okay so to add to this thread.

yesterday I wanted to check the fan circuit, I had no test meter or even a light so heres what i did.

I'd like to mention its possible to run this with the fan still in the car, but I though my dad tested this and he said it was bad so I just went ahead and took it out.

I removed the temp sensor wires and plugged them together, this eliminates the temp sensor, so if it works rigged this way and doesn't when u plug it back in and run the car, you know the temp sensor is the problem.

attached a wire to the fan and ran it to a ground, if its still in the car, just bolt the ground back down.

removed the inline fuse and plugged the fan straight in.

removed the relay, turned on the ignition, and started connected terminals 2 at a time with a wire.

it didn't work. Whats left? Check the fuse, it was blown. After replacing i managed to get the fan on in this manner.
I put the relay back on and tried again. Nothing. this told me it was the relay.

in the same circumstances, you could pretty much put different things on to see what the issue was. The inline fuse for example, wasn't blown but i thought maybe something about the springloaded setup was faulty.

basically you want to hardwire the entire fan system and then add pieces in one at a time until it doesn't work. Thats your problem.


also, if you live in a hot environment where you don't have to ever worry about the car heating up its REALLY easy to set the fan up to run when the car is on. Just remove the relay and hardwire 85 to 30/51 and it will turn on with the ignition.


someone tell me if anything i said is totally stupid and im just lucky whatever it was worked, im really terrible with electronics haha.

 

Good.

That 41mm closed sounds like it "might" be e tad long when open. It looks like a 32mm throated stat, so will open 8mm, which equals 49mm approx, which will be TOO long.

Also at 41mm, those by-pass ports will be closed when COLD, and that is a NO NO, they MUST be open when the engine is cold, or other things will go haywire, TRUST ME.

I reckon the new stats you got are an incorrect crossreference to the Dayco DT18A I use, and suggested way back. Either the parts guys have got it wrong, or packaging is incorrect, but if your measurements are true/correct they are WRONG.

Your state that your old stats measured 35mm COLD, and that is what you are looking for, coz they should open to 43mm HOT, but I think you also said that the old stats did NOT open when boiled, so they are toast, but "correct length".

I will send you a PM of some "all time classics" have a look at some 1930's V16 etc cars, and the 1936 Cord, which is "front wheel drive". Nothing new in the car industry, especially if you remove the badge and actaully look at the "workings", it is all basically the same.

 

the new thermostat which ill post the numbers for later if someone runs across them at the store are about 39mm closed and 47 open.

for people who don't feel like converting here its about 1.5 inches closed and 1.9 open

 

maybe im not thinking about how this works properly...but when it heats up you want it to open and close off the bypass port right??

So as long as its not blocked cold and its blocked hot what makes a difference


hmmm....i guess if its was waaaay to big it couldn't open fully, and although the bypass is closed off the flow rate into the radiator is reduced compared to normal? but thats what the spring is for right, it should just keep compressing regardless...

 

Basically yes.

However the ratio of closing the port, versus the opening of flow MUST be considered. If the by-pass closes too soon, AND the flow to the radiator is not open enough, things will just go pear shaped. That is why I selected that stat, coz there is plenty of opening BEFORE the by-pass is 100% closed, and then there is the margin for additional opening as required, and the small spring will compress of course, BUT, only so far.

I still reckon those stats you got are too long, and YES they will close that port, but it will be very early in the proceedings, and I reckon that the small spring (and disc) dont have enough travel to allow the stat to get to correct opening position for 90c running temps, let alone a tad more for safety reasons. That disc will run out of travel and jam the stat, flow TO the radiator will be restricted, and, YES, the port will be closed, and the engine will get DAMN hot.

As I said, those "old" units are 35mm (according to your writings), with a 32mm throat (from the photo), and will open to 43mm, JUST RIGHT. Obviously they are toast. BUT correct spec, based on what I see, and what you say.

Maybe, and I mean MAYBE Jaguar have sorted this error, as it was 12 years ago I stumbled across it. I dont go anywhere near a dealer unless absolutely stuck in hole, so I do not have up to date info. Just that gut feeling that if those stats are TOO short that engine is going to be toast in a real hurry, and that is not why I run many V12's.

 

Oh boy, I suffered all this grief in 1976 ! the head pullers are a really good idea, do use loads of WD40 or something, and I always worked the head(s) up and down to break up the corrosion that develops in between the stud and the alloy head. You WILL need a tool to hold the camwheel when removed from the cam, and read up on how to retract the chain tensioner, another tool and some work to understand how it works. Good luck !!