Pulled LHS thermostat while draining the coolant. It is 180F (says on it)

Did the boiling water test. I boiled the water but i did not observe any changes.

Here is how the thermostat looked like after boiling, which is the same as before boiling.

Is it currently in the closed position? And the fact that it did not "open" during boiling means it needs to go? Right?

 

That you observed no movement of the mechanism condemns the unit, yes.

I'm not sure if it's open or closed. A view from the top, through the opening where your string is attached, would be better.

I am wondering of it is physically broken. I *think* the parts have separated. See the section with the squared-off notches? I think the piece directly below those notches should be attached to it. Not sure. But, in any case, the thermostat needs replacing. I replace both. Get the correct ones. Some are not correct for a V12 even though the catalogs say otherwise. Several threads on the subject

Cheers
DD

 

Got it. I played with it and figured out how to open/close it manually.

Yes, it was closed and it remained closed while boiling. It is going to the trash. Currently testing the RHS one. But will likely replace both

So, this means I was driving with a ticking bomb then...

 

Nevermind. Just re-tested both. Both appear to be working: both open when above 180F

Phew...

Though I am not sure how wide the opening is supposed to be?

 

It is not so much how large the opening is, as the water is forced through it by the ater pump. More so that the rear disc covers the bypass hole inside the thermostat housing. If it does NOT block off the rear opening, then your cooling system isn't functioning correctly. Meaning the some of the hot water gets circulated around the engine again and again instead of it ALL going through the radiator.

 

I've never measured but I'd say that fully opened vs fully closed amounts to about .375" of travel, maybe a bit more.

Cheers
DD

 

I have to disagree.

Let's say the thermostat opens 50% and remains stuck in that position. You'd then have a smaller opening for the coolant to travel thru and less coolant reaching the radiator, despite the water pump's effort at pushing the coolant through the system. The engine might overheat.

Agreed !

Cheers
DD

 

I remember reading Greg's write up on thermostat fiasco.

Just measured distance to the outer disk in open position (while boiling). One showed 40.5" and another 39.7". So, not quite 41" Greg advocated.

I will go ahead and purchase new ones. (And test them before putting them in)

 

Stats open approx 8mm, or approx 25% of the diameter of the bore.

You need at LEAST 41mm when wide open, and 43mm is preferred, coz stats do NOT work at wide open, they constantly move as engine temps alter.

180 or whatever is the "crack" temp, whish means that's when the stat actually cracks the seat, and is wide open 12degC above that.


This I wrote a looooong time ago.

V12 thermostat fiasco explained.pdf

 

In case somebody is interested, here is how insides of t-stat housing look like. (I put the camera right against the opening)

By the way, what do people normally use as a sealant when installing a new gasket? I have a sealant for oil gaskets. Will it work for t-stat gasket, too? Or because t-stat comes in contact with coolant an not oil, a different type of sealant is needed?

 

I just the later black Jaguar gaskets. Steel core with a coating of something on them. Work really well and don't need retorquing. Kind of like mini Cometic headgaskets.

 

Sorry, What kind of "coating of something" you applied? Does it matter? Or it can be any sealant? (Including oil gasket sealant?)

 

The coating was on the steel core of the gasket. Factory applied to make a complete gasket. You don't have to do anything, just use them right out of the bag.

 

Another question about thermostats.

Kirby's book recommends to drill a small 1/8" hole in the flange if an aftermarket thermostat comes without a jiggle pin.

I got Stant super duty t-stats.

Do they have jiggle pins?

If not, where exactly is this small 1/8" hole supposed to be drilled? Does anybody have a picture of the hole?

 

Nearly all have a small hole somewhere. It should be at the top and in an area which is not covered by a gasket.

 

Does this one have it? (It's a stant replacement I got)

 

Nope.

Drill a 3/32 hole smack thru the "S" of USA, all done.

Make sure the hole is at 12 o'clock when installed, drink BEER, lots of it.

 

Thanks. And the idea behind this hole?

So that small amount of coolant can sip through and go to radiator even when engine is cold? Bu't why does it matter? Or, put differently, what could go wrong if there is no hole?

 

The hole, with or without the jiggle pin, is to help prevent air locks

Cheers
DD

 

As stated here thousands of times.

If ya dont get the air out of a V12 and allow a passage for it at all times, it WILL overheat, and ruin your bank balance.

That hole, jiggle pun, whatever at 12 o'clock is coz air is at the top of any area, usually, and it will simply slide thru that hole, out via the not so simple air bleed system, and allow proper operation of the stat. Air behind the stat, in enough volume, will prevent the stat from opening, as it only works in liguid.

Also, air pockets that become steam pockets, are very destructive. The V12 does get these pockets around #5 & 6 cylinders on both sides if bleeding is not done properly, and the air bleed system is not maintained.