Reading this thread:

https://www.jaguarforums.com/forum/x...xhaust-236114/

I felt terrible for the poster, and how disheartening it must have been for him. I was also filled with a sense of dread.

I'm lucky that I didn't suffer his fate, and I must confess that I have been a bad V12 custodian. I didn't replace the heater hoses when I last pulled the radiator for re-coring and replaced ALL the other hoses and belts. Not intentionally, but there so many other tasks like new fan, clutch, etc and other things on the "list" of must dos that I guess I just didn't pay attention to the back of the engine or if I did, they look so hard to get to that I could have thought 'yeah maybe later'. Today, I look at them and I'm still not sure how replace that lower one.

Even worse, my thermostats were put in at Browns Lane and haven't been touched since. When I actually thought about them back when I had the cooling system apart, I couldn't find a replacement that had both the proper dimensions (per the Wizard Down Under) and jiggle pins. I must have taken the 'if it ain't broke' path rather than risk putting in the wrong kind.

Well... I guess I should stop mucking about, and get to it. I've been researching thermostats trying to find what Grant recommended, and almost gave up and was just going to order either the Tridon TT228-180 or the Dayco DT18A from Australia to be certain. I did some more digging and noticed that Dayco was also listed for the early 80s Mazda RX7. Which led me to several models of MotoRad units and I discovered some interesting innovations. One is a high flow thermostat that increases flow by 50%. The other is Fail Safe thermostat. Apparently, in an overheating situation the higher heat can cause standard thermostats to fail, and they fail in a 'closed' position which is the last thing anyone needs if the engine is already hot under the collar. These Fail Safe units have an additional bit that locks it into a wide open position.

I think each of these fit Grant's specifications, but I'd appreciate if he could confirm:

https://motorad.com/motorad-catalog/.../?pid=2028-180

https://motorad.com/motorad-catalog/.../?pid=7228-180

Also what does the collective wisdom think is a better trade off, High Flow or Fail Safe? One XJS specialist parts supplier sells and recommends 77C thermostats and claims they run cooler, but I'm not sure you really want the V12 running below target temp. What do the experts think -- 77C, 82C, or 88C?

Thanks

 

I say 82 degrees. See post 2 in this thread:
https://www.jaguarforums.com/forum/x...ywhere-213647/

 

I agree with Greg. 77C is for the Carby V12.

Hi-flow/standard, mmmmm.

Tridon here have Hi Flow. I tried one a loooong time ago in the S2 XJ6 (same arrangement as the V12 only one stat), and had issues. removed it and fitted a standard flow, and all good. My understanding, from years in Truck Coolling, is the liquid can flow through the radiator TOO quickly, and not have sufficient time to be cooled.

Likened to the "mechanics" that remove a stat, and then claim the engine runs cooler. YES, because the radiator is blocked to a point that WITH a stat the flow is too slow, and without a stat that flow is where it is needed to be cooled. Remove that blockage, the engine runs too hot without a stat, fact.

The Failsafe are a good idea. Their claim to fame is failing wide open, GOOD, as apposed to a standard stat the generally fails shut, or partway, and the engine quickly melts from the inside out. I have never used them, see no need, and I have never had a stat fail anyway. Remember, stats are ALWAYS moving, that is how they keep that optimum temp inside the engine.

Jiggle pin, NO jiggle pin, its your car. I have never been pedantic about it

BUT

There MUST be a bleed hole, AND that bleed hole MUST be at the 12 O'clock position when installed.
The stats I used back in the day with Jiggle Pins RATTLED, and YES, all my V12's were silent, apart from the Injector clicking.
If the stat I get has a Jiggle Pin, I simply cut it off, and install with the hole as mentioned. If NO hole, I drill one, and install as mentioned, simple.

Hope that helps somewhat.

 

I have used Gates 33188S with no problems. I did quite a bit of searching and I could either find thermostats with a jiggle pin, but the incorrect foot length, or those with the correct foot length and no pin. I opted for the correct length and drilled a small bleed hole.

Replacing dealer supplied Waxstat thermostats ( with the wrong foot length) with eh Gates produced noticeably lower running temps, even though both were rated for the same temperature. I think it was simply because the bypass was being closed as deigned and all the water was actually going through the radiator. It was particularity apparent in hot weather with the AC on.

I bought mine at Rockauto,com and they were not expensive.

 

Thanks, it looks like the measurement specs are identical between the Gates 33188S and the MotoRad 7228-180, and they are both listed for mid '80's Jaguar XJ6s (makes sense that cash strapped Jaguar might use the same 'stat in the 5.3 V12 that it did in the 4.2 six). The MotoRad comes with the jiggle pin air valve, and was the only one I could find that did.

I wonder if the difference between the correct spec older style 'stat and the current ones that people have found don't completely close the bypass isn't actually an intentional engineering change. Here's my theory, in response to increasing EPA or CARB restrictions, they changed the 'stats to slightly increase the running temperature to increase gas mileage. It would be the cheapest and fastest way to eke about a little better MPG.

 

Besides the rattle, is there any actual advantage to the Jiggle Pin? For instance does it help overcome water tension to help air vent?

When I have the 'stats out will the 12 O'clock position be obvious?

Thanks

 

Jaguar did use the same thermostat for the V12's and 4.2 6 cylinder. Jaguar wouldn't have jury rigged the spacing of the bypass foot to control the water temperature, they would have specified a different temperature wax capsule in the thermostat. As they did actually, as thermostats increased in temperature from 74 in the 60's to 82 then 88 for the Series III XJ6.

The 12 o clock position simply means to have the jiggle pin or bleed hole at the top when you install the thermostat, to let any air bubbles past. The air rises, so the hole needs to be at the highest point when the thermostat is installed.

I don't see a jiggle pin in the photos of the Motorad, and the spec says it doesn't have one: https://www.rockauto.com/en/moreinfo...483806&jsn=255

 

This is from the actual MotoRad catalog: https://motorad.com/motorad-catalog/.../?pid=7228-180

 

Except we know that actual Jaguar part number units had the different spacing IIRC. I could see a scenario where a jump to a higher temp 'stat might be too high temp increase, but allowing wide open flow to the radiator with some bleed off to the bypass might get the normal running increase they were looking for. It could just be a bureaucratic part numbering error of course, but this wouldn't be the first time that Jaguar Engineering found a convenient bodge to solve something.

 

In the description underneath though it says: "Jiggle pin weep hole: No"

 

Good catch! I guess only the high flow version has the Jiggle Pin.

 

I ordered the Gates 33188S thermostats and they just arrived. It looks like, contrary to the specs on the Gates website, that it does have a jiggle pin/check valve. The dimensions appear to be correct.

See photos

Should I snip off the jiggle pin or leave it?

I'm going to do the heater hoses and thermostats this weekend, any tips or advice on doing the heater hoses? It's so tight back there.

Thanks

 

Just leave them in place. They are ready to install.

Interesting that they have the pins, the ones I ordered did not.

 

I'm trying to start this job, but OMG how do you even get to the lower heater hose on the LH side?

Any help is appreciated.

 

Bueller? Bueller? Anyone?

I'd really appreciate a clue here.

Do I have to remove the throttle pedestal to get an angle and view to the LH heater valve hose clip? Anything else have to be removed?

 

Slowly remove everything that is in your way and put it all back together when done. Remove rods, cross pipe, throttle cable (don't move the set nuts too much at all and carefully move cable away) pull off rear most left hand FI plug and wire (I think I did) and the throttle stand is kind easy if need be, 4 10mm bolts... Sounds like a lot but it really ain't so bad. For me, it was all good because without having an exact way to say it, things were and still are pretty messy back there.

Make sure you position clamps so that the bolt/screw is facing in an orientation so that it can be accessed to tighten/loosen.

It might also help to unbolt the heater tap/valve from the fire wall once lots of that stuff is out of the way. Also, it enables ya to go around the car and get a hand on things from the RH side when it's needed,,, one leg sticking up in the air, reaching, lol... All fun and games til someone gets hurt, hahahaha...

 

Lots of patience. I was able to loosen the existing clamp at most 1/16th of a turn at a time. Then discovered the old hose had permanently bonded to the spigot. I ended up cutting parts of the hose off with a serrated bread knife. The new one went on easily.

 

Adding to:
Disconnect the battery, there are POWER studs real close by.
Balance pipe off
Use a flexible nut runner, and loosen the clamps
Reach in with a SHARP cutting knofe, and CAREFULLY slice the hose lengthways, and you are done.

That Flexible nut runner has saved my a&se so many times, and for $20, 30 years ago, well paid for.

 

Use a flexible nut runner, and loosen the clamps.......

so cool, never seen one of these before, I am going to order one, this looks like the right thing.
https://www.kctoolco.com/wera-028150...ut-driver-7mm/

Keep the updates coming - this is on my to do list!!!!
Watching someone do this job help understand what is needed, works for me.

 

I have one called a snakdriver. Has a hex end on it to fit various socket adapters or screwdriver bits. Has a small light on the end too. Similar to this one: