More Info!
In the August 2019 JAGUAR WORLD Q &A is a question about a XJS starting to run hotter, the car had a refreshed radiator and newer water pump. The owner was requesting help, they turned to Craig Talbot of Canada to reply. After timing and fuel he stated that 42mm stats were required to insure the bypass was completely blocked so all the flow would go to the radiator. He tried eight different brands and none except the Gates opened that far, 43mm for that brand, all the others stoped at 38/39 mm which would allow for a 3/4mm gap to recycle hot water through the engine! In my test of the MOTORAD in boiling water it does only go to 38mm fully open. So to be sure that the bypass is closed the Gates is the only one that goes past 42mm.
Now it does not have the bigger opening like the MotoRad but all the flow should be directed to the radiator, So unless you make a piece like John to block the bypass it looks like only the Gates will actually assure it being blocked!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
62
Waaaay back in the day, didn’t these things come with a rubber seal wrapped around that disk? I guess that’d add a mm or two to its closing length. Or am I just imagining that? I swear it’s been too long…
Has anyone actually measured the depth to the bypass port? And where do we measure it from? The bottom of the thermostat flange, or the top of the thermostat flange?
I think in most cases, that is plenty of cooling. Maybe if you had a racing engine, would you need to insure 100% cooling.
Re-reading this, I retract my calculation. It was quite idiotic.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
64
That’s not a valid calculation. Being 4mm open is pretty much fully open. You don’t have to pull the disc all the way back to level with the thermostat mounting flange to be fully open.
Has anyone measured this and bothered reporting? Yes.
Have people acted on this by either putting a foot on their thermostats or a thicker base on the housing? Yes
Do any of you read the archives? No.
That includes the old photo albums… Oh does it?
Where do you suppose 42mm comes from?
Shall we start another thread titled "my gauge shows just past “N blah blah blah”?
That’s terrible logic.If the average thermostat moves about 8mm open to closed, then one which only goes far enough to be 4mm short leaves you a 50:50 split not the 92% of the way there, as you thought.
Even this is poor logic though, as the 50% to the bypass is a straight 6inches easy unobstructed route back to the engine, whilst the 50% to the radiator is several feet of travel before then going through a restriction - i.e.the radiator and then coming back. Put bluntly, not being able to close the bypass is massively throwing away potential radiator (and cooling fan) capacity and loading up the water flow bias towards the bypass.
If you look at my earlier post you will see the housing and the bypass port, I measured with that ruler, where I got the 1 5/8’s length you need for the plate to close the bypass. The MotoRad is not even to 1 1/2 so it has a gap, so did the stock one in the picture. A rubber seal would be nice if it closed the gap, but it would have to be thick. I agree that 3-4mm is a significant leak since it probably is under greater suction being so near the pump. I do not know who Craig Talbot is (are you on this site?) but he seemed to feel that completely closing the port is important.
I will put in the Gates and see what happens, although I got the 180f stats so it will not be a straight comparison.
Dan
Also I did do a search, saw nothing about the reach of the stats. Also Craig implied that the wax stats might loose some of their reach over time, maybe like the AAV going bad over time.
,
Paul,
No jiggle pin! will have to drill. I hope John will offer up a small production run so you can have the bigger opening and full range in the same stat!
Dan
I have used the Gates thermos also ordered from Rock Auto and drilled hole with great results both verified by needle and infrared gun.
Shortly thereafter out of my cat-like curiosity I changed them to the Motorad high flow as described above-John gave me the part number several months ago and I installed those.
I didn’t notice any thermal variance. If I had, I surely would have recorded it. I was careful to test during similar ambient temperatures.
They both worked well but now I have a nice month-old set of Gates thermostats I am trying to figure out what to do with lol.
so with one set you got complete bypass closure but maybe less flow, the other set better flow with incomplete bypass closure! I wonder if that balanced out? was the changes better than before?
Not sure how long you have been on this list.
Those of us who have been here for 30 or more years will tell you that there are no new questions or problems. Every question has been asked many times before, is some cases is slightly different contexts.
I have learned to be patient, to keep giving new list members the benefit of my experience, (the choice to accept of ignore is always up to them) because someday they will be in a position to pass on their collective knowledge.
BTW the search functions are rarely used, and this applies to virtually all discussion lists.
Don’t let that prevent you from contributing. (Smile)
3 Likes
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
73
That’s a hair over 41mm, so confirms the 42mm number.
I agree with that, even though if the upper 1/3 of the radiator is completely obstructed, the B bank thermostat opening fully would result in a complete halt to coolant flow in the B bank. I would hope that an owner had their radiator serviced before it got that far, when it was only partially obstructed.
Oh, yeah, I think that’s typical thermostat behavior.
John’s little extender is starting to look like a good idea. I’m thinking, though, that perhaps a better idea (other than buying Gates thermostats) might be to construct a seat on the bypass port that raises it perhaps 4mm, thereby allowing the use of commonly-available thermostats with jiggle pins off the shelf. Perhaps a press-in thing? John?
Marek already did that way before me I chose to mount a spacer on thermostat, because it was much easier to work on a thermostat then pressing a spacer into the housing on the car and I didn’t want to mess with removing the housing.
Dear Bernard,
I’m glad you are patient because I am about to chew your ear. It is of course your choice to accept or ignore what comes next.
I don’t wish to thread hijack but the archives are an important resource and simply churning old topics makes them more and more inaccessible to everyone without increasing the quality therein contained. People will then stop using them because they can’t easily find what they want. Eventually, the good and the great stop replying to topics because repeating one’s self isn’t a very useful way of spending one’s time and it simply isn’t interesting.
To say there are no new questions is just a load of absolute tosh. Not only have Jaguar released plenty of new models, with new engines and new electronics in the past 30 years, but the possibilities open to the end user have massively changed in that time. Thirty years ago, no one was 3D printing bits to repair your turn indicators, no one was remanufacturing s1 front lights for the concours community, no one was posting up datalogs of how the cooling system worked, nor making teflon valve stem seals for your engine or a myriad of rubber, plastic or replacement components for our cars. Nor was there a substantial membership producing the knowledge base of expertise that has become the archive. You will probably receive a notification of this via an iphone app and some people will use the same gadget to post pictures or videos in real time to help explain or diagnose what is going on with their cars now that the site has changed from an email distribution list to a graphics based website. Thirty years ago you probably couldn’t even get a shop manual as a pdf. I also confidently predict there will be new problems in thirty years time - perhaps people will ask what colour the cup holders should be on an I-pace as they want to enter it in a concours competition or why does the new Jaguar Teleport not work with these cheap crappy aftermarket Chinese flux capacitors…
As to not being sure how long someone has been on the list, you could just click on their icon and look at their statistics. I was most surprised when I looked.
I think I may just buy Gates thermostats and be done with it. I’m currently running 180F Motorad regular stats. My temps run 180F-195F city driving in 70F+ ambient temps.
New info…they creep up to 200F in 85F ambient temps.
I agree with Greg I was just going with the Gates and regular flow, but I did take one of the Motorads to my hardware store to see if there was a gasket or seal that might fit the blocking plate. Looking through the plumbing section, I came across a 1/2 inch copper female pipe adapter that looked promising. The tube just fits the bypass hole and the threaded section could be machined down.
This is how both looked when I was done, the tube was 1/4 inch for the bypass, and the extended part was 3/16th, and It still had a open passage. I used some high temp silicon to hold them in place and after three days of driving they seem to be OK. The MotoRad stats are 180f and my gauge does show that, no great change in the rad temp, but I feel that at least I am not recycling hot coolent to the pump and all the outflow must go to the radiator.
FYI, I am running 180F Motorad thermostats, and 190F/174F aux fan thermostat. Car runs between 180F - 200F.
Aux fan turns on at 200F, will bring it down to 185F before turning off. ONLY creeps up to 200F on hot days (85F) with stop and go traffic. Driving at 20-40 mph, temp is usually 180F-185F.
I chose to mount a spacer on thermostat, because it was much easier to work on a thermostat then pressing a spacer into the housing on the car and I didn’t want to mess with removing the housing.
