I bought some from Jaguar Heritage recently, they supplied EBC3576, waxstat branded 82 degrees C. Closed distance measured with calipers between the 2 discs is 34mm. Are these the correct size?

 

Grant produced a document about incorrectly dimensioned v12 thermostat.

He stated correct size 54mm diameter thermostat, which was 35mm "closed", and 43mm "open"

 

I just got two '3576' thermostats as well, in Jaguar packaging, Waxstat brand. These were 31mm closed and 43mm open

On my car the distance from the thermostat mounting face to the face of the bypass hole is 41 mm.

So with the thermostat fully open, the rear disc should indeed close off the bypass port.

Cheers
DD

 

Indeed Doug, I have quoted Grant's really useful explanation of Jaguar V12 thermostat problem below.


V12 thermostat fiasco explained

This is my findings, AND the solution to temperature gauge "floating syndrome", that many people are frustrated by.

Remove both your thermostats.

Note the by-pass disc on the bottom, THIS IS THE MOST IMPORTANT PART OF THE THERMOSTAT.

Look up inside the housing you just removed the thermostat from, and note the ‘spigot hole" that is facing you. This is the by-pass port, and its face is prone to pitting. I have never seen a pitted one, but check it anyway.

Now comes the fun bit.

Measure the distance from the mounting face to that spigot face. It will be approx 41mm.

Test your thermostats, boil them, use a heat gun, whatever, you are going to replace them anyway, but do this just to humour yourself. My old units, Jaguar brand, only opened 39mm, YOU SURE, hell yes. Did it too many times, 39mm flat out. Now this is 2 mm at least too short to close that by-pass port 100%, and that port needs to be closed 100% for the cooling system to work anywhere near correctly.

Just to clarify what a thermostat does, I know, you know all this stuff, but just humour me for a few lines, PLEASE.

The thermostat has an opening temp, and a fully open temp, now anywhere in between these 2 temps is where the thermostat is constantly operating, it is constantly opening and closing, it is never satisfied, so in real terms, IT WORKS BLOODY HARD, and it wears out.

Just to clear up another "story" that persists out in mechanic land, the opening temp of a thermostat is in fact its "crack temperature", meaning that is the temp at which the thermostat actually STARTS to open, commonly known as the "crack temp", and the thermostat is "fully open" 12degC above that. So an 82c stat will crack open at 82c, and be fully open at 94c, follow, good, it is simple. Now if your cooling system does not do as it should, the engine temp can get above 94c, which causes the stat to "fully open" and stay there, IT HAS NOW LOST CONTROL OF THE COOLING SYSTEM, and overheating is just up the road.

Further to that, the radiator is expected to lower the temp of the fluid by approx 12-15c, so the bottom hose temp is about 80c +/-, and that is why the temp switch on the HE in the bottom hose housing is set at 85c, and brings on the auxillary fan to assist cooling the beast down. Bottom hose sensing is way more accurate than top hose sensing.

The thermostat/s are constantly opening and closing to keep the cooling system at a happy medium, which is usually around 90c +/-, and does a good job at it, BUT, yes there is a BUT, that by-pass port MUST be closed, or else about 30% of the coolant NEVER sees the radiator, do the maths, simple as.

I purchased 2 new Jaguar units, same thing, too short. I was employed as the Spare parts manager for a Jaguar dealer at the time, and raised this with Jaguar Australia. No idea was the response, maybe there is something wrong with your car, politician in the making hahaha. NO, this is the case with 5 cars I have at my disposal, so I reckon Jaguar have messed up somewhere.

I never got an answer, gave up, retired from the dealer.

I searched on my own brain cells, and found a Tridon cooling system catalogue, very informative, and found in their listings a 54mm diameter thermostat, which was 35mm "closed", and 43mm "open", perfect.

This is a Tridon No is TT228-180, Dayco No is DT18A, and fits Ford cars down here and some others. I have used this thermostat now in some 12 odd V12's, both Pre HE, and HE, and the cooling system is so well behaved it is downright scary, and I mean that seriously.

NOTATION 31/8/2015: The Dayco website NOW lists this DT18A as the correct thermostat for the V12 engines. Maybe my emails finally got read, who knows.

I replace all my Jaguar thermostats every 3-5 years, coz as I said, they do work hard, they are cheap, and engines are NOT.

 

My one cent

 

looks like more coolant flow, with the brass colored one at 32MM. cant see the blockoff plate tho?

as long as it opens enough , any measure for that spec, relative to each other?

Ron

 

cant determine which is what size from your photo. Waxstat on left? Looks to be 25.5mm? Unknown brand on right? Could be 24.5mm? Can you clarify sizes and brands?

I know stant offers high flow versions of this stat. I've never seen any specs though.

 

i have used the Stant HI flow on many GM cars, but have never seen one with the important blockoff plate!

that is needed for jag cooling system.

but in place of that option , i drill some flow holes on side of Stant/GM Hiflow, and plug off the bypass hole,works great in moderate to hot climates!

donno how good in super cold climates,,(dont want to find out ethier).lol.

Yes ,i'm always modifying something!

 

I have read all the write ups on this subject with intrigue. I didn't realise all the implications of not getting the correct stats or how the system worked. Great info from grant and lots of others . I am a bit confused however and can anyone tell me what to buy in the U.K. For an 89 5.3 as it appears jaguar can't be trusted on this one. Also would this part need drilling and if so where etc? Many thanks for any help and all contributors to this thread.

 

There is a little foot on the thermostat that blocks off the bypass ports. It's important than this foot extends far enough out to seal off the port, it appears that some thermostats stop short, so the port is never covered.

So no drilling, just making sure the foot part is long enough.

 

Full opening is 41mm. See also: https://www.jaguarforums.com/forum/x...ing-v12-99400/

 

That maybe superior in diameter but I'm not sure I like the jiggle pin being that far inward, nor do I like 41 mm opening. We have seen 43mm regularly, allowing definite closing which is relieved a bit by the spring. Don't forget there isn't necessarily anything desirable about a higher flow rate. Recall that removing a Tstat altogether is ineffective, as the coolant doesn't have enough time to transfer heat.

My EBC Jaguar stats are also Waxstats made in England with a 34mm depth closed. I also recall the figures 43mm and 41mm when I last tested to ensure the replacement would work.

 

Thanks for the info. Is 41 mm ok or 43 mm better?

 

Can you suggest a U.K. Replacement? At the risk of sounding daft are both sides the same? Cheers

 

Brinny
Buy them from David Manners, their aftermarket ones. They will be fine and they are cheap, I recently helped a friend fit a couple.

 

Another thermostat related question - when squeezing one of the main hoses going to the radiator with the cap off are you supposed to hear a metal clinking noise from somewhere inside? Can someone go try and let me know before I resume my anxiety attack.

 

Yes, that should be the jiggle pins in the thermostats moving.

 

NORMAL.

That would be the jigle pin "jiggling".

Have a drink, a BIG one, your Jag it fit and well.

 

 

The "coolant moving too fast to absorb heat" thing has been debated for years. I've read some opinions, fairly convincing, that suggest it's a myth....but the study of thermodynamics is way beyond my pay grade so I can't really judge. It's pretty easy to express opinion as fact and sound convincing to the ill-informed

Cheers
DD