S1 vaccum lines to air filter box

Hi gang, I’m looking for a vacuum diagram that shows the correct connections of the lines to the air intake box. It has been a long time since have worked on the system and I can’t for the life of me remember the correct placement of the lines form the intact heat valve to the air valve on the intake.I know it goes between the temp sensor on the intake, the hot water valve port on the manifold and the door on the intake. The shop manual is useless as it only shows the heater and vent controls. Thanks

Do you mean the vacuum source, Lawrence…?

Haines has a comprehensive vacuum diagram for the S1 - though like all diagrams, does not show the physical locations and routing…

xj6 85 Sov Europe (UK/NZ)

That is the problem with all Jaguar manuals. It’s like they were written by Microsoft.
I know where the vacuum source is on the manifold. What I don’t remember is how the hoses are connected between the thermostatic vacuum switch on the manifold and the temperature sensor and hot air door on the air cleaner box. The illustration in the shop manual shows only two hoses attached to the thermo switch, unless the inner nipple is a vent. Not sure.

Crudely, Lawrence; vacuum source goes to the ‘one-way’ valve - then two hoses goes, respectively, one to the vacuum reservoir (engine compartment) and one, with branches, feeding the heater sensing unit (in the cabin), the heater control modulator (dash) and the air flap modulator (dash). The latter is connected to the air flap modulator, and the heater control modulator is again connected to another spigot on heater sensing unit. Which has a separate spigot to the heater valve…phew…

But the main point is that the physical routing of vacuum hoses is a matter of convenience - like electric wires; it is where they are connected that counts. Jaguar routing was not consistent; - routing varied with equipment levels, market, model year - and sometimes by assembly workers’ whims…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

Hi Lawrence - I see from your profile you have a 72 XJ6 - is it a US Emissions Spec Car?
If so the big vacuum switch with the 3 ports sticking sideways out of the front of the manifold is only used to control the Vacuum retard module on the distributor during high-temp conditions. It defeats vacuum retard at idle when the car is hot to keep it from overheating. Only 2 of the ports are used - the 2 farthest out from the manifold. None of it is connected to the air cleaner heat valve system.

The intake heat air valve on the air cleaner is a thermostatic device that has it’s own vacuum signal supplied by a vac line under the manifold. It’s line is connected directly to a small port located under the manifold between the carbs but closer to the rear one and closest to the block (There is another vac port in front of it on the manifold that is for the HVAC controls in the car)

The way it connects is from the port under the manifold, to the one port on the vacuum switch attached to the air cleaner (doesn’t matter which). Then another line goes from the other port on the vac switch to the device that opens and closes the door in the air cleaner.

Hope that makes sense.
72 XJ6 (x2)
73 XJ6

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I have a US emission spec. I have already rebuilt the entire vacuum system for the heater controls. I want to get the heat valved door on the air cleaner working correctly. What you are missing in your description is the thermostatic switch that operates on hot water in the manifold. There is a small nipple forward on the manifold that should have a hose connected to one of the nipples on this thermo switch, The switch closes when the water temp rises, cutting off the vacuum to the heat door. I can find no diagram showing the vacuuum lines between the thermo switch and the sensor between the carbs and the heat door. There are three nipples on the thermo switch but one may be an atmospheric port. I’m going to have to test it and see how it operates, The line from the thermo switch probably should go to the sensor and then the door, The sensor would regulate the door based on the temp of the air entering the carbs. It’s just frustrating that there isn’t any good documentation. The manuals show the thermal switch but don’t identify the lines. Thanks for your input. At least I have heat in the cabin. Maybe next year I’ll tackle the A/C.

I don’t mean to be argumentative but that’s not quite correct. The only thermostatic control of the air cleaner heat door is the temp sensor in the air cleaner’s back plate. There’s no reason to also have a water temperature input to that system - the air around the exhaust manifold heats up pretty quick, closing the temp sensor in the air cleaner (shutting off vacuum) which allows the door to return to it’s normal state which is open.

The thermo switch with 3 nipples labeled ‘C’, ‘D’ and ‘M’ is completely separate from that system. ‘M’ is open to the atmosphere - the closest to the manifold. That 3-port thermal switch regulates vacuum to the distributor’s vac retard capsule (another pollution control device) to avoid an overheat condition when coolant temp reaches 220 degrees F.

There is documentation but it’s in multiple locations which is kind of hard to share. The nipple on the bottom of the intake manifold that provides vacuum for the air cleaner intake heat door is the port I mentioned above.

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I believe you are right. It has been a long time since I worked on these Jags for a living and my memory of these things is cloudy. To make matters worse, whoever had their hands on this car before I got it 2 years ago made quite a mess of things. Thanks again for your input!

Lawrence - here is something that may help. It’s from the S1 parts manual for emission controlled cars.
I certainly know how you feel about previous owners making a mess, especially when they screw around with ancient emission controls - The gulp-valve and anti-run-on device may as well be flux-capacitors :slight_smile:
S1 XJ6 Vacuum Switch

That looks about right. Yup, gulp valve and air pump are all gone.