybe 4-5) are permanently expanded.

If one was fail to expand and stay coiled then you are right the flaps would stay closed overheating the motor.

[vw@micron.net]

Originally posted by JP Noonan:
All the broken ones I've seen (not a lot mind you, maybe 4-5) are permanently expanded.

If one was fail to expand and stay coiled then you are right the flaps would stay closed overheating the motor.

AND if the motor overheats, the Tstat always ends up expanding into a big long noodle
The springs in the flaps and the above point make the system fail safe.

My 76 2 liter had a broken T stat cable. 5 minutes and a second pair of hands to help guide the cable up through the hole, and all was well.

Steve

[3D914]

I guess I'll be the odd man out, JP.

When I inspected and tore down my engine (after running far to close to the temp gauge redline), my thermo was locked in the closed position. Even the boiling test mentioned previously failed to open it.

Consequently the flaps were always closed, resulting in a quick warm up and potential meltdown. So much for fail-safe systems!

Regards,


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Gerard
74-914 2.0L
3D914
rodrigos6@juno.com

[George Simmons]

Thanks for all the responses. I feel sure that the flaps have failed to the open position as you guys say they should. I was afraid that the thermostat was somehow tied to an adjustment which would make the engine run rich until it warms up. Or maybe it does?! Does it?

Thanks, George

[Bleyseng]

No they are not hooked to anything to make the car run rich. All they do is shut down the air flow when cold to speed up warming of the engine to operating tempature.
The AAR valve controls the idle speed when cold, it bleeds air into the system to boost the idle.
Geoff

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76 914 2.0L