While looking around the engine bay, I noticed what appears to be a disconnected hose. See the picture. I found it floundering around under the air filter cover, left-hand-side (driver side, US).

Does anybody know what it is and whether it should be connected to something and if yes what?

 

Don't have much experience with the V12's, but I thought it was either to the throttle body on the bottom, or the bottom/back of the airbox assembly?

 

Well, since I have an almost identical kitty (only a year older), I decided to go and see if I can locate this hose in my '86. I took the air filter cover out on both cars, to give myself more space.

I was looking and looking for a similar hose in '86, but could not find it! Nothing was going in the throttle body from the bottom. (Only from the top.)

And then I had an idea: maybe I was not looking in the right area?

After couple of minutes I think I found it. I think this disconnected hose is the vacuum hose that was supposed to be connected to the white plastic fitting on top of the distributor? Whoever was working in the Vee last before me appeared to forget to connect the vacuum hose to the rotor. Accidentally or on purpose.

Why I said it might have been on purpose... I connected the hose to the distributor. Took the car around the block. Maybe it was my imagination, but I don't think so. The engine started to "stumble" more. Almost like temporary loss of power, before catching up. Over and over. Could this be because I connected that hose back to the distributor???

 

More than likely just the distributor vent hose. It should have no bearing on performance or timing. Should connect to spigot on the larger hose connecting air cleaner box to AAV.

 

Where does the other end go?

 

Hmmm, the distributors don't have a vacuum advance on these, so I would agree its just a vent tube to allow air to circulate to prevent moisture build up inside. I'm with NJ2003XJ8, where does the other end go?

 

This shows the hoses for the distributor vent system:

https://www.jaguarclassicparts.com/u...up-to-v-157115

The hose marked "to extra air valve" actually goes to the large hose that's between the LH air filter housing and the AAV, item #4 in this illustration


https://www.jaguarclassicparts.com/u...alve-5-3-litre


Cheers
DD

 

The other end of the hose is "buried" along the block. Cannot see very well down there unless the air intake assembly is taken off.

So, there is no big problem if it is disconnected? Its real purpose is to take the moisture away from the distributor?

 

There is a distributor ventilation system on your car that prevents petrol fume buildup in the dizzy and thus risk of explosion.


You should have a small filter by the wing brace that has a hose on it that leads to the side of the dizzy towards the rear of it. Then a hose comes out of the dizzy top and goes to a small plastic fitting into the intake hose from the back of the airbox to the AAV. Thus system sucks air through the dizzy.


This plastic bit fails, of the hose can just drop of it. This could, repeat could, be the hose. See this diagram:

 

Thanks. I assume it is the one. I located a similar hose connected to the top of the distributor. And I also remember seeing the other one, that connects to the back of the distributor, when getting into the Vee while checking spark plugs.

I will try to take more pictures underneath the air intake to see if the other end of the hose connects to the fitting like in the diagram

 

Doug and Grant should be right, from the looks of the size and location, it runs from the AAV to the dizzy

 

doud is very correct
I have a 1992
when I bought it I found this (what looked like a fuel filter for a lawn mower on it and I thought some bozo had put it in there?
Wrong!
https://www.jaguarclassicparts.com/u...up-to-v-157115
so I went out and bought a new one ... make sure that hose flow air freely through it and that the filter is new and good
it take air filter in and through the dist. with another hose that has vacuum from the manifold

 

You probably already know this and the word "manifold" wasn't what you meant but the hose should NOT be connected to the manifold.
It connects indirectly to air cleaner backplate.

 

I stand corrected
guess what, a source of vacuum

https://www.jaguarclassicparts.com/u...-5-3-6-0-litre

but not to the air cleaner back plate...


hmm.....

 

The source of vacuum for the vent system is a nipple coming off the hose that goes to the air filter housing backing plate, as shown in other illustrations in this thread


Cheers
DD

 

What Doug said.

 

Jonathan
Hose 4 in the diagram I posted supplies filtered air from the B bank aircleaner back plate to the AAV (for both cold start and tickover air supply). The AAV in effect bypasses the throttle butterflies and sends air directly into the manifolds. The distributor vent pipe is connected to Hose 4, as shown in the diagram, which supplies "suck" to pull fresh air through the distributor into the manifold via the AAV.
Greg

 

Adding to that.

The elbow #5 is the plastic item in question, and if you have one that is intact, buy a lottery ticket, it is a special moment.

The system has NO vacuam as such. The hoses and elbow are in a "draft" air supply to the AAV, as already said. Huge draft when the AAV is open (cold engine) and much less when the AAV is closed (hot engine).

It is only on the HE engine as original. The PreHE had no such system originally, but with cap replacement there "may be" a vent spigot. Most replacement caps for the larger Lucas distributor are of the vented design, simply due to rationalisation of spare parts.

Without this draft vent system connected, the risk of a cap explosion due to engine vent fumes rising into the cap space is large enough to be a worry. It usually only occurs as start up is attempted after a hot shutdown, and a distinct "whoosh/pop" is the odd sound heard by the driver, and the failure of the engine to start, oops. Mine blew the cap clean off, in many pieces, and imbedded it in the bonnet insulation. My fault, I had a kink in the hose to the AAV elbow.

 

Adding to that: The plastic thingy is NLA and could be replaced by a suitable brass 90 degree fitting. BUT the Hose 4 is also NLA. I recently helped a friend get over this by buying a suitable hose (ie 1 inch diameter with a 90 degree bend) and installing into it one of these:

https://www.viperperformance.co.uk/h...one-hoses.html


One of the range of which handily comes in the right ID for the dizzy spigot, and will not fail in the heat. Works fine.
Greg

 

Forgot that one Greg.

I used a Honda Civic, OLD CIVIC, top radiator hose, when I still had that AAV nonsense. Just wandered through the racks at work until I found what looked OK.