I am in process of replacing leaky seals (#4) while the harmonic balancer is being rebuilt by Dale's. I haven't removed anything yet, but it looks a little easier to remove the water pipe/thermostat housing (#1) in order to slide out the pipe and seals. Are there coolant passages under the mountings of the pipe, with gaskets (#17) in between? The drawing shows one under the manifold (#10), but the Service Manual says there are two gaskets (#17) needed for this assembly. Not one, or three, but two.


The right-hand diagram doesn't really clear this up. Again the Service Manual states that two gaskets (#16) are needed here, but doesn't show the placement of the gaskets.


New coolant hoses will be installed during this repair. I want to make sure I get to everything while it's dry. Thanks all, for your V12 expertise.

 

There are 8 of those gaskets per engine, so 2 per housing.

The bolts that secure those housings to the head are well known to BREAK, so be prepared for some drilling and so on.

If you dont break any, DRINK HEAPS, she will bite you somewhere else, FOR SURE.

 

I just got done doing mine. Four gaskets per side, two in the front two in the rear. Be careful when removing the bolts one of my ftont one snapped off when remove it. I found the front ones were more rusted the the rear ones. The last front bolt I didnt want to mess with fearing it too would snapp, got some advice from other Jag oweners to spray it with penatrating oil for a couple of days than used a impact gun on it at the lowest setting, worked well. The bolt was very rusted. I replaced all of my bolts. Trying to find the torque specs for these bolts

 

You have parts at the rear in those pics l have never seen on any of my V12's. What model variant are the pics for and what year is your car?
As others have said there is normally 4 gaskets required each side for the water rail assembly but the setup you show may well require 2 per side for the front casting and a totally different gasket for whatever it is pictured at the rear.

 

I replaced those #3 seals a while back. They were so hard and cracked don't know how the weren't leaking. I also replaced the two water rails,#2 with stainless pipe from McMaster-Carr (3/4" ?I THINK?). Also had a machine shop weld 1/2" bungs in the SS rails for temp gauge sensor's, one for each gauge. Yes I now have three temp gauges......necessary, probably not.

 

Thank you for the replies. Sorry for the confusion, I didn't realize the 6.0 in the XJ12 has a different setup along the water rails than the 6.0 XJS, as well as the 5.3.

The XJ12 6.0 does not have water rail connections at the rear of the block. The front rails and thermostat housings are "similar" to a degree and use the same sealing bush on the pipes. I will get some of those gaskets (all EBC9634). On my 6.0 the water pipe comes from the "idle speed control manifold," which apparently has a gasket under it (shown by #17 above) where the assembly mounts to the head. It is nearly underneath the main intake runners, but it would probably be worth the extra effort to replace those gaskets if I can. Hoses #20 and #22 feed the idle speed air into the intake manifold.

I will use great caution when removing the bolts, thank you for that warning! Updates to follow.

 

What do you know, there is a coolant outlet in the head above each exhaust port. In the 5.3, the middle two are blanked off (#14) and have a gasket EBC9634 (#15) under each plate. Maybe you did know, but I didn't!

The 6.0 XJ12 has the first three outlets in use: first two for water rail/thermostat housing, the third for the heated idle speed control manifold, with about a 3" pipe connecting them. Left side, the last outlet is a heater matrix take-off port.

Point being that there are six of these gaskets on each side of the engine on both the 5.3 and the 6.0. Good fortune would never require attention to the gaskets on the blanking plates.

Which brings up another question. Is it really a good idea for cooling's sake to have some of those passages blanked off? Ok, I suppose there is a goodly amount of heat exchange and flow characteristics study that went into the design. I'm sure the engineers knew what they were doing. But it seems odd that on the 6.0, the rear three on each side would be blanked.

I found that Uro makes the replacement bushings and Eurospare makes the gaskets. They are pricey for what they are, but need outweighs cost. It is not possible for me to get these items locally, so off to the internet! Available on Ebay, amongst other sites.

Good news, all the bolts came loose with little to no fuss, under the "least amount of gentle force" that I could apply to accomplish it. The bolts are in very good condition too. That's a relief!

 

The V12 version in the E Type used all the water ports in the head. Racers also use them, regardless of the version. A famous Australian specialist called Norman Lutz (Warrjon knows him well) has a modification for the HE 5.3 engine, whereby water is forced preferentially towards the rear of the engine by reducing on size the front water manifold exit holes. This is to help prevent water "short-circuiting" from the pump straight out of the front of the heads through the front water manifold. called the "Lutz mod" quite a few of us have done it. As (as you indicated) Jaguar did away with the rear manifold outlets on the 6 litre versions, how much of a problem in real life road use the OEM water path is, I have no idea.
Having said all that, Roger Bywater of AJ6 Engineering is pretty sceptical it matters at all! This is what my front water manifolds looked like having done the mod. It certainly does something, because afterwards, the temperature gauge read noticeably higher, which seemed to indicate that hotter water from the rear of the engine was indeed being forced more to the front.

 

I did the "Lutz Mod" also. Yours looks very professional, I just made the aluminum spacers with holes way. The only thing I changed was the size of the 1/8" hole in the front. I believe I made it 3/16. Thoughts were "1/8 was a little too restrictive". don't really think that 1/16 bigger hole matters though.

 

Good thread! Wondering if anyone has advice on best installation method for new seals - my pipes are in great condition, and I have the 4 x URO C37990 seals. I was thinking just soapy water as a lubricant for installation. Any other thoughts? Thanks!

 

I put a smear of high temp silicone round the outside of the seal.